Recent progress of transition metal nitrides for efficient electrocatalytic water splitting

The hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) constitute the two main processes in electrochemical water splitting to produce high-purity hydrogen and oxygen as alternatives to fossil fuel. Catalysts are crucial to high-efficiency conversion of water to hydrogen and oxygen. Although transition metal nitrides (TMNs) are promising HER and OER catalysts due to the unique electronic structure and high electrical conductivity, single-phase nitrides have inferior activity compared to Pt-group metals because of the unsatisfactory metal-hydrogen (M-H) bonding strength. TMNs-based composites in combination with other metals, carbon materials, and metallic compounds have been demonstrated to possess improved catalytic properties because the modified electronic structure leads to balanced M-H bonding strength, synergistic effects, and improved electrochemical stability. Herein, recent progress pertaining to TMNs is reviewed from the perspective of advanced catalysts for electrochemical water splitting. The challenges and future opportunities confronting TMNs-based catalysts are also discussed.