Developing novel earth-abundant electrocatalysts with highly efficient and durable activity for the oxygen evolution reaction (OER) is in great demand in the clean hydrogen production. Herein, an amorphous mixed cobalt–iron hydroxide (CoFe(OH)_x) with a uniform hollow hierarchical structure is exploited and applied in the OER. The amorphous structure can supply abundant defects and reaction sites, and the hollow hierarchical microspheres with numerous vertically grown nanosheets on the shell can provide sufficient contact between electrolyte and active species, thus exposing abundant accessible active sites for electrocatalysis. As a result, the as-prepared CoFe(OH)_x exhibits a superior electrocatalytic OER activity in alkaline medium with a low overpotential of 293 mV at a current density of 10 mA cm⁻² and a small Tafel slope of 67.4 mV dec⁻¹. CoFe(OH)_x also shows significantly enhanced OER activity compared to Co(OH)₂ owing to its optimized electronic structure and conductivity tuned by the introduction of Fe. The turnover frequency of CoFe(OH)_x (55.7 × 10⁻³ s⁻¹) is 8.8 times larger than that of Co(OH)₂ (6.3 × 10⁻³ s⁻¹). This work paves a way for rational design of hollow structured bimetal hydroxides with enhanced electrocatalytic performance.

中文翻译：

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非晶态的CoFe（OH）x空心分级结构：氧气释放反应的高效耐用电催化剂

在清洁氢气的生产中，迫切需要开发对氧气释放反应（OER）具有高效和持久活性的新型地球富集电催化剂。在本文中，具有均匀空心分级结构的非晶态混合钴铁氢氧化物（CoFe（OH）_x）被开发出来并应用于OER。无定形结构可以提供大量的缺陷和反应位点，并且在外壳上具有许多垂直生长的纳米片的空心分层微球可以在电解质和活性物质之间提供足够的接触，从而暴露出大量可触及的活性位点以进行电催化。结果，制备的CoFe（OH）_x在10 mA cm ^-2的电流密度和67.4 mV dec ^-1的小Tafel斜率的碱性介质中，具有293 mV的低过电势，在碱性介质中显示出优异的电催化OER活性。与Co（OH）₂相比，CoFe（OH）_x还显示出显着增强的OER活性，这归因于其优化的电子结构和通过引入Fe调节的电导率。CoFe（OH）_x（55.7×10 ^-3 s ^-1）的周转频率是Co（OH）₂（6.3×10 ^-3 s ^-1）的8.8倍）。这项工作为合理设计具有增强的电催化性能的中空结构双金属氢氧化物铺平了道路。