ZnTe/SnS2 heterojunction for photo-electrocatalysis of CO2 to CO

Photoelectrochemical (PEC) reduction of CO₂ is a promising strategy to convert CO₂ into chemical fuels for alleviating environmental crisis. However, modulation of photo-electrocatalytic processes to obtain a desired performance remains challenges due to the complicated PEC kinetics for CO₂ reduction. Herein, we present ZnTe/SnS₂ type II heterojunction photo-catalyst that facilitates light absorption for PEC reduction of CO₂ toward CO production with an improved selectivity and photo-stability compared to the pure ZnTe electrode. The study of charge transfer at the ZnTe/SnS₂ heterojunction interface with density functional theory (DFT) calculation and scanning electrochemical microscopy (SECM) characterization reveals that the photo-generated charge by ZnTe can flow quickly through the ZnTe/SnS₂ interface to participate CO₂ reduction reaction driven by the built-in electric potential of the type II heterojunction. The ZnTe/SnS₂ photocathode achieves a photocurrent density of 2.35 mA∙cm⁻² and a CO faradic efficiency of 87 % at −1.78 V (vs. Fc⁺/Fc) under standard illumination in a CO₂-saturated tetrabutylammonium hexafluorophosphate in acetonitrile electrolyte, and retains approximately 87 % of its initial photocurrent after one-hour of continuous illumination test. Consequently, a generation rate of 56.0 μM∙cm^−2∙h⁻¹ for CO can be obtained on this electrode.