Partial Oxidation-Engineered Dendritic α-Fe2O3@Fe Photoanode: Enhanced Photoelectrochemical Water-Splitting Performance and Pt-Modified Stability

As a renewable energy source, solar energy holds significant potential for addressing future energy and environmental challenges. Concurrently, hydrogen (H2), as a clean and renewable energy carrier, has garnered substantial attention. Photoelectrocatalytic water splitting to produce H2 represents an emerging green technology for converting solar energy into hydrogen energy, which has been highly valued by researchers. The key to advancing this technology lies in identifying photoelectrode materials with high catalytic activity and stability. In this study, dendritic α-Fe was synthesized via electrodeposition at the optimal potential of −1.4 V vs. Ag/AgCl for 300 s, and the photoelectrocatalytic performance of α-Fe2O3@Fe was enhanced through partial oxidation annealing at 300 °C for 6 h. This approach effectively addressed the issue of the short carrier transport distance in α-Fe2O3. The resulting partially oxidized α-Fe2O3@Fe(300 °C, 6 h) exhibited a photocurrent density of 281.1 μA/cm2 at +0.55 V vs. Ag/AgCl, which was 2.23 times higher than that of the fully oxidized dendritic α-Fe2O3(500 °C, 2 h) (125.8 μA/cm2). The influence of deposition potential on photoelectrocatalytic performance was systematically explored, and the optimal deposition potential was identified. Additionally, surface modification with 0.15 wt% Pt (ultra-low loading) was employed to further improve the photocatalytic stability of α-Fe2O3(500 °C, 2 h). After continuous operation for 2 h, the photocurrent of the surface-modified sample decreased by only 6.5%, indicating a substantial enhancement in stability.