Interfacial oxygen vacancies yielding long-lived holes in hematite mesocrystal-based photoanodes

• Published in: Nature communications Vol. 10; no. 1; pp. 4832 - 12
• Main Authors: Zhang, Zhujun, Karimata, Izuru, Nagashima, Hiroki, Muto, Shunsuke, Ohara, Koji, Sugimoto, Kunihisa, Tachikawa, Takashi
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 23.10.2019; Nature Publishing Group; Nature Portfolio
• Subjects: 147/137; 639/301/299/886; 639/638/439/890; 639/638/675; Carrier density; Charge efficiency; Depletion; Efficiency; Electrodes; Energy conversion; Energy conversion efficiency; Extreme values; Hematite; Humanities and Social Sciences; Light; multidisciplinary; Nanocrystals; Nanoparticles; Oxidation; Oxygen; Photoanodes; Radiation; Recombination; Science; Science (multidisciplinary); Structural hierarchy; Thick films; Vacancies; Water splitting
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-019-12581-z

Hematite (α-Fe 2 O 3 ) is one of the most promising candidates as a photoanode materials for solar water splitting. Owing to the difficulty in suppressing the significant charge recombination, however, the photoelectrochemical (PEC) conversion efficiency of hematite is still far below the theoretical limit. Here we report thick hematite films (∼1500 nm) constructed by highly ordered and intimately attached hematite mesocrystals (MCs) for highly efficient PEC water oxidation. Due to the formation of abundant interfacial oxygen vacancies yielding a high carrier density of ∼10 20  cm −3 and the resulting extremely large proportion of depletion regions with short depletion widths (<10 nm) in hierarchical structures, charge separation and collection efficiencies could be markedly improved. Moreover, it was found that long-lived charges are generated via excitation by shorter wavelength light (below ∼500 nm), thus enabling long-range hole transfer through the MC network to drive high efficiency of light-to-energy conversion under back illumination. The performance of hematite (α-Fe 2 O 3 ) photoanodes is limited by fast charge recombination. Here, authors develop hematite mesocrystal-based photoanodes with abundant interfacial oxygen vacancies for highly efficient solar water splitting under back illumination.