Porous ZnO@ZnSe nanosheet array for photoelectrochemical reduction of CO2

Photoelectrochemical (PEC) cell is a meaningful way to fulfil carbon dioxide (CO2) conversion to valueadded chemicals, but the exploration of ideal photocathode materials with high photo-conversion efficiency remains a challenge. Herein, porous ZnO@ZnSe core/shell nanosheet array on fluorine doped-tin oxide (FTO) glass is synthesized via dissolution-recrystallization mechanism by using ZnO nanosheet array as the template, and is used for the first time as the photocathode for PEC reduction of CO2. The effect of ZnSe loading amount on PEC responses of composite electrode is investigated in detail. Under the irradiation of visible light, the optimized ZnO@ZnSe photocathode exhibits onset potentials at 0.39 V (vs. RHE) in CO2-purged 0.5M NaHCO3 solution and achieves the photocurrent of 1.17 mA cm(-2) at -0.11 V (vs. RHE). Interestingly, the competitive H-2 evolution reaction can be suppressed effectively and thereby the selectivity for CO2 reduction reactions especially for CO formation is increased when the applied voltage became more negative. The faradic efficiency of CO increases dramatically from 4.2% at 0.2 V to 52.9% at -0.4 V and the electron selectivity for CO2 reduction increases from 70.1% to 96.6% accordingly. These results demonstrate that ZnO@ZnSe composite electrode can work as promising photocathode for efficient CO2 reduction. (C) 2018 Elsevier Ltd. All rights reserved.