Transition metal-phosphorus-based materials for electrocatalytic energy conversion reactions

Transition metal-phosphorus-based materials (TM-Ps) represent a broad range of systems from transition metal-phosphorus-carbon (TM-P-C) to transition metal phosphide, phosphate and phosphonate, which have attracted considerable attention due to their great potential in electrochemical energy conversion and storage technologies, such as water electrolysis, fuel cells and metal-air batteries. Recent studies have proven that TM-P-C can act as an efficient oxygen reduction reaction (ORR) catalyst in the cathodic compartment of fuel cells. Transition metal phosphides (TMPs) are explored for hydrogen evolution reaction (HER) with high activity and stability over a wide pH range of 0-14. In addition, TMPs are found to exhibit striking electrocatalytic performance for the oxygen evolution reaction (OER) in alkaline media. Relevant research into transition metal phosphate and phosphonate is relatively scarce, but several studies prove their potential in the field of electrocatalytic OER. Herein, this review focuses on the recent progress in TM-Ps, with the aim of giving a systematic summary of their fabrication, characterization, as well as catalytic performance and mechanisms in a series of key energy conversion reactions including ORR, HER and OER. Remarks on the perspectives and challenges for future development of energy-related applications are finally provided.