Iron Oxide Photoanode for Glycerol-Assisted Hydrogen Production at 8.87 mA cm^-2

Iron oxide (α-Fe₂O₃) is an attractive photoanode for photoelectrochemical water splitting because of its abundance, suitable band gap, and stability in water, yet its practical use remains limited by poor charge transport and sluggish water oxidation. Here we show that these limitations can be addressed using a Ge and Ti co-doped Fe₂O₃ photoanode that couples glycerol oxidation with cathodic hydrogen evolution under simulated one-sun illumination (100 mW cm^-2). In 1.0 M NaOH containing 2.0 M glycerol, the photoanode delivers a photocurrent density of 8.87 mA cm^-2 at 1.23 V versus the reversible hydrogen electrode, above the practical benchmark of 8.1 mA cm^-2. Ge incorporation also enables selective oxidation of glycerol to tartronic acid, a value-added product of glycerol oxidation. Electrochemical analyses and density functional theory calculations suggest that Ge and Ti co-doping improves charge utilisation, while Ge additionally promotes the tartronic acid-forming pathway.