Understanding the catalytic mechanism at real catalytically active layer is essential for the advancement of water oxidation.Nevertheless,it is difficult to explore the surface effect of active layer of catalysts on o...Understanding the catalytic mechanism at real catalytically active layer is essential for the advancement of water oxidation.Nevertheless,it is difficult to explore the surface effect of active layer of catalysts on oxygen evolution reaction(OER)independently because of the coexistence of bulk phase and surfaceactive layer.Herein,by designing ultra-thin shell amorphous CoO_(x)hollow nanospheres,we explored the effect of single catalytic active layer on OER activity,further revealing the surface catalytic mechanism for seawater oxidation.The amorphous catalytic active layer CoO_(x)contain phosphates(CoO_(x)PO_(4)),induced by completely bulk reconstruction of CoP_(x)hollow nanospheres.Compared with autologous crystalline CoO,amorphous catalytic active species CoO_(x)-PO_(4)possesses higher OER performance with ultralow overpotential of 229 mV to achieve 10 mA cm^(-2).Remarkably,self-built phosphate film could effectively block chloride anions and implement robust seawater oxidation.This work brings direct insights of the surface effect of amorphous catalytic active layer on water oxidation,which is critical for the performance optimization of water oxidation.展开更多
Atomically precise metal nanoclusters(NCs)have been deemed as a new generation of metal nanomaterials in the field of solar energy conversion due to their unique atomic stacking manner,quantum confinement effects,ligh...Atomically precise metal nanoclusters(NCs)have been deemed as a new generation of metal nanomaterials in the field of solar energy conversion due to their unique atomic stacking manner,quantum confinement effects,light-harvesting capability and multitude of active sites.Nonetheless,wide-spread application of monometallic NCs is blocked by the ultrashort carrier lifespan,uncontrollable charge transport pathway,and light-induced poor stability,impeding the construction of robust and stable metal NC-based photosystems.Herein,we report the fabrication of stable alloy(Au_(1-x)Pt_(x))NCs photosystem,for which tailor-made negatively charged l-glutathione(GSH)-capped Au_(1-x)Pt_(x)NCs as the building blocks are controllably deposited on the Bi VO_(4)(BVO)by a self-assembly approach for steering enhanced light absorption and interfacial charge transfer over alloy NCs-based photoanodes(Au_(1-x)Pt_(x)/BVO).The self-assembled Au_(1-x)Pt_(x)/BVO composite photoanode exhibits the significantly enhanced photoelectrochemical water oxidation performances compared with pristine BVO and Au_(x)/BVO photoanodes,which is caused by the Pt atom doping into the Au_(x)NCs for elevating photosensitivity and boosting the stability.The synergy of Au and Pt atoms in alloy NCs protects the gold core from rapid oxidation,improving the photostability and accelerating the surface charge transfer kinetics.Our work would significantly inspire ongoing interest in unlocking the charge transport characteristics of atomically precise alloy NCs for solar energy conversion.展开更多
In-situ observation of the charge transfer plays a key role in understanding the working mechanism of hematite for solar water oxidation.Here by using in-situ X-ray absorption spectroscopy(XAS),the electron injection ...In-situ observation of the charge transfer plays a key role in understanding the working mechanism of hematite for solar water oxidation.Here by using in-situ X-ray absorption spectroscopy(XAS),the electron injection from illuminated hematite(photon-excited electron)to the surface carbon layer can be clearly identified,which can facilitate the charge separation and then improve the performance.As a result,the carbon-coated and Sn-doped hematite photoanode(C-Sn-Fe_(2)O_(3))shows a greatly enhanced photocurrent density of 2.3 mA/cm^(2) at 1.23 VRHE,which is 2.3 times that of the pristine hematite.The injected electron can modify the chemical state of surface groups in the carbon layer and be quickly transferred to the electrode due to the high conductivity of the carbon layer,leaving behind the high-valence Fe^(4+)with high oxidation capability to enhance the performance.By coupling with the FeNiOOH co-catalyst,the photoanode can finally achieve a high photocurrent density of 3.0 mA/cm^(2) at 1.23 VRHE with a low onset potential of 0.76 VRHE.The understanding of the charge migration route by using in-situ XAS offers a novel way for the design of highly efficient solar water oxidation materials.展开更多
Photoelectrochemical water oxidation reaction (PEC-WOR) as a sustainable route to produce H_(2)O_(2) is attractive but limited by low activity and poor product selectivity of photoanodes due to limited photogenerated ...Photoelectrochemical water oxidation reaction (PEC-WOR) as a sustainable route to produce H_(2)O_(2) is attractive but limited by low activity and poor product selectivity of photoanodes due to limited photogenerated charge efficiency and unfavorable thermodynamics. Herein, by crystal orientation engineering, the WO_(3) photoanode exposing (200) facets achieves both superior WOR activity (15.4 mA cm^(−2) at 1.76 VRHE) and high selectivity to H_(2)O_(2) (∼70%). Comprehensive experimental and theoretical investigations discover that the high PEC-WOR activity of WO_(3)-(200) is attributed to the rapid photogenerated charge separation/transfer both in bulk and at interfaces of WO_(3)-(200) facet, which reduces the charge transfer resistance. This, coupling with the unique defective hydrogen bonding network at the WO_(3)-(200)/electrolyte interface evidenced by operando PEC Fourier transform infrared spectroscopy, facilitating the outward-transfer of the WOR-produced H^(+), lowers the overall reaction barrier for the PEC-WOR. The superior selectivity of PEC-WOR to H_(2)O_(2) is ascribed to the unique defective hydrogen bonding network alleviated adsorption of ∗OH over the WO_(3)-(200) facet, which specially lowers the energy barrier of the 2-electron pathway, as compared to the 4-electron pathway. This work addresses the significant role of crystal orientation engineering on photoelectrocatalytic activity and selectivity, and sheds lights on the underlying PEC mechanism by understanding the water adsorption behaviors under illumination. The knowledge gained is expected to be extended to other photoeletrochemical reactions.展开更多
Photoelectrochemical water oxidation(PEC-WO)as a green and sustainable route to produce H_(2)O_(2)has attracted extensive attentions.However,water oxidation to H_(2)O_(2)via a 2e^(-) pathway is thermodynamically more ...Photoelectrochemical water oxidation(PEC-WO)as a green and sustainable route to produce H_(2)O_(2)has attracted extensive attentions.However,water oxidation to H_(2)O_(2)via a 2e^(-) pathway is thermodynamically more difficult than to O_(2)via a 4e^(-)pathway.Herein,with a series of BiVO_(4)-based photoanodes,the decisive factors determining the PEC activity and selectivity are elucidated,combining a comprehensive experimental and theoretical investigations.It is discovered that the ZnO/BiVO_(4)photoanode(ZnO/BVO)forms a Type-Ⅱheterojunction in energy level alignment.The accelerated photogenerated charge separation/transfer dynamics generates denser surface holes and higher surface photovoltage.Therefore,the activity of water oxidation reaction is promoted.The selectivity of PEC-WO to H_(2)O_(2)is found to be potential-dependent,i.e.,at the lower potentials(PEC-dominated),surface hole density determines the selectivity;and at the higher potentials(electrochemical-dominated),surface reaction barriers govern the selectivity.For the ZnO/BVO heterojunction photoanode,the higher surface hole density facilitates the generation of OH·and the subsequent OH·/OH·coupling to form H_(2)O_(2),thus rising up with potentials;at the higher potentials,the 2-electron pathway barrier over ZnO/BVO surface is lower than over BVO surface,which benefits from the electronic structure regulation by the underlying ZnO alleviating the over-strong adsorption of^(*)OH on BVO,thus,the two-electron pathway to produce H_(2)O_(2)is more favored than on BVO surface.This work highlights the crucial role of band energy structure of semiconductors on both PEC reaction activity and selectivity,and the knowledge gained is expected to be extended to other photoeletrochemical reactions.展开更多
Water/seawater oxidation determines the hydrogen production efficiency of water/seawater splitting.De-veloping high-efficiency,conductive,stable,and erosion-resisting transition metal-based layered double hydroxide(TM...Water/seawater oxidation determines the hydrogen production efficiency of water/seawater splitting.De-veloping high-efficiency,conductive,stable,and erosion-resisting transition metal-based layered double hydroxide(TM-LDH)is crucial to water/seawater oxidation.Hence,amorphous high-entropy FeCoNiCr-LDH is fabricated by one-step electrodeposition to promote water/seawater oxidation.Coupling of high entropy,Cr cation leaching,congenetic CrO_(4)^(2-)adsorption,and amorphization to facilitate electrochem-ical reconstruction.The advanced strategy enhances active sites,reaction kinetics,reaction selectivity,conductivity,stability,and corrosion resistance with the electrostatic chlorine-repellent layer.The in-situ Cr leaching and congenetic CrO_(4)^(2-)adsorption-induced electrochemical reconstruction are identified by cyclic voltammetry(CV)activation,in-situ Bode plots,and electrochemical impedance spectroscopy(EIS)plots,ex-situ Raman and ultraviolet-visible spectrophotometry(UV-Vis).The OER active species of oxy-hydroxides are also formed during electrochemical reconstruction.Moreover,control tests of soaking and extra CrO_(4)^(2-)additive verify the superiorities of electrochemical reconstruction with in-situ Cr leaching and congenetic CrO_(4)^(2-)adsorption.Accordingly,FeCoNiCr-LDH exhibits excellent electrochemical perfor-mances with low overpotentials of 193/225 mV at 10 mA cm^(-2),high Faradaic efficiencies of 99.3%/97.4%and strong stability for alkaline water/simulated seawater oxidation,respectively.This study provides one innovative strategy to construct efficient water/seawater oxidation electrocatalysts,showing the great the-oretical significance and practical values in industrial water/seawater splitting for hydrogen production.展开更多
Flower-like 3D CuO microspheres were synthesized and used to photo-catalyze water oxidation under visible light.The structure of the CuO microspheres was characterized by scanning electron microscopy,transmission elec...Flower-like 3D CuO microspheres were synthesized and used to photo-catalyze water oxidation under visible light.The structure of the CuO microspheres was characterized by scanning electron microscopy,transmission electron microscopy,infrared,powder X-ray diffraction,electron dispersive spectroscopy,Raman and X-ray photoelectron spectroscopy（XPS）.This is the first time that a copper oxide was demonstrated as a photocatalytic water oxidation catalyst under near neutral conditions.The catalytic activity of CuO microspheres in borate buffer shows the best performance with O2 yield of 11.5%.No change in the surface properties of CuO before and after the photocatalytic reaction was seen by XPS,which showed good catalyst stability.A photocatalytic water oxidation reaction mechanism catalyzed by the CuO microspheres was proposed.展开更多
Polyvinyl alcohol is a refractory compound widely used in industry. Here we report supercritical water oxidation of polyvinyl alcohol solution and desizing wastewater with and without sodium hydroxide addition. Howeve...Polyvinyl alcohol is a refractory compound widely used in industry. Here we report supercritical water oxidation of polyvinyl alcohol solution and desizing wastewater with and without sodium hydroxide addition. However, it is difficult to implement complete degradation of organics even though polyvinyl alcohol can readily crack under supercritical water treatment. Sodium hydroxide had a significant catalytic effect during the supercritical water oxidation of polyvinyl alcohol. It appears that the OH ion participated in the C-C bond cleavage of polyvinyl alcohol molecules, the CO2-capture reaction and the neutralization of intermediate organic acids, promoting the overall reactions moving in the forward direction. Acetaldehyde was a typical intermediate product during reaction. For supercritical water oxidation of desizing wastewater, a high destruction rate （98.25%） based on total organic carbon was achieved. In addition, cases where initial wastewater was alkaline were favorable for supercritical water oxidation treatment, but salt precipitation and blockage issues arising during the process need to be taken into account seriously.展开更多
The destruction of toxic organic wastewaters from munitions demilitarization and complex industrial chemical clearly becomes an overwhelming problem if left to conventional treatment processes. Two options, incinerati...The destruction of toxic organic wastewaters from munitions demilitarization and complex industrial chemical clearly becomes an overwhelming problem if left to conventional treatment processes. Two options, incineration and supercritical water oxidation （SCWO）, exist for the complete destruction of toxic organic wastewaters. Incinerator has associated problems such as very high cost and public resentment; on the other hand, SCWO has proved to be a very promising method for the treatment of many different wastewaters with extremely efficient organic waste destruction 99.99% with none of the emissions associated with incineration. In this review, the concepts of SCWO, result and present perspectives of application, and industrial status of SCWO are critically examined and discussed.展开更多
The 2,4,6-trinitrotoluene （TNT） is a potential carcinogens and TNT contaminated wastewater, which could not be effectively disposed with conventional treatments. The supercritical water oxidation （SCWO） to treat T...The 2,4,6-trinitrotoluene （TNT） is a potential carcinogens and TNT contaminated wastewater, which could not be effectively disposed with conventional treatments. The supercritical water oxidation （SCWO） to treat TNT contaminated wastewater was studied in this article, The TNT concentration in wastewater was measured by high-performance liquid chromatograph （HPLC） and the degraded intermediates were analyzed using GC-MS. The results showed that SCWO could degrade TNT efficiently in the presence of oxygen. The reaction temperature, pressure, residence time and oxygen excess were the main contributing factors in the process. The decomposition of TNT was accelerated as the temperature or residence time increased. At 550℃, 24 MPa, 120 s and oxygen excess 300%, TNT removal rate could exceed 99.9%. Partial oxidation occured in SCWO without oxygen. It was concluded that supercritical water was a good solvent and had excellent oxidation capability in the existence of oxygen. The main intermediates of TNT during SCWO included toluene, 1,3,5-trinitrobenzene, nitrophenol, naphthalene, fluorenone, dibutyl phthalate, alkanes and several dimers based on the intermediate analysis. Some side reactions, such as coupled reaction, hydrolysis reaction and isomerization reaction may take place simultaneously when TNT was oxidized by SCWO.展开更多
Some aromatic compounds, phenol, aniline and nitrobenzene, were oxidized in supercritical water. It was experimentally found that the chemical oxygen demand (COD) removal efficiency of these organic compounds can achi...Some aromatic compounds, phenol, aniline and nitrobenzene, were oxidized in supercritical water. It was experimentally found that the chemical oxygen demand (COD) removal efficiency of these organic compounds can achieve a high level more than 90% in a short residence time at temperatures high enough. As temperature, pressure and residence time increase, the COD removal efficiencies of the organic compounds would all increase. It is also found that temperature and residence time offer greater influences on the oxidation process than pressure. The difficulty in oxidizing these three compounds is in the order of nitrobenzene ＞ aniline ＞ Phenol. In addition, it is extremely difficult to oxidize aniline and nitrobenzene to CO2 and H2O at the temperature lower than 873.15 K and 923.15 K, respectively. Only at the temperature higher than 873.15 K and 923.15 K, respectively, the COD removal efficiencies of 90% of aniline and nitrobenzene can be achieved.展开更多
The realization of efficient oxygen evolution reaction(OER) is critical to the development of multiple sustainable energy conversion and storage technologies, especially hydrogen production via water electrolysis. To ...The realization of efficient oxygen evolution reaction(OER) is critical to the development of multiple sustainable energy conversion and storage technologies, especially hydrogen production via water electrolysis. To achieve the massive application of hydrogen energy and mass-scale hydrogen production from water splitting drives the pursuit of competent precious-metal-free electrocatalysts in acidic media, where the hydrogen evolution reaction(HER) is more facilitated. However, the development of high-efficient and acid-stable OER electrocatalysts, which are robust to function stably at high oxidation potentials in the acidic electrolyte, remains a great challenge. This article contributes a focused, perceptive review of the up-to-date approaches toward this emerging research field. The OER reaction mechanism and fundamental requirements for oxygen evolution electrocatalysts in acid are introduced. Then the progress and new discoveries of precious-metal-free active materials and design concepts with regard to the improvement of the intrinsic OER activity are discussed. Finally, the existing scientific challenges and the outlooks for future research directions to the fabrication of emerging, earth-abundant OER electrocatalysts in acid are pointed out.展开更多
It is critical to developing electrocatalysts with highly active and cost-effective for oxygen evolution to resolve environmental pollution and energy issues,in which FeNi-based nanomaterials hold a great promise.Here...It is critical to developing electrocatalysts with highly active and cost-effective for oxygen evolution to resolve environmental pollution and energy issues,in which FeNi-based nanomaterials hold a great promise.Herein,(Fe_(0.33 )Ni_(0.67))S_(2) and(Fe_(0.33 )Ni_(0.67))S_(2)/reduced graphene oxide(rGO)-x%(x=10,20) composites,which exhibited highly efficient oxygen evolution reaction(OER)electrocatalytic activity under alkaline conditions,were synthesized via a hydrothermal approach and following thermal treatment with sulfur powders.Benefiting from the integrated structure of(Fe_(0.33 )Ni_(0.67))S_(2)and support of conductive graphene backbones,(Fe_(0.33 )Ni_(0.67))S_(2)/rGO-20%electrocatalyst showed the best OER activity with an overpotential of 172 mV at 10 mA·cm^(-2)and Tafel slopes of 45 mV·decade^(-1).The composition,phase,and surface structure of the catalyst were characterized before and after OER reaction.The results indicated that crystal phase of the catalyst was reconstructed to the amorphous crystalline features after OER,with oxidation of iron-nickel sulfide and appearance of Ni-Fe oxo/hydroxide species,which may play a crucial role in the high OER performance as the catalytic-active.Moreover,in a two-electrode system towards overall water splitting with(Fe_(0.33 )Ni_(0.67))S_(2)/rGO-20%/NF and Pt/C/NF as the anode and cathode,respectively,the catalysts exhibited excellent catalytic performance with the voltage of only 1.42 V at 10 mA·cm^(-2).展开更多
BiVO_(4) has been attracting a lot of interest in photoelectrochemical (PEC) water oxidation due to its efficient solar absorption and appropriate band positions.So far,sluggish water oxidation kinetics and fast photo...BiVO_(4) has been attracting a lot of interest in photoelectrochemical (PEC) water oxidation due to its efficient solar absorption and appropriate band positions.So far,sluggish water oxidation kinetics and fast photogenerated charge recombination still hinder the PEC performance ofBiVO_(4) .In this study,a novel PEC photoanode was designed by depositing ultrathin FeOOH nanolayers on the surface of nanoporousBiVO_(4) electrode,followed by modification with a cobaloxime (Co(dmgH)_(2)(4-COOH-py)Cl) molecular cocatalyst.Under irradiation of a 100 mW cm^(-2)(AM 1.5G) Xe lamp,the photocurrent density of the cobaloxime/FeOOH/BiVO_(4) composite photoanode reached 5.1 mA cm^(-2)at 1.23 V vs.RHE in 1.0 M potassium borate buffer solution (pH=9.0).The onset potential of the optimal cobaloxime/FeOOH/BiVO_(4) photoanode exhibited a 460 m V cathodic shift relative to bareBiVO_(4) .In addition,the surface charge injection efficiency of the composite photoanode reached~80%at 1.23 V vs.RHE and the incident photon-to-current efficiency (IPCE) reached~88%at 420 nm.展开更多
Oxygen evolution reaction(OER)is pivotal to drive green hydrogen generation from water electrolysis,but yet is strictly overshadowed by the sluggish reaction kinetics.Earth-abundant and cut-price transitionmetal compo...Oxygen evolution reaction(OER)is pivotal to drive green hydrogen generation from water electrolysis,but yet is strictly overshadowed by the sluggish reaction kinetics.Earth-abundant and cut-price transitionmetal compounds,particularly Co Fe layered-double-hydroxides(LDHs),show the distinct superiorities in contrast to noble metals and their derivatives.In this review,we firstly underline their fundamental issues in electrocatalytic water oxidation,including Co Fe LDHs crystal structure,the surface of(hydr)oxides confined to OER and the controversial roles of Fe species,aiming at understanding the structure-related activity and catalytic mechanism.Advanced approaches for optimizing OER activity of Co Fe LDHs are then comprehensively overviewed,which will shed light on the different working mechanisms and provide a concise analysis of their unique advantages.Finally,a perspective on the future development of Co Fe LDHs electrocatalysts is offered.We hope this review can give a concise and explicit guidance for the development of transition-metal-based electrocatalysts in the energy field.展开更多
Cobalt-based oxides,with high abundance,good stability and excellent catalytic performance,are regarded as promising photocatalysts for artificial photosynthetic systems to alleviate foreseeable energy shortages and g...Cobalt-based oxides,with high abundance,good stability and excellent catalytic performance,are regarded as promising photocatalysts for artificial photosynthetic systems to alleviate foreseeable energy shortages and global warming.Herein,for the first time,a series of novel spongy porous CDs@CoOx materials were synthesized to act as an efficient and stable bifunctional photocatalyst for water oxidation and CO2 reduction.Notably,the preparation temperatures visibly influence the morphologies and photocatalytic performances of the CDs@CoOx.Under the optimal conditions,a maximum O2 yield of 40.4% and pretty apparent quantum efficiency(AQE)of 58.6% at 460 nm were obtained over CDs@CoOx-300 for water oxidation.Similarly,the optimized sample CDs@CoOx-300 manifests significant enhancement on the CO2-to-CO conversion with a high selectivity of 89.3% and CO generation rate of 8.1μmol/h,which is superior to most previous cobalt-based catalysts for CO2 reduction.The composite CDs@CoOx-300 not only exposes more active sites but also facilitates electron transport,which results in excellent photocatalytic activity.In addition,the boosted photocatalytic behavior is attributed to the synergistic effect between CoOx and CDs,which was verified by the photocatalytic activity control experiments and electrochemical characterization.The work offers a novel strategy to fabricate a high performance bifunctional photocatalyst for water oxidation and CO2 reduction.展开更多
The oxygen evolution reaction(OER)activity of single-atom catalysts(SACs)is closely related to the coordination environment of the active site.Oxygencoordinated atomic metal species bring about unique features beyond ...The oxygen evolution reaction(OER)activity of single-atom catalysts(SACs)is closely related to the coordination environment of the active site.Oxygencoordinated atomic metal species bring about unique features beyond nitrogen-coordinated atomic metal species due to the fact that the M-O bond is weaker than the M-N bond.Herein,a series of metal-oxygen-carbon structured low-nucleus clusters(LNCs)are successfully anchored on the surface of multiwalled carbon nanotubes(M-MWCNTs,M=Ni,Co,or Fe)through a foolproof low-temperature gas transfer(300℃)method without any further treatment.The morphology and coordination configuration of the LNCs at the atomic level were confirmed by comprehensive characterizations.The synthetic Ni-MWCNTs electrocatalyst features excellent OER activity and stability under alkaline conditions,transcending the performances of Co-MWCNTs,Fe-MWCNTs and RuO_(2).Density functional theory calculations reveal that the moderate oxidation of low-nucleus Ni clusters changes the unoccupied orbital of Ni atoms,thereby lowering the energy barrier of the OER rate-limiting step and making the OER process more energy-efficient.This study demonstrates a novel versatile platform for large-scale manufacturing of oxygen-coordinated LNC catalysts.展开更多
The destruction of methylphosphonic acid （MPA）, a final product by hydrolysis/neutralization of organophosphorus agents such as sarin and VX （O-ethyl S-[2-（diisopropylamino）ethyl] methylphosphonothionate）, was i...The destruction of methylphosphonic acid （MPA）, a final product by hydrolysis/neutralization of organophosphorus agents such as sarin and VX （O-ethyl S-[2-（diisopropylamino）ethyl] methylphosphonothionate）, was investigated in a a bench-scale, continuous concentric vertical double wall reactor under supercritical water oxidation condition. The experiments were conducted at a temperature range of 450–600°C and a fixed pressure of 25 MPa. Hydrogen peroxide was used as an oxidant. The destruction efficiency （DE） was monitored by analyzing total organic carbon （TOC） and MPA concentrations using ion chromatography on the liquid effluent samples. The results showed that the DE of MPA up to 99.999% was achieved at a reaction temperature of 600°C, oxygen concentration of 113% storichiometric requirement, and reactor residence time of 8 sec. On the basis of the data derived from experiments, a global kinetic rate equation for the DE of MPA and DE of TOC were developed by nonlinear regression analysis. The model predictions agreed well with the experimental data.展开更多
Developing efficient water oxidation catalysts(WOCs)with earth‐abundant elements still remains a challenging task for artificial photosynthesis.Iron‐based WOC is a promising candidate because it is economically chea...Developing efficient water oxidation catalysts(WOCs)with earth‐abundant elements still remains a challenging task for artificial photosynthesis.Iron‐based WOC is a promising candidate because it is economically cheap,little toxic and environmentally friendly.In this study,we found that the catalytic water oxidation activity on amorphous iron‐based oxide/hydroxide(FeOx)can be decreased by an order of magnitude after the dehydration process at room temperature.Thermogravimetric analysis,XRD and Raman results indicated that the dehydration process of FeOx at room temperature causes the almost completely loss of water molecule with no bulk structural changes.Based on this finding,we prepared hydrated ultrasmall(ca.2.2 nm)FeOx nanoparticles of amorphous feature,which turns out to be extremely active as WOC with turnover frequency(TOF)up to 9.3 s^-1 in the photocatalytic Ru(bpy)3^2+‐Na2S2O8 system.Our findings suggest that future design of active iron‐based oxides as WOCs requires the consideration of their hydration status.展开更多
Water oxidation is significant in both natural and artificial photosynthesis.In nature,water oxidation occurs at the oxygen‐evolving center of photosystem II,and leads to the generation of oxygen,protons,and electron...Water oxidation is significant in both natural and artificial photosynthesis.In nature,water oxidation occurs at the oxygen‐evolving center of photosystem II,and leads to the generation of oxygen,protons,and electrons.The last two are used for fixation of carbon dioxide to give carbohydrates.In artificial processes,the coupling of water oxidation to evolve O2and water reduction to evolve H2is known as water splitting,which is an attractive method for solar energy conversion and storage.Because water oxidation is a thermodynamically uphill reaction and is kinetically slow,this reaction causes a bottleneck in large‐scale water splitting.As a consequence,the development of new and efficient water oxidation catalysts(WOCs)has attracted extensive attention.Recent efforts have identified a variety of mononuclear earth‐abundant transition‐metal complexes as active and stable molecular WOCs.This review article summarizes recent progress in research on mononuclear catalysts that are based on first‐row transition‐metal elements,namely manganese,iron,cobalt,nickel,and copper.Particular attention is paid to catalytic mechanisms and the key O?O bond formation steps.This information is critical for designing new catalysts that are highly efficient and stable.展开更多
基金support from the Starting Research Funds of Hebei University of Science and Technology,the National Natural Science Foundation of China(22109038)the Hebei Natural Science Foundation(D2022208001)the S&T Program of Hebei(21344601D,242G4601Z)。
文摘Understanding the catalytic mechanism at real catalytically active layer is essential for the advancement of water oxidation.Nevertheless,it is difficult to explore the surface effect of active layer of catalysts on oxygen evolution reaction(OER)independently because of the coexistence of bulk phase and surfaceactive layer.Herein,by designing ultra-thin shell amorphous CoO_(x)hollow nanospheres,we explored the effect of single catalytic active layer on OER activity,further revealing the surface catalytic mechanism for seawater oxidation.The amorphous catalytic active layer CoO_(x)contain phosphates(CoO_(x)PO_(4)),induced by completely bulk reconstruction of CoP_(x)hollow nanospheres.Compared with autologous crystalline CoO,amorphous catalytic active species CoO_(x)-PO_(4)possesses higher OER performance with ultralow overpotential of 229 mV to achieve 10 mA cm^(-2).Remarkably,self-built phosphate film could effectively block chloride anions and implement robust seawater oxidation.This work brings direct insights of the surface effect of amorphous catalytic active layer on water oxidation,which is critical for the performance optimization of water oxidation.
基金The support by the award Program for Minjiang scholar professorship is greatly acknowledgedfinancially supported by the National Natural Science Foundation of China(Nos.21703038,22072025)The financial support from State Key Laboratory of Structural Chemistry,Fujian Institute of Research on the Structure of Matter,Chinese Academy of Science is acknowledged(No.20240018)。
文摘Atomically precise metal nanoclusters(NCs)have been deemed as a new generation of metal nanomaterials in the field of solar energy conversion due to their unique atomic stacking manner,quantum confinement effects,light-harvesting capability and multitude of active sites.Nonetheless,wide-spread application of monometallic NCs is blocked by the ultrashort carrier lifespan,uncontrollable charge transport pathway,and light-induced poor stability,impeding the construction of robust and stable metal NC-based photosystems.Herein,we report the fabrication of stable alloy(Au_(1-x)Pt_(x))NCs photosystem,for which tailor-made negatively charged l-glutathione(GSH)-capped Au_(1-x)Pt_(x)NCs as the building blocks are controllably deposited on the Bi VO_(4)(BVO)by a self-assembly approach for steering enhanced light absorption and interfacial charge transfer over alloy NCs-based photoanodes(Au_(1-x)Pt_(x)/BVO).The self-assembled Au_(1-x)Pt_(x)/BVO composite photoanode exhibits the significantly enhanced photoelectrochemical water oxidation performances compared with pristine BVO and Au_(x)/BVO photoanodes,which is caused by the Pt atom doping into the Au_(x)NCs for elevating photosensitivity and boosting the stability.The synergy of Au and Pt atoms in alloy NCs protects the gold core from rapid oxidation,improving the photostability and accelerating the surface charge transfer kinetics.Our work would significantly inspire ongoing interest in unlocking the charge transport characteristics of atomically precise alloy NCs for solar energy conversion.
基金the support from NSRL for the XAS experiments.This work was financially supported by the National Key R&D Program of China(No.2020YFA0406103)the National Natural Science Foundation of China(No.U1932211)+1 种基金the Collaborative Innovation Center of Suzhou Nano Science&Technology,the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)the 111 Project.
文摘In-situ observation of the charge transfer plays a key role in understanding the working mechanism of hematite for solar water oxidation.Here by using in-situ X-ray absorption spectroscopy(XAS),the electron injection from illuminated hematite(photon-excited electron)to the surface carbon layer can be clearly identified,which can facilitate the charge separation and then improve the performance.As a result,the carbon-coated and Sn-doped hematite photoanode(C-Sn-Fe_(2)O_(3))shows a greatly enhanced photocurrent density of 2.3 mA/cm^(2) at 1.23 VRHE,which is 2.3 times that of the pristine hematite.The injected electron can modify the chemical state of surface groups in the carbon layer and be quickly transferred to the electrode due to the high conductivity of the carbon layer,leaving behind the high-valence Fe^(4+)with high oxidation capability to enhance the performance.By coupling with the FeNiOOH co-catalyst,the photoanode can finally achieve a high photocurrent density of 3.0 mA/cm^(2) at 1.23 VRHE with a low onset potential of 0.76 VRHE.The understanding of the charge migration route by using in-situ XAS offers a novel way for the design of highly efficient solar water oxidation materials.
基金supported by the National Natural Science Foundation of China(22478211,22179067)the Major Fundamental Research Program of Natural Science Foundation of Shandong Province(ZR2022ZD10).
文摘Photoelectrochemical water oxidation reaction (PEC-WOR) as a sustainable route to produce H_(2)O_(2) is attractive but limited by low activity and poor product selectivity of photoanodes due to limited photogenerated charge efficiency and unfavorable thermodynamics. Herein, by crystal orientation engineering, the WO_(3) photoanode exposing (200) facets achieves both superior WOR activity (15.4 mA cm^(−2) at 1.76 VRHE) and high selectivity to H_(2)O_(2) (∼70%). Comprehensive experimental and theoretical investigations discover that the high PEC-WOR activity of WO_(3)-(200) is attributed to the rapid photogenerated charge separation/transfer both in bulk and at interfaces of WO_(3)-(200) facet, which reduces the charge transfer resistance. This, coupling with the unique defective hydrogen bonding network at the WO_(3)-(200)/electrolyte interface evidenced by operando PEC Fourier transform infrared spectroscopy, facilitating the outward-transfer of the WOR-produced H^(+), lowers the overall reaction barrier for the PEC-WOR. The superior selectivity of PEC-WOR to H_(2)O_(2) is ascribed to the unique defective hydrogen bonding network alleviated adsorption of ∗OH over the WO_(3)-(200) facet, which specially lowers the energy barrier of the 2-electron pathway, as compared to the 4-electron pathway. This work addresses the significant role of crystal orientation engineering on photoelectrocatalytic activity and selectivity, and sheds lights on the underlying PEC mechanism by understanding the water adsorption behaviors under illumination. The knowledge gained is expected to be extended to other photoeletrochemical reactions.
基金financially supported by the National Natural Science Foundation of China(22478211,22179067,22372017)the Major Fundamental Research Program of Natural Science Foundation of Shandong Province(ZR2022ZD10)。
文摘Photoelectrochemical water oxidation(PEC-WO)as a green and sustainable route to produce H_(2)O_(2)has attracted extensive attentions.However,water oxidation to H_(2)O_(2)via a 2e^(-) pathway is thermodynamically more difficult than to O_(2)via a 4e^(-)pathway.Herein,with a series of BiVO_(4)-based photoanodes,the decisive factors determining the PEC activity and selectivity are elucidated,combining a comprehensive experimental and theoretical investigations.It is discovered that the ZnO/BiVO_(4)photoanode(ZnO/BVO)forms a Type-Ⅱheterojunction in energy level alignment.The accelerated photogenerated charge separation/transfer dynamics generates denser surface holes and higher surface photovoltage.Therefore,the activity of water oxidation reaction is promoted.The selectivity of PEC-WO to H_(2)O_(2)is found to be potential-dependent,i.e.,at the lower potentials(PEC-dominated),surface hole density determines the selectivity;and at the higher potentials(electrochemical-dominated),surface reaction barriers govern the selectivity.For the ZnO/BVO heterojunction photoanode,the higher surface hole density facilitates the generation of OH·and the subsequent OH·/OH·coupling to form H_(2)O_(2),thus rising up with potentials;at the higher potentials,the 2-electron pathway barrier over ZnO/BVO surface is lower than over BVO surface,which benefits from the electronic structure regulation by the underlying ZnO alleviating the over-strong adsorption of^(*)OH on BVO,thus,the two-electron pathway to produce H_(2)O_(2)is more favored than on BVO surface.This work highlights the crucial role of band energy structure of semiconductors on both PEC reaction activity and selectivity,and the knowledge gained is expected to be extended to other photoeletrochemical reactions.
基金financially supported by the Natural Science Foundation of Hebei Province(No.B2024208055)the Science Re-search Project of Hebei Education Department(No.QN2022180)the Hebei University of Science and Technology Funding for basic scientific research operations(No.2024XLM022).
文摘Water/seawater oxidation determines the hydrogen production efficiency of water/seawater splitting.De-veloping high-efficiency,conductive,stable,and erosion-resisting transition metal-based layered double hydroxide(TM-LDH)is crucial to water/seawater oxidation.Hence,amorphous high-entropy FeCoNiCr-LDH is fabricated by one-step electrodeposition to promote water/seawater oxidation.Coupling of high entropy,Cr cation leaching,congenetic CrO_(4)^(2-)adsorption,and amorphization to facilitate electrochem-ical reconstruction.The advanced strategy enhances active sites,reaction kinetics,reaction selectivity,conductivity,stability,and corrosion resistance with the electrostatic chlorine-repellent layer.The in-situ Cr leaching and congenetic CrO_(4)^(2-)adsorption-induced electrochemical reconstruction are identified by cyclic voltammetry(CV)activation,in-situ Bode plots,and electrochemical impedance spectroscopy(EIS)plots,ex-situ Raman and ultraviolet-visible spectrophotometry(UV-Vis).The OER active species of oxy-hydroxides are also formed during electrochemical reconstruction.Moreover,control tests of soaking and extra CrO_(4)^(2-)additive verify the superiorities of electrochemical reconstruction with in-situ Cr leaching and congenetic CrO_(4)^(2-)adsorption.Accordingly,FeCoNiCr-LDH exhibits excellent electrochemical perfor-mances with low overpotentials of 193/225 mV at 10 mA cm^(-2),high Faradaic efficiencies of 99.3%/97.4%and strong stability for alkaline water/simulated seawater oxidation,respectively.This study provides one innovative strategy to construct efficient water/seawater oxidation electrocatalysts,showing the great the-oretical significance and practical values in industrial water/seawater splitting for hydrogen production.
基金supported by the National Natural Science Foundation of China(21173105,21172098)~~
文摘Flower-like 3D CuO microspheres were synthesized and used to photo-catalyze water oxidation under visible light.The structure of the CuO microspheres was characterized by scanning electron microscopy,transmission electron microscopy,infrared,powder X-ray diffraction,electron dispersive spectroscopy,Raman and X-ray photoelectron spectroscopy（XPS）.This is the first time that a copper oxide was demonstrated as a photocatalytic water oxidation catalyst under near neutral conditions.The catalytic activity of CuO microspheres in borate buffer shows the best performance with O2 yield of 11.5%.No change in the surface properties of CuO before and after the photocatalytic reaction was seen by XPS,which showed good catalyst stability.A photocatalytic water oxidation reaction mechanism catalyzed by the CuO microspheres was proposed.
基金supported by the National High Technology Research and Development Program of China (No.2006AA06Z313)the Program for New Century Excellent Talents in University of Chinese Education Ministry (No.NCET-07-0678)the Opened Fund of Jiangsu Key Lab for Clean Energy and Power Machinery Engineering (No.QK08003)
文摘Polyvinyl alcohol is a refractory compound widely used in industry. Here we report supercritical water oxidation of polyvinyl alcohol solution and desizing wastewater with and without sodium hydroxide addition. However, it is difficult to implement complete degradation of organics even though polyvinyl alcohol can readily crack under supercritical water treatment. Sodium hydroxide had a significant catalytic effect during the supercritical water oxidation of polyvinyl alcohol. It appears that the OH ion participated in the C-C bond cleavage of polyvinyl alcohol molecules, the CO2-capture reaction and the neutralization of intermediate organic acids, promoting the overall reactions moving in the forward direction. Acetaldehyde was a typical intermediate product during reaction. For supercritical water oxidation of desizing wastewater, a high destruction rate （98.25%） based on total organic carbon was achieved. In addition, cases where initial wastewater was alkaline were favorable for supercritical water oxidation treatment, but salt precipitation and blockage issues arising during the process need to be taken into account seriously.
基金Project supported by the Korea Institute of Science and Technology (KIST).
文摘The destruction of toxic organic wastewaters from munitions demilitarization and complex industrial chemical clearly becomes an overwhelming problem if left to conventional treatment processes. Two options, incineration and supercritical water oxidation （SCWO）, exist for the complete destruction of toxic organic wastewaters. Incinerator has associated problems such as very high cost and public resentment; on the other hand, SCWO has proved to be a very promising method for the treatment of many different wastewaters with extremely efficient organic waste destruction 99.99% with none of the emissions associated with incineration. In this review, the concepts of SCWO, result and present perspectives of application, and industrial status of SCWO are critically examined and discussed.
基金Project supported by the Science Technology Foundation of Educational Department(No.204020).
文摘The 2,4,6-trinitrotoluene （TNT） is a potential carcinogens and TNT contaminated wastewater, which could not be effectively disposed with conventional treatments. The supercritical water oxidation （SCWO） to treat TNT contaminated wastewater was studied in this article, The TNT concentration in wastewater was measured by high-performance liquid chromatograph （HPLC） and the degraded intermediates were analyzed using GC-MS. The results showed that SCWO could degrade TNT efficiently in the presence of oxygen. The reaction temperature, pressure, residence time and oxygen excess were the main contributing factors in the process. The decomposition of TNT was accelerated as the temperature or residence time increased. At 550℃, 24 MPa, 120 s and oxygen excess 300%, TNT removal rate could exceed 99.9%. Partial oxidation occured in SCWO without oxygen. It was concluded that supercritical water was a good solvent and had excellent oxidation capability in the existence of oxygen. The main intermediates of TNT during SCWO included toluene, 1,3,5-trinitrobenzene, nitrophenol, naphthalene, fluorenone, dibutyl phthalate, alkanes and several dimers based on the intermediate analysis. Some side reactions, such as coupled reaction, hydrolysis reaction and isomerization reaction may take place simultaneously when TNT was oxidized by SCWO.
基金the Research Foundation of SINOPEC(No. X596006) and Cao Guangbiao's Advanced Research Foundation of Zhejiang University.
文摘Some aromatic compounds, phenol, aniline and nitrobenzene, were oxidized in supercritical water. It was experimentally found that the chemical oxygen demand (COD) removal efficiency of these organic compounds can achieve a high level more than 90% in a short residence time at temperatures high enough. As temperature, pressure and residence time increase, the COD removal efficiencies of the organic compounds would all increase. It is also found that temperature and residence time offer greater influences on the oxidation process than pressure. The difficulty in oxidizing these three compounds is in the order of nitrobenzene ＞ aniline ＞ Phenol. In addition, it is extremely difficult to oxidize aniline and nitrobenzene to CO2 and H2O at the temperature lower than 873.15 K and 923.15 K, respectively. Only at the temperature higher than 873.15 K and 923.15 K, respectively, the COD removal efficiencies of 90% of aniline and nitrobenzene can be achieved.
基金financial support of the National Natural Science Foundation of China (21962008, 51464028)Candidate Talents Training Fund of Yunnan Province (2017PY269SQ, 2018HB007)Yunnan Ten Thousand Talents Plan Young & Elite Talents Project (YNWR-QNBJ-2018-346)。
文摘The realization of efficient oxygen evolution reaction(OER) is critical to the development of multiple sustainable energy conversion and storage technologies, especially hydrogen production via water electrolysis. To achieve the massive application of hydrogen energy and mass-scale hydrogen production from water splitting drives the pursuit of competent precious-metal-free electrocatalysts in acidic media, where the hydrogen evolution reaction(HER) is more facilitated. However, the development of high-efficient and acid-stable OER electrocatalysts, which are robust to function stably at high oxidation potentials in the acidic electrolyte, remains a great challenge. This article contributes a focused, perceptive review of the up-to-date approaches toward this emerging research field. The OER reaction mechanism and fundamental requirements for oxygen evolution electrocatalysts in acid are introduced. Then the progress and new discoveries of precious-metal-free active materials and design concepts with regard to the improvement of the intrinsic OER activity are discussed. Finally, the existing scientific challenges and the outlooks for future research directions to the fabrication of emerging, earth-abundant OER electrocatalysts in acid are pointed out.
基金financially supported by the National Natural Science Foundation of China (No.52002363)the Aeronautical Science Foundation of China (No.2020Z054025002)+1 种基金Shandong Provincial Natural Science Foundation Project (No. ZR2021ME083)the Undergraduate Innovation Training Program Fund of Liaocheng University (No.cxcy2021108)
文摘It is critical to developing electrocatalysts with highly active and cost-effective for oxygen evolution to resolve environmental pollution and energy issues,in which FeNi-based nanomaterials hold a great promise.Herein,(Fe_(0.33 )Ni_(0.67))S_(2) and(Fe_(0.33 )Ni_(0.67))S_(2)/reduced graphene oxide(rGO)-x%(x=10,20) composites,which exhibited highly efficient oxygen evolution reaction(OER)electrocatalytic activity under alkaline conditions,were synthesized via a hydrothermal approach and following thermal treatment with sulfur powders.Benefiting from the integrated structure of(Fe_(0.33 )Ni_(0.67))S_(2)and support of conductive graphene backbones,(Fe_(0.33 )Ni_(0.67))S_(2)/rGO-20%electrocatalyst showed the best OER activity with an overpotential of 172 mV at 10 mA·cm^(-2)and Tafel slopes of 45 mV·decade^(-1).The composition,phase,and surface structure of the catalyst were characterized before and after OER reaction.The results indicated that crystal phase of the catalyst was reconstructed to the amorphous crystalline features after OER,with oxidation of iron-nickel sulfide and appearance of Ni-Fe oxo/hydroxide species,which may play a crucial role in the high OER performance as the catalytic-active.Moreover,in a two-electrode system towards overall water splitting with(Fe_(0.33 )Ni_(0.67))S_(2)/rGO-20%/NF and Pt/C/NF as the anode and cathode,respectively,the catalysts exhibited excellent catalytic performance with the voltage of only 1.42 V at 10 mA·cm^(-2).
基金financially supported by the National Key Research and Development Program of China (2017YFA0402800)the National Natural Science Foundation of China (U1932214, 51772285)the National Synchrotron Radiation Laboratory at USTC。
文摘BiVO_(4) has been attracting a lot of interest in photoelectrochemical (PEC) water oxidation due to its efficient solar absorption and appropriate band positions.So far,sluggish water oxidation kinetics and fast photogenerated charge recombination still hinder the PEC performance ofBiVO_(4) .In this study,a novel PEC photoanode was designed by depositing ultrathin FeOOH nanolayers on the surface of nanoporousBiVO_(4) electrode,followed by modification with a cobaloxime (Co(dmgH)_(2)(4-COOH-py)Cl) molecular cocatalyst.Under irradiation of a 100 mW cm^(-2)(AM 1.5G) Xe lamp,the photocurrent density of the cobaloxime/FeOOH/BiVO_(4) composite photoanode reached 5.1 mA cm^(-2)at 1.23 V vs.RHE in 1.0 M potassium borate buffer solution (pH=9.0).The onset potential of the optimal cobaloxime/FeOOH/BiVO_(4) photoanode exhibited a 460 m V cathodic shift relative to bareBiVO_(4) .In addition,the surface charge injection efficiency of the composite photoanode reached~80%at 1.23 V vs.RHE and the incident photon-to-current efficiency (IPCE) reached~88%at 420 nm.
基金National Natural Science Foundation of China(Nos.21773093 and 22175077)Natural Science Foundation of Guangdong Province(Nos.2021A1515012351 and 2017B030306004)Guangdong Special Support Program(No.2017TQ04N224)。
文摘Oxygen evolution reaction(OER)is pivotal to drive green hydrogen generation from water electrolysis,but yet is strictly overshadowed by the sluggish reaction kinetics.Earth-abundant and cut-price transitionmetal compounds,particularly Co Fe layered-double-hydroxides(LDHs),show the distinct superiorities in contrast to noble metals and their derivatives.In this review,we firstly underline their fundamental issues in electrocatalytic water oxidation,including Co Fe LDHs crystal structure,the surface of(hydr)oxides confined to OER and the controversial roles of Fe species,aiming at understanding the structure-related activity and catalytic mechanism.Advanced approaches for optimizing OER activity of Co Fe LDHs are then comprehensively overviewed,which will shed light on the different working mechanisms and provide a concise analysis of their unique advantages.Finally,a perspective on the future development of Co Fe LDHs electrocatalysts is offered.We hope this review can give a concise and explicit guidance for the development of transition-metal-based electrocatalysts in the energy field.
文摘Cobalt-based oxides,with high abundance,good stability and excellent catalytic performance,are regarded as promising photocatalysts for artificial photosynthetic systems to alleviate foreseeable energy shortages and global warming.Herein,for the first time,a series of novel spongy porous CDs@CoOx materials were synthesized to act as an efficient and stable bifunctional photocatalyst for water oxidation and CO2 reduction.Notably,the preparation temperatures visibly influence the morphologies and photocatalytic performances of the CDs@CoOx.Under the optimal conditions,a maximum O2 yield of 40.4% and pretty apparent quantum efficiency(AQE)of 58.6% at 460 nm were obtained over CDs@CoOx-300 for water oxidation.Similarly,the optimized sample CDs@CoOx-300 manifests significant enhancement on the CO2-to-CO conversion with a high selectivity of 89.3% and CO generation rate of 8.1μmol/h,which is superior to most previous cobalt-based catalysts for CO2 reduction.The composite CDs@CoOx-300 not only exposes more active sites but also facilitates electron transport,which results in excellent photocatalytic activity.In addition,the boosted photocatalytic behavior is attributed to the synergistic effect between CoOx and CDs,which was verified by the photocatalytic activity control experiments and electrochemical characterization.The work offers a novel strategy to fabricate a high performance bifunctional photocatalyst for water oxidation and CO2 reduction.
基金Leading Innovative and Entrepreneur Team Introduction Program of Zhejiang,Grant/Award Number:2019R01006National Key R&D Program of China,Grant/Award Number:2018YFB0104300。
文摘The oxygen evolution reaction(OER)activity of single-atom catalysts(SACs)is closely related to the coordination environment of the active site.Oxygencoordinated atomic metal species bring about unique features beyond nitrogen-coordinated atomic metal species due to the fact that the M-O bond is weaker than the M-N bond.Herein,a series of metal-oxygen-carbon structured low-nucleus clusters(LNCs)are successfully anchored on the surface of multiwalled carbon nanotubes(M-MWCNTs,M=Ni,Co,or Fe)through a foolproof low-temperature gas transfer(300℃)method without any further treatment.The morphology and coordination configuration of the LNCs at the atomic level were confirmed by comprehensive characterizations.The synthetic Ni-MWCNTs electrocatalyst features excellent OER activity and stability under alkaline conditions,transcending the performances of Co-MWCNTs,Fe-MWCNTs and RuO_(2).Density functional theory calculations reveal that the moderate oxidation of low-nucleus Ni clusters changes the unoccupied orbital of Ni atoms,thereby lowering the energy barrier of the OER rate-limiting step and making the OER process more energy-efficient.This study demonstrates a novel versatile platform for large-scale manufacturing of oxygen-coordinated LNC catalysts.
基金supported by Agency for Defense Development,Korea and Korea Institute of Scienceand Technology
文摘The destruction of methylphosphonic acid （MPA）, a final product by hydrolysis/neutralization of organophosphorus agents such as sarin and VX （O-ethyl S-[2-（diisopropylamino）ethyl] methylphosphonothionate）, was investigated in a a bench-scale, continuous concentric vertical double wall reactor under supercritical water oxidation condition. The experiments were conducted at a temperature range of 450–600°C and a fixed pressure of 25 MPa. Hydrogen peroxide was used as an oxidant. The destruction efficiency （DE） was monitored by analyzing total organic carbon （TOC） and MPA concentrations using ion chromatography on the liquid effluent samples. The results showed that the DE of MPA up to 99.999% was achieved at a reaction temperature of 600°C, oxygen concentration of 113% storichiometric requirement, and reactor residence time of 8 sec. On the basis of the data derived from experiments, a global kinetic rate equation for the DE of MPA and DE of TOC were developed by nonlinear regression analysis. The model predictions agreed well with the experimental data.
基金supported by the Basic Research Program of China(973 Program,2014CB239403)National Natural Science Foundation of China(21522306,21633009)Key Research Program of Frontier Sciences,CAS(QYZDY-SSW-JSC023)
文摘Developing efficient water oxidation catalysts(WOCs)with earth‐abundant elements still remains a challenging task for artificial photosynthesis.Iron‐based WOC is a promising candidate because it is economically cheap,little toxic and environmentally friendly.In this study,we found that the catalytic water oxidation activity on amorphous iron‐based oxide/hydroxide(FeOx)can be decreased by an order of magnitude after the dehydration process at room temperature.Thermogravimetric analysis,XRD and Raman results indicated that the dehydration process of FeOx at room temperature causes the almost completely loss of water molecule with no bulk structural changes.Based on this finding,we prepared hydrated ultrasmall(ca.2.2 nm)FeOx nanoparticles of amorphous feature,which turns out to be extremely active as WOC with turnover frequency(TOF)up to 9.3 s^-1 in the photocatalytic Ru(bpy)3^2+‐Na2S2O8 system.Our findings suggest that future design of active iron‐based oxides as WOCs requires the consideration of their hydration status.
基金supported by Thousand Talents Program of Chinathe National Natural Science Foundation of China (21101170,21573139,and 21773146)+1 种基金the Fundamental Research Funds for the Central Universitiesthe Research Funds of Shaanxi Normal University
文摘Water oxidation is significant in both natural and artificial photosynthesis.In nature,water oxidation occurs at the oxygen‐evolving center of photosystem II,and leads to the generation of oxygen,protons,and electrons.The last two are used for fixation of carbon dioxide to give carbohydrates.In artificial processes,the coupling of water oxidation to evolve O2and water reduction to evolve H2is known as water splitting,which is an attractive method for solar energy conversion and storage.Because water oxidation is a thermodynamically uphill reaction and is kinetically slow,this reaction causes a bottleneck in large‐scale water splitting.As a consequence,the development of new and efficient water oxidation catalysts(WOCs)has attracted extensive attention.Recent efforts have identified a variety of mononuclear earth‐abundant transition‐metal complexes as active and stable molecular WOCs.This review article summarizes recent progress in research on mononuclear catalysts that are based on first‐row transition‐metal elements,namely manganese,iron,cobalt,nickel,and copper.Particular attention is paid to catalytic mechanisms and the key O?O bond formation steps.This information is critical for designing new catalysts that are highly efficient and stable.
