Facile and Large-Area Preparation of Porous Ag₃PO₄ Photoanodes for Enhanced Photoelectrochemical Water Oxidation

Photoelectrochemical (PEC) water splitting is a promising approach for renewable energy, where the development of efficient photoelectrodes, especially photoanodes for water oxidation is still challenging. In this paper, we report the novel solution-processed microcrystalline Ag 3 PO 4 photoanodes with tunable porosity depending on the reaction time. These porous Ag 3 PO 4 films were grown on large-area (4.5 × 4.5 cm 2 ) silver substrates via an air-exposed and room-temperature immersion reaction. Enhanced light absorption abilities were exhibited by the synthesized Ag 3 PO 4 films with optimized porosity resulted from prolonged reaction times (≥20 h), due to which appreciable water splitting performance was demonstrated when they were utilized as photoanodes. Particularly, the highly porous 20 h Ag 3 PO 4 photoanode presented a photocurrent density of around 4.32 mA/cm 2, which is nearly three times higher than that of the nonporous 1 h Ag 3 PO 4 photoanode (1.48 mA/cm 2 ) at 1 V vs Ag/AgCl. Moreover, superior stability of the 20 h Ag 3 PO 4 photoanode has also been confirmed by the 5 h successive PEC water splitting experiment. Therefore, both the scalable and facile fabrication method, and considerable photoactivity and stability of these Ag 3 PO 4 photoanodes together suggest their great potential for efficient solar-to-fuel energy conversion and other PEC applications.