A novel type of composite electrode based on nmltiwalled carbon nanotubes coated with sheet-like cobalt hydroxide particles was used in supercapacitors. Cobalt hydroxide cathodlcally deposited fiom Co（NO3）O2 solutio...A novel type of composite electrode based on nmltiwalled carbon nanotubes coated with sheet-like cobalt hydroxide particles was used in supercapacitors. Cobalt hydroxide cathodlcally deposited fiom Co（NO3）O2 solution with carbon nanotubes as matrix exhibited large pseudo-capacitance of 322 F/g in 1 mol/L KOH. To characterize the cobalt hydroxide nanocomposite electrode, a charge-discharge cycling test, cyclic voltammetry, and an impedance test were done. This cobalt hydroxide composite exhibiting excellent pseudo-capacitive behavior （i.c. high reversibility, high specific capacitance, low impedance）, was demonstrated to be a candidate for the application of electrochemical supercapacitors. A combined capacitor consisting of cobalt hydroxide composite as a cathode and activated carbon fiber as an anode was reported. The electrochemical pcrformance of the combined capacitor was characterized by cyclic voltammetry and a dc charge/discharge test. The combined capacitor showed ideal capacitor behavior with an extended operating voltage of 1.4 V. According to the extended operating voltage, the energy density of the combined capacitor at a current density of 100 mA/cm^2 was found to be 11 Wh/kg. The combined capacitor exhibited high-energy density and stable power characteristics,展开更多
Hollow microsphere structure cobalt hydroxide(h-Co(OH)2) was synthesized via an optimized solvothermal-hydrothermal process and applied to activate peroxymonosulfate(PMS) for degradation of a typical pharmaceutically ...Hollow microsphere structure cobalt hydroxide(h-Co(OH)2) was synthesized via an optimized solvothermal-hydrothermal process and applied to activate peroxymonosulfate(PMS) for degradation of a typical pharmaceutically active compound,ibuprofen(IBP).The material characterizations confirmed the presence of the microscale hollow spheres with thin nanosheets shell in h-Co(OH)2,and the crystalline phase was assigned to a-Co(OH)2.h-Co(OH)2 could efficiently activate PMS for radicals production,and 98.6% of IBP was degraded at 10 min.The activation of PMS by h-Co(OH)2 was a pHindependent process,and pH 7 was the optimum condition for the activation-degradation system.Scavenger quenching test indicated that the sulfate radical(SO4^·-) was the primary reactive oxygen species for IBP degradation,which contributed to 75.7%.Fukui index(f^-) based on density functional theory(DFT) calculation predicted the active sites of IBP molecule for SO4^·- attack,and then IBP degradation pathway was proposed by means of intermediates identification and theoretical calculation.The developed hollow Co(OH)2 used to efficiently activate PMS is promising and innovative alternative for organic contaminants removal from water and wastewater.展开更多
In this study,hierarchical MXene@ZIF-67/core-shell/yolk-shell cobalt hydroxide(MXene@CS-ZCH/MXene@YS-ZCH)and MXene@hollow cobalt hydroxide(MXene@Ho-CH)composites were prepared via the in situ gradient etching of a cub...In this study,hierarchical MXene@ZIF-67/core-shell/yolk-shell cobalt hydroxide(MXene@CS-ZCH/MXene@YS-ZCH)and MXene@hollow cobalt hydroxide(MXene@Ho-CH)composites were prepared via the in situ gradient etching of a cubic ZIF-67 loaded MXene.The interlayer hierarchical cobalt hydroxide nanostructures ensure efficient electron transfer and the three-dimensional(3D)configurations avoid the accumulation/self-aggregation of two-dimensional(2D)layered materials.Meanwhile,the MXene can significantly improve electron transfer as a conductive substrate.The MXene@Ho-CH electrode shows excellent rate performance and cycling stability.This work provides a strategy for achieving MXene compositing with hierarchical core-shell/yolk-shell/hollow(CS/YS/Ho)structured MOF derivatives for electrochemical energy storage.展开更多
Due to the low cost,abundant reserves and redox-active features,electrocatalysts based on 3d transition metals have been thoroughly evaluated and are considered promising candidates to the current commercial noble met...Due to the low cost,abundant reserves and redox-active features,electrocatalysts based on 3d transition metals have been thoroughly evaluated and are considered promising candidates to the current commercial noble metal-based materials.Designing elaborate structures and favorable phase composition is regarded as effective to improve the activity in electrocatalysis.展开更多
Rational regulation of the coordination environment of Ru active sites by employing layered transition metal hydroxides as the substrate could achieve high catalytic performance towards the oxygen evolution reaction(O...Rational regulation of the coordination environment of Ru active sites by employing layered transition metal hydroxides as the substrate could achieve high catalytic performance towards the oxygen evolution reaction(OER)and the oxygen reduction reaction(ORR).However,it is still challenging to clarify the interactions between the Ru catalysts and the layered transition metal hydroxides in different phases and also to unveil the mechanism responsible for the boosted performance.展开更多
Electrocatalytic nitrate reduction reaction(NO_(3)RR)to ammonia provides a promising approach to environmental preservation and sustainable energy production,but suffers from a low yield rate and poor Faradic efficien...Electrocatalytic nitrate reduction reaction(NO_(3)RR)to ammonia provides a promising approach to environmental preservation and sustainable energy production,but suffers from a low yield rate and poor Faradic efficiency,ascribed to the sluggish active hydrogen(H^(*))generation via water dissociation.Herein,single Ru atoms anchored Co(OH)_(2)(Ru1/Co(OH)_(2))catalysts are synthesized for selective nitrate reduction to ammonia,which exhibits an excellent NH_(3)yield rate of 4200μg h^(-1)cm^(-2)and a high NH_(3)Faradic efficiency of 97%at-0.33 V versus reversible hydrogen electrode,outperforming the counterpart Co(OH)_(2)and the mostly reported electrocatalysts.Experimental and theoretical results reveal that the addition of Ru atoms can boost H^(*)generation and decrease the hydrogenation energy barrier on Ru1/Co(OH)_(2),leading to enhanced NO_(3)RR performance.An integrated system of electrochemical NO_(3)RR electrolyzer and in-situ NH_(3)recovery is present,where the electrochemical NO_(3)RR can be coupled with a hydrazine oxidation reaction to achieve a more highly efficient and electricity-saving system for NH_(3)recovery.This work provides guidance for the rational design of high-performance NO_(3)RR electrocatalysts by the effective regulation of H^(*)generation and holds great promise for simultaneous nitrate-containing wastewater treatment and resource recovery.展开更多
The oxygen evolution reaction(OER)is regarded as the bottleneck of electrolytic water splitting.Thus,developing robust earth-abundant electrocatalysts for efficient OER has received a great deal of attention and it is...The oxygen evolution reaction(OER)is regarded as the bottleneck of electrolytic water splitting.Thus,developing robust earth-abundant electrocatalysts for efficient OER has received a great deal of attention and it is an ongoing scientific challenge.Herein,hierarchical hollow nanorods assembled with ultrathin mesoporous cobalt silicate hydroxide nanosheets(denoted as CoSi)were successfully fabricated,using the silica nanotube derived from halloysite as a sacrificial template,via a simple hydrothermal method.The resulting cobalt silicate hydroxide nanosheets stack with thicknesses∼10 nm,as confirmed by transmis-sion electron microscopy.The elaborated nanoarchitecture possesses a high specific surface area(SSA)al-lowing good exposure to the cobalt active centers exhibiting superior catalytic activity vs analogs synthe-sized using sodium silicate.Among all as-prepared CoSi samples,those synthesized at 150℃(CoSi-150)exhibited the minimum overpotential of∼347 mV at a current density of 10 mA cm^(-2).In addition,CoSi-150 also exhibited superior performance against typical cobalt-based catalysts,and its surface hydroxyl groups were beneficial for the enhancement of OER performance.Furthermore,the CoSi-150 showed ex-cellent durability and stability after the 105 s chronopotentiometry test in 1 M KOH.This design concept provides a new strategy for the low-cost preparation of high-quality cobalt water splitting electrocata-lysts.展开更多
β-Co(OH)2 with three-dimensional(3-D)structures was prepared by a simple hydrothermal method.It was found that the amount of cetyltrimethylammonium bromide(CTAB),the pH value,and the reaction time all had an importan...β-Co(OH)2 with three-dimensional(3-D)structures was prepared by a simple hydrothermal method.It was found that the amount of cetyltrimethylammonium bromide(CTAB),the pH value,and the reaction time all had an important influence on the formation of this morphology.The products were characterized by X-ray diffraction,energy-dispersive X-ray analysis,and scanning electron microscopy.A possible mechanism of the formation of the 3-D microstructures ofβ-Co(OH)2 was proposed.展开更多
Layered α-cobalt hydroxides Co（OH1.65 Cl0.35.0.5H2O （1）, Co（OH）1.75（NO3）0.25.0.1H2O（2） with unique macro- and microscale morphologies have been synthesised by a low temperature, ammonia-controlled vapour-dif...Layered α-cobalt hydroxides Co（OH1.65 Cl0.35.0.5H2O （1）, Co（OH）1.75（NO3）0.25.0.1H2O（2） with unique macro- and microscale morphologies have been synthesised by a low temperature, ammonia-controlled vapour-diffusion method. The materials have thin film morphologies and were characterized by X-ray powder diffraction （XRD） and field emission scanning electron microscopy （FESEM）.展开更多
Cobalt hydroxide has been emerging as a promising catalyst for the electrocatalytic oxidation reactions,including the oxygen evolution reaction(OER)and glucose oxidation reaction(GOR).Herein,we prepared cobalt hydroxi...Cobalt hydroxide has been emerging as a promising catalyst for the electrocatalytic oxidation reactions,including the oxygen evolution reaction(OER)and glucose oxidation reaction(GOR).Herein,we prepared cobalt hydroxide nanoparticles(CoHP)and cobalt hydroxide nanosheets(CoHS)on nickel foam.In the electrocatalytic OER,CoHS shows an overpotential of 306 mV at a current density of 10 mA·cm^-2.This is enhanced as compared with that of CoHP(367 mV at 10 mA·cm^-2).In addition,CoHS also exhibits an improved performance in the electrocatalytic GOR.The improved electrocatalytic performance of CoHS could be due to the higher ability of the two-dimensional nanosheets on CoHS in electron transfer.These results are useful for fabricating efficient catalysts for electrocatalytic oxidation reactions.展开更多
Combining urea oxidation reaction(UOR) with hydrogen evolution reaction(HER) is an effective method for energy saving and highly efficient electrocatalytic hydrogen production. Herein, molybdenumincorporated cobalt ca...Combining urea oxidation reaction(UOR) with hydrogen evolution reaction(HER) is an effective method for energy saving and highly efficient electrocatalytic hydrogen production. Herein, molybdenumincorporated cobalt carbonate hydroxide nanoarrays(CoxMoyCH) are designed and synthesized as a bifunctional catalyst towards UOR and HER. Benefiting from the Mo doping, the dispersed nanoarray structure and redistributed electron density, the CoxMoyCH catalyst display outstanding catalytic performance and durability for both HER and UOR, affording the overpotential of 82 m V for HER and delivering a low potential of the 1.33 V for UOR(vs. reversible hydrogen electrode, RHE) to attain a current density of 10 m A cm^(-2), respectively. Remarkably, when CoxMoyCH was applied as bifunctional catalyst in a twoelectrode electrolyzer, a working voltage of 1.40 V is needed in urea-assisted water electrolysis at10 m A cm^(-2) and without apparent decline for 40 h, outperforming the working voltage of 1.51 V in conventional water electrolysis.展开更多
A new design route was presented to fabricate cobalt aluminum-layered double hydroxide(CoAl-LDH)thin layers whichgrow on carbon spheres(CSs)through a growth method.The CoAl-LDH thin layers consist of nanoflakes with a...A new design route was presented to fabricate cobalt aluminum-layered double hydroxide(CoAl-LDH)thin layers whichgrow on carbon spheres(CSs)through a growth method.The CoAl-LDH thin layers consist of nanoflakes with a thickness of20nm.The galvanostatic charge-discharge test of the CoAl-LDH/CSs composite shows a great specific capacitance of1198F/g at1A/g(based on the mass of the CoAl-LDH/CSs composite)in6mol/L KOH solution,and the composite displays an impressive specificcapacitance of920F/g even at a high current density of10A/g.Moreover,the composite remains a specific capacitance of928F/gafter1000cycles at2A/g,and the specific capacitance retention is84%,indicating that the composite has high specific capacitance,excellent rate capability and good cycling stability in comparison to pristine CoAl-LDH.展开更多
In this work,a facile chelation-mediated route was developed to fabricate ultrathin cobalt(oxy)hydroxides(CoOOH)nanosheets on hematite photoanode(Fe_(2)O_(3)).The route contains two steps of the adsorption of[Co-EDTA]...In this work,a facile chelation-mediated route was developed to fabricate ultrathin cobalt(oxy)hydroxides(CoOOH)nanosheets on hematite photoanode(Fe_(2)O_(3)).The route contains two steps of the adsorption of[Co-EDTA]^(2-)species on Fe_(2)O_(3) nanorod array followed by the hydrolysis in alkaline solution.The resulting CoOOH/Fe_(2)O_(3) exhibits a remarkably improved photocurrent density of 2.10 mA cm^(-2) at 1.23 V vs.RHE,which is ca.2.8 times that of bare Fe_(2)O_(3).In addition,a negative shift of onset potential ca.200 mV is achieved.The structural characterizations reveal the chelate EDTA plays important roles that enhance the adsorption of Co species and the formation of contact between CoOOH and Fe_(2)O_(3).(Photo)electrochemical analysis suggests,besides providing active sites for water oxidation,CoOOH at large extent promotes the charge separation and the charge transfer via passivating surface states and suppressing charge recombination.It also found CoOOH possesses some oxygen vacancies,which could act as trapping centers for photogenerated holes and facilitate the charge separation.Intensity modulated photocurrent spectroscopy(IMPS)shows that,under low applied potential the water oxidation mainly occurs on CoOOH,while under high applied potential the water oxidation could occur on both CoOOH and Fe_(2)O_(3).The findings not only provide an efficient strategy for designing ultrathin(oxy)hydroxides on semiconductors for PEC applications but also put forward a new insight on the role of CoOOH during water oxidation.展开更多
Two-dimensional layered double hydroxides(LDHs)have been identified as promising electrocatalysts for the oxygen evolution reaction(OER);however,the simple and effective synthesis of high-quality LDHs remains extremel...Two-dimensional layered double hydroxides(LDHs)have been identified as promising electrocatalysts for the oxygen evolution reaction(OER);however,the simple and effective synthesis of high-quality LDHs remains extremely challenging and the active sites have not been clarified.Herein,we report a facile solution-reaction method for preparing an ultrathin(thickness<2 nm)nonprecious CoFe-based LDH.Co_(1)Fe_(0.2) LDH delivers a current density of 10 mA cm^(-2) and a high turnover frequency of 0.082 s^(-1) per total 3d metal atoms at a low overpotential of 256 mV.Its mass activity is 277.9 A g^(-1) at an overpotential of 300 mV for the OER.Kinetic studies reveal the Co site as the main active center for the OER.The doped Fe lowers the reaction barrier by accelerating the charge-transfer process.Theoretical calculations reveal that the surface Co sites adjacent to Fe atoms are the active centers for the OER and the subsurface Fe dopants excessively weaken the OH^(*)adsorption,thus increasing the energy barrier of the rate-determining step.This study can guide the rational design of high-performance CoFe-based LDHs for water splitting.展开更多
The glassy carbon (GC) electrode modified with a monolayer nickel hydroxide (GC/Ni(OH) 2) was prepared by immersion of GC substrate in 1.0×10 -3 mol/L NiSO 4 solution, and then cyclic voltammetric scannin...The glassy carbon (GC) electrode modified with a monolayer nickel hydroxide (GC/Ni(OH) 2) was prepared by immersion of GC substrate in 1.0×10 -3 mol/L NiSO 4 solution, and then cyclic voltammetric scanning in 0.20 mol/L KOH. Similarly, GC/Co(OH) 2 electrode was prepared too. The experiments showed that the voltammetric behavior of GC/Ni(OH) 2 electrode in 0.20 mol/L KOH is more stable than that of GC/ Co(OH) 2. It was found that the GC/Ni(OH) 2 electrode acts as an effective electrocatalysis for the oxidation of hydrazine.展开更多
Nickel–cobalt double hydroxide is gaining significant interest due to its high theoretical specific capacitance.However,its tendency to agglomerate and low electrical conductivity present major challenges for its app...Nickel–cobalt double hydroxide is gaining significant interest due to its high theoretical specific capacitance.However,its tendency to agglomerate and low electrical conductivity present major challenges for its application.This study employed a one-step hydrothermal method to integrate exfoliated few-layer MXene materials with NiCo-LDH,facilitating the uniform vertical growth of NiCo-LDH nanosheets on the surface of the MXene,effectively minimizing agglomeration.Additionally,the interfacial synergy between MXene and NiCo-LDH enhances the transfer of electrons from NiCo-LDH to MXene,resulting in an electron-rich MXene and an oxygen vacancy-rich NiCo-LDH.Together,these characteristics significantly improve the electrochemical performance of the material at high current densities,achieving 7776 W kg⁻¹ and 66.96 W h kg⁻¹ at 15 A g⁻¹.After cycling 40000 times,it retains an impressive capacity retention rate of 89.5%.These findings demonstrate that MXene materials effectively tackle the main challenges associated with NiCo-LDH,opening new possibilities for their application in electrode materials.展开更多
Metal hydroxides and oxyhydroxides are efficient catalysts for electrochemical oxygen evolution reactions.Herein,we employed a Co-MOF with a tunable structure,high porosity and easy preparation as a precursor to synth...Metal hydroxides and oxyhydroxides are efficient catalysts for electrochemical oxygen evolution reactions.Herein,we employed a Co-MOF with a tunable structure,high porosity and easy preparation as a precursor to synthesize a bimetal-doped oxyhydroxide/hydroxide electrocatalyst by sequential electrochemical-Lewis acid co-etching and electrosorption doping.This unique co-etching method successfully introduced the high-valent metal ion Hf4+,as well as the electrosorption efficiently doped Fe3+,into the catalyst.Experimental studies and theoretical simulations indicate that the introduction of Hf4+optimized the OER kinetics,and the introduction of Fe3+lowered the overpotential.This synthetic strategy of doping high-valent metal ions provides a new avenue for designing high-performance electrocatalysts.展开更多
Amorphous hydroxide on a foamed nickel substrate was fabricated by a simple and efficient electrospinning method for the first time.In untreated alkaline medium,amorphous cobalt(Co)-iron(Fe)hydroxide showed oxygen-evo...Amorphous hydroxide on a foamed nickel substrate was fabricated by a simple and efficient electrospinning method for the first time.In untreated alkaline medium,amorphous cobalt(Co)-iron(Fe)hydroxide showed oxygen-evolution advantages over the typical reference catalyst(RuO_(2)).When tested with a three-electrode system in 1 M KOH,the obtained amorphous PVP/CoFe_(1.3)nanofibers possessed remarkable catalytic activity and stability for the oxygen evolution reaction(OER)with a low overpotential of 0.267 V at 100 mA cm^(-2)and a low Tafel slope of 47.43 mV dec^(-1).The amorphous CoFe microfibers were synthesized by electrospinning,and stable CoFe hydroxides can be further formed in the alkaline environment.The synergistic effect between two different amorphous CoFe-based hydroxides contributed to excellent electrocatalytic activity.Therefore,the design of amorphous CoFe hydroxide enabled the development of a high-efficiency OER catalyst and opens possibilities for the large-scale and environmentally friendly production of water splitting.展开更多
Herein,we employ a partial phase conversion strategy to transform cobalt/nickel carbonate hydroxide(Co_(x)Ni_(y)CH)nanosheet arrays in an Fe-containing KOH electrolyte.The optimized sample exhibits remarkable electroc...Herein,we employ a partial phase conversion strategy to transform cobalt/nickel carbonate hydroxide(Co_(x)Ni_(y)CH)nanosheet arrays in an Fe-containing KOH electrolyte.The optimized sample exhibits remarkable electrocatalytic activity(η_(50)=256 mV,51 mV dec^(−1))and good stability(18 h)with negligible morphology change in a 1 M KOH solution,outperforming most reported cobalt–nickel-based electrocatalysts.From our research,it is found that the Fe impurity in the KOH electrolyte plays an important role in achieving high OER performance.展开更多
In pursuit of high-performance supercapacitors(SCs)with exceptional electrochemical capacitive pro perties,the logical design of sophisticated architectures composed of multiple modules presents a crucial challenge.He...In pursuit of high-performance supercapacitors(SCs)with exceptional electrochemical capacitive pro perties,the logical design of sophisticated architectures composed of multiple modules presents a crucial challenge.Herein,a facile in situ“growth–conversion–oxidation”route is designed to obtain a core–shell structured nanorod-like CoO@NiCo layered double hydroxide(LDH)with abundant oxygen vacancies on a Ni foam substrate(NCLO)for high performance supercapacitors.Density functional theory(DFT)-based computations reveal that NCLO has an enhanced density of states(DOS)in the vicinity of the Fermi energy level suggesting an increased electrical conductivity attributed to the existence of oxygen vacancies in NCLO.Notably,NCLO displays an impressive specific capacitance of 333.3 mA h g^(−1)(2264.2 Fg^(−1)at 1 A g^(−1)).Furthermore,the NCLO//AC asymmetric supercapacitor(ASC)device exhibits an out standing capacity retention rate of 90.8%following 10000 cycles and a remarkable energy density reach ing up to 63.8 W h kg^(−1)at 800.0 W kg^(−1).Our work highlights the feasibility of utilizing vacancy engineer ing and distinctive structural features as an innovative strategy for achieving energy storage materials with an extraordinary performance.展开更多
文摘A novel type of composite electrode based on nmltiwalled carbon nanotubes coated with sheet-like cobalt hydroxide particles was used in supercapacitors. Cobalt hydroxide cathodlcally deposited fiom Co（NO3）O2 solution with carbon nanotubes as matrix exhibited large pseudo-capacitance of 322 F/g in 1 mol/L KOH. To characterize the cobalt hydroxide nanocomposite electrode, a charge-discharge cycling test, cyclic voltammetry, and an impedance test were done. This cobalt hydroxide composite exhibiting excellent pseudo-capacitive behavior （i.c. high reversibility, high specific capacitance, low impedance）, was demonstrated to be a candidate for the application of electrochemical supercapacitors. A combined capacitor consisting of cobalt hydroxide composite as a cathode and activated carbon fiber as an anode was reported. The electrochemical pcrformance of the combined capacitor was characterized by cyclic voltammetry and a dc charge/discharge test. The combined capacitor showed ideal capacitor behavior with an extended operating voltage of 1.4 V. According to the extended operating voltage, the energy density of the combined capacitor at a current density of 100 mA/cm^2 was found to be 11 Wh/kg. The combined capacitor exhibited high-energy density and stable power characteristics,
基金partially supported by the National Natural Science Foundation of China(Nos.21906001 and 51721006)supported by MOE Key Laboratory of Resources and Environmental Systems Optimization(NCEPU)
文摘Hollow microsphere structure cobalt hydroxide(h-Co(OH)2) was synthesized via an optimized solvothermal-hydrothermal process and applied to activate peroxymonosulfate(PMS) for degradation of a typical pharmaceutically active compound,ibuprofen(IBP).The material characterizations confirmed the presence of the microscale hollow spheres with thin nanosheets shell in h-Co(OH)2,and the crystalline phase was assigned to a-Co(OH)2.h-Co(OH)2 could efficiently activate PMS for radicals production,and 98.6% of IBP was degraded at 10 min.The activation of PMS by h-Co(OH)2 was a pHindependent process,and pH 7 was the optimum condition for the activation-degradation system.Scavenger quenching test indicated that the sulfate radical(SO4^·-) was the primary reactive oxygen species for IBP degradation,which contributed to 75.7%.Fukui index(f^-) based on density functional theory(DFT) calculation predicted the active sites of IBP molecule for SO4^·- attack,and then IBP degradation pathway was proposed by means of intermediates identification and theoretical calculation.The developed hollow Co(OH)2 used to efficiently activate PMS is promising and innovative alternative for organic contaminants removal from water and wastewater.
基金supported by the National Natural Science Foundation of China(U1904215)the Natural Science Foundation of Jiangsu Province(BK20200044)the Changjiang Scholars Program of Chinese Ministry of Education(Q2018270).
文摘In this study,hierarchical MXene@ZIF-67/core-shell/yolk-shell cobalt hydroxide(MXene@CS-ZCH/MXene@YS-ZCH)and MXene@hollow cobalt hydroxide(MXene@Ho-CH)composites were prepared via the in situ gradient etching of a cubic ZIF-67 loaded MXene.The interlayer hierarchical cobalt hydroxide nanostructures ensure efficient electron transfer and the three-dimensional(3D)configurations avoid the accumulation/self-aggregation of two-dimensional(2D)layered materials.Meanwhile,the MXene can significantly improve electron transfer as a conductive substrate.The MXene@Ho-CH electrode shows excellent rate performance and cycling stability.This work provides a strategy for achieving MXene compositing with hierarchical core-shell/yolk-shell/hollow(CS/YS/Ho)structured MOF derivatives for electrochemical energy storage.
基金support by National Natural Science Foundation of China(51874357,51872333)Hunan Provincial Natural Science Foundation of China(2019JJ10006)X.L.acknowledges support from Shenghua Scholar Program of Central South University.R.M.acknowledges support from JSPS KAKENNHI(18H03869).
文摘Due to the low cost,abundant reserves and redox-active features,electrocatalysts based on 3d transition metals have been thoroughly evaluated and are considered promising candidates to the current commercial noble metal-based materials.Designing elaborate structures and favorable phase composition is regarded as effective to improve the activity in electrocatalysis.
基金funded by the Natural Science Foundation of Jiangsu Province(BK20190759)the Science Fund for Distinguished Young Scholars,Nanjing Forestry University(JC2019002).
文摘Rational regulation of the coordination environment of Ru active sites by employing layered transition metal hydroxides as the substrate could achieve high catalytic performance towards the oxygen evolution reaction(OER)and the oxygen reduction reaction(ORR).However,it is still challenging to clarify the interactions between the Ru catalysts and the layered transition metal hydroxides in different phases and also to unveil the mechanism responsible for the boosted performance.
基金supported by the National Natural Science Foundation of China(grant nos.22206054,U21A20286,and 22478310)the Fundamental Research Funds for the Central China Normal University.
文摘Electrocatalytic nitrate reduction reaction(NO_(3)RR)to ammonia provides a promising approach to environmental preservation and sustainable energy production,but suffers from a low yield rate and poor Faradic efficiency,ascribed to the sluggish active hydrogen(H^(*))generation via water dissociation.Herein,single Ru atoms anchored Co(OH)_(2)(Ru1/Co(OH)_(2))catalysts are synthesized for selective nitrate reduction to ammonia,which exhibits an excellent NH_(3)yield rate of 4200μg h^(-1)cm^(-2)and a high NH_(3)Faradic efficiency of 97%at-0.33 V versus reversible hydrogen electrode,outperforming the counterpart Co(OH)_(2)and the mostly reported electrocatalysts.Experimental and theoretical results reveal that the addition of Ru atoms can boost H^(*)generation and decrease the hydrogenation energy barrier on Ru1/Co(OH)_(2),leading to enhanced NO_(3)RR performance.An integrated system of electrochemical NO_(3)RR electrolyzer and in-situ NH_(3)recovery is present,where the electrochemical NO_(3)RR can be coupled with a hydrazine oxidation reaction to achieve a more highly efficient and electricity-saving system for NH_(3)recovery.This work provides guidance for the rational design of high-performance NO_(3)RR electrocatalysts by the effective regulation of H^(*)generation and holds great promise for simultaneous nitrate-containing wastewater treatment and resource recovery.
基金supported by the Central Government Guiding Local Science and Technology Development Fund Projects(No.236Z4108G)China Scholarship Council,the National Natu-ral Science Foundation of China(No.51874115)+2 种基金the Open Project of State Key Laboratory of Environment-friendly Energy Materials(No.22kfhg09)the Open Project of Key Laboratory of Solid Waste Treatment and Resource Recycle of Ministry of Education(No.22kfgk01)the Youth Talent Support Program of Hebei Province,the Giant Plan Innovation Team Project of Hebei Province,and the Excellent Young Scientist Foundation of Hebei province,China(No.E2018202241).
文摘The oxygen evolution reaction(OER)is regarded as the bottleneck of electrolytic water splitting.Thus,developing robust earth-abundant electrocatalysts for efficient OER has received a great deal of attention and it is an ongoing scientific challenge.Herein,hierarchical hollow nanorods assembled with ultrathin mesoporous cobalt silicate hydroxide nanosheets(denoted as CoSi)were successfully fabricated,using the silica nanotube derived from halloysite as a sacrificial template,via a simple hydrothermal method.The resulting cobalt silicate hydroxide nanosheets stack with thicknesses∼10 nm,as confirmed by transmis-sion electron microscopy.The elaborated nanoarchitecture possesses a high specific surface area(SSA)al-lowing good exposure to the cobalt active centers exhibiting superior catalytic activity vs analogs synthe-sized using sodium silicate.Among all as-prepared CoSi samples,those synthesized at 150℃(CoSi-150)exhibited the minimum overpotential of∼347 mV at a current density of 10 mA cm^(-2).In addition,CoSi-150 also exhibited superior performance against typical cobalt-based catalysts,and its surface hydroxyl groups were beneficial for the enhancement of OER performance.Furthermore,the CoSi-150 showed ex-cellent durability and stability after the 105 s chronopotentiometry test in 1 M KOH.This design concept provides a new strategy for the low-cost preparation of high-quality cobalt water splitting electrocata-lysts.
基金supported by the National Natural Science Foundation of China(Grant No.20873020)
文摘β-Co(OH)2 with three-dimensional(3-D)structures was prepared by a simple hydrothermal method.It was found that the amount of cetyltrimethylammonium bromide(CTAB),the pH value,and the reaction time all had an important influence on the formation of this morphology.The products were characterized by X-ray diffraction,energy-dispersive X-ray analysis,and scanning electron microscopy.A possible mechanism of the formation of the 3-D microstructures ofβ-Co(OH)2 was proposed.
文摘Layered α-cobalt hydroxides Co（OH1.65 Cl0.35.0.5H2O （1）, Co（OH）1.75（NO3）0.25.0.1H2O（2） with unique macro- and microscale morphologies have been synthesised by a low temperature, ammonia-controlled vapour-diffusion method. The materials have thin film morphologies and were characterized by X-ray powder diffraction （XRD） and field emission scanning electron microscopy （FESEM）.
基金the financial support from the National Natural Science Foundation of China(Grant Nos.11761141006,81822024 and 21605102)the National Key Research and Development Program of China(Grant No.2017YFC1200904).
文摘Cobalt hydroxide has been emerging as a promising catalyst for the electrocatalytic oxidation reactions,including the oxygen evolution reaction(OER)and glucose oxidation reaction(GOR).Herein,we prepared cobalt hydroxide nanoparticles(CoHP)and cobalt hydroxide nanosheets(CoHS)on nickel foam.In the electrocatalytic OER,CoHS shows an overpotential of 306 mV at a current density of 10 mA·cm^-2.This is enhanced as compared with that of CoHP(367 mV at 10 mA·cm^-2).In addition,CoHS also exhibits an improved performance in the electrocatalytic GOR.The improved electrocatalytic performance of CoHS could be due to the higher ability of the two-dimensional nanosheets on CoHS in electron transfer.These results are useful for fabricating efficient catalysts for electrocatalytic oxidation reactions.
基金financially supported by the National Natural Science Foundation of China(52025013,22121005)the 111 Project(B12015)+1 种基金Haihe Laboratory of Sustainable Chemical Transformationsthe Fundamental Research Funds for the Central Universities。
文摘Combining urea oxidation reaction(UOR) with hydrogen evolution reaction(HER) is an effective method for energy saving and highly efficient electrocatalytic hydrogen production. Herein, molybdenumincorporated cobalt carbonate hydroxide nanoarrays(CoxMoyCH) are designed and synthesized as a bifunctional catalyst towards UOR and HER. Benefiting from the Mo doping, the dispersed nanoarray structure and redistributed electron density, the CoxMoyCH catalyst display outstanding catalytic performance and durability for both HER and UOR, affording the overpotential of 82 m V for HER and delivering a low potential of the 1.33 V for UOR(vs. reversible hydrogen electrode, RHE) to attain a current density of 10 m A cm^(-2), respectively. Remarkably, when CoxMoyCH was applied as bifunctional catalyst in a twoelectrode electrolyzer, a working voltage of 1.40 V is needed in urea-assisted water electrolysis at10 m A cm^(-2) and without apparent decline for 40 h, outperforming the working voltage of 1.51 V in conventional water electrolysis.
基金Project(21471162) supported by the National Natural Science Foundation of ChinaProject(2015H6016) supported by the Science and Technology Project of Fujian Province,China
文摘A new design route was presented to fabricate cobalt aluminum-layered double hydroxide(CoAl-LDH)thin layers whichgrow on carbon spheres(CSs)through a growth method.The CoAl-LDH thin layers consist of nanoflakes with a thickness of20nm.The galvanostatic charge-discharge test of the CoAl-LDH/CSs composite shows a great specific capacitance of1198F/g at1A/g(based on the mass of the CoAl-LDH/CSs composite)in6mol/L KOH solution,and the composite displays an impressive specificcapacitance of920F/g even at a high current density of10A/g.Moreover,the composite remains a specific capacitance of928F/gafter1000cycles at2A/g,and the specific capacitance retention is84%,indicating that the composite has high specific capacitance,excellent rate capability and good cycling stability in comparison to pristine CoAl-LDH.
基金supported by the National Natural Science Foundation of China(51502078)the Major Project of Science and Technology,Education Department of Henan Province(19A150019 and 19A150018)+2 种基金the Science and Technology Research Project of Henan Province(192102310490 and 182102410090)the program for Science&Technology Innovation Team in Universities of Henan Province(19IRTSTHN029)supported by the U.S.Department of Energy,Office of Science,Office of Basic Energy Sciences,Chemical Sciences,Geosciences,and Biosciences Division,Catalysis Science program。
文摘In this work,a facile chelation-mediated route was developed to fabricate ultrathin cobalt(oxy)hydroxides(CoOOH)nanosheets on hematite photoanode(Fe_(2)O_(3)).The route contains two steps of the adsorption of[Co-EDTA]^(2-)species on Fe_(2)O_(3) nanorod array followed by the hydrolysis in alkaline solution.The resulting CoOOH/Fe_(2)O_(3) exhibits a remarkably improved photocurrent density of 2.10 mA cm^(-2) at 1.23 V vs.RHE,which is ca.2.8 times that of bare Fe_(2)O_(3).In addition,a negative shift of onset potential ca.200 mV is achieved.The structural characterizations reveal the chelate EDTA plays important roles that enhance the adsorption of Co species and the formation of contact between CoOOH and Fe_(2)O_(3).(Photo)electrochemical analysis suggests,besides providing active sites for water oxidation,CoOOH at large extent promotes the charge separation and the charge transfer via passivating surface states and suppressing charge recombination.It also found CoOOH possesses some oxygen vacancies,which could act as trapping centers for photogenerated holes and facilitate the charge separation.Intensity modulated photocurrent spectroscopy(IMPS)shows that,under low applied potential the water oxidation mainly occurs on CoOOH,while under high applied potential the water oxidation could occur on both CoOOH and Fe_(2)O_(3).The findings not only provide an efficient strategy for designing ultrathin(oxy)hydroxides on semiconductors for PEC applications but also put forward a new insight on the role of CoOOH during water oxidation.
文摘Two-dimensional layered double hydroxides(LDHs)have been identified as promising electrocatalysts for the oxygen evolution reaction(OER);however,the simple and effective synthesis of high-quality LDHs remains extremely challenging and the active sites have not been clarified.Herein,we report a facile solution-reaction method for preparing an ultrathin(thickness<2 nm)nonprecious CoFe-based LDH.Co_(1)Fe_(0.2) LDH delivers a current density of 10 mA cm^(-2) and a high turnover frequency of 0.082 s^(-1) per total 3d metal atoms at a low overpotential of 256 mV.Its mass activity is 277.9 A g^(-1) at an overpotential of 300 mV for the OER.Kinetic studies reveal the Co site as the main active center for the OER.The doped Fe lowers the reaction barrier by accelerating the charge-transfer process.Theoretical calculations reveal that the surface Co sites adjacent to Fe atoms are the active centers for the OER and the subsurface Fe dopants excessively weaken the OH^(*)adsorption,thus increasing the energy barrier of the rate-determining step.This study can guide the rational design of high-performance CoFe-based LDHs for water splitting.
文摘The glassy carbon (GC) electrode modified with a monolayer nickel hydroxide (GC/Ni(OH) 2) was prepared by immersion of GC substrate in 1.0×10 -3 mol/L NiSO 4 solution, and then cyclic voltammetric scanning in 0.20 mol/L KOH. Similarly, GC/Co(OH) 2 electrode was prepared too. The experiments showed that the voltammetric behavior of GC/Ni(OH) 2 electrode in 0.20 mol/L KOH is more stable than that of GC/ Co(OH) 2. It was found that the GC/Ni(OH) 2 electrode acts as an effective electrocatalysis for the oxidation of hydrazine.
基金supported by the Major Science and Technology Projects for Independent Innovation of China FAW Group Co.,Ltd(Grant No.20220301018GX and 20220301019GX).
文摘Nickel–cobalt double hydroxide is gaining significant interest due to its high theoretical specific capacitance.However,its tendency to agglomerate and low electrical conductivity present major challenges for its application.This study employed a one-step hydrothermal method to integrate exfoliated few-layer MXene materials with NiCo-LDH,facilitating the uniform vertical growth of NiCo-LDH nanosheets on the surface of the MXene,effectively minimizing agglomeration.Additionally,the interfacial synergy between MXene and NiCo-LDH enhances the transfer of electrons from NiCo-LDH to MXene,resulting in an electron-rich MXene and an oxygen vacancy-rich NiCo-LDH.Together,these characteristics significantly improve the electrochemical performance of the material at high current densities,achieving 7776 W kg⁻¹ and 66.96 W h kg⁻¹ at 15 A g⁻¹.After cycling 40000 times,it retains an impressive capacity retention rate of 89.5%.These findings demonstrate that MXene materials effectively tackle the main challenges associated with NiCo-LDH,opening new possibilities for their application in electrode materials.
基金supported by the Natural Science Foundation of Jiangsu Province(Grant No.BK20230069 and BK20200044)the National Natural Science Foundation of China(Grant No.U1904215 and 21673203)+1 种基金the Changjiang Scholars Program of the Ministry of Education(Q2018270)the Six Talent Peaks Project in Jiangsu Province and the Top Talent Project of Yangzhou University.
文摘Metal hydroxides and oxyhydroxides are efficient catalysts for electrochemical oxygen evolution reactions.Herein,we employed a Co-MOF with a tunable structure,high porosity and easy preparation as a precursor to synthesize a bimetal-doped oxyhydroxide/hydroxide electrocatalyst by sequential electrochemical-Lewis acid co-etching and electrosorption doping.This unique co-etching method successfully introduced the high-valent metal ion Hf4+,as well as the electrosorption efficiently doped Fe3+,into the catalyst.Experimental studies and theoretical simulations indicate that the introduction of Hf4+optimized the OER kinetics,and the introduction of Fe3+lowered the overpotential.This synthetic strategy of doping high-valent metal ions provides a new avenue for designing high-performance electrocatalysts.
基金National Natural Science Foundation of China(21473013,51203008,21771021,and 21822501)Beijing Nova Program(xx2018115)+1 种基金Fundamental Research Funds for the Central UniversitiesAnalytical and Measurements Fund of Beijing Normal University。
文摘Amorphous hydroxide on a foamed nickel substrate was fabricated by a simple and efficient electrospinning method for the first time.In untreated alkaline medium,amorphous cobalt(Co)-iron(Fe)hydroxide showed oxygen-evolution advantages over the typical reference catalyst(RuO_(2)).When tested with a three-electrode system in 1 M KOH,the obtained amorphous PVP/CoFe_(1.3)nanofibers possessed remarkable catalytic activity and stability for the oxygen evolution reaction(OER)with a low overpotential of 0.267 V at 100 mA cm^(-2)and a low Tafel slope of 47.43 mV dec^(-1).The amorphous CoFe microfibers were synthesized by electrospinning,and stable CoFe hydroxides can be further formed in the alkaline environment.The synergistic effect between two different amorphous CoFe-based hydroxides contributed to excellent electrocatalytic activity.Therefore,the design of amorphous CoFe hydroxide enabled the development of a high-efficiency OER catalyst and opens possibilities for the large-scale and environmentally friendly production of water splitting.
基金financially supported by the Science and Technology Project of Guangxi(AD19245104,AD19245154 and AD19110003)Doctoral Fund Project,Guangxi University of Science and Technology(19Z24,19Z23 and 18Z12)+1 种基金Guangxi Youth Science Foundation(2021GXNSFBA075025)the Open Project Program of Key Laboratory of Preparation and Application of Environmental Friendly Materials(Jilin Normal University),Ministry of Education,China(no.2020012).
文摘Herein,we employ a partial phase conversion strategy to transform cobalt/nickel carbonate hydroxide(Co_(x)Ni_(y)CH)nanosheet arrays in an Fe-containing KOH electrolyte.The optimized sample exhibits remarkable electrocatalytic activity(η_(50)=256 mV,51 mV dec^(−1))and good stability(18 h)with negligible morphology change in a 1 M KOH solution,outperforming most reported cobalt–nickel-based electrocatalysts.From our research,it is found that the Fe impurity in the KOH electrolyte plays an important role in achieving high OER performance.
基金supported by the Doctoral Start-up Foundation of Liaoning Province(2020-BS-237,2022-BS-300)the Key Project of Education Department of Liaoning Province of China(LJKZ1010)+1 种基金the General Cultivation of Scientific Research Projects of Bohai University(0522xn042)the Doctoral Start-up Foundation of Bohai University(0520bs045).
文摘In pursuit of high-performance supercapacitors(SCs)with exceptional electrochemical capacitive pro perties,the logical design of sophisticated architectures composed of multiple modules presents a crucial challenge.Herein,a facile in situ“growth–conversion–oxidation”route is designed to obtain a core–shell structured nanorod-like CoO@NiCo layered double hydroxide(LDH)with abundant oxygen vacancies on a Ni foam substrate(NCLO)for high performance supercapacitors.Density functional theory(DFT)-based computations reveal that NCLO has an enhanced density of states(DOS)in the vicinity of the Fermi energy level suggesting an increased electrical conductivity attributed to the existence of oxygen vacancies in NCLO.Notably,NCLO displays an impressive specific capacitance of 333.3 mA h g^(−1)(2264.2 Fg^(−1)at 1 A g^(−1)).Furthermore,the NCLO//AC asymmetric supercapacitor(ASC)device exhibits an out standing capacity retention rate of 90.8%following 10000 cycles and a remarkable energy density reach ing up to 63.8 W h kg^(−1)at 800.0 W kg^(−1).Our work highlights the feasibility of utilizing vacancy engineer ing and distinctive structural features as an innovative strategy for achieving energy storage materials with an extraordinary performance.
