Basics, developments, and strategies of transition metal phosphides toward electrocatalytic water splitting: beyond noble metal catalysts

Abstract

Electrocatalysts used for water electrolysis have been widely studied to decrease the overpotential and increase their stability and economic feasibility. Among the various candidates, transition metal phosphides (TMPs) display notably high electrocatalytic activity and stability under both acidic and alkaline conditions owing to the incorporation of P. As the number of studies focusing on TMPs has rapidly increased owing to their remarkable physicochemical properties, it is necessary to investigate the most recent advances in TMPs for hydrogen and oxygen evolution reactions (HER and OER, respectively). In addition to recent progress, this article arranges and reviews the HER and OER mechanisms, activity origins, synthetic processes that use various P sources, and effective strategies for enhancing the catalytic performance of TMPs. Furthermore, the current challenges faced by TMPs are discussed, indicating the route to be undertaken. Through this review article, we aim to guide future perspectives on TMP-based electrocatalysts for HER and OER.