Electrocatalytic CO_(2)reduction into CO has been regarded as one of the most promising strategies for sustainable carbon cycles at ambient conditions,but still faces challenges to achieve both high product selectivit...Electrocatalytic CO_(2)reduction into CO has been regarded as one of the most promising strategies for sustainable carbon cycles at ambient conditions,but still faces challenges to achieve both high product selectivity and large current density.Here,we report a Ni_(4)N/Ni_(3)ZnC_(0.7)heterostructured electrocatalyst embedded in accordion-like N-doped carbon through a simple molten salt annealing strategy.The optimal Ni_(4)N/Ni_(3)ZnC_(0.7)electrocatalyst achieves a high CO Faraday efficiency of 92.3%and a large total current density of-15.8 m A cm^(-2)at-0.8 V versus reversible hydrogen electrode,together with a long-term stability about 30 h.Density functional theory results reveal that the energy barrier for*COOH intermediate formation largely decreased on Ni_(4)N/Ni_(3)ZnC_(0.7)heterostructure compared with Ni_(4)N and Ni_(3)ZnC_(0.7),thus giving rise to enhanced activity and selectivity.A rechargeable Zn-CO_(2)battery is further assembled with Ni_(4)N/Ni_(3)ZnC_(0.7)catalyst as the cathode,which shows a maximum power density of 0.85 mW cm^(-2)and excellent stability.展开更多
锌-空气电池(ZAB)因其能量密度高、环境友好、成本低以及安全性高而备受关注.然而,空气电极上的氧还原反应(ORR)动力学缓慢,严重限制了ZAB的输出功率.尽管铂基催化剂展现出优异的ORR催化活性,但高昂的成本制约其大规模商业化应用.因此,...锌-空气电池(ZAB)因其能量密度高、环境友好、成本低以及安全性高而备受关注.然而,空气电极上的氧还原反应(ORR)动力学缓慢,严重限制了ZAB的输出功率.尽管铂基催化剂展现出优异的ORR催化活性,但高昂的成本制约其大规模商业化应用.因此,迫切需要开发高效、低成本的ORR电催化剂.研究表明,具有原子分散Co-N4活性位点的Co-N-C单原子催化剂是理想的ORR非贵金属催化剂,但其仍然存在与反应关键中间体结合能较高的难题.目前的研究主要通过调控单原子配位环境与增大活性位点密度来提高Co-N-C催化剂的活性,但如何精确控制中心金属电子结构以及避免高温下金属原子的团聚仍面临巨大挑战.除了单原子活性位点外,催化剂载体的键合结构、电荷分布状态亦会影响载体本身和单原子位点的催化活性.然而,现有的研究主要聚焦于单原子位点或无金属催化剂单方面活性的提升,关于它们之间的相互作用对于催化性能影响的研究相对很少.为了进一步提高Co单原子催化剂的催化活性,本文通过简单的模板法与NH3二次处理策略制备了氮掺杂缺陷碳负载的Co-N_(5)位点单原子催化剂.电感耦合等离子体发射光谱结果表明,单原子Co的金属负载量高达2.57 wt%.此外,相比于未经过NH3二次处理的Co-Nx/HC样品,Co-N_(5)/DHC样品在电子顺磁共振谱中g=2.003处呈现出更明显的共振信号,在C 1s高分辨谱中具有更低的C-C(sp2杂化)/C-N(sp3杂化)比例以及明显增加的吡啶氮信号,证实了Co-N_(5)/DHC显著提升的氮掺杂碳缺陷浓度并具有丰富的边界/缺陷位点.同时,X射线吸收谱与球差矫正透射电子显微镜结果表明所制备的样品为原子分散的Co-N_(5)结构,从而证明成功制备了缺陷氮掺杂碳耦合Co-N_(5)位点单原子催化剂.电化学测试结果表明,缺陷氮掺杂碳耦合Co-N_(5)位点后表现较好的ORR性能,半波电位达到0.877 V,明显高于Co-Nx/HC对比样品和商业化Pt/C催化剂.Koutecky-Levich曲线和旋转盘环电极测试结果表明,Co-N_(5)/DHC催化剂的高效4e-反应路径.且在10000次的加速老化测试中,Co-N_(5)/DHC半波电位仅降低了7 m V,稳定性优于Pt/C.以Co-N_(5)/DHC为阴极催化剂组装的ZAB开路电压为1.45 V,峰值输出功率密度能够达到160.7 m W cm^(-2),并能提供766.2 m A h gZn-1的比容量,展现出较高的应用前景.密度泛函理论计算表明,Co-N_(5)位点与缺陷氮掺杂碳的相互作用诱导Co中心位点电子的重新分布,降低了ORR反应能垒.综上,本文为设计与合成高性能的Co单原子催化剂,用于先进的可再生能源转换系统提供了一种新思路.展开更多
High performance of the generation,stabilization and manipulation of magnetic skyrmions prompts the application of topological multilayers in spintronic devices.Skyrmions in synthetic antiferromagnets(SAF)have been co...High performance of the generation,stabilization and manipulation of magnetic skyrmions prompts the application of topological multilayers in spintronic devices.Skyrmions in synthetic antiferromagnets(SAF)have been considered as a promising alternative to overcome the limitations of ferromagnetic skyrmions,such as the skyrmion Hall effect and stray magnetic field.Here,by using the Lorentz transmission electron microscopy,the interconversion between the single domain,labyrinth domain and skyrmion state can be observed by the combined manipulation of electric current and magnetic field in a Hall balance(a SAF with the core structure of[Co/Pt]_(4)/NiO/[Co/Pt]_(4)showing perpendicular magnetic anisotropy).Furthermore,high-density room temperature skyrmions can be stabilized at zero field while the external stimulus is removed and the skyrmion density is tunable.The generation and manipulation method of skyrmions in Hall balance in this study opens up a promising way to engineer SAF-skyrmion-based memory devices.展开更多
Nickel-nitrogen-carbon single-atom catalysts have attracted widespread interest for CO_(2)electroreduction but they suffer from poor stability.Herein,we report on the preparation of Cl-and N-doped porous carbon nanosh...Nickel-nitrogen-carbon single-atom catalysts have attracted widespread interest for CO_(2)electroreduction but they suffer from poor stability.Herein,we report on the preparation of Cl-and N-doped porous carbon nanosheets with atomically dispersed NiN_(4)Cl active sites(NiN_(4)Cl-ClNC)through a molten-salt-assisted pyrolysis strategy.The optimized NiN_(4)Cl-ClNC catalyst delivers exceptional CO_(2)conversion activity with outstanding stability for over 220 h at−0.7 V versus RHE and a high CO Faradaic efficiency of 98.7%at a CO partial current density of 12.4 mA cm^(−2).Moreover,NiN_(4)Cl-ClNC displays a remarkable CO partial current density of approximately 349.4 mA cm^(−2)in flow-cell,meeting the requirements of industrial applications.Operando attenuated total reflectance surface-enhanced infrared absorption spectroscopy and density functional theory calculations are used to understand the outstanding activity and stability.Results reveal that the introduced axial Ni-Cl bond on the Ni center and Cl─C bond on the carbon support synergetically induce electronic delocalization,which not only stabilizes Ni against leaching but also facilitates the formation of the COOH*intermediate that is found to be the rate-determining step.展开更多
Even though various nickel-nitrogen-carbon(Ni-N-C)combinations are prospective low-cost catalysts for the CO_(2)electroreduction reaction(CO_(2)RR),which is one avenue for attaining carbon neutrality,the detailed role...Even though various nickel-nitrogen-carbon(Ni-N-C)combinations are prospective low-cost catalysts for the CO_(2)electroreduction reaction(CO_(2)RR),which is one avenue for attaining carbon neutrality,the detailed role of different N species has hardly been investigated.Here,we report a hollow porous N-doped carbon nanofiber with NiNX-pyridinic N active species(denoted as h-Ni-N-C)developed using a facile electrospinning and SiO_(2)space-confined pyrolysis strategy.The NiNX-pyridinic N species are facilely generated during the pyrolysis process,giving rise to enhanced activity and selectivity for the CO_(2)RR.The optimized h-Ni-N-C exhibits a high CO Faradaic efficiency of 91.3%and a large current density of−15.1 mA cm^(−2)at−0.75 V versus reversible hydrogen electrode in an H-cell.Density functional theory(DFT)results show that NiN4-pyridinic N species demonstrate a lower free energy for the catalyst's rate-determining step than isolated NiN4 and pyridinic N species,without affecting the desorption of CO∗intermediate.展开更多
基金financially supported by the National Key Research and Development Program,China(2018YFB1502503)the 2021 Talent Introduction Project of Chongqing Medical and Pharmaceutical College(ygz2021104)。
文摘Electrocatalytic CO_(2)reduction into CO has been regarded as one of the most promising strategies for sustainable carbon cycles at ambient conditions,but still faces challenges to achieve both high product selectivity and large current density.Here,we report a Ni_(4)N/Ni_(3)ZnC_(0.7)heterostructured electrocatalyst embedded in accordion-like N-doped carbon through a simple molten salt annealing strategy.The optimal Ni_(4)N/Ni_(3)ZnC_(0.7)electrocatalyst achieves a high CO Faraday efficiency of 92.3%and a large total current density of-15.8 m A cm^(-2)at-0.8 V versus reversible hydrogen electrode,together with a long-term stability about 30 h.Density functional theory results reveal that the energy barrier for*COOH intermediate formation largely decreased on Ni_(4)N/Ni_(3)ZnC_(0.7)heterostructure compared with Ni_(4)N and Ni_(3)ZnC_(0.7),thus giving rise to enhanced activity and selectivity.A rechargeable Zn-CO_(2)battery is further assembled with Ni_(4)N/Ni_(3)ZnC_(0.7)catalyst as the cathode,which shows a maximum power density of 0.85 mW cm^(-2)and excellent stability.
文摘锌-空气电池(ZAB)因其能量密度高、环境友好、成本低以及安全性高而备受关注.然而,空气电极上的氧还原反应(ORR)动力学缓慢,严重限制了ZAB的输出功率.尽管铂基催化剂展现出优异的ORR催化活性,但高昂的成本制约其大规模商业化应用.因此,迫切需要开发高效、低成本的ORR电催化剂.研究表明,具有原子分散Co-N4活性位点的Co-N-C单原子催化剂是理想的ORR非贵金属催化剂,但其仍然存在与反应关键中间体结合能较高的难题.目前的研究主要通过调控单原子配位环境与增大活性位点密度来提高Co-N-C催化剂的活性,但如何精确控制中心金属电子结构以及避免高温下金属原子的团聚仍面临巨大挑战.除了单原子活性位点外,催化剂载体的键合结构、电荷分布状态亦会影响载体本身和单原子位点的催化活性.然而,现有的研究主要聚焦于单原子位点或无金属催化剂单方面活性的提升,关于它们之间的相互作用对于催化性能影响的研究相对很少.为了进一步提高Co单原子催化剂的催化活性,本文通过简单的模板法与NH3二次处理策略制备了氮掺杂缺陷碳负载的Co-N_(5)位点单原子催化剂.电感耦合等离子体发射光谱结果表明,单原子Co的金属负载量高达2.57 wt%.此外,相比于未经过NH3二次处理的Co-Nx/HC样品,Co-N_(5)/DHC样品在电子顺磁共振谱中g=2.003处呈现出更明显的共振信号,在C 1s高分辨谱中具有更低的C-C(sp2杂化)/C-N(sp3杂化)比例以及明显增加的吡啶氮信号,证实了Co-N_(5)/DHC显著提升的氮掺杂碳缺陷浓度并具有丰富的边界/缺陷位点.同时,X射线吸收谱与球差矫正透射电子显微镜结果表明所制备的样品为原子分散的Co-N_(5)结构,从而证明成功制备了缺陷氮掺杂碳耦合Co-N_(5)位点单原子催化剂.电化学测试结果表明,缺陷氮掺杂碳耦合Co-N_(5)位点后表现较好的ORR性能,半波电位达到0.877 V,明显高于Co-Nx/HC对比样品和商业化Pt/C催化剂.Koutecky-Levich曲线和旋转盘环电极测试结果表明,Co-N_(5)/DHC催化剂的高效4e-反应路径.且在10000次的加速老化测试中,Co-N_(5)/DHC半波电位仅降低了7 m V,稳定性优于Pt/C.以Co-N_(5)/DHC为阴极催化剂组装的ZAB开路电压为1.45 V,峰值输出功率密度能够达到160.7 m W cm^(-2),并能提供766.2 m A h gZn-1的比容量,展现出较高的应用前景.密度泛函理论计算表明,Co-N_(5)位点与缺陷氮掺杂碳的相互作用诱导Co中心位点电子的重新分布,降低了ORR反应能垒.综上,本文为设计与合成高性能的Co单原子催化剂,用于先进的可再生能源转换系统提供了一种新思路.
基金supported by the Science Center of the National Science Foundation of China(Grant No.52088101)the National Natural Science Foundation of China(Grant Nos.11874408,52130103,51901025,and 11904025)+1 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB33030100)the Youth Innovation Promotion Association of Chinese Academy of Sciences(Grant No.CAS Y201903)。
文摘High performance of the generation,stabilization and manipulation of magnetic skyrmions prompts the application of topological multilayers in spintronic devices.Skyrmions in synthetic antiferromagnets(SAF)have been considered as a promising alternative to overcome the limitations of ferromagnetic skyrmions,such as the skyrmion Hall effect and stray magnetic field.Here,by using the Lorentz transmission electron microscopy,the interconversion between the single domain,labyrinth domain and skyrmion state can be observed by the combined manipulation of electric current and magnetic field in a Hall balance(a SAF with the core structure of[Co/Pt]_(4)/NiO/[Co/Pt]_(4)showing perpendicular magnetic anisotropy).Furthermore,high-density room temperature skyrmions can be stabilized at zero field while the external stimulus is removed and the skyrmion density is tunable.The generation and manipulation method of skyrmions in Hall balance in this study opens up a promising way to engineer SAF-skyrmion-based memory devices.
基金Sichuan Science and Technology Program,Grant/Award Number:2023YFH0026。
文摘Nickel-nitrogen-carbon single-atom catalysts have attracted widespread interest for CO_(2)electroreduction but they suffer from poor stability.Herein,we report on the preparation of Cl-and N-doped porous carbon nanosheets with atomically dispersed NiN_(4)Cl active sites(NiN_(4)Cl-ClNC)through a molten-salt-assisted pyrolysis strategy.The optimized NiN_(4)Cl-ClNC catalyst delivers exceptional CO_(2)conversion activity with outstanding stability for over 220 h at−0.7 V versus RHE and a high CO Faradaic efficiency of 98.7%at a CO partial current density of 12.4 mA cm^(−2).Moreover,NiN_(4)Cl-ClNC displays a remarkable CO partial current density of approximately 349.4 mA cm^(−2)in flow-cell,meeting the requirements of industrial applications.Operando attenuated total reflectance surface-enhanced infrared absorption spectroscopy and density functional theory calculations are used to understand the outstanding activity and stability.Results reveal that the introduced axial Ni-Cl bond on the Ni center and Cl─C bond on the carbon support synergetically induce electronic delocalization,which not only stabilizes Ni against leaching but also facilitates the formation of the COOH*intermediate that is found to be the rate-determining step.
基金This work was financially supported by National Key Research and Development Program of China(2018YFB1502503).
文摘Even though various nickel-nitrogen-carbon(Ni-N-C)combinations are prospective low-cost catalysts for the CO_(2)electroreduction reaction(CO_(2)RR),which is one avenue for attaining carbon neutrality,the detailed role of different N species has hardly been investigated.Here,we report a hollow porous N-doped carbon nanofiber with NiNX-pyridinic N active species(denoted as h-Ni-N-C)developed using a facile electrospinning and SiO_(2)space-confined pyrolysis strategy.The NiNX-pyridinic N species are facilely generated during the pyrolysis process,giving rise to enhanced activity and selectivity for the CO_(2)RR.The optimized h-Ni-N-C exhibits a high CO Faradaic efficiency of 91.3%and a large current density of−15.1 mA cm^(−2)at−0.75 V versus reversible hydrogen electrode in an H-cell.Density functional theory(DFT)results show that NiN4-pyridinic N species demonstrate a lower free energy for the catalyst's rate-determining step than isolated NiN4 and pyridinic N species,without affecting the desorption of CO∗intermediate.
