Synthesis and characterization of WO3 photoanodes for efficient photoelectrochemical water splitting

Choosing suitable photoanode materials is the most critical aspect for photoelectrochemical (PEC) water splitting. The low efficiency of PEC water splitting photoanodes restricts their widespread application for large-scale H 2 production. Herein, we prepared WO 3 photoanodes with controllable structures via hydrothermal-electrophoretic deposition and seed-mediated hydrothermal synthesis, achieving ex situ assembly and in situ growth on FTO glass substrates. Under simulated sunlight irradiation, the photoelectric current density of the WO 3 photoanode prepared by in situ hydrothermal synthesis exceeds 1.0 mA/cm² (at 1.23 V vs. RHE), significantly higher than that of the WO 3 photoanode prepared by ex situ assembly (which is less than 0.3 mA/cm² at 1.23 V vs. RHE). By contrast, the in situ preparation of the WO 3 photoanode using tungsten powder and H 2 O 2 as raw materials exhibits the enhanced photocurrent density of 1.27 mA/cm² at 1.23 V vs. RHE. The excellent PEC performance of the resulting sample could be attributed to the ordered charge transport channels from the two-dimensional (2D) nanoplates structure, the enhanced electron-hole pairs separation from the superior crystallinity of WO 3 and the strong binding between the WO 3 nanoplates and the FTO substrate. Additionally, the effect of calcination temperature on the PEC performance of the prepared WO 3 was further investigated. This work provides a way for the synthesis of environmentally friendly and cost-effective photoanodes for efficient photoelectrochemical water splitting.