Performance Prediction of Multiple Photoanodes Systems for Unbiased Photoelectrochemical Water Splitting

Photoelectrochemical (PEC) water splitting without an external bias is a promising approach to convert solar energy into chemical energy. Metal oxide semiconductors, such as TiO2, BiVO4, and Fe2O3, are widely used as front photoanode in tandem cells due to their high photovoltage, light transmittance, and excellent stability in aqueous solutions as well as their low cost. However, connecting a photoanode with a photocathode directly with the same area will lead to power mismatch due to the lower photocurrent density of the photoanode side. This Letter describes a basic computational model to determine the optimal structure of a tandem cell composed of multiple photoanodes and a photocathode by considering the photocurrent density and the cost of per-unit area of photoanodes. TiO2, BiVO4, and Fe2O3 are used to prove the feasibility of this computational model. In addition, the fill factor of output power in tandem cell is obtained to evaluate whether the power of photoanode and photocathode is appropriately matched. The optimal structure of multiphotoanode is a two-layer TiO2||BiVO4 in an equal area, which is predicted by this computational model and confirmed by experimental results.