Recent Development of Transition Metal-based Amorphous Electrocatalysts for Water Splitting

Electrochemical water splitting, including the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), is a promising hydrogen production technology. However, in practice, the high overpotentials and sluggish reaction kinetics associated with the anode OER process are the major obstacles to the smooth progress of electrocatalytic water splitting. Amorphous electrocatalysts, a crucial family of functional materials, exhibit unexpected performance due to their special short-range ordered and long-range disordered atom arrangement, abundant defect sites and adjustable composition. To date, while numerous recent publications showcase promising results for transition metal-based amorphous electrocatalysts, including amorphous metal phosphide and metal hydroxide electrocatalysts with remarkable HER and OER properties respectively, the utilization of single-function HER or OER catalysts tends to augment system complexity for water electrolysis, thereby escalating the cost of hydrogen production. In this regard, amorphous HER/OER bifunctional electrocatalysts are desired. In this review, we summarize the recent development on transition metal-based amorphous catalysts for electrochemical water splitting. The design strategies for constructing HER/OER bifunctional transition-metal-based amorphous electrocatalysts are highlighted here, also including the exploration of relationship between catalyst structures and their remarkably improved performance. Finally, the possibilities of amorphous bifunctional catalysts for practical industrial applications are evaluated and future research direction are suggested. This review summarizes and discusses recent progress in various design and synthesis strategies of transition metal-based amorphous materials, such as metal oxides/hydroxides, phosphides, and borides. Additionally, the relationship between catalyst microstructures and their enhanced performance were strengthened. Specifically, these innovative catalyst design strategies are summarized, including morphological control, defect engineering, heterostructure design and surface reconstruction. image