Porous ZnO@ZnSe nanosheet array for photoelectrochemical reduction of CO2

Photoelectrochemical (PEC) cell is a meaningful way to fulfil carbon dioxide (CO 2 ) conversion to value-added 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 CO 2 . 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 CO 2 -purged 0.5 M NaHCO 3 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 CO 2 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 CO 2 reduction increases from 70.1% to 96.6% accordingly. These results demonstrate that ZnO@ZnSe composite electrode can work as promising photocathode for efficient CO 2 reduction.