Highly Efficient Photoelectrochemical Reduction of CO2 at Low Applied Voltage Using 3D Co-Pi/BiVO4/SnO2 Nanosheet Array Photoanodes.

To solve the increasing level of carbon dioxide (CO2) in the atmosphere, the bismuth vanadate (BiVO4)-based photoanode for photoelectrochemical (PEC) water oxidation has been considered as a promising candidate of power supply for CO2 reduction because of its low price and relatively narrow band gap. Nevertheless, the PEC capability of BiVO4 photoelectrodes is restricted by the short carrier diffusion length, undesirable electron transport ability, and slow oxygen evolution rate. To overcome these shortcomings, we design and fabricate a novel ternary hybrid composite of 3D Co-Pi/BiVO4/SnO2 nanosheet array (NSA) photoanodes. Benefiting from the high light-harvesting ability of NSAs, effective separation of electron-hole pairs for the BiVO4/SnO2 heterojunction, and fast water oxidation rate of Co-Pi, the hybrid system exhibited 20.2-times enhancement in photocurrent and a significant cathodic shift about the onset potential of water oxidation reaction compared with single BiVO4. Coupled with the Au nanoparticle cathode, the PEC cell exhibited a 90.0% faradaic efficiency for CO2 reduction under a small applied voltage of 1.10 V and saved more than 50% of electric energy compared to the general electrochemical cell. We believe that the fabricated 3D Co-Pi/BiVO4/SnO2 NSAs with remarkably enhanced PEC performance could provide clean power for the modern society via reduction reaction on pollution gases.