不同碱溶液表面处理对稀土镁镍基储氢合金的影响

摘要

The rare earth-Mg-Ni (RE-Mg-Ni) based hydrogen storage alloy was treated in the same concentration of 6 mol·L-1 LiOH,NaOH,and KOH aqueous solutions.The effects of different alkaline solutions and the treating times on the morphologies and compositions of the alloy surfaces and the electrochemical characters of the alloy electrodes have been investigated.The alloy electrode treated in 6 mol ·L-1 NaOH for 10 min shows the best electrochemical properties.LiOH solution could remove Mg element and diminish the oxygen species on the alloy surface effectively.The alloy surface layer formed in LiOH solution was more unfavorable for H adsorption and desorption but had good resistance for further corrosion.The alloy electrode treated with 6 mol· L-1 LiOH had the best cyclic durability.With the increase of the treating time,the reduction of the discharge capacity was the largest for the alloy electrode treated with 6 mol· L-1 NaOH solution because of the dissolution of a large amount of rare earth (RE) and Al elements,and the loose surface layer containing mainly rare earth hydroxides.%采用相同浓度即6 mol·L-1 LiOH、NaOH和KOH对稀土镁镍基储氢合金进行表面处理,研究了不同碱溶液和不同处理时间对合金表面形貌、组成和电极电化学性能的影响.研究表明,合金经6 mol· L-1 NaOH溶液处理10 min后具有最好的综合电化学性能.但随着处理时间的延长,采用6 mol· L-1 NaOH溶液处理的合金放电容量衰减明显,实验证明这是由合金表面稀土元素和Al元素的大量溶解进入碱溶液造成的.3种碱溶液比较,LiOH溶液能有效去除合金表面镁元素减少合金在碱溶液处理过程中的氧化,虽然形成的表面不利于H在合金表面的吸脱附,却能有效提高合金在碱溶液中的抗腐蚀能力,提高合金的循环稳定性.