Recent advances of anion regulated NiFe-based electrocatalysts for water oxidation

Increasing energy demand has spurred extensive research on the development of efficient and pollution-free alternative energy conversion and storage technologies. Water oxidation is a critically limiting anodic reaction of electrochemical water splitting and has been a research hotspot. However, significantly high overpotentials are usually required to overcome the large energy barriers of water oxidation. NiFe-based electrocatalysts have been suggested to be prospective candidates towards water oxidation, but improvement of their intrinsic activity still demands in-depth investigations. Over the past decades, anionic regulation has attracted increasing attention as a strategy to enhance the intrinsic activity of NiFe-based oxides/(oxy) hydroxides through tuning the electronic structures of cation active sites. This review focuses primarily on the recent advances of anion regulated NiFe-based electrocatalysts (NiFe oxides/(oxy)hydroxides) for water oxidation. Specifically, we highlight the water oxidation activity that is associated with different synthesis strategies and structural characterization studies of various NiFe oxides/(oxy) hydroxides regulated by different anions. By reviewing the advantages and limitations of these synthesis strategies, the future developing directions of NiFe-based energy materials are also prospected.