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 (CO 2 ) in the atmosphere, the bismuth vanadate (BiVO 4 )-based photoanode for photoelectrochemical (PEC) water oxidation has been considered as a promising candidate of power supply for CO 2 reduction because of its low price and relatively narrow band gap. Nevertheless, the PEC capability of BiVO 4 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/BiVO 4 /SnO 2 nanosheet array (NSA) photoanodes. Benefiting from the high light-harvesting ability of NSAs, effective separation of electron–hole pairs for the BiVO 4 /SnO 2 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 BiVO 4 . Coupled with the Au nanoparticle cathode, the PEC cell exhibited a 90.0% faradaic efficiency for CO 2 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/BiVO 4 /SnO 2 NSAs with remarkably enhanced PEC performance could provide clean power for the modern society via reduction reaction on pollution gases.