Dual modification on hematite to minimize small polaron effects and charge recombination for sustainable solar water splitting

Abstract

Hematite nanostructures are strong candidates for the development of sustainable water splitting technologies. However, major challenges exist in improving charge density and minimizing charge recombination rates for a competitive photoelectrochemical performance based on hematite without compromising sustainability aspects. Here we develop a synthetic strategy to leverage earth-abundant Al³⁺ and Zr⁴⁺ in a dual-chemical modification to synergistically minimize small polaron effects and interfacial charge recombination. The solution-based method simultaneously induces Al³⁺ doping of the hematite crystal lattice while Zr⁴⁺ forms interfacial excess, creating a single-phased homogeneous nanostructured thin film. The engineered photoanode increased photocurrent from 0.7 mA cm⁻² for pristine hematite up to 4.5 mA cm⁻² at 1.23 V and beyond 6.0 mA cm⁻² when applying an overpotential of 300 mV under simulated sunlight illumination (100 mW cm⁻²). The results demonstrate the potential of dual-modification design using solution-based processes to enable sustainable energy technologies.