Influence of Successive Zirconium and Beryllium Codoping Strategies on Advancing Bulk and Surface Properties of Hematite Photoanodes for Boosting Photoelectrochemical Water Splitting

Photoelectrochemical (PEC) water splitting activity of Fe₂O₃ is restricted by the rapid recombination of photocarriers both in bulk and on the surface and slack water oxidation kinetics. Herein, this work describes a method for designing and constructing a Fe₂O₃ photoanode by sequential in-situ and ex-situ incorporation of dopants for an effective PEC water splitting strategy. In-situ Zr doping can be used to improve the bulk conductivity of the photoanode by augmenting the majority carriers while generating surface defects that limit effective water oxidation at the photoelectrode/electrolyte interface. Therefore, the main emphasis of this study is on ex-situ codoping with Be, which boosts the surface charge transfer properties via the passivation of surface-trapping states, thus leading to effective hole migration to the electrolyte. As a consequence, the Zr/Be codoped Fe₂O₃ photoanode (Zr/Be-HT) attained an 83% improved photocurrent density (1.92 mA/cm²) than that of bare-Fe₂O₃ at a water oxidation potential of 1.23 V vs. RHE. Mott-Schottky plots, electrochemical impedance spectroscopy, a transient time constant, and bulk and surface charge separation efficiency evaluations were conducted to comprehend the functions of Zr and Be dopants. Finally, the Co-Pi cocatalyst-coated Zr/Be-HT photoanode produced 33.75 and 17.76 μmol/h H₂ and O₂ gases, respectively, at 1.23 V vs. RHE. This codoping strategy could lead to a more sustainable and efficient method for producing hydrogen fuel.