Distinctive ternary CdS/Ni2P/g-C3N4 composite for overall water splitting: Ni2P accelerating separation of photocarriers

Abstract Efficient overall water splitting over semiconductor photocatalyst is vital but difficult for resolving the energy and environmental crises. In this report, a novel transition metal phosphide Ni 2 P-based ternary CdS/Ni 2 P/g-C 3 N 4 composite was constructed for achieving efficient overall water splitting activity under visible light (λ > 420 nm). The H 2 and O 2 evolution ratios are 15.56 and 7.75 μmol·g –1  h –1 over CdS/Ni 2 P/g-C 3 N 4 with 3 wt% Ni 2 P, respectively, which is 4.02 times higher than that of binary type II CdS/g-C 3 N 4 . The separation efficiency of photocarriers of CdS/Ni 2 P/g-C 3 N 4 is enhanced through greatly speeding up the transfer efficiency of electrons from the conduction band of g-C 3 N 4 to that of CdS using Ni 2 P as electron-bridge, proved by the photoluminescence, transient photocurrent measurements and electrochemical impendence spectroscopy. The significant finding of this paper sheds light on the important role of transition metal phosphide as electron-bridge to connect the two conduction bands of type II semiconductor heterojuction for strengthening the separation efficiency of photocarriers.