Highly active and durable electrocatalysts towards oxygen reduction reaction(ORR)are imperative for the commercialization application of proton exchange membrane fuel cells.By manipulating ligand effect,structural con...Highly active and durable electrocatalysts towards oxygen reduction reaction(ORR)are imperative for the commercialization application of proton exchange membrane fuel cells.By manipulating ligand effect,structural control,and strain effect,we report here the precise preparation of Mo-doped Pt_(3)Co alloy nanowires(Pt_(3)Co-Mo NWs)as the efficient catalyst towards ORR with high specific activity(0.596 mA cm^(−2))and mass activity(MA,0.84 A mg^(−1)_(Pt)),much higher than those of undoped counterparts.Besides activity,Pt_(3)Co-Mo NWs also demonstrate excellent structural stability and cyclic durability even after 50,000 cycles,again surpassing control samples without Mo dopants.According to the strain maps and DFT calculations,Mo dopants could modify the electronic structure of both Pt and Co to achieve not only optimized oxygen-intermediate binding energy on the interface but also increased the vacancy formation energy of Co,together leading to enhanced activity and durability.This work provides not only a facile methodology but also an in-depth investigation of the relationship between structure and properties to provide general guidance for future design and optimization.展开更多
An electrocatalyst with heterogeneous nanostructure, especially the hierarchical one, generally shows a more competitive activity than that of its single-component counterparts for oxygen evolution reaction(OER), due ...An electrocatalyst with heterogeneous nanostructure, especially the hierarchical one, generally shows a more competitive activity than that of its single-component counterparts for oxygen evolution reaction(OER), due to the synergistically enhanced kinetics on enriched active sites and reconfigured electronic band structure. Here this work introduces hierarchical heterostructures into a NiMo@NiS/MoS_(2)@Ni_(2)S_(2)/MoO_(x)(NiMoS) composite by one-pot controlled moderative sulfidation. The optimal solvent composition and addition of NaOH enable NiMoS to own loose and porous structures, smaller nanoparticle sizes, optimal phase composition and chemical states of elements, improving the OER activity of NiMoS. To achieve current densities of 50 and 100 mA cm^(-1), small overpotentials of 275 and 306 mV are required respectively, together with a minor Tafel slope of 58 mV dec^(-1), which outperforms most reported sulfide catalysts and IrO_(2). The synergistic effects in the hierarchical heterostructures expose more active sites,adjust the electronic band structure, and enable the fast charge transfer kinetics, which construct an optimized local coordination environment for high OER electrocatalytic activity. Furthermore, the hierarchical heterostructures suppress the distinct lowering of electrical conductivity and collapse of pristine structures resulted from the metal oxidation and synchronous S leaching during OER, yielding competitive catalytic stability.展开更多
In this work,we have applied molybdenum(Mo)and titanium(Ti)co-doping to solve the degradation of Ni-rich cathodes.The modified cathode,i.e.,Li(Ni_(0.89)Co_(0.05)Mn_(0.05)Mo_(0.005)Ti_(0.005))O_(2) holds a stable struc...In this work,we have applied molybdenum(Mo)and titanium(Ti)co-doping to solve the degradation of Ni-rich cathodes.The modified cathode,i.e.,Li(Ni_(0.89)Co_(0.05)Mn_(0.05)Mo_(0.005)Ti_(0.005))O_(2) holds a stable structure with expanded crystal lattice distance which improves Li ion diffusion kinetics.The dopants have suppressed the growth of primary particles,formed a coating on the surface,and promoted the elongated morphology.Moreover,the mechanical strength of these particles has increased,as confirmed by the nanoindentation test,which can help suppress particle cracking.The detrimental H2-H3 phase transition has been postponed by 90 mV allowing the cathode to operate at a higher voltage.A better cycling stability over 100 cycles with 69%capacity retention has been observed.We believe this work points out a way to improve the cycling performance,Coulombic efficiency and capacity retention in Ni-rich cathodes.展开更多
Thermoelectric water spitting to hydrogen systems has great potential in the production of environment-friendly fuel using renewable solar energy in the future.In this work,we prepared porous nanosheet Mo doping Ni_(5...Thermoelectric water spitting to hydrogen systems has great potential in the production of environment-friendly fuel using renewable solar energy in the future.In this work,we prepared porous nanosheet Mo doping Ni_(5)P_(4)catalysts on nickel foam with efficient hydrogen evolution reaction(HER)and oxygen evolution reaction(OER)performance in alkaline media.Density Functional Theory(DFT)calculations and experimental studies have shown that Mo doping deadeneds the interaction between H and O atomic orbitals of transition state water molecules,effectively weakening the activation energy of H_(2)O dissociation.Therefore,Mo doping is favorable for enhancing HER activity with overpotential at 10 mA cm^(-2)of 93 mV and Tafel slope of 40.1 mV dec^(-1)in 1 M KOH.Besides,it exhibits high alkaline OER activity with an ultra-low overpotential of 200 mV at 10 mA cm^(-2).Moreover,this catalyst only needs 1.537 V in a dual-electrode configuration of the electrolytic cell,which is much lower than the commercial Pt/C-RuO_(2)couple(1.614 V).In addition,we have developed and constructed a solar thermoelectric generator(TEG)that is capable of floating on water.This TEG has a continuous power output and an exceptionally long lifespan,providing a stable power supply to the synthesized catalyst electrolyzer.It can produce a maximum power output of over 90 mW,meeting the requirement of converting solar radiation heat into usable electricity.As a result,the system achieves productivity of 0.11 mL min^(-1)H_(2).This solar thermal energy conversion technology shows the possibility of large-scale industrial production of H_(2)and provides a new idea for exploring heat source utilization.展开更多
P2-type layered transition-metal oxides with high energy density and rich variety have attracted extensive attention for sodium-ion batteries(SIBs)in grid-scale energy storage application,but they usually suffer from ...P2-type layered transition-metal oxides with high energy density and rich variety have attracted extensive attention for sodium-ion batteries(SIBs)in grid-scale energy storage application,but they usually suffer from sluggish kinetics and large volume change upon cycling.Herein,we designed a highperformance P2-type Na_(0.67)Ni_(0.31)Mn_(0.67)Mo_(0.02)O_(2)(NNMMO)cathode with regulated electronic environment and Na^(+)zigzag ordering modulation via high-valence Mo6+stabilization engineering.The achieved NNMMO cathode exhibits a high-rate capability with a reversible capacity of 77.2 m Ah/g at 10 C and a long cycle life with a capacity retention of 75%at 2 C after 1000 cycles.In addition,in situ X-ray diffraction and ex-situ X-ray absorption fine structure spectroscopy characterizations verify that the presence of Mo^(6+)also stabilizes the desodiated structure through a pinning effect,achieving an extremely low volume change of 1.04%upon Na^(+)extraction.The quantified diffusional analysis and theoretical calculations demonstrate that the Mo^(6+)-doping improves the Na+diffusion kinetics,optimizes the energy band structure and enhances the TM-O bond strength.Additionally,the as-fabricated pouch cells by paring NNMMO cathode and hard carbon anode show impressive cycling stability with an energy density of 296.7 Wh/kg.This study broadens the perspective for high-valence metal ion doping to obtain superior cathode materials and pave the way for developing high-energy-density SIBs.展开更多
A core shell structured C@MoxTi1-xO2-δnanocrystal with a functionalized interface(C@MTNC-FI)was fabricated via the hydrothermal method with subsequent annealing derived from tetrabutyl orthotitanate.The formation of ...A core shell structured C@MoxTi1-xO2-δnanocrystal with a functionalized interface(C@MTNC-FI)was fabricated via the hydrothermal method with subsequent annealing derived from tetrabutyl orthotitanate.The formation of anatase TiO2 was inhibited by the simultaneous presence of the hydrothermal etching/regrowth process,infiltration of Mo dopants and carbon coating,which endows the C@MTNC-FI with an ultrafine crystalline architecture that has a Mo-functionalized interface and carbon-coated shell.Pt Ru nanoparticles(NPs)were supported on C@MTNC-FI by employing a microwave-assisted polyol process(MAPP).The obtained Pt Ru/C@MTNC-FI catalyst has 2.68 times higher mass activity towards methanol electrooxidation than that of the un-functionalized catalyst(Pt Ru/C@TNC)and 1.65 times higher mass activity than that of Pt Ru/C catalyst with over 25%increase in durability.The improved catalytic performance is due to several aspects including ultrafine crystals of TiO2 with abundant grain boundaries,Mofunctionalized interface with enhanced electron interactions,and core shell architecture with excellent electrical transport properties.This work suggests the potential application of an interface-functionalized crystalline material as a sustainable and clean energy solution.展开更多
Designing highly active and stable noble-metal-free electrocatalysts for water splitting over a wide pH range is critical yet remains significantly challenging.In this work,Mo-doped CoP nanoparticles(Mo-CoP)supported ...Designing highly active and stable noble-metal-free electrocatalysts for water splitting over a wide pH range is critical yet remains significantly challenging.In this work,Mo-doped CoP nanoparticles(Mo-CoP)supported and enwrapped by porous single-atomic-Co doped carbon framework(Co-N-C)were designed and prepared by a simple one-pot pyrolysis method.The Mo-CoP/Co-N-C electrocatalyst exhibits superior performance with low overpotentials of only 45 mV for hydrogen evolution reaction(HER)and 201 mV for oxygen evolution reaction(OER)in 1 M KOH at 10 mA cm^(-2)current density.Such excellent catalytic activity can be ascribed to enhanced intrinsic activity,large surface area,and highly exposed active sites.Meanwhile,an extremely small overpotential of only 250 mV is required for a large current density of 500 mA cm^(-2)in HER,which exceeds the performance of benchmark 10%Pt/C.Besides,Mo-CoP/Co-N-C also exhibits superior HER performance in acidic and neutral mediums,with overpotentials of only 41 and 98 mV in 0.5 M H_(2)SO_(4),and 1 M PBS,respectively,thus achieving efficient water splitting at a wide pH range.The long-term stabilities are guaranteed with no significant decline of catalytic activities for more than 24 h in all electrolytes,which can be ascribed to the carbon layer encapsulation structure.Addition-ally,in overall water splitting,the electrocatalytic cell consisting of the as-synthesized Mo-CoP/Co-N-C only requires a cell voltage of 1.611 V at 100 mA cm^(-2)with excellent stability,exceeding that of the benchmark Pt/C||RuO(2) couple(1.645 V at 100 mA cm^(-2)).This work not only presents a highly efficient electrocatalyst for pH-universal water splitting but also provides a new perspective for the design and construction of transition metal catalysts with excellent stability.展开更多
A novel Mo-doped CuO catalyst is developed and used for low-temperature NH_(3)-SCR reaction.Compared with the undoped CuO sample,the Mo doped CuO catalyst shows an increased SCR performance with above 80%NO_(x) conver...A novel Mo-doped CuO catalyst is developed and used for low-temperature NH_(3)-SCR reaction.Compared with the undoped CuO sample,the Mo doped CuO catalyst shows an increased SCR performance with above 80%NO_(x) conversion at 175℃.The XRD and Raman results have confirmed the incorporation of Mo metal ions into CuO lattice to form Mo-O-Cu species which may be related to the enhanced SCR activity.The XPS and UV-vis results reveal the creation of electron interaction between Cu and Mo in this Mo-O-Cu system which provides an increased amount of Lewis and Brønsted acid sites,thereby promoting the adsorption capacity of NH_(3) and NO_(x) as verified by NH_(3)-TPD and NO_(x)-TPD characterization.Besides,it also promotes the formation of oxygen vacancies,leading to the increasing of chemisorbed oxygen species,which improves the NO oxidation to NO_(2) activity.Furthermore,in situ DRIFTS technology was also used to study the reaction mechanism of this Mo doped CuO catalyst.The formed NO_(2) could react with NHx(x=3,2)species to enhance the low-temperature NH_(3)-SCR activity via the"fast-SCR"reaction pathway.The nitrate and nitrite ad-species may react with NH_(3) and NH4^(+)ad-species through the L-H pathway.展开更多
NiFe(oxy)hydroxide(NiFeOOH)is recognized as a highly active non-precious metal catalyst in alkaline water electrolysis due to its exceptional catalytic properties.In this work,high valence molybdenum(Mo)is introduced ...NiFe(oxy)hydroxide(NiFeOOH)is recognized as a highly active non-precious metal catalyst in alkaline water electrolysis due to its exceptional catalytic properties.In this work,high valence molybdenum(Mo)is introduced to improve the electronic structure and enhance the electrical conductivity of NiFeOOH for oxygen evolution reaction(OER).The introduction of Mo results in a Mo-doped NiFeOOH catalyst with a significantly reduced overpotential of 205 mV at 10 mA/cm^(2)and a Tafel slope of 31.7 mV/dec,enabling stable operation for up to 170 h.Both empirical experiment and theory simulations are employed to gain insight into the 3d-electron interactions between molybdenum and nickel(Ni),iron(Fe)in Mo-doped NiFeOOH.The results indicate that Mo-doping enhances the valence states of Ni and Fe,leading to a shift in the d-band center of the bimetallic active sites.This modification affects the transformation of Mo-doped NiFeOOH into theγ-NiFeOOH active phase.This potent combination lends credence to its potential suitability and utility in OER applications.展开更多
Li-rich layered oxide(LLO),e.g.,Li_(1.12)[Mn_(0.56)Ni_(0.16)Co_(0.08)]O_(2)(LRMO),is considered as a promising cathode material due to its superior Li-storage capability.However,the poor cycling stability and large vo...Li-rich layered oxide(LLO),e.g.,Li_(1.12)[Mn_(0.56)Ni_(0.16)Co_(0.08)]O_(2)(LRMO),is considered as a promising cathode material due to its superior Li-storage capability.However,the poor cycling stability and large voltage decay,which are related to the phase transition,limit its industrialization process.Herein,a Mo-doped LRMO(Li_(1.12)[Mn_(0.56)Ni_(0.16)Co_(0.08)]_(0.98)Mo_(0.02)O_(2),LRMO-Mo2.0%)was successfully synthesized via a simple combination of co-precipitation with high-temperature calcination for solving the mentioned above-disadvantages.Compared with the pristine counterpart,the as-prepared LRMO-Mo2.0%shows more excellent electrochemical performance in terms of rate capability(reversible capacity of 118 mA·h·g^(−1) at 5 C),cyclic ability(94.3%capacity retention after 100 cycles at 0.2 C)and discharge midpoint voltage decay(0.11 V after 100 cycles).Systematic investigation of structural evolution and electrochemical kinetics elucidate that the synergic effect of robust oxygen framework and layered/spinel heterostructure is the key to its performance improvement.Such synergy helps to stabilize the layered structure by curbing the structural transformation and oxygen escaping during the electrochemical cycling.This work paved the way for the simple and efficient preparation of highly stable LLO cathode materials.展开更多
Regulating the electronic and geometric structures of electrocatalysts is an effective strategy to boost their catalytic properties.Herein,a coral-like nanostructure is assembled with Mo-doped Pt clusters to form a hi...Regulating the electronic and geometric structures of electrocatalysts is an effective strategy to boost their catalytic properties.Herein,a coral-like nanostructure is assembled with Mo-doped Pt clusters to form a highly active catalyst toward the oxygen reduction reaction(ORR).The advantages of a Mo-doped porous skeleton,grain boundaries,and MoOx species on the Pt cluster surfaces synergistically boost the electrocatalytic performance.This unique architecture delivers 3.5-and 2.8-fold higher mass and specific activities,respectively,than commercial Pt/C.Density functional theory calculations reveal that the Mo-doped Pt clusters have an optimized Pt–O bond length of 2.110Å,which weakens the adsorption energy of the intermediate O*to yield great ORR activity.Moreover,the catalyst shows a decay in the half-wave potential of only 8 mV after 10,000 cycles of accelerated durability testing.The high stability arises from the increased dissociation energy of Pt atoms and the stable architecture of the coral-like structure of clusters.展开更多
A series of Mo-doped ZnO photocatalysts with different Mo-dopant concentrations have been prepared by a grind- ing-calcination method. The structure of these photocatalysts was characterized by a variety of methods, i...A series of Mo-doped ZnO photocatalysts with different Mo-dopant concentrations have been prepared by a grind- ing-calcination method. The structure of these photocatalysts was characterized by a variety of methods, including N2 physical adsorption, X-ray diffraction （XRD）, scanning electron microscopy （SEM）, Fourier transform infrared （FT-IR） spectroscopy, photoluminescence （PL） emission spectroscopy, and UV-vis diffuse reflectance spectroscopy （DRS）. It was found that Mo6＋ could enter into the crystal lattice of ZnO due to the radius of MO6＋ （0.065 nm） being smaller than that of Zn2＋ （0.083 nm）. XRD results indicated that Mo6＋ suppressed the growth of ZnO crystals. The FT-IR spectroscopy results showed that the ZnO with 2 wt.% Mo-doping has a higher level of surface hydroxyl groups than pure ZnO. PL spectroscopy indicated that ZnO with 2 wt.% Mo-doping also exhibited the largest reduction in the intensity of the emission peak at 390 nm caused by the recombi- nation of photogenerated hole-electron pairs. The activities of the Mo-doped ZnO photocatalysts were investigated in the pho- tocatalytic degradation of acid orange II under UV light （2 = 365 nm） irradiation. It was found that ZnO with 2 wt.% Mo-doping showed much higher photocatalytic activity and stability than pure ZnO. The high photocatalytic performance of the Mo-doped ZnO can be attributed to a great improvement in the surface properties of ZnO, higher crystallinity and lower recombination rate of photogenerated hole-electron （e-/h＋） pairs. Moreover, the undoped Mo species may exist in the form of MoO3 and form MoO3/ZnO heterojunctions which further favors the separation of e/h＋ pairs.展开更多
Organic thermoelectrics(OTEs)have been recently intensively investigated as they hold promise for flexible,large-area,and low-cost energy generation or heating–cooling devices for appealing applications,for example,w...Organic thermoelectrics(OTEs)have been recently intensively investigated as they hold promise for flexible,large-area,and low-cost energy generation or heating–cooling devices for appealing applications,for example,wearable energy harvesting.In the past 7 years,n-type OTEs have witnessed a sharp increase in their performance thanks to significant progress in developing and understanding the fundamental physical properties of n-type OTE materials as well as the working principle and physical processes of the TE devices.展开更多
基金financially supported by the Natural Sciences and Engineering Research Council of Canada(NSERC),through the Discovery Grant Program(RGPIN-2018-06725RGPIN-201705080)+2 种基金the Discovery Accelerator Supplement Grant program(RGPAS-2018-522651)by the New Frontiers in Research Fund-Exploration program(NFRFE-2019-00488)support from the University of Alberta and Future Energy Systems(FES)。
文摘Highly active and durable electrocatalysts towards oxygen reduction reaction(ORR)are imperative for the commercialization application of proton exchange membrane fuel cells.By manipulating ligand effect,structural control,and strain effect,we report here the precise preparation of Mo-doped Pt_(3)Co alloy nanowires(Pt_(3)Co-Mo NWs)as the efficient catalyst towards ORR with high specific activity(0.596 mA cm^(−2))and mass activity(MA,0.84 A mg^(−1)_(Pt)),much higher than those of undoped counterparts.Besides activity,Pt_(3)Co-Mo NWs also demonstrate excellent structural stability and cyclic durability even after 50,000 cycles,again surpassing control samples without Mo dopants.According to the strain maps and DFT calculations,Mo dopants could modify the electronic structure of both Pt and Co to achieve not only optimized oxygen-intermediate binding energy on the interface but also increased the vacancy formation energy of Co,together leading to enhanced activity and durability.This work provides not only a facile methodology but also an in-depth investigation of the relationship between structure and properties to provide general guidance for future design and optimization.
基金financial supports from the National Natural Science Foundation of China (52004155,51690164, and 51805321)the China Postdoctoral Science Foundation (2020M681261)the Science and Technology Commission of Shanghai Municipality (19XD1401600 and 19010500300)。
文摘An electrocatalyst with heterogeneous nanostructure, especially the hierarchical one, generally shows a more competitive activity than that of its single-component counterparts for oxygen evolution reaction(OER), due to the synergistically enhanced kinetics on enriched active sites and reconfigured electronic band structure. Here this work introduces hierarchical heterostructures into a NiMo@NiS/MoS_(2)@Ni_(2)S_(2)/MoO_(x)(NiMoS) composite by one-pot controlled moderative sulfidation. The optimal solvent composition and addition of NaOH enable NiMoS to own loose and porous structures, smaller nanoparticle sizes, optimal phase composition and chemical states of elements, improving the OER activity of NiMoS. To achieve current densities of 50 and 100 mA cm^(-1), small overpotentials of 275 and 306 mV are required respectively, together with a minor Tafel slope of 58 mV dec^(-1), which outperforms most reported sulfide catalysts and IrO_(2). The synergistic effects in the hierarchical heterostructures expose more active sites,adjust the electronic band structure, and enable the fast charge transfer kinetics, which construct an optimized local coordination environment for high OER electrocatalytic activity. Furthermore, the hierarchical heterostructures suppress the distinct lowering of electrical conductivity and collapse of pristine structures resulted from the metal oxidation and synchronous S leaching during OER, yielding competitive catalytic stability.
基金support from Queensland University of Technology,Brisbane,Queensland,Australiafinancial support from ARC Discovery Project(DP210103266).
文摘In this work,we have applied molybdenum(Mo)and titanium(Ti)co-doping to solve the degradation of Ni-rich cathodes.The modified cathode,i.e.,Li(Ni_(0.89)Co_(0.05)Mn_(0.05)Mo_(0.005)Ti_(0.005))O_(2) holds a stable structure with expanded crystal lattice distance which improves Li ion diffusion kinetics.The dopants have suppressed the growth of primary particles,formed a coating on the surface,and promoted the elongated morphology.Moreover,the mechanical strength of these particles has increased,as confirmed by the nanoindentation test,which can help suppress particle cracking.The detrimental H2-H3 phase transition has been postponed by 90 mV allowing the cathode to operate at a higher voltage.A better cycling stability over 100 cycles with 69%capacity retention has been observed.We believe this work points out a way to improve the cycling performance,Coulombic efficiency and capacity retention in Ni-rich cathodes.
基金supported by the Hainan Provincial Natural Science Foundation of China(Nos.522MS038 and 522QN282)the National Natural Science Foundation of China(Nos.52172086 and 52301268)the Start-up Research Foundation of Hainan University(No.KYQD(ZR)-22019).
文摘Thermoelectric water spitting to hydrogen systems has great potential in the production of environment-friendly fuel using renewable solar energy in the future.In this work,we prepared porous nanosheet Mo doping Ni_(5)P_(4)catalysts on nickel foam with efficient hydrogen evolution reaction(HER)and oxygen evolution reaction(OER)performance in alkaline media.Density Functional Theory(DFT)calculations and experimental studies have shown that Mo doping deadeneds the interaction between H and O atomic orbitals of transition state water molecules,effectively weakening the activation energy of H_(2)O dissociation.Therefore,Mo doping is favorable for enhancing HER activity with overpotential at 10 mA cm^(-2)of 93 mV and Tafel slope of 40.1 mV dec^(-1)in 1 M KOH.Besides,it exhibits high alkaline OER activity with an ultra-low overpotential of 200 mV at 10 mA cm^(-2).Moreover,this catalyst only needs 1.537 V in a dual-electrode configuration of the electrolytic cell,which is much lower than the commercial Pt/C-RuO_(2)couple(1.614 V).In addition,we have developed and constructed a solar thermoelectric generator(TEG)that is capable of floating on water.This TEG has a continuous power output and an exceptionally long lifespan,providing a stable power supply to the synthesized catalyst electrolyzer.It can produce a maximum power output of over 90 mW,meeting the requirement of converting solar radiation heat into usable electricity.As a result,the system achieves productivity of 0.11 mL min^(-1)H_(2).This solar thermal energy conversion technology shows the possibility of large-scale industrial production of H_(2)and provides a new idea for exploring heat source utilization.
基金partly supported by the National Natural Science Foundation of China(Nos.12275189 and 11705015)Natural Science Foundation of the Jiangsu Higher Education Institutions(No.23KJA430001)Collaborative Innovation Center of Suzhou Nano Science&Technology。
文摘P2-type layered transition-metal oxides with high energy density and rich variety have attracted extensive attention for sodium-ion batteries(SIBs)in grid-scale energy storage application,but they usually suffer from sluggish kinetics and large volume change upon cycling.Herein,we designed a highperformance P2-type Na_(0.67)Ni_(0.31)Mn_(0.67)Mo_(0.02)O_(2)(NNMMO)cathode with regulated electronic environment and Na^(+)zigzag ordering modulation via high-valence Mo6+stabilization engineering.The achieved NNMMO cathode exhibits a high-rate capability with a reversible capacity of 77.2 m Ah/g at 10 C and a long cycle life with a capacity retention of 75%at 2 C after 1000 cycles.In addition,in situ X-ray diffraction and ex-situ X-ray absorption fine structure spectroscopy characterizations verify that the presence of Mo^(6+)also stabilizes the desodiated structure through a pinning effect,achieving an extremely low volume change of 1.04%upon Na^(+)extraction.The quantified diffusional analysis and theoretical calculations demonstrate that the Mo^(6+)-doping improves the Na+diffusion kinetics,optimizes the energy band structure and enhances the TM-O bond strength.Additionally,the as-fabricated pouch cells by paring NNMMO cathode and hard carbon anode show impressive cycling stability with an energy density of 296.7 Wh/kg.This study broadens the perspective for high-valence metal ion doping to obtain superior cathode materials and pave the way for developing high-energy-density SIBs.
基金the National Natural Science Foundation of China (Grant Nos. 21273058, 21673064, 51802059 and 21503059)China Postdoctoral Science Foundation (Grant Nos. 2018M631938, 2018T110307 and 2017M621284)+1 种基金Heilongjiang Postdoctoral Fund (LBH-Z17074)Fundamental Research Funds for the Central Universities (Grant No. HIT. NSRIF. 2019040 and 2019041)
文摘A core shell structured C@MoxTi1-xO2-δnanocrystal with a functionalized interface(C@MTNC-FI)was fabricated via the hydrothermal method with subsequent annealing derived from tetrabutyl orthotitanate.The formation of anatase TiO2 was inhibited by the simultaneous presence of the hydrothermal etching/regrowth process,infiltration of Mo dopants and carbon coating,which endows the C@MTNC-FI with an ultrafine crystalline architecture that has a Mo-functionalized interface and carbon-coated shell.Pt Ru nanoparticles(NPs)were supported on C@MTNC-FI by employing a microwave-assisted polyol process(MAPP).The obtained Pt Ru/C@MTNC-FI catalyst has 2.68 times higher mass activity towards methanol electrooxidation than that of the un-functionalized catalyst(Pt Ru/C@TNC)and 1.65 times higher mass activity than that of Pt Ru/C catalyst with over 25%increase in durability.The improved catalytic performance is due to several aspects including ultrafine crystals of TiO2 with abundant grain boundaries,Mofunctionalized interface with enhanced electron interactions,and core shell architecture with excellent electrical transport properties.This work suggests the potential application of an interface-functionalized crystalline material as a sustainable and clean energy solution.
基金The authors gratefully thank the National Natural Science Foun-dation of China(Nos.22278431 and 21776302)for the financial support of this work.
文摘Designing highly active and stable noble-metal-free electrocatalysts for water splitting over a wide pH range is critical yet remains significantly challenging.In this work,Mo-doped CoP nanoparticles(Mo-CoP)supported and enwrapped by porous single-atomic-Co doped carbon framework(Co-N-C)were designed and prepared by a simple one-pot pyrolysis method.The Mo-CoP/Co-N-C electrocatalyst exhibits superior performance with low overpotentials of only 45 mV for hydrogen evolution reaction(HER)and 201 mV for oxygen evolution reaction(OER)in 1 M KOH at 10 mA cm^(-2)current density.Such excellent catalytic activity can be ascribed to enhanced intrinsic activity,large surface area,and highly exposed active sites.Meanwhile,an extremely small overpotential of only 250 mV is required for a large current density of 500 mA cm^(-2)in HER,which exceeds the performance of benchmark 10%Pt/C.Besides,Mo-CoP/Co-N-C also exhibits superior HER performance in acidic and neutral mediums,with overpotentials of only 41 and 98 mV in 0.5 M H_(2)SO_(4),and 1 M PBS,respectively,thus achieving efficient water splitting at a wide pH range.The long-term stabilities are guaranteed with no significant decline of catalytic activities for more than 24 h in all electrolytes,which can be ascribed to the carbon layer encapsulation structure.Addition-ally,in overall water splitting,the electrocatalytic cell consisting of the as-synthesized Mo-CoP/Co-N-C only requires a cell voltage of 1.611 V at 100 mA cm^(-2)with excellent stability,exceeding that of the benchmark Pt/C||RuO(2) couple(1.645 V at 100 mA cm^(-2)).This work not only presents a highly efficient electrocatalyst for pH-universal water splitting but also provides a new perspective for the design and construction of transition metal catalysts with excellent stability.
基金supported by the National Natural Science Foundation of China(Nos.21806017,21876019)the Fundamental Research Funds for the Central Universities(No.DUT20RC(4)003)National Key Research and Development Program of China(No.2019YFC1903903).
文摘A novel Mo-doped CuO catalyst is developed and used for low-temperature NH_(3)-SCR reaction.Compared with the undoped CuO sample,the Mo doped CuO catalyst shows an increased SCR performance with above 80%NO_(x) conversion at 175℃.The XRD and Raman results have confirmed the incorporation of Mo metal ions into CuO lattice to form Mo-O-Cu species which may be related to the enhanced SCR activity.The XPS and UV-vis results reveal the creation of electron interaction between Cu and Mo in this Mo-O-Cu system which provides an increased amount of Lewis and Brønsted acid sites,thereby promoting the adsorption capacity of NH_(3) and NO_(x) as verified by NH_(3)-TPD and NO_(x)-TPD characterization.Besides,it also promotes the formation of oxygen vacancies,leading to the increasing of chemisorbed oxygen species,which improves the NO oxidation to NO_(2) activity.Furthermore,in situ DRIFTS technology was also used to study the reaction mechanism of this Mo doped CuO catalyst.The formed NO_(2) could react with NHx(x=3,2)species to enhance the low-temperature NH_(3)-SCR activity via the"fast-SCR"reaction pathway.The nitrate and nitrite ad-species may react with NH_(3) and NH4^(+)ad-species through the L-H pathway.
基金supported by the National Natural Science Foundation of China(Grant No.52376209)China Postdoctoral Science Foundation(Grant Nos.2020M673386 and 2020T130503)China Fundamental Research Funds for the Central Universities.
文摘NiFe(oxy)hydroxide(NiFeOOH)is recognized as a highly active non-precious metal catalyst in alkaline water electrolysis due to its exceptional catalytic properties.In this work,high valence molybdenum(Mo)is introduced to improve the electronic structure and enhance the electrical conductivity of NiFeOOH for oxygen evolution reaction(OER).The introduction of Mo results in a Mo-doped NiFeOOH catalyst with a significantly reduced overpotential of 205 mV at 10 mA/cm^(2)and a Tafel slope of 31.7 mV/dec,enabling stable operation for up to 170 h.Both empirical experiment and theory simulations are employed to gain insight into the 3d-electron interactions between molybdenum and nickel(Ni),iron(Fe)in Mo-doped NiFeOOH.The results indicate that Mo-doping enhances the valence states of Ni and Fe,leading to a shift in the d-band center of the bimetallic active sites.This modification affects the transformation of Mo-doped NiFeOOH into theγ-NiFeOOH active phase.This potent combination lends credence to its potential suitability and utility in OER applications.
基金This work was supported by the National Natural Science Foundation of China(Grant No.51964017,Grant No.51874151)the Jiangxi Provincial Natural Science Foundation(Grant No.20212BAB214004)+1 种基金the Jiangxi Provincial Education Office Natural Science Fund Project(Grant No.GJJ201413)the Jiangxi University of Science and Technology College Student Innovation and Entrepreneurship Training Program Support Project(Grant No.DC2019-042).
文摘Li-rich layered oxide(LLO),e.g.,Li_(1.12)[Mn_(0.56)Ni_(0.16)Co_(0.08)]O_(2)(LRMO),is considered as a promising cathode material due to its superior Li-storage capability.However,the poor cycling stability and large voltage decay,which are related to the phase transition,limit its industrialization process.Herein,a Mo-doped LRMO(Li_(1.12)[Mn_(0.56)Ni_(0.16)Co_(0.08)]_(0.98)Mo_(0.02)O_(2),LRMO-Mo2.0%)was successfully synthesized via a simple combination of co-precipitation with high-temperature calcination for solving the mentioned above-disadvantages.Compared with the pristine counterpart,the as-prepared LRMO-Mo2.0%shows more excellent electrochemical performance in terms of rate capability(reversible capacity of 118 mA·h·g^(−1) at 5 C),cyclic ability(94.3%capacity retention after 100 cycles at 0.2 C)and discharge midpoint voltage decay(0.11 V after 100 cycles).Systematic investigation of structural evolution and electrochemical kinetics elucidate that the synergic effect of robust oxygen framework and layered/spinel heterostructure is the key to its performance improvement.Such synergy helps to stabilize the layered structure by curbing the structural transformation and oxygen escaping during the electrochemical cycling.This work paved the way for the simple and efficient preparation of highly stable LLO cathode materials.
基金the financial support from the National Natural Science Foundation of China(22379078).
文摘Regulating the electronic and geometric structures of electrocatalysts is an effective strategy to boost their catalytic properties.Herein,a coral-like nanostructure is assembled with Mo-doped Pt clusters to form a highly active catalyst toward the oxygen reduction reaction(ORR).The advantages of a Mo-doped porous skeleton,grain boundaries,and MoOx species on the Pt cluster surfaces synergistically boost the electrocatalytic performance.This unique architecture delivers 3.5-and 2.8-fold higher mass and specific activities,respectively,than commercial Pt/C.Density functional theory calculations reveal that the Mo-doped Pt clusters have an optimized Pt–O bond length of 2.110Å,which weakens the adsorption energy of the intermediate O*to yield great ORR activity.Moreover,the catalyst shows a decay in the half-wave potential of only 8 mV after 10,000 cycles of accelerated durability testing.The high stability arises from the increased dissociation energy of Pt atoms and the stable architecture of the coral-like structure of clusters.
基金supported by the National Natural Science Foundation ofChina (21067004)the Natural Science Foundation of Jiangxi Province,China (2010GZH0048)Jiangxi Province Educatien Department of Science and Technology Project (GJJ 12344)
文摘A series of Mo-doped ZnO photocatalysts with different Mo-dopant concentrations have been prepared by a grind- ing-calcination method. The structure of these photocatalysts was characterized by a variety of methods, including N2 physical adsorption, X-ray diffraction （XRD）, scanning electron microscopy （SEM）, Fourier transform infrared （FT-IR） spectroscopy, photoluminescence （PL） emission spectroscopy, and UV-vis diffuse reflectance spectroscopy （DRS）. It was found that Mo6＋ could enter into the crystal lattice of ZnO due to the radius of MO6＋ （0.065 nm） being smaller than that of Zn2＋ （0.083 nm）. XRD results indicated that Mo6＋ suppressed the growth of ZnO crystals. The FT-IR spectroscopy results showed that the ZnO with 2 wt.% Mo-doping has a higher level of surface hydroxyl groups than pure ZnO. PL spectroscopy indicated that ZnO with 2 wt.% Mo-doping also exhibited the largest reduction in the intensity of the emission peak at 390 nm caused by the recombi- nation of photogenerated hole-electron pairs. The activities of the Mo-doped ZnO photocatalysts were investigated in the pho- tocatalytic degradation of acid orange II under UV light （2 = 365 nm） irradiation. It was found that ZnO with 2 wt.% Mo-doping showed much higher photocatalytic activity and stability than pure ZnO. The high photocatalytic performance of the Mo-doped ZnO can be attributed to a great improvement in the surface properties of ZnO, higher crystallinity and lower recombination rate of photogenerated hole-electron （e-/h＋） pairs. Moreover, the undoped Mo species may exist in the form of MoO3 and form MoO3/ZnO heterojunctions which further favors the separation of e/h＋ pairs.
文摘Organic thermoelectrics(OTEs)have been recently intensively investigated as they hold promise for flexible,large-area,and low-cost energy generation or heating–cooling devices for appealing applications,for example,wearable energy harvesting.In the past 7 years,n-type OTEs have witnessed a sharp increase in their performance thanks to significant progress in developing and understanding the fundamental physical properties of n-type OTE materials as well as the working principle and physical processes of the TE devices.
