Surface states modulation of ZnTe via ultrathin ZnO layer as efficient photocathodes for CO2 reduction reaction

Surface states strongly affect charge transfer at the semiconductor/electrolyte interface and thus the total power conversion efficiency of photoelectrochemical CO2 reduction. In this study, we report surface states modulation of ZnTe via ultrathin ZnO layer formed with a one-step hydrothermal method. The resulting photocathode achieved an impressive performance (−7.70 mA cm−2, 93.88% CO selectivity at −2.56 V vs. Fc+/Fc) and stability (10 hours) in CO2-saturated acetonitrile with 0.1 M TBAPF6 electrolyte. Detailed investigation including electrochemical impedance spectroscopy and DFT calculation reveals the surface modification of ZnTe with ultrathin ZnO layer reduces the energy disorder, thereby increasing the electron utilization involved in the CO2 reduction reaction. This work provides an in-depth analysis of the charge transfer process at the semiconductor/electrolyte interface from the perspective of surface states and has the potential to stimulate further excellent research in this area.