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

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. A dual-modification strategy enables the design of hematite with synergistic Al3+ bulk doping and Zr4+ interfacial segregation for improved performance as a photoanode.