Gradient Surface\nGallium-Doped Hematite Photoelectrode\nfor Enhanced Photoelectrochemical Water Oxidation

Hematite is a promising material for photoelectrochemical\n(PEC)\nwater oxidation, but its photocurrent is limited by bulk charge recombination\nand poor oxidation kinetics. In this study, we report a high-performance\nFe<sub>2</sub>O<sub>3</sub> photoanode achieved through gradient surface\ngallium doping, utilizing a Ga<sub>2</sub>O<sub>3</sub> overlayer\non FeOOH precursors via atomic layer deposition (ALD) and co-annealing\nfor Ga diffusion. The Ga-doped layer passivates surface states and\nmodifies the band structure, creating a built-in electric field that\nenhances the charge separation efficiency. Following the electrodeposition\nof CoFeO<sub><i>x</i></sub> as a cocatalyst, the resulting\nCoFe-Ga:Fe<sub>2</sub>O<sub>3</sub> photoanode exhibited a notable\nnegative shift in onset potential by approximately 100 mV, a high\nphotocurrent density of 2.6 mA cm<sup>–2</sup> at 1.23 V versus\nRHE, and excellent long-term PEC stability over 40 h. This work presents\nan effective strategy for enhancing the PEC performance of photoelectrodes\nthrough advanced surface coatings.