The development of the hydrogen electrode is vital for the application of alkaline polymer electrolyte fuel cells(APEFCs).In this study,a series of Ni(OH)_2 decorated Ni/C catalysts(Ni(OH)_2-Ni/C) were prepared by a t...The development of the hydrogen electrode is vital for the application of alkaline polymer electrolyte fuel cells(APEFCs).In this study,a series of Ni(OH)_2 decorated Ni/C catalysts(Ni(OH)_2-Ni/C) were prepared by a three-step electrochemical treatment of Ni/C.The existence of Ni(OH)_2 was demonstrated by X-ray photoelectron spectroscopy(XPS),and the surface molar ratio of Ni(OH)_2/Ni of the samples was estimated via an electrochemical method.The HOR catalytic activity of the catalysts was evaluated by a rotation disk electrode(RDE) method,and a "volcano plot" was established between the HOR exchange current(j0) and the surface molar ratio of Ni(OH)_2/Ni.On top of the "volcano",the surface molar ratio of Ni(OH)_2/Ni is1.1:1,the j0 of which was 6.8 times of that of Ni/C.The stability of the samples toward HOR was evaluated to be good.Our study added a systematic experimental evidence to the HOR research,showing that the HOR catalytic activity of Ni can be deliberately controlled via decoration of Ni(OH)_2,which may help understanding the HOR mechanism on Ni.展开更多
Research on the reaction mechanism of ethanol oxidation reaction(EOR) is important for the development of highly active EOR electro-catalysts. One of the main difficulties in the EOR study is the quantitative analysis...Research on the reaction mechanism of ethanol oxidation reaction(EOR) is important for the development of highly active EOR electro-catalysts. One of the main difficulties in the EOR study is the quantitative analysis of the non-volatile products. Conventional on-line electrochemical flowing transmission infrared spectroscopy(ETIRS) can only collect a part of the carbonate products of EOR in alkaline media, making the further quantitative study impossible. Herein, a new ETIRS system has been designed and prepared by employing a cation-exchange membrane(Nafion) in the sampling hood. The using of the Nafion membrane can prevent the anions crossing over by confining the generated carbonates in the sampling hood without diffusing into the bulk electrolyte. Therefore, the collection efficiency of the carbonate products as well as the test accuracy of the carbonate current efficiency has been significantly improved. The result of CO stripping reaction shows that ca. 100% of the carbonate product is able to be collected in alkaline media by this new system. The influence of the experimental temperature to the carbonate current efficiency has been further studied on Pt/C toward EOR in alkaline media.展开更多
Nafion as a universal polymer ionomer was widely applied for nanocatalysts electrode preparation.However,the effect of Nafion on electrocatalytic performance was often overlooked,especially for CO_(2)electrolysis.Here...Nafion as a universal polymer ionomer was widely applied for nanocatalysts electrode preparation.However,the effect of Nafion on electrocatalytic performance was often overlooked,especially for CO_(2)electrolysis.Herein,the key roles of Nafion for CO_(2)RR were systematically studied on Cu nanoparticles(NPs)electrocatalyst.We found that Nafion modifier not only inhibit hydrogen evolution reaction(HER)by decreasing the accessibility of H_(2)O from electrolyte to Cu NPs,and increase the CO_(2)concentration at electrocatalyst interface for enhancing the CO_(2)mass transfer process,but also activate CO_(2)molecule by Lewis acid-base interaction between Nafion and CO_(2)to accelerate the formation of^(*)CO,which favor of C–C coupling for boosting C_(2)product generation.Owing to these features,the HER selectivity was suppressed from 40.6%to 16.8%on optimal Cu@Nafion electrode at-1.2 V versus reversible hydrogen electrode(RHE),and as high as 73.5%faradaic efficiencies(FEs)of C_(2)products were achieved at the same applied potential,which was 2.6 times higher than that on bare Cu electrode(~28.3%).In addition,Nafion also contributed to the long-term stability by hinder Cu NPs morphology reconstruction.Thus,this work provides insights into the impact of Nafion on electrocatalytic CO_(2)RR performance.展开更多
Proton exchange membranes （PEMs） are a key material for proton exchange membrane fuel cells （PEM-FCs）, Non-fluorinated hydrocarbon PEMs are low-cost alternatives to Nation, but limited by the low pro-ton conductiv...Proton exchange membranes （PEMs） are a key material for proton exchange membrane fuel cells （PEM-FCs）, Non-fluorinated hydrocarbon PEMs are low-cost alternatives to Nation, but limited by the low pro-ton conductivity, because of the weak phase segregation structure and narrow ion-transport channels.Various efforts have been taken to improve the performance of hydrocarbon PEMs, but mostly with com-plex methodologies. Here we demonstrate a simple, yet very efficient method to create phase segrega-tion structure inside a typical hydrocarbon PEM, sulfonated poly（ether ether ketone） （SPEEK）. By sim-ply adding appropriate amounts of water into the DMF solvent, the resulting SPEEK membrane exhibitswidened ion-transport channels, with the phase size of 2.7 nm, as indicated by both molecular dynamic（MD） simulations and transmission electron microscope （TEM） observations, and the proton conductivityis thus improved by 200%. These findings not only further our fundamental understanding of hydrocarbonPEMs, but are also valuable to the development of low-cost and practical fuel cell technologies.展开更多
Although most transition metals have been tested as the promoter to Pt for electrocatalysis toward fuel cell reactions,semi-conductor elements,such as Si,have hitherto not been examined.Here we report a simple synthes...Although most transition metals have been tested as the promoter to Pt for electrocatalysis toward fuel cell reactions,semi-conductor elements,such as Si,have hitherto not been examined.Here we report a simple synthesis of intermetallic Pt2Si electrode using magnetron sputtering and the electrocatalysis toward ethanol oxidation reaction（EOR）.In comparison to Pt,the intermetallic Pt2Si surface turns out to be much more active in catalyzing the EOR：the onset potential shifts negatively by 150 mV,and the current density at 0.6 V increases by a magnitude of one order.Such an enormous enhancement in EOR catalysis is ascribed to the promotion effects of Si,which can not only provide active surface oxygenated species to accelerate the removal of COads,but also strongly alter the electronic property of Pt,as clearly indicated by the core-level shift in XPS spectrum.展开更多
The hybrid optical pumping spin exchange relaxation free(HOPSERF)atomic co-magnetometers make ultrahigh sensitivity measurement of inertia achievable.The wall relaxation rate has a big effect on the polarization and f...The hybrid optical pumping spin exchange relaxation free(HOPSERF)atomic co-magnetometers make ultrahigh sensitivity measurement of inertia achievable.The wall relaxation rate has a big effect on the polarization and fundamental sensitivity for the co-magnetometer,but it is often neglected in the experiments.However,there is almost no work about the systematic analysis of the influence factors on the polarization and the fundamental sensitivity of the HOPSERF co-magnetometers.Here we systematically study the polarization and the fundamental sensitivity of 39K-85Rb-21Ne and 133Cs-85Rb-21Ne HOPSERF co-magnetometers with low polarization limit and the wall relaxation rate.The 21Ne number density,the power density and wavelength of pump beam will affect the polarization greatly by affecting the pumping rate of the pump beam.We obtain a general formula on the fundamental sensitivity of the HOPSERF co-magnetometers due to shot-noise and the fundamental sensitivity changes with multiple systemic parameters,where the suitable number density of buffer gas and quench gas make the fundamental sensitivity highest.The fundamental sensitivity 7.5355×10^-11 rad·s^-1·Hz^-1/2 of 133Cs-85Rb-21Ne co-magnetometer is higher than the ultimate theoretical sensitivity 2×10^-10 rad·s^-1·Hz^-1/2 of K-21Ne co-magnetometer.展开更多
An environmentally friendly precursor, adenosine, has been used as a dual source of C and N to synthesize nitrogen-doped carbon catalyst with/without Fe. A hydrothermal carbonization method has been used and water is ...An environmentally friendly precursor, adenosine, has been used as a dual source of C and N to synthesize nitrogen-doped carbon catalyst with/without Fe. A hydrothermal carbonization method has been used and water is the carbonization media. The morphology of samples with/without Fe component has been compared by HRTEM, and the result shows that Fe can promote the graphitization of carbon. Further electro-chemical test shows that the oxygen reduction reaction（ORR） catalytic activity of Fe-containing sample（C–Fe N） is much higher than that of the Fe-free sample（C–N）. Additionally, the intermediates of C–Fe N formed during each synthetic procedure have been thoroughly characterized by multiple methods,and the function of each procedure has been discussed. The C–Fe N sample exhibits high electro-catalytic stability and superior electro-catalytic activity toward ORR in alkaline media, with its half-wave potential 20 mV lower than that of commercial Pt/C（40 wt%）. It is further incorporated into alkaline polymer electrolyte fuel cell（APEFC） as the cathode material and led to a power density of 100 m W/cm;.展开更多
Recent discoveries of dynamic ice Ⅶ and superionic ice highlight the importance of ionic diffusions in discriminating high-pressure(P) water phases.The rare event nature and the chemical bond breaking associated with...Recent discoveries of dynamic ice Ⅶ and superionic ice highlight the importance of ionic diffusions in discriminating high-pressure(P) water phases.The rare event nature and the chemical bond breaking associated with these diffusions,however,make extensive simulations of these processes unpractical to ab initio and inappropriate for force field based methods.Using a first-principles neural network potential,we performed a theoretical study of water at 5-70 GPa and 300-3000 K.Long-time dynamics of protons and oxygens were found indispensable in discriminating several subtle states of water,characterized by proton’s and oxygen ion’s diffusion coefficients and the distribution of proton’s displacements.Within dynamic ice Ⅶ,two types of proton transfer mechanisms,i.e.,translational and rotational transfers,were identified to discriminate this region further into dynamic ice Ⅶ T and dynamic ice Ⅶ R.The triple point between ice Ⅶ,superlonic ice(SI),and liquid exists because the loosening of the bee oxygen skeleton is prevented by the decrease of interatomic distances at high P’s.The melting of ice Ⅶ above ~40 GPa can be understood as a process of two individual steps:the melting of protons and the retarded melting of oxygens,responsible for the forming of SI.The boundary of the dynamic ice VIF and SI lies on the continuation line ice Ⅶ’s melting curve at low P’s.Based on these,a detailed phase diagram is given,which may shed light on studies of water under P’s in a wide range of interdisciplinary sciences.展开更多
Self-intercalated van der Waals magnets,characterized by self-intercalating native atoms into van der Waals layered structures with intrinsic magnetism,exhibit a variety of novel physical properties.Here,using first-p...Self-intercalated van der Waals magnets,characterized by self-intercalating native atoms into van der Waals layered structures with intrinsic magnetism,exhibit a variety of novel physical properties.Here,using first-principles calculations and Monte Carlo simulations,we report a self-intercalated van der Waals ferromagnet,Cr_(3)Ge_(2)Te_(6),which has a high Curie temperature of 492 K.We find that Cr_(3)Ge_(2)Te_(6)is nearly half-metallic with a spin polarization reaching up to 90.9%.Due to the ferromagnetism and strong spin-orbit coupling effect in Cr_(3)Ge_(2)Te_(6),a large anomalous Hall conductivity of 138Ω^(-1)·cm^(-1)and 305Ω^(-1)·cm^(-1)can be realized when its magnetization is along its magnetic easy axis and hard axis,respectively.By doping electrons(holes)into Cr_(3)Ge_(2)Te_(6),these anomalous Hall conductivities can be increased up to 318Ω^(-1)·cm^(-1)(648Ω^(-1)·cm^(-1)).Interestingly,a five-layer Cr_(3)Ge_(2)Te_(6)thin film retains room-temperature ferromagnetism with a higher spin polarization and larger anomalous Hall conductivity.Our study demonstrates that Cr_(3)Ge_(2)Te_(6)is a novel room-temperature self-intercalated ferromagnet with high-spin polarization and large anomalous Hall conductivity,offering great opportunities for designing nano-scale electronic devices.展开更多
基金supported by the National Natural Science Foundation of China (21573167,21633008,91545205)the Innovative Research Team in Wuhan University (2042017kf0232)+1 种基金the National Key Research and Development Program (2016YFB0101203)the Fundamental Research Funds for the Central Universities (2014203020207)
文摘The development of the hydrogen electrode is vital for the application of alkaline polymer electrolyte fuel cells(APEFCs).In this study,a series of Ni(OH)_2 decorated Ni/C catalysts(Ni(OH)_2-Ni/C) were prepared by a three-step electrochemical treatment of Ni/C.The existence of Ni(OH)_2 was demonstrated by X-ray photoelectron spectroscopy(XPS),and the surface molar ratio of Ni(OH)_2/Ni of the samples was estimated via an electrochemical method.The HOR catalytic activity of the catalysts was evaluated by a rotation disk electrode(RDE) method,and a "volcano plot" was established between the HOR exchange current(j0) and the surface molar ratio of Ni(OH)_2/Ni.On top of the "volcano",the surface molar ratio of Ni(OH)_2/Ni is1.1:1,the j0 of which was 6.8 times of that of Ni/C.The stability of the samples toward HOR was evaluated to be good.Our study added a systematic experimental evidence to the HOR research,showing that the HOR catalytic activity of Ni can be deliberately controlled via decoration of Ni(OH)_2,which may help understanding the HOR mechanism on Ni.
基金supported by the National Natural Science Foundation of China(21872108 , 21573167 , 21633008 and 91545205)the National Key Research and Development Program (2016YFB0101203)the Fundamental Research Funds for the Central Universities (2014203020207)
文摘Research on the reaction mechanism of ethanol oxidation reaction(EOR) is important for the development of highly active EOR electro-catalysts. One of the main difficulties in the EOR study is the quantitative analysis of the non-volatile products. Conventional on-line electrochemical flowing transmission infrared spectroscopy(ETIRS) can only collect a part of the carbonate products of EOR in alkaline media, making the further quantitative study impossible. Herein, a new ETIRS system has been designed and prepared by employing a cation-exchange membrane(Nafion) in the sampling hood. The using of the Nafion membrane can prevent the anions crossing over by confining the generated carbonates in the sampling hood without diffusing into the bulk electrolyte. Therefore, the collection efficiency of the carbonate products as well as the test accuracy of the carbonate current efficiency has been significantly improved. The result of CO stripping reaction shows that ca. 100% of the carbonate product is able to be collected in alkaline media by this new system. The influence of the experimental temperature to the carbonate current efficiency has been further studied on Pt/C toward EOR in alkaline media.
基金financially supported by the Natural Science Foundation of Guangdong Province (2022A1515012359)the National Natural Science Foundation of China (21902121)+1 种基金the STU Scientific Research Foundation for Talents (NTF21020)the 2020 Li Ka Shing Foundation Cross-Disciplinary Research Grant (2020LKSFG09A)。
文摘Nafion as a universal polymer ionomer was widely applied for nanocatalysts electrode preparation.However,the effect of Nafion on electrocatalytic performance was often overlooked,especially for CO_(2)electrolysis.Herein,the key roles of Nafion for CO_(2)RR were systematically studied on Cu nanoparticles(NPs)electrocatalyst.We found that Nafion modifier not only inhibit hydrogen evolution reaction(HER)by decreasing the accessibility of H_(2)O from electrolyte to Cu NPs,and increase the CO_(2)concentration at electrocatalyst interface for enhancing the CO_(2)mass transfer process,but also activate CO_(2)molecule by Lewis acid-base interaction between Nafion and CO_(2)to accelerate the formation of^(*)CO,which favor of C–C coupling for boosting C_(2)product generation.Owing to these features,the HER selectivity was suppressed from 40.6%to 16.8%on optimal Cu@Nafion electrode at-1.2 V versus reversible hydrogen electrode(RHE),and as high as 73.5%faradaic efficiencies(FEs)of C_(2)products were achieved at the same applied potential,which was 2.6 times higher than that on bare Cu electrode(~28.3%).In addition,Nafion also contributed to the long-term stability by hinder Cu NPs morphology reconstruction.Thus,this work provides insights into the impact of Nafion on electrocatalytic CO_(2)RR performance.
基金financially supported by the National Key Research and Development Program of China (2016YFB0101203)the National Natural Science Foundation of China (91545205,21633008)
文摘Proton exchange membranes （PEMs） are a key material for proton exchange membrane fuel cells （PEM-FCs）, Non-fluorinated hydrocarbon PEMs are low-cost alternatives to Nation, but limited by the low pro-ton conductivity, because of the weak phase segregation structure and narrow ion-transport channels.Various efforts have been taken to improve the performance of hydrocarbon PEMs, but mostly with com-plex methodologies. Here we demonstrate a simple, yet very efficient method to create phase segrega-tion structure inside a typical hydrocarbon PEM, sulfonated poly（ether ether ketone） （SPEEK）. By sim-ply adding appropriate amounts of water into the DMF solvent, the resulting SPEEK membrane exhibitswidened ion-transport channels, with the phase size of 2.7 nm, as indicated by both molecular dynamic（MD） simulations and transmission electron microscope （TEM） observations, and the proton conductivityis thus improved by 200%. These findings not only further our fundamental understanding of hydrocarbonPEMs, but are also valuable to the development of low-cost and practical fuel cell technologies.
基金supported by the National Basic Research Program(2012CB932800,2012CB215503)the National Science Foundation of China(21125312,21203142)the Doctoral Fund of Ministry of Education of China(20110141130002)
文摘Although most transition metals have been tested as the promoter to Pt for electrocatalysis toward fuel cell reactions,semi-conductor elements,such as Si,have hitherto not been examined.Here we report a simple synthesis of intermetallic Pt2Si electrode using magnetron sputtering and the electrocatalysis toward ethanol oxidation reaction（EOR）.In comparison to Pt,the intermetallic Pt2Si surface turns out to be much more active in catalyzing the EOR：the onset potential shifts negatively by 150 mV,and the current density at 0.6 V increases by a magnitude of one order.Such an enormous enhancement in EOR catalysis is ascribed to the promotion effects of Si,which can not only provide active surface oxygenated species to accelerate the removal of COads,but also strongly alter the electronic property of Pt,as clearly indicated by the core-level shift in XPS spectrum.
基金Project supported by the National Key R&D Program of China(Grant No.2016YFA0301500)the National Natural Science Foundation of China(Grant No.61835013)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant Nos.XDB01020300 and XDB21030300)。
文摘The hybrid optical pumping spin exchange relaxation free(HOPSERF)atomic co-magnetometers make ultrahigh sensitivity measurement of inertia achievable.The wall relaxation rate has a big effect on the polarization and fundamental sensitivity for the co-magnetometer,but it is often neglected in the experiments.However,there is almost no work about the systematic analysis of the influence factors on the polarization and the fundamental sensitivity of the HOPSERF co-magnetometers.Here we systematically study the polarization and the fundamental sensitivity of 39K-85Rb-21Ne and 133Cs-85Rb-21Ne HOPSERF co-magnetometers with low polarization limit and the wall relaxation rate.The 21Ne number density,the power density and wavelength of pump beam will affect the polarization greatly by affecting the pumping rate of the pump beam.We obtain a general formula on the fundamental sensitivity of the HOPSERF co-magnetometers due to shot-noise and the fundamental sensitivity changes with multiple systemic parameters,where the suitable number density of buffer gas and quench gas make the fundamental sensitivity highest.The fundamental sensitivity 7.5355×10^-11 rad·s^-1·Hz^-1/2 of 133Cs-85Rb-21Ne co-magnetometer is higher than the ultimate theoretical sensitivity 2×10^-10 rad·s^-1·Hz^-1/2 of K-21Ne co-magnetometer.
基金financially supported by the National Natural Science Foundation of China(21573167,21633008,91545205,21125312)National Key Research and Development Program(2016YFB0101203)+2 种基金the National Basic Research Program(2012CB932800,2012CB215500)the Doctoral Fund of Ministry of Education of China(20110141130002)the Fundamental Research Funds for the Central Universities(2014203020207)
文摘An environmentally friendly precursor, adenosine, has been used as a dual source of C and N to synthesize nitrogen-doped carbon catalyst with/without Fe. A hydrothermal carbonization method has been used and water is the carbonization media. The morphology of samples with/without Fe component has been compared by HRTEM, and the result shows that Fe can promote the graphitization of carbon. Further electro-chemical test shows that the oxygen reduction reaction（ORR） catalytic activity of Fe-containing sample（C–Fe N） is much higher than that of the Fe-free sample（C–N）. Additionally, the intermediates of C–Fe N formed during each synthetic procedure have been thoroughly characterized by multiple methods,and the function of each procedure has been discussed. The C–Fe N sample exhibits high electro-catalytic stability and superior electro-catalytic activity toward ORR in alkaline media, with its half-wave potential 20 mV lower than that of commercial Pt/C（40 wt%）. It is further incorporated into alkaline polymer electrolyte fuel cell（APEFC） as the cathode material and led to a power density of 100 m W/cm;.
基金Supported by the National Basic Research Program of China under Grant Nos.2016 YFA0300900 and 2017YFA0205003the National Science Foundation of China under Grant Nos.11774003.11634001.11934003,and 11774072.D.Pan also acknowledges the support from Hong Kong Research Grands Council(Nos.ECS-26305017 and GRF-16307618)+1 种基金the Alfred R.Sloan Foundation through the Deep Carbon Observatory(DCO)the Croucher Foundation through the Croucher Innovation Award.
文摘Recent discoveries of dynamic ice Ⅶ and superionic ice highlight the importance of ionic diffusions in discriminating high-pressure(P) water phases.The rare event nature and the chemical bond breaking associated with these diffusions,however,make extensive simulations of these processes unpractical to ab initio and inappropriate for force field based methods.Using a first-principles neural network potential,we performed a theoretical study of water at 5-70 GPa and 300-3000 K.Long-time dynamics of protons and oxygens were found indispensable in discriminating several subtle states of water,characterized by proton’s and oxygen ion’s diffusion coefficients and the distribution of proton’s displacements.Within dynamic ice Ⅶ,two types of proton transfer mechanisms,i.e.,translational and rotational transfers,were identified to discriminate this region further into dynamic ice Ⅶ T and dynamic ice Ⅶ R.The triple point between ice Ⅶ,superlonic ice(SI),and liquid exists because the loosening of the bee oxygen skeleton is prevented by the decrease of interatomic distances at high P’s.The melting of ice Ⅶ above ~40 GPa can be understood as a process of two individual steps:the melting of protons and the retarded melting of oxygens,responsible for the forming of SI.The boundary of the dynamic ice VIF and SI lies on the continuation line ice Ⅶ’s melting curve at low P’s.Based on these,a detailed phase diagram is given,which may shed light on studies of water under P’s in a wide range of interdisciplinary sciences.
基金Project supported by the National Key R&D Program of China(Grant No.2022YFA1403301)the National Natural Science Foundation of China(Grant Nos.12474247 and 92165204)+1 种基金the Guangdong Provincial Key Laboratory of Magnetoelectric Physics and Devices(Grant No.2022B1212010008)the support from the Fundamental Research Funds for the Central Universities,Sun Yat-Sen University(Grant No.24qnpy108)。
文摘Self-intercalated van der Waals magnets,characterized by self-intercalating native atoms into van der Waals layered structures with intrinsic magnetism,exhibit a variety of novel physical properties.Here,using first-principles calculations and Monte Carlo simulations,we report a self-intercalated van der Waals ferromagnet,Cr_(3)Ge_(2)Te_(6),which has a high Curie temperature of 492 K.We find that Cr_(3)Ge_(2)Te_(6)is nearly half-metallic with a spin polarization reaching up to 90.9%.Due to the ferromagnetism and strong spin-orbit coupling effect in Cr_(3)Ge_(2)Te_(6),a large anomalous Hall conductivity of 138Ω^(-1)·cm^(-1)and 305Ω^(-1)·cm^(-1)can be realized when its magnetization is along its magnetic easy axis and hard axis,respectively.By doping electrons(holes)into Cr_(3)Ge_(2)Te_(6),these anomalous Hall conductivities can be increased up to 318Ω^(-1)·cm^(-1)(648Ω^(-1)·cm^(-1)).Interestingly,a five-layer Cr_(3)Ge_(2)Te_(6)thin film retains room-temperature ferromagnetism with a higher spin polarization and larger anomalous Hall conductivity.Our study demonstrates that Cr_(3)Ge_(2)Te_(6)is a novel room-temperature self-intercalated ferromagnet with high-spin polarization and large anomalous Hall conductivity,offering great opportunities for designing nano-scale electronic devices.
