Controllable synthesis of crystal-amorphous heterostructures in transition metal phosphide and enhancement mechanism for overall water splitting

Abstract

The crystal-amorphous (c-a) heterostructure is a promising structure for electrocatalysts in water electrolysis. In this study, stable, efficient, and abundant c-a interfaces were formed by synchronously synthesizing crystalline FeP and amorphous MoP on foam ferrum by controlling the crystalline phase transition temperature. In 1 M KOH, the a-MoP/FeP@FF catalyst showed overpotentials of 75 mV and 253 mV for HER and OER processes, respectively, at a current density of j10. The Tafel slopes were small at 60 mV∙dec−1 and 77 mV∙dec−1 for HER and OER, respectively. Theoretical calculations indicate that the c-a interface optimizes the overall electronic structure, enabling Mo and Fe to have excellent HER and OER activity, respectively. The two types of active sites collaborate fully to promote overall water splitting. This study confirms that the c-a heterostructure can significantly enhance the catalytic performance of transition metal phosphides and explains the mechanism of enhanced catalytic activity. This synthesis method and reaction mechanism not only apply to other transition metal phosphides but also provide reference for other types of catalysts.