Construction homojunction and co-catalyst in ZnIn2S4 photoelectrode by Co ion doping for efficient photoelectrochemical water splitting

The performance of ZnIn2S4 for photoelectrocatalytic (PEC) water splitting is commonly limited by a large amount of recombination of photo-generated carriers in surface and bulk. In this work, the Co2+ is in-corporated into ZnIn2S4 through one-pot hydrothermal method. The deeply doped Co2+ can form a homojunction with the Mg-doped ZnIn2S4 for promoting the separation and transfer of carriers in the bulk via changing the gradient energy level. In addition, the Co2+ on the surface can be used as reaction sites for water oxidation to promote the utilization efficiency of the charge at the surface, which act as a co-catalyst for oxygen production. The dual effect of Co2+ doping makes the ZnIn2S4 homojunction achieve a significant photocurrent density of 0.92 mA/cm(2) at 1.23 V vs. RHE, which is 7.49 times than that of pure ZnIn2S4. The charge separation efficiency (eta(bulk)) and charge transfer efficiency (eta(surface)) of ZnIn2S4 homojunction are 2.94 times and 2.45 times than ZnIn2S4, which can reach to 33.4% and 58.5%, respectively. Therefore, this work can stimulate ongoing interest in designing doped photoelectrodes for water splitting with multiple effects. (C) 2021 Elsevier B.V. All rights reserved.