La and Mn-doped cobalt spinel oxygen evolution catalyst for proton exchange membrane electrolysis

Finding electrocatalysts using earth-abundant materials as a replacement to iridium for oxygen-evolution reaction (OER) in proton exchange membrane water electrolyzer (PEMWE) represents a critical step in reducing the cost for green hydrogen production. We report here a nanofibrous cobalt spinel catalyst co-doped with lanthanum and manganese prepared from zeolitic imidazolate framework embedded in electrospun polymer fiber. The catalyst demonstrated a low overpotential of 353 millivolts at 10 milliamperes per square centimeter and a low degradation for OER over 360 hours in acidic electrolyte. PEMWE containing this catalyst at anode demonstrated a current density of 2000 milliamperes per square centimeter at 2.47 volts (Nafion® 115 membrane) or 4000 milliamperes per square centimeter at 3.00 volt (Nafion® 212 membrane), and low degradation in accelerated-stress-test. High-resolution electronic microscopy and operando X-ray absorption spectroscopy, combined with computational modeling, revealed the different functions of lanthanum, manganese, and cobalt in enabling enhanced activity, conductivity and acidic tolerance within the OER operating window.

以地球储量丰富的材料替代质子交换膜水电解槽（proton exchange membrane water electrolyzer, PEMWE）中析氧反应（oxygen-evolution reaction, OER）所用的铱基电催化剂，是降低绿氢生产成本的关键环节。本文报道了一种由嵌入静电纺丝聚合物纤维的沸石咪唑酯骨架（zeolitic imidazolate framework, ZIF）制备的共掺杂镧与锰的纳米纤维状钴尖晶石催化剂。该催化剂在10毫安每平方厘米的电流密度下展现出353毫伏的低过电位，且在酸性电解质中历经360小时的析氧反应测试后降解程度极低。将该催化剂用作阳极的质子交换膜水电解槽，在搭载纳菲昂®115膜时可在2.47伏特下实现2000毫安每平方厘米的电流密度，搭载纳菲昂®212膜时则可在3.00伏特下达到4000毫安每平方厘米的电流密度，且在加速应力测试中表现出优异的抗降解特性。结合高分辨电子显微镜、原位X射线吸收光谱与计算建模的表征结果，研究揭示了镧、锰与钴在析氧反应工作窗口内，分别对提升催化活性、导电性与酸性耐受性的不同作用机制。