Gradient Surface Gallium-Doped Hematite Photoelectrode for Enhanced Photoelectrochemical Water Oxidation.

Hematite is a promising material for photoelectrochemical (PEC) water oxidation, but its photocurrent is limited by bulk charge recombination and poor oxidation kinetics. In this study, we report a high-performance FeO photoanode achieved through gradient surface gallium doping, utilizing a GaO overlayer on FeOOH precursors via atomic layer deposition (ALD) and co-annealing for Ga diffusion. The Ga-doped layer passivates surface states and modifies the band structure, creating a built-in electric field that enhances the charge separation efficiency. Following the electrodeposition of CoFeO as a cocatalyst, the resulting CoFe-Ga:FeO photoanode exhibited a notable negative shift in onset potential by approximately 100 mV, a high photocurrent density of 2.6 mA cm at 1.23 V versus RHE, and excellent long-term PEC stability over 40 h. This work presents an effective strategy for enhancing the PEC performance of photoelectrodes through advanced surface coatings.