Developing non-precious catalysts as Pt substitutes for electrochemical hydrogen evolution reaction(HER)with superior stability in acidic electrolyte is of critical importance for large-scale,low-cost hydrogen product...Developing non-precious catalysts as Pt substitutes for electrochemical hydrogen evolution reaction(HER)with superior stability in acidic electrolyte is of critical importance for large-scale,low-cost hydrogen production from water.Herein,we report a CoCrFeNiAl high-entropy alloy(HEA)electrocatalyst with self-supported structure synthesized by mechanical alloying and spark plasma sintering(SPS)consolidation.The HEA after HF treatment and in situ electrochemical activation for 4000 cycles of cyclic voltammetry(HF-HEAa2)presents favourable activity with overpotential of 73 mV to reach a current density of 10 mA cm^(2) and a Tafel slope of 39.7 mV dec1.The alloy effect of Al/Cr with Co/Fe/Ni at atomic level,high-temperature crystallization,as well as consolidation by SPS endow CoCrFeNiAl HEA with high stability in 0.5 M H2SO4 solution.The superior performance of HF-HEAa2 is related with the presence of metal hydroxides/oxides groups on HEA.展开更多
Carbide boronizing is a promising approach to obtain fine grained boron carbide based ceramics with improved mechanical properties. In this work, reaction process, microstructural characteristics and mechanical proper...Carbide boronizing is a promising approach to obtain fine grained boron carbide based ceramics with improved mechanical properties. In this work, reaction process, microstructural characteristics and mechanical properties of BxC-TaB2(x = 3.7, 4.9, 7.1) ceramics were comprehensively investigated via this method. Dense BxC-TaB2 ceramics with refined microstructure were obtained from submicro tantalum carbide and boron powder mixtures at 1800℃/50 MPa/5 min by spark plasma sintering. The stoichiometry of boron carbide was determined from lattice parameters and Raman shift. It was found that uniformly distributed TaB2 grains in the BxC matrix is favor of the densification process and restricting grain growth.Besides, planar defects with high density were observed from the as-formed B7.1 C grains and transient stress was considered to contribute to the densification involved with plastic deformation. Microstructural observations indicate the dissolution of oxygen in the TaB2 lattice and most of the B7.1 C/TaB2 phase boundaries were clean. Owing to the highly faulted structure and finer grain size, as-obtained BxC-TaB2 ceramics exhibit high Vickers hardness(33.3–34.4 GPa at 9.8 N) and relatively high flexural strength ranging from 440 to 502 MPa.展开更多
高熵合金(HEA)不仅是有潜力的电化学析氧反应的催化剂,也可以用作电催化剂的载体.本文采用HF处理高熵合金使其羟基化(HF-HEA),然后再进行原位电化学活化,从而得到一种新型高效的CoCrFeNiAlHEA负载的Co,Fe,Ni-(O)OH电催化剂.该电催化剂仅...高熵合金(HEA)不仅是有潜力的电化学析氧反应的催化剂,也可以用作电催化剂的载体.本文采用HF处理高熵合金使其羟基化(HF-HEA),然后再进行原位电化学活化,从而得到一种新型高效的CoCrFeNiAlHEA负载的Co,Fe,Ni-(O)OH电催化剂.该电催化剂仅用240 m V超电势就可产生10 m A cm^-2的电流密度,Tafel斜率为52.7 m V dec^-1.本研究发现Cr和Al促进了HEA/Co,Fe,Ni-(O)OH的电化学活性.Cr和Al不仅增加了HF-HEA表面Ni(OH)x/Ni OOH的Ni^3+/Ni^2+摩尔比例,而且在电化学活化过程中Cr^3+和Al^3+的溶出增加了HF-HEA的电化学活性表面积.展开更多
基金financially supported by the National Natural Science Foundation of China (51521001 and 51832003)the Fundamental Research Funds for the Central Universities
基金National Natural Science Foundation of China(51521001,51832003)Fundamental Research Funds for the Central Universities(WUT:2019IB002)National College Students Innovation and Entrepreneurship Training Program(2019-C-B1-25).
文摘Developing non-precious catalysts as Pt substitutes for electrochemical hydrogen evolution reaction(HER)with superior stability in acidic electrolyte is of critical importance for large-scale,low-cost hydrogen production from water.Herein,we report a CoCrFeNiAl high-entropy alloy(HEA)electrocatalyst with self-supported structure synthesized by mechanical alloying and spark plasma sintering(SPS)consolidation.The HEA after HF treatment and in situ electrochemical activation for 4000 cycles of cyclic voltammetry(HF-HEAa2)presents favourable activity with overpotential of 73 mV to reach a current density of 10 mA cm^(2) and a Tafel slope of 39.7 mV dec1.The alloy effect of Al/Cr with Co/Fe/Ni at atomic level,high-temperature crystallization,as well as consolidation by SPS endow CoCrFeNiAl HEA with high stability in 0.5 M H2SO4 solution.The superior performance of HF-HEAa2 is related with the presence of metal hydroxides/oxides groups on HEA.
基金financially supported by the National Natural Science Foundation of China (Nos. 51521001 and 51832003)
文摘Carbide boronizing is a promising approach to obtain fine grained boron carbide based ceramics with improved mechanical properties. In this work, reaction process, microstructural characteristics and mechanical properties of BxC-TaB2(x = 3.7, 4.9, 7.1) ceramics were comprehensively investigated via this method. Dense BxC-TaB2 ceramics with refined microstructure were obtained from submicro tantalum carbide and boron powder mixtures at 1800℃/50 MPa/5 min by spark plasma sintering. The stoichiometry of boron carbide was determined from lattice parameters and Raman shift. It was found that uniformly distributed TaB2 grains in the BxC matrix is favor of the densification process and restricting grain growth.Besides, planar defects with high density were observed from the as-formed B7.1 C grains and transient stress was considered to contribute to the densification involved with plastic deformation. Microstructural observations indicate the dissolution of oxygen in the TaB2 lattice and most of the B7.1 C/TaB2 phase boundaries were clean. Owing to the highly faulted structure and finer grain size, as-obtained BxC-TaB2 ceramics exhibit high Vickers hardness(33.3–34.4 GPa at 9.8 N) and relatively high flexural strength ranging from 440 to 502 MPa.
基金financially supported by the National Natural Science Foundation of China(51521001 and 51832003)the Fundamental Research Funds for the Central Universities(WUT:2019IB002)the Students Innovation and Entrepreneurship Training Program(2019-C-B1-25)。
文摘高熵合金(HEA)不仅是有潜力的电化学析氧反应的催化剂,也可以用作电催化剂的载体.本文采用HF处理高熵合金使其羟基化(HF-HEA),然后再进行原位电化学活化,从而得到一种新型高效的CoCrFeNiAlHEA负载的Co,Fe,Ni-(O)OH电催化剂.该电催化剂仅用240 m V超电势就可产生10 m A cm^-2的电流密度,Tafel斜率为52.7 m V dec^-1.本研究发现Cr和Al促进了HEA/Co,Fe,Ni-(O)OH的电化学活性.Cr和Al不仅增加了HF-HEA表面Ni(OH)x/Ni OOH的Ni^3+/Ni^2+摩尔比例,而且在电化学活化过程中Cr^3+和Al^3+的溶出增加了HF-HEA的电化学活性表面积.
