Accelerated charge transport of Ti and Zr co-doped Fe2O3 photoanodes by a super-hydrophilic metal-phytate coating for efficient photoelectrochemical water oxidation

The extensive solid-liquid interface between the photoanode and the electrolyte solution impedes the kinetics of the oxygen evolution reaction (OER), resulting in a photoelectrochemical (PEC) water splitting efficiency that falls short of theoretical predictions. In this study, by depositing a metal-phytate complex (CoCu-PA) coating onto Ti, Zr co-doped Fe 2 O 3 via a hydrothermal method, we successfully fabricated a CoCu-PA/Ti,Zr:Fe 2 O 3 composite photoanode for water oxidation. Various characterization techniques and electrochemical analyses indicated that Ti, Zr co-doping enhanced the conductivity of Fe 2 O 3 . More importantly, owing to the highly hydrophilic property of CoCu-PA, the charge transfer resistance at the interface between the composite photoanode and the solution is significantly reduced. Furthermore, a built-in electric field was formed within the photoanode, facilitating the rapid migration of photogenerated charges and their efficient injection into the electrolyte to participate in the OER. As a result, the CoCu-PA coating enhanced the OER kinetics of the composite photoanode and led to a photocurrent density of 3.4 mA/cm 2 . This study offers new insights into the design of composite photoanodes to improve charge migration efficiency both within the bulk material and at the solid-liquid interface.