Zhang Xinyu, Feng Chao, Dong Bin, Liu Chenguang, Chai Yongming
State Key Laboratory of Heavy Oil Processing, College of Chemistry and Chemical Engineering, China University of Petroleum (East China), Qingdao, 266580, P. R. China.
Adv Mater. 2023 Mar;35(13):e2207066. doi: 10.1002/adma.202207066. Epub 2023 Feb 13.
The design and maintenance of highly active sites in an acidic environment is vital and challenging for the oxygen evolution reaction (OER). In this work, it is found that the obtained CoO under high applied potential can be stable on MnO host in acidic environment, which may act as an effective means to solve the instability of cobalt-based electrocatalyst. The significant improvement of acidic OER activity (6.9 times) and stability (46.4 times) of 90-Co-MnO (treated by molten salt with more Co deposition sites) demonstrates the advantages of this approach. In situ Raman and the Pourbaix diagram suggest that the enhanced performance derives from the stable presence of CoO at the voltage >1.8 V versus reversible hydrogen electrode (RHE). However, when the potential is <1.8 V, the corresponding other cobalt species is too unstable to facilitate the OER. Density functional theorycalculations reveal that the deposited cobalt oxides can act as active sites, thus effectively reducing the reaction energy barrier of the rate-determining step. This work provides a new perspective for enhancing the stability of cobalt-based electrocatalyst. In the future, the dual consideration of applied potential and stable species of active element in the Pourbaix diagram may be a new direction for developing acid-stable electrocatalysts.
在酸性环境中设计和维持高活性位点对于析氧反应（OER）至关重要且具有挑战性。在这项工作中，发现高外加电势下获得的CoO在酸性环境中可稳定存在于MnO载体上，这可能是解决钴基电催化剂不稳定性的有效手段。90-Co-MnO（经熔盐处理，具有更多Co沉积位点）的酸性OER活性显著提高（6.9倍），稳定性提高（46.4倍），证明了这种方法的优势。原位拉曼光谱和Pourbaix图表明，性能增强源于相对于可逆氢电极（RHE）在电压>1.8 V时CoO的稳定存在。然而，当电势<1.8 V时，相应的其他钴物种过于不稳定，无法促进OER。密度泛函理论计算表明，沉积的钴氧化物可作为活性位点，从而有效降低速率决定步骤的反应能垒。这项工作为提高钴基电催化剂的稳定性提供了新的视角。未来，在Pourbaix图中同时考虑外加电势和活性元素的稳定物种可能是开发耐酸电催化剂的新方向。
