In recent years, applications of metal-organic frameworks (MOFs) in electrocatalysis, including hydrogen and oxygen evolution reactions, have attracted increasing attention for renewable energy conversion. Herein, the fabrication of core-shell structured Co₃O₄@MOF-74 catalysts is proposed and realized with the tunable thickness of MOF shell layers, where Co₃O₄ nanowire arrays prefabricated on Ni foam are employed as the template as well as the metal source to react with organic ligands to achieve the MOF layers. Importantly, the optimized Co₃O₄@MOF-74 structures exhibit much enhanced catalytic activities towards oxygen evolution reaction (OER), requiring an impressively low overpotential of 285 mV to afford a current density of 50 mA cm⁻² together with a small Tafel slope of 43 mV/dec, as compared with the pristine Co₃O₄ sample. By investigating the Co₃O₄@MOF-74 structure after OER stability test, the conversion of MOF-74 into cobalt hydroxide shell layers is thoroughly characterized and confirmed, suggesting the in situ electrochemical conversion of MOF structures during the electrochemical process. All these results do not only uncover the changes in crystalline and chemical structures of MOFs for electrocatalytic reactions, but also help to comprehend and design novel MOFs as efficient and robust electrocatalysts for practical utilization.

近年来，金属有机框架（MOF）在电催化中的应用，包括氢和氧的释放反应，已引起可再生能源转化的越来越多的关注。在此，提出并实现了MOF壳层厚度可调的核壳结构Co ₃ O ₄ @ MOF-74催化剂的制备方法，该方法以Ni泡沫上预制的Co ₃ O ₄纳米线阵列为模板，以及金属源与有机配体反应以形成MOF层。重要的是，优化的Co ₃ O ₄@ MOF-74结构对氧释放反应（OER）表现出大大增强的催化活性，需要极低的285 mV超电势才能提供50 mA cm ^-2的电流密度以及43 mV / dec的小Tafel斜率，因为与原始的Co ₃ O ₄样品进行比较。通过对OER稳定性测试后的Co ₃ O ₄ @ MOF-74结构进行研究，可以彻底表征和确认MOF-74向氢氧化钴壳层的转化，这表明它是原位的MOF结构在电化学过程中的电化学转化。所有这些结果不仅揭示了用于电催化反应的MOF的晶体和化学结构的变化，而且还有助于理解和设计新颖的MOF，将其作为有效，耐用的电催化剂用于实际应用。