Ni对非晶态Co-B合金电化学储氢性能的影响

Influence of Ni on Electrochemical Hydrogen Storage Property of Amorphous Co-B Alloy

通过化学还原共沉积法引入元素Ni制备了三元非晶态Co-Ni-B合金,并研究了元素Ni对非晶Co-B合金电化学储氢性能的影响。结果表明,含镍23.8at%非晶态Ni-Co-B合金的可逆放电容量约为250mAh/g,较非晶Co-B合金下降约20mAh/g,但循环稳定性二者相同,即在650mA/g的高电流密度下循环60次容量几乎保持不变。但进一步增加Ni含量,含镍35.8at%的非晶态Ni-Co-B合金的放电容量和循环稳定性都较不掺杂时发生大幅下降。但是,元素Ni的引入能有效抑制高电流密度充电过程中Co-B合金表面大量氢气的析出,减小电极放电电压平台和容量在循环过程中的波动。这可能得益于以下2个原因:(1)非晶Ni-Co-B合金对水分解的电催化活性降低;(2)吸附态氢原子在非晶Ni-Co-B合金基体中的扩散速度高于在Co-B合金中的扩散速度。

A series of ternary amorphous Ni-Co-B alloys were prepared by a chemical reduction codeposition method with Ni introduction and influence of Ni on electrochemical hydrogen storage property of the amorphous Co-B alloys was investigated. Results show that at a charge/discharge rate of 650 mA/g, the amorphous Ni-Co-B alloy with Ni content of 23.8 at% has a reversible discharge capacity of about 250 mAh/g, 20 mAh/g lower than amorphous Co-B alloy does. Discharge capacity of the two samples keeps almost unchanged after 60 cycles. Nevertheless, the amorphous Ni-Co-B alloy with Ni content of 35.8 at% shows much lower discharge capacity and capacity retention during cycling than amorphous Co-B alloy does under the same condition. However, a positive effect of Ni on electrochemical hydrogen storage of Co-B alloy is also found, i.e. element Ni could suppress H2 evolution on the surface of the amorphous Co-B alloy at a high charge rate and reduce the fluctuation of discharge potential plateau and discharge capacity during cycling. It could be attributed to that Ni decreases electrocatalytic activity for H20 dissociation on the surface and improves hydrogen diffusion rate for amorphous Co-B alloy bulk.