A mechanism study on MoO2 electrodeposition from ammonium molybdate solution was presented via linear sweep voltammetry,species distribution diagram,Raman spectra,Fourier transform infrared spectrometry and X-ray diff...A mechanism study on MoO2 electrodeposition from ammonium molybdate solution was presented via linear sweep voltammetry,species distribution diagram,Raman spectra,Fourier transform infrared spectrometry and X-ray diffractometry.The results show that there exist two reducible species in ammonium molybdate aqueous solution,i.e.Mo7 O24^6- and molybdenum ammonium complex.In weak acid medium without NH4^+,an obvious reduction peak denoting the reduction of Mo7 O24^6- to molybdenum(Ⅳ)oxides emerges at around-0.7 V(vs SCE).While in neutral and basic solutions without NH4^+,the dominant species changes to MoO4^2-,and accordingly,no reduction peak appears except hydrogen evolution.NH4^+ plays an important role in MoO2 electrodeposition.A new current peak appears at-1.25 V(vs SCE)in both acid and basic solutions,which is attributed to the reduction of molybdenum complex.The effects of solution composition and the electrodeposition conditions on the current efficiency were discussed systematically.By optimizing the electrodeposition conditions,the current efficiency can reach up to51.9%.展开更多
Conventional Li-O2 battery is hardly considered as a next-generation flexible electronics thus far,since it is inflexible,bulk,and limited by the absence of the adjustable cell configuration.Here,we report a binder-fr...Conventional Li-O2 battery is hardly considered as a next-generation flexible electronics thus far,since it is inflexible,bulk,and limited by the absence of the adjustable cell configuration.Here,we report a binder-free and flexible electrode of x wt%MoO2 NPs/CTs(x=6,16,and 28).A cell with 16 wt% MoO2 NPs/CTs displays a good cyclability over 240 cycles with a low overpotential of 0.33 V on the 1st cycle at a constant current density of 0.2 mA cm-2,a considerable rate performance,a superior reversibility associated with the desired formation and degradation of Li2O2,and a high electrochemical stability even under stringent bending and twisting conditions.Our work represents a promising progress in the material development and architecture design of O2 electrode for flexible Li-O2 batteries.展开更多
Hierarchical mesoporous MoO2/Mo2C/C microspheres,which are composed of primary nanoparticles with a size of about 30 nm,have been designed and synthesized through polymer regulation and subsequent carbonization proces...Hierarchical mesoporous MoO2/Mo2C/C microspheres,which are composed of primary nanoparticles with a size of about 30 nm,have been designed and synthesized through polymer regulation and subsequent carbonization processes.The as-synthesized microspheres were characterized by XRD,Raman,SEM,TEM,XPS measurements and so on.It was found that polyethylene glycol acted as a structure-directing agent,mild reducing agent and carbon source in the formation of these hierarchical mesoporous Mo O2/Mo2C/C microspheres.Moreover,the electrochemical property of the microspheres was also investigated in this work.Evaluated as an anode material for lithium ion batteries,the hierarchical mesoporous Mo O2/Mo2C/C electrode delivered the discharge specific capacities of 665 and 588 m Ah/g after 100 cycles at current densities of 100 and 200 m A/g,respectively.The satisfactory cycling performance and controllable process facilitate the practical applications of the hierarchical mesoporous Mo O2/Mo2C/C as a potential anode material in high-energy density lithium-ion batteries.展开更多
The electrocatalytic hydrogen evolution reaction(HER)is one of the most promising ways for low-cost hydrogen production in the future.In this work,hetero S atoms were introduced into the MoO2 to enhance the catalytic ...The electrocatalytic hydrogen evolution reaction(HER)is one of the most promising ways for low-cost hydrogen production in the future.In this work,hetero S atoms were introduced into the MoO2 to enhance the catalytic activity by simultaneously adjusting electron structure,engineering lattice defect,and increasing oxygen vacancies.And the S doped MoO2 nanosheets with proper S doping amount show the enhanced performance for HER.The optimized catalyst shows a small onset overpotential as low as 120 mV,a low overpotential of 176 mV at the current density of 10 mA/cm^2 which is decreased 166 mV compared to that of the pristine MoO2 nanosheets,a low Tafel slope of 57 mV/decade,and a high turnover frequency of 0.13 H2/s per active site at 150 mV.This finding proposes an effective strategy to prepare nonprecious metal oxide catalyst for enhancing HER performance by rationally doping hetero atoms.展开更多
Hydrogen is one of the most promising energy carriers to replace fossil fuels and electrolyzing water to produce hydrogen is a very effective method.However,designing highly active and stable non-precious metal hydrog...Hydrogen is one of the most promising energy carriers to replace fossil fuels and electrolyzing water to produce hydrogen is a very effective method.However,designing highly active and stable non-precious metal hydrogen evolution electrocatalysts that can be used in universal pH is a huge challenge.Here,we have reported a simple strategy to develop a highly active and durable non-precious MoO2-Ni electrocatalyst for hydrogen evolution reaction(HER)in a wide pH range.The MoO2-Ni catalyst exhibits a superior electrocatalytic performance with low overpotentials of 46,69,and 84 mV to reach-10 mA cm-2 in 1.0 M KOH,0.5 M H2SO4,and 1.0 M PBS electrolytes,respectively.At the same time,the catalyst also shows outstanding stability over a wide pH range.It is particularly noted that the catalytic performance of MoO2-Ni in alkaline solution is comparable to the highest performing catalysts reported.The outstanding HER performance is mainly attributed to the collective effect of the rational morphological design,electronic structure engineering,and strong interfacial coupling between MoO2 and Ni in heterojunctions.This work provides a viable method for the synthesis of inexpensive and efficient HER electrocatalysts for the use in wide pH ranges.展开更多
Inspired by the promising hydrogen production in the solar thermochemical(STC)cycle based on non-stoichiometric oxides and the operation temperature decreasing effect of methane reduction,a high-fuel-selectivity and C...Inspired by the promising hydrogen production in the solar thermochemical(STC)cycle based on non-stoichiometric oxides and the operation temperature decreasing effect of methane reduction,a high-fuel-selectivity and CH4-introduced solar thermochemical cycle based on MoO2/Mo is studied.By performing HSC simulations,the energy upgradation and energy conversion potential under isothermal and non-isothermal operating conditions are compared.In the reduction step,MoO2:CH4=2 and 1020 K<Tred<1600 K are found to be most favorable for syngas selectivity and methane conversion.Compared to the STC cycle without CH4,the introduction of methane yields a much higher hydrogen production,especially at the lower temperature range and atmospheric pressure.In the oxidation step,a moderately excessive water is beneficial for energy conversion whether in isothermal or non-isothermal operations,especially at H2O:Mo=4.In the whole STC cycle,the maximum non-isothermal and isothermal efficiency can reach 0.417 and 0.391 respectively.In addition,the predicted efficiency of the second cycle is also as high as 0.454 at Tred=1200 K and Toxi=400 K,indicating that MoO2 could be a new and potential candidate for obtaining solar fuel by methane reduction.展开更多
基金Project(51374185) supported by the National Natural Science Foundation of China
文摘A mechanism study on MoO2 electrodeposition from ammonium molybdate solution was presented via linear sweep voltammetry,species distribution diagram,Raman spectra,Fourier transform infrared spectrometry and X-ray diffractometry.The results show that there exist two reducible species in ammonium molybdate aqueous solution,i.e.Mo7 O24^6- and molybdenum ammonium complex.In weak acid medium without NH4^+,an obvious reduction peak denoting the reduction of Mo7 O24^6- to molybdenum(Ⅳ)oxides emerges at around-0.7 V(vs SCE).While in neutral and basic solutions without NH4^+,the dominant species changes to MoO4^2-,and accordingly,no reduction peak appears except hydrogen evolution.NH4^+ plays an important role in MoO2 electrodeposition.A new current peak appears at-1.25 V(vs SCE)in both acid and basic solutions,which is attributed to the reduction of molybdenum complex.The effects of solution composition and the electrodeposition conditions on the current efficiency were discussed systematically.By optimizing the electrodeposition conditions,the current efficiency can reach up to51.9%.
基金supported by National Key R&D Program of China (2016YFB0100500)Special fund of key technology research and development projects (20180201097GX)(20180201099GX)(20180201096GX),Jilin province science and technology department+5 种基金The R&D Program of power batteries with low temperature and high energy,Science and Technology Bureau of Changchun (19SS013)Key Subject Construction of Physical Chemistry of Northeast Normal UniversityGeneral Financial Grant from the China Postdoctoral Science Foundation (Grant 2016M601363)Fundamental Research Funds for the Central Universities (Grant 2412017QD011)Jilin Scientific and Technological Development Program (Grant 20180520143JH)National Natural Science Foundation of China (Grant 21805030)。
文摘Conventional Li-O2 battery is hardly considered as a next-generation flexible electronics thus far,since it is inflexible,bulk,and limited by the absence of the adjustable cell configuration.Here,we report a binder-free and flexible electrode of x wt%MoO2 NPs/CTs(x=6,16,and 28).A cell with 16 wt% MoO2 NPs/CTs displays a good cyclability over 240 cycles with a low overpotential of 0.33 V on the 1st cycle at a constant current density of 0.2 mA cm-2,a considerable rate performance,a superior reversibility associated with the desired formation and degradation of Li2O2,and a high electrochemical stability even under stringent bending and twisting conditions.Our work represents a promising progress in the material development and architecture design of O2 electrode for flexible Li-O2 batteries.
基金supported by the National Natural Science Foundation of China(No.21376251 and 21406233)the National Basic Research Development Program of China(2013CB632600)
文摘Hierarchical mesoporous MoO2/Mo2C/C microspheres,which are composed of primary nanoparticles with a size of about 30 nm,have been designed and synthesized through polymer regulation and subsequent carbonization processes.The as-synthesized microspheres were characterized by XRD,Raman,SEM,TEM,XPS measurements and so on.It was found that polyethylene glycol acted as a structure-directing agent,mild reducing agent and carbon source in the formation of these hierarchical mesoporous Mo O2/Mo2C/C microspheres.Moreover,the electrochemical property of the microspheres was also investigated in this work.Evaluated as an anode material for lithium ion batteries,the hierarchical mesoporous Mo O2/Mo2C/C electrode delivered the discharge specific capacities of 665 and 588 m Ah/g after 100 cycles at current densities of 100 and 200 m A/g,respectively.The satisfactory cycling performance and controllable process facilitate the practical applications of the hierarchical mesoporous Mo O2/Mo2C/C as a potential anode material in high-energy density lithium-ion batteries.
基金supported by the Research Project of the Key Laboratory of Functional Materials Physics and Chemistry of the Ministry of Education(2017005)the National Natural Science Foundation of China(Nos.51571072 and 51871078)Heilongjiang Science Foundation(No.E2018028).
文摘The electrocatalytic hydrogen evolution reaction(HER)is one of the most promising ways for low-cost hydrogen production in the future.In this work,hetero S atoms were introduced into the MoO2 to enhance the catalytic activity by simultaneously adjusting electron structure,engineering lattice defect,and increasing oxygen vacancies.And the S doped MoO2 nanosheets with proper S doping amount show the enhanced performance for HER.The optimized catalyst shows a small onset overpotential as low as 120 mV,a low overpotential of 176 mV at the current density of 10 mA/cm^2 which is decreased 166 mV compared to that of the pristine MoO2 nanosheets,a low Tafel slope of 57 mV/decade,and a high turnover frequency of 0.13 H2/s per active site at 150 mV.This finding proposes an effective strategy to prepare nonprecious metal oxide catalyst for enhancing HER performance by rationally doping hetero atoms.
基金supported by the National Natural Science Foundation of China(21965005)Natural Science Foundation of Guangxi Province(2018GXNSFAA294077 and 2018GXNSFAA281220)Project of High-Level Talents of Guangxi(F-KA18015 and 2018ZD004)。
文摘Hydrogen is one of the most promising energy carriers to replace fossil fuels and electrolyzing water to produce hydrogen is a very effective method.However,designing highly active and stable non-precious metal hydrogen evolution electrocatalysts that can be used in universal pH is a huge challenge.Here,we have reported a simple strategy to develop a highly active and durable non-precious MoO2-Ni electrocatalyst for hydrogen evolution reaction(HER)in a wide pH range.The MoO2-Ni catalyst exhibits a superior electrocatalytic performance with low overpotentials of 46,69,and 84 mV to reach-10 mA cm-2 in 1.0 M KOH,0.5 M H2SO4,and 1.0 M PBS electrolytes,respectively.At the same time,the catalyst also shows outstanding stability over a wide pH range.It is particularly noted that the catalytic performance of MoO2-Ni in alkaline solution is comparable to the highest performing catalysts reported.The outstanding HER performance is mainly attributed to the collective effect of the rational morphological design,electronic structure engineering,and strong interfacial coupling between MoO2 and Ni in heterojunctions.This work provides a viable method for the synthesis of inexpensive and efficient HER electrocatalysts for the use in wide pH ranges.
基金supported by the Innovation Practice Training Program of College Students,Chinese Academy of Sciences(Application No.20184000028)the Practical Training Program of Beijing University of Higher Education High-level Talents Cross-cultivation(No.16053225)the National Natural Science Foundation of China(Grant Nos.51476163,51806209 and 81801768).
文摘Inspired by the promising hydrogen production in the solar thermochemical(STC)cycle based on non-stoichiometric oxides and the operation temperature decreasing effect of methane reduction,a high-fuel-selectivity and CH4-introduced solar thermochemical cycle based on MoO2/Mo is studied.By performing HSC simulations,the energy upgradation and energy conversion potential under isothermal and non-isothermal operating conditions are compared.In the reduction step,MoO2:CH4=2 and 1020 K<Tred<1600 K are found to be most favorable for syngas selectivity and methane conversion.Compared to the STC cycle without CH4,the introduction of methane yields a much higher hydrogen production,especially at the lower temperature range and atmospheric pressure.In the oxidation step,a moderately excessive water is beneficial for energy conversion whether in isothermal or non-isothermal operations,especially at H2O:Mo=4.In the whole STC cycle,the maximum non-isothermal and isothermal efficiency can reach 0.417 and 0.391 respectively.In addition,the predicted efficiency of the second cycle is also as high as 0.454 at Tred=1200 K and Toxi=400 K,indicating that MoO2 could be a new and potential candidate for obtaining solar fuel by methane reduction.
