Fluorination-enabled Reconstruction of NiFe Electrocatalysts for Efficient Water Oxidation
Qiucheng Xu, Hao Jiang, Xuezhi Duan, Zheng Jiang, Yanjie Hu, Shannon W. Boettcher, Weiyu Zhang, Shaojun Guo, Chunzhong Li
Abstract
Developing low-cost and efficient electrocatalysts to accelerate oxygen evolution reaction (OER) kinetics is vital for water and carbon-dioxide electrolyzers. The fastest-known water oxidation catalyst, Ni(Fe)OxHy, usually produced through an electrochemical reconstruction of precatalysts under alkaline condition, has received substantial attention. However, the reconstruction in the reported catalysts usually leads to a limited active layer and poorly controlled Fe-activated sites. Here, we demonstrate a new electrochemistry-driven F-enabled surface-reconstruction strategy for converting the ultrathin NiFeOxFy nanosheets into an Fe-enriched Ni(Fe)OxHy phase. The activated electrocatalyst shows a low OER overpotential of 218 ± 5 mV at 10 mA cm–2 and a low Tafel slope of 31 ± 4 mV dec–1, which is among the best for NiFe-based OER electrocatalysts. Such superior performance is caused by the effective formation of the Fe-enriched Ni(Fe)OxHy active-phase that is identified by operando Raman spectroscopy and the substantially improved surface wettability and gas-bubble-releasing behavior.