Stabilization of a Mn-Co oxide during oxygen evolution in alkaline media

Improving the stability of electrocatalysts for the oxygen evolution reaction (OER) through materials design has received less attention than improving their catalytic activity. We explored the effects of Mn addition to a cobalt oxide for stabilizing the catalyst by comparing single phase CoO_x and (Co_0.7Mn_0.3)O_x films electro­deposited in alkaline solution. The obtained disordered films were classified as layered oxides using X-ray absorption spectroscopy (XAS). The CoO_x films showed a constant decrease in the catalytic activity during cycling, confirmed by oxygen detection, while that of (Co_0.7Mn_0.3)O_x remained constant within error as measured by electrochemical metrics. These trends were rationalized based on XAS analysis of the metal oxidation states, which were Co^2.7+ and Mn^3.7+ in the bulk and similar near the surface of (Co_0.7Mn_0.3)O_x, before and after cycling. Thus, Mn in (Co_0.7Mn_0.3)O_x successfully stabilized the bulk catalyst material and its surface activity during OER cycling. The development of stabilization approaches is essential to extend the durability of OER catalysts.

相较于提升析氧反应（Oxygen Evolution Reaction, OER）电催化剂的催化活性，通过材料设计优化其稳定性的研究受关注程度远低于前者。本研究通过对比在碱性溶液中电沉积得到的单相CoOₓ与(Co₀.₇Mn₀.₃)Oₓ薄膜，探究了向氧化钴中添加锰对催化剂的稳定效果。经X射线吸收光谱（X-ray Absorption Spectroscopy, XAS）表征，所得无序薄膜被归类为层状氧化物。循环测试过程中，CoOₓ薄膜的催化活性持续衰减，该现象经氧气检测得到验证；而(Co₀.₇Mn₀.₃)Oₓ薄膜的催化活性在误差范围内保持稳定，该结果通过电化学测试指标得以证实。通过对金属氧化态的XAS分析，可合理解释上述实验趋势：循环测试前后，(Co₀.₇Mn₀.₃)Oₓ块体中的金属氧化态分别为Co²·⁷+与Mn³·⁷+，其表面附近的氧化态与块体保持一致。由此可见，(Co₀.₇Mn₀.₃)Oₓ中的锰元素可在OER循环测试过程中，有效稳定催化剂块体材料及其表面催化活性。开发高效稳定化策略对延长OER催化剂的耐久性至关重要。