Plasma-implanted Ti-doped hematite photoanodes with enhanced photoelectrochemical water oxidation performance

Hematite (α-Fe₂O₃) is recognized as a promising photoelectrode material for photoelectrochemical (PEC) water splitting, as a result of its abundance, non-toxicity, suitable bandgap, and photochemical stability. Nevertheless, the undesirable physical and photophysical behaviors, such as poor conductivity, short diffusion length, and rapid charge-carrier recombination, seriously restrict PEC water splitting efficiency of hematite semiconductors. Herein, we fabricate nanoporous titanium (Ti)-doped α-Fe₂O₃ thin films by a facile hydrothermal reaction, subsequently utilizing energetic plasma ion implantation with a post-annealing process to significantly enhance the photoelectrochemical water oxidation performance of hematite. On the basis of materials characterization and electrochemical analysis, the optimized Ti-doped Fe₂O₃, i.e., Ti-4-Fe₂O₃, exhibits improved photocurrents of 0.55 and 1.07 mA cm⁻² at 1.23 and 1.5 V versus RHE respectively under illumination of 100 mW/cm² with AM 1.5 G spectrum, showing approximately 1.6-fold increases compared to pristine Fe₂O₃. We attribute this increase to improved charge carrier transport induced by Ti doping that reduces the recombination of light-driven charge carriers. The work utilizing plasma-assisted doping technique provides new insights into the surface engineering of photo-responsive semiconductors for the development of emerging hydrogen technologies.