Hierarchical Zr-doped Fe₂O₃ photoanodes decorated with in situ Au nanoparticles via a surfactant-assisted one-step hydrothermal approach for efficient photoelectrochemical water splitting

Achieving highly effective catalytic activity in photoelectrochemical (PEC) water splitting has become a challenge in the fabrication of Fe₂O₃ photoanodes due to their poor electrical conductivity and surface charge recombination. This study outlines a one-step hydrothermal route for the design of surfactant-assisted in situ Au nanoparticle (NP)-integrated Zr-doped Fe₂O₃ photoanodes for PEC water splitting. A cetyltrimethylammonium bromide (CTAB) surfactant and Au-incorporated Zr-doped Fe₂O₃ photoanode achieved a photocurrent density of 2.30 mA cm⁻² at 1.23 V vs. RHE (1.23 V_RHE). CTAB promoted the adsorption of Au NPs on the Zr-FeOOH during the synthesis, while Au NPs accelerated the charge transfer kinetics. The loaded Au NPs enhanced the separation of photo-generated electron-hole pairs; as a consequence, Au NPs effectively shuttled the holes from the hematite to the photoelectrode/electrolyte interface, leading to improved photocatalytic activity. Further, the optimized Zr-HT/CTAB/Au photoanode exhibited an intrinsic solar-to-chemical conversion (ISTC) efficiency of 1.034%. Moreover, impressively, the deposition of a NiCo(OH)_x cocatalyst enhanced the PEC performance to 2.72 mA cm⁻² at 1.23 V_RHE. This study presents a potentially fruitful strategy for simultaneous in situ decoration of a surfactant and Au NPs with photoanodes for PEC water splitting.