Journal
JOURNAL OF PHYSICAL CHEMISTRY LETTERS
Volume -, Issue -, Pages 879-887Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.jpclett.2c03643
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Compared to the bare Fe2O3 (0001) surface, an alpha-Ga2O3 overlayer reduces surface states and suppresses charge recombination, resulting in a cathodic shift in the onset potential for water oxidation.
Hematite (alpha-Fe2O3) is a promising photoanode material for photoelectrochemical water splitting. Surface-passivating layers are effective in improving water oxidation kinetics; however, the passivation mechanism is not fully understood due to the complexity of interfacial reactions. Focusing on the Fe-terminated Fe2O3 (0001) surface that exhibits surface states in the band gap, we perform ab initio quantum dynamics simulations to study the effect of an alpha-Ga2O3 overlayer on charge recombination. The overlayer eliminates surface states and suppresses charge recombination 4-fold. This explains in part the observed cathodic shift in the onset potential for water oxidation. The increased charge carrier lifetime is an outcome of two factors, energy gap and electron-vibrational coupling, with a positive contribution from the former but a negative contribution from the latter. This work presents an advance in the atomistic time-domain understanding of the influence of surface passivation on charge recombination dynamics and provides guidance for designing novel alpha-Fe2O3 photoanodes.
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