Dynamically activating Ni-based catalysts with self-anchored mononuclear Fe for efficient water oxidation

Abstract

Rational design of pre-catalysts to in situ form active structures is vital for efficient catalysis, especially when surface reconstruction occurs. Here we report a surface engineering strategy to form highly active surfaces on Ni-based catalysts (NiMo in this work) under oxygen evolution reaction (OER) conditions. The NiMo catalyst is decorated with mononuclear Fe-O5 species on its surface. During the OER reconstruction process, the Fe-O5 species will further bond to the surface of Ni oxyhydroxide reconstructed from NiMo. In situ X-ray absorption spectroscopy and theoretical calculations reveal that the Fe-O5 species anchored on Ni oxyhydroxide are easily oxidized under OER conditions, which compensates for the charges of Ni and increases the reducibility of Ni active sites. As a result, such a catalyst shows a 33-fold increase in intrinsic activity compared with the NiMo catalyst, which also decreases the full cell voltage by 0.72 V at 500 mA cm−2 in an anion exchange membrane electrolyzer compared with the IrO2 catalyst.