The discovery of efficient,selective,and stable electrocatalysts can be a key point to produce the largescale chemical fuels via electrochemical CO_(2) reduction(ECR).In this study,an earth-abundant and nontoxic ZnO-b...The discovery of efficient,selective,and stable electrocatalysts can be a key point to produce the largescale chemical fuels via electrochemical CO_(2) reduction(ECR).In this study,an earth-abundant and nontoxic ZnO-based electrocatalyst was developed for use in gas-diffusion electrodes(GDE),and the effect of nitrogen(N)doping on the ECR activity of ZnO electrocatalysts was investigated.Initially,a ZnO nanosheet was prepared via the hydrothermal method,and nitridation was performed at different times to control the N-doping content.With an increase in the N-doping content,the morphological properties of the nanosheet changed significantly,namely,the 2D nanosheets transformed into irregularly shaped nanoparticles.Furthermore,the ECR performance of Zn O electrocatalysts with different N-doping content was assessed in 1.0 M KHCO_(3) electrolyte using a gas-diffusion electrode-based ECR cell.While the ECR activity increased after a small amount of N doping,it decreased for higher N doping content.Among them,the N:ZnO-1 h electrocatalysts showed the best CO selectivity,with a faradaic efficiency(FE_(CO))of 92.7%at-0.73 V vs.reversible hydrogen electrode(RHE),which was greater than that of an undoped Zn O electrocatalyst(FE_(CO)of 63.4%at-0.78 V_(RHE)).Also,the N:ZnO-1 h electrocatalyst exhibited outstanding durability for 16 h,with a partial current density of-92.1 mA cm^(-2).This improvement of N:ZnO-1 h electrocatalyst can be explained by density functional theory calculations,demonstrating that this improvement of N:ZnO-1 h electrocatalyst comes from(ⅰ)the optimized active sites lowering the free energy barrier for the rate-determining step(RDS),and(ⅱ)the modification of electronic structure enhancing the electron transfer rate by N doping.展开更多
Photoelectrochemical(PEC)water splitting is regarded as the most promising method to generate“green hydrogen”,and zinc oxide(ZnO)has been identified as one of the promising candidates for PEC water splitting owing t...Photoelectrochemical(PEC)water splitting is regarded as the most promising method to generate“green hydrogen”,and zinc oxide(ZnO)has been identified as one of the promising candidates for PEC water splitting owing to its straddling band alignment with the water redox level.However,its PEC performance is limited due to its wide bandgap and anticipated by photocorrosion in an aqueous medium.In this work,we present strategic improvements in the PEC water splitting performance of ZnO nanowires(NWs)by nitrogen(N)-doping along with photostability by the core–shell deposition of a NiOOH cocatalyst.Highly crystalline hierarchical ZnO NWs were fabricated on Si NWs(ZnO-Si HNWs)using a metal organic chemical vapor deposition approach.The NWs were then N-doped by annealing in an NH_(3) atmosphere.The N-doped ZnO-Si HNWs(N:ZnO-Si HNWs)showed enhanced visible light absorption,and suppressed recombination of the photogenerated carriers.As compared to ZnO-Si HNWs(0.045 m A cm^(-2) at 1.23 V vs RHE),the N:ZnO-Si HNWs(0.34 m A cm^(-2) at 1.23 V vs RHE)annealed in NH^(3) ambient for 3 h at 600℃showed 7.5-fold enhancement in the photocurrent density.NiOOH-deposited N:ZnO-Si HNW photoanodes with a photostability of 82.21%over 20000 s showed 10.69-fold higher photocurrent density(0.48 m A cm^(-2) at 1.23 V vs RHE)than ZnO-Si HNWs.展开更多
基金supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) (Grant Nos.2018R1A6A1A03024334,2019R1A2C1007637,2021M3I3A1082880,2021R1I1A1A01044174)the Basic Science Research Capacity Enhancement Project through Korea Basic Science Institute (Grant No.2019R1A6C1010024)。
文摘The discovery of efficient,selective,and stable electrocatalysts can be a key point to produce the largescale chemical fuels via electrochemical CO_(2) reduction(ECR).In this study,an earth-abundant and nontoxic ZnO-based electrocatalyst was developed for use in gas-diffusion electrodes(GDE),and the effect of nitrogen(N)doping on the ECR activity of ZnO electrocatalysts was investigated.Initially,a ZnO nanosheet was prepared via the hydrothermal method,and nitridation was performed at different times to control the N-doping content.With an increase in the N-doping content,the morphological properties of the nanosheet changed significantly,namely,the 2D nanosheets transformed into irregularly shaped nanoparticles.Furthermore,the ECR performance of Zn O electrocatalysts with different N-doping content was assessed in 1.0 M KHCO_(3) electrolyte using a gas-diffusion electrode-based ECR cell.While the ECR activity increased after a small amount of N doping,it decreased for higher N doping content.Among them,the N:ZnO-1 h electrocatalysts showed the best CO selectivity,with a faradaic efficiency(FE_(CO))of 92.7%at-0.73 V vs.reversible hydrogen electrode(RHE),which was greater than that of an undoped Zn O electrocatalyst(FE_(CO)of 63.4%at-0.78 V_(RHE)).Also,the N:ZnO-1 h electrocatalyst exhibited outstanding durability for 16 h,with a partial current density of-92.1 mA cm^(-2).This improvement of N:ZnO-1 h electrocatalyst can be explained by density functional theory calculations,demonstrating that this improvement of N:ZnO-1 h electrocatalyst comes from(ⅰ)the optimized active sites lowering the free energy barrier for the rate-determining step(RDS),and(ⅱ)the modification of electronic structure enhancing the electron transfer rate by N doping.
基金supported by the National Research Foundation of Korea(NRF),funded by the Ministry of Education,Science,and Technology(2018R1A6A1A03024334,NRF-2019R1A2C1006360)supported by Basic Science Research Capacity Enhancement Project through Korea Basic Science Institute(National Research Facilities and Equipment Center)grant funded by the Ministry of Education(2019R1A6C1010024)。
文摘Photoelectrochemical(PEC)water splitting is regarded as the most promising method to generate“green hydrogen”,and zinc oxide(ZnO)has been identified as one of the promising candidates for PEC water splitting owing to its straddling band alignment with the water redox level.However,its PEC performance is limited due to its wide bandgap and anticipated by photocorrosion in an aqueous medium.In this work,we present strategic improvements in the PEC water splitting performance of ZnO nanowires(NWs)by nitrogen(N)-doping along with photostability by the core–shell deposition of a NiOOH cocatalyst.Highly crystalline hierarchical ZnO NWs were fabricated on Si NWs(ZnO-Si HNWs)using a metal organic chemical vapor deposition approach.The NWs were then N-doped by annealing in an NH_(3) atmosphere.The N-doped ZnO-Si HNWs(N:ZnO-Si HNWs)showed enhanced visible light absorption,and suppressed recombination of the photogenerated carriers.As compared to ZnO-Si HNWs(0.045 m A cm^(-2) at 1.23 V vs RHE),the N:ZnO-Si HNWs(0.34 m A cm^(-2) at 1.23 V vs RHE)annealed in NH^(3) ambient for 3 h at 600℃showed 7.5-fold enhancement in the photocurrent density.NiOOH-deposited N:ZnO-Si HNW photoanodes with a photostability of 82.21%over 20000 s showed 10.69-fold higher photocurrent density(0.48 m A cm^(-2) at 1.23 V vs RHE)than ZnO-Si HNWs.
