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Scaling up photoelectrochemical (PEC) devices for green hydrogen production is a significant challenge that requires robust and cost-effective production methods. In this study, hematite photoelectrodes has been synthesized using a cost-effective polymeric precursor solution, resulting in homogeneous ultra-thin films (~125 nm) with areas up to 200 cm2. We observed a substantial photocurrent drop as photoelectrode area increases, addressed by modifying the precursor solution with Hf4+. This modification improves the morphology and films adherence, leading to simultaneous grain|grain interface segregation and a modified FTO|hematite interface. As a result, film conductivity increases, reducing the photocurrent drop at larger photoelectrode areas. The improved charge separation and surface charge injection efficiencies allows a homogeneous photocurrent of 1.6 mA cm⁻2 at 1.45V across a 15.75 m2 electrode area, using less than 70 μg of photoactive material. Cost analysis study indicates that this low-energy fabrication method is a significant step forward in green hydrogen production, contributing to sustainable and efficient green hydrogen technologies. 

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. 

The work demonstrates a three-fold increase in photoelectrochemical efficiency of hematite nanorods as a result of the combination of Hafnium surface doping and the incorporation of a ZrO2 underlayer on FTO. While the ZrO2 layer reduced the electron loss from the back-injection into the FTO contact support, Hafnium surface doping did not significantly alter the hematite lattice structure. But rather, Hafnium induced nanorod diameter reduction from 32 ± 2 and 26 ± 2 nm, with a consequent increase in the active surface area. The linear sweep voltammetry measurements with 100 mW cm−2 illumination in a 500 nm photoanode thickness showed a photocurrent density of 2.07 mA cm−2 at 1.23 V in a reversible hydrogen electrode (RHE). The value contrasts with the bare hematite rods (0.75 mA cm−2), highlighting the photoanode design's role in improving solar power hydrogen production.