Zr–Ge co-doping and co-catalyst modification enable efficient charge separation and low onset overpotential in hematite photoanodes for photoelectrochemical antibacterial and environmental applications^†

Ge–Zr co-doped α-Fe₂O₃ photoanodes decorated with NiFeO_x cocatalysts were developed to enhance photoelectrochemical (PEC) degradation of organic dyes and bacterial contaminants under 1-sun illumination. The incorporation of Ge⁴⁺ increased carrier density and electrical conductivity, thereby facilitating bulk charge transport, while Zr⁴⁺ modulated surface states and suppressed surface recombination. The NiFeO_x cocatalyst further improved surface charge separation by accelerating hole utilization through the oxygen evolution reaction (OER). During organic pollutant degradation, the addition of Cu²⁺ ions significantly enhanced reactive oxygen species (ROS) generation via a Fenton-like Cu²⁺/Cu⁺ redox cycle, leading to increased production of superoxide (^•O₂⁻) and hydroxyl (^•OH) radicals. Under optimal conditions, the NiFeO_x/Zr–Ge-Fe₂O₃ photoanode achieved over 75% degradation of Orange II dye, more than 65% decomposition of bisphenol A (BPA), and 98% bacterial inactivation under simulated sunlight. Scavenger experiments identified ^•O₂⁻ as the dominant reactive species, with ^•OH and photogenerated holes contributing synergistically. Electrochemical impedance spectroscopy (EIS) revealed that Cu²⁺ ions improved interfacial charge transfer, underscoring the combined effects of cocatalyst decoration and redox mediation in optimizing charge transport and reaction kinetics. Overall, this work presents a synergistic strategy integrating elemental co-doping, cocatalyst engineering, and redox mediation to achieve efficient PEC degradation of environmental pollutants.