Rational Dual-Site Doping of the Hematite Photoanode Unlocks Efficient Solar Water Splitting

Hematite (α-Fe₂O₃) is a promising photoanode for solar water splitting, while its performance is fundamentally limited by low bulk electron mobility and severe surface charge recombination. Doping has been demonstrated to be an effective strategy to address these issues at the atomic level. Herein, we present a rational dual-site doping design that synergistically enhances bulk charge transport and suppresses surface recombination. In situ ytterbium (Yb³⁺) doping in the bulk modulates the local chemical environment of Fe³⁺ and introduces lattice distortion, which is favorable for improving bulk charge transport behavior. Meanwhile, ex situ zirconium (Zr⁴⁺) surface modification effectively suppresses interfacial charge recombination through surface state regulation. In addition, the hybrid microwave annealing (HMA) process promotes the formation of porous nanostructures. Benefiting from these synergistic effects, the optimized Yb,Zr:Fe₂O₃ photoanode achieves a remarkable photocurrent density of 3.51 mA cm^-2 at 1.23 V_RHE under AM 1.5 G illumination (100 mW cm^-2), along with an enhanced operational stability. This work demonstrates the efficacy of dual-functional doping in engineering high-performance hematite photoanodes and provides a strategic framework for rational design of advanced metal oxide photoelectrodes.