A highly efficient photocatalytic methanol fuel cell based on non-noble metal photoelectrodes: Study on its energy band engineering via experimental and density functional theory method

Abstract Photocatalytic fuel cell (PFC) is considered as a new energy source due to its cooperative conversion capacity of both solar energy and chemical energy. In this work, a highly efficient ZnO/BiVO4 photoanode is synthesized on fluorine-doped tin oxide (FTO) by continuous electrodeposition and hydrothermal method. Then, a visible-light driven dual photoelectrode photocatalytic methanol fuel cell (PMFC) consisted of the ZnO/BiVO4 photoanode and Cu2O photocathode is designed and constructed. Electrochemical results show that the short-circuit current density (Jsc), the open-circuit voltage (Voc) and the maximum power output (Pmax) of the prepared PMFC can reach 5.18 mA/cm2, 0.82 V and 0.91 mW/cm2 under simulated solar irradiation, respectively. Surface photovoltage (SPV) transients reveal the charge transporting dynamics in semiconductor heterojunction, and photoelectrochemical experiments further confirmed the light-induced methanol oxidation and oxygen reduction process. Under illumination, an interior potential difference between n-type ZnO/BiVO4 and p-type Cu2O actuate the electrons on the photoanode to transfer through the external circuit to photocathode, combining with the holes and generating electricity. The built-in electric field from the ZnO (002) surface to the BiVO4 (001) surface is confirmed based on the theoretical calculation of density functional theory (DFT).