Design and assembly of TZCS/PO/Ni2P-MnOx composite with homojunction plus protection layer plus cocatalyst structure for photocatalytic overall water splitting

Herein, we synthesize a phosphate (PO) protection layer and various cocatalysts (Ni2P and MnOx) on the twinned Zn0.5Cd0.5S (TZCS) photocatalyst by a two-step photochemical synthesis method. The initial photocatalytic hydrogen production rate of TZCS/PO/Ni2P-MnOx composite with homojunction + protection layer + cocatalyst structure reaches 1.36 mmol h-1 g-1, which is about 1.72 and 2.56 times higher than WZCS/PO/Ni2PMnOx and ZZCS/PO/Ni2P-MnOx photocatalysts (WZCS and ZZCS are abbreviations of wurtzite Zn0.5Cd0.5S and zinc-blende Zn0.5Cd0.5S solid solutions), respectively. The average photocatalytic hydrogen and oxygen production rate of TZCS/PO/Ni2P-MnOx are 1.21 mmol h-1 g-1 and 0.59 mmol h-1 g-1 within 12 h, which are close to the theoretical ratio of 2: 1. The excellent photocatalytic overall water splitting performance can be rationalized by the separation, transmission and application process of photogenerated electron-hole pairs, which can be efficiently separated and transported by the homojunction structure and further penetrate the PO protection layer, so that they have a greater chance of being captured by the Ni2P and MnOx cocatalysts, which can be used as the active catalytic site for the H2 and O2 production reaction, respectively.

Automated summary

A phosphate (PO) protection layer and various cocatalysts (Ni2P and MnOx) were synthesized on the twinned Zn0.5Cd0.5S (TZCS) photocatalyst using a two-step photochemical synthesis method. The TZCS/PO/Ni2P-MnOx composite with homojunction + protection layer + cocatalyst structure exhibited a higher initial photocatalytic hydrogen production rate compared to other photocatalysts. The excellent overall water splitting performance of TZCS/PO/Ni2P-MnOx was attributed to the efficient separation and transmission of photogenerated electron-hole pairs by the homojunction structure, as well as their capture by Ni2P and MnOx cocatalysts.