Microwave-assisted sequential Pt/Al attachment on FeOOH for fabrication of highly efficient hematite photoanodes: Synergistic effect of Pt/Al co-doping and Al₂O₃ passivation layer

This article presents the fabrication and systematic analyses of Pt and Al co-doped hematite photoanodes utilizing a simple microwave process to improve the photoelectrochemical (PEC) performance of hematite. The Pt/Al dual ions doping synergistically elevated the photocurrent of hematite by 48% at 1.23 V versus (vs.) the reversible hydrogen electrode (RHE) (1.55 mA/cm²), and resulted in an obvious decrease in the onset potential (compared to that of the solely Pt-doped hematite), demonstrating that Al contributes as both a bulk dopant and a surface passivation layer for water oxidation. The enhanced photoelectrochemical response is a result of the synergy of Pt/Al co-doping, which increases the donor density and decreases the electron transport time while the unintended formation of Al₂O₃ improves the surface charge transfer kinetics. The optimized Pt(1.2%)/Al(2.5 mM) co-doped hematite (Pt/Al-HT) photoanode achieved the highest incident photon-to-current efficiency (IPCE) of 33% at 350 nm at 1.23 V vs. RHE. Further, we explored in detail the mechanism of microwave-assisted attachment of each dopant to FeOOH and charge transfer in Pt/Al-HT photoanodes. This highlights the potential of microwave-assisted dual ions doping to advance hematite PEC performance for solar water splitting.