Transition metal phosphides as noble-metal-alternative co-catalysts for solar hydrogen production

Hydrogen (H2) emerges as a highly promising contender for replacing conventional fossil fuels due to its high combustion heat value and net-zero greenhouse gas emission. Photocatalytic H2 generation through semiconductor-based water splitting represents a clean and sustainable technology in the field. Developing highly efficient and abundant source semiconductor materials, along with co-catalysts, is paramount in achieving the industrial-level H2 evolution by photocatalysis technology. In recent years, transition-metal phosphides (TMPs) have emerged as powerful co-catalysts for photocatalytic reactions due to their cost-effectiveness, abundant reserves in the earth's crust, and favorable physicochemical properties, thus offering a viable alternative to conventional precious metal materials. In this review, we first provide a concise historical overview and outline the structure of TMPs. The synthetic strategies of TMPs are subsequently systematically analyzed based on diverse phosphorus sources. Additionally, this review provides a comprehensive summary of the recent research endeavors conducted on TMPs as potential photocatalytic co-catalysts for efficient hydrogen generation through photocatalysis. Eventually, this review briefly addresses the prevailing key concerns, proposed countermeasures, and forthcoming challenges associated with enhancing the efficiency of photocatalytic H2 evolution in TMPs.