skip to main content

Title: Photo-driven oxidation of water on α-Fe{sub 2}O{sub 3} surfaces: An ab initio study

Adopting the theoretical scheme developed by the Nørskov group [see, for example, Nørskov et al., J. Phys. Chem. B 108, 17886 (2004)], we conducted a density functional theory study of photo-driven oxidation processes of water on various terminations of the clean hematite (α-Fe{sub 2}O{sub 3}) (0001) surface, explicitly taking into account the strong correlation among the 3d states of iron through the Hubbard U parameter. Six best-known terminations, namely, Fe − Fe −O{sub 3}− (we call S{sub 1}), O− Fe − Fe − (S{sub 2}), O{sub 2}− Fe − Fe −(S{sub 3}), O{sub 3}− Fe − Fe − (S{sub 4}), Fe −O{sub 3}− Fe − (S{sub 5}), and O− Fe −O{sub 3}−(S{sub 6}), are first exposed to water, the stability of resulting surfaces is investigated under photoelectrochemical conditions by considering different chemical reactions (and their reaction free energies) that lead to surfaces covered by O atoms or/and OH groups. Assuming that the water splitting reaction is driven by the redox potential for photogenerated holes with respect to the normal hydrogen electrode, U{sub VB}, at voltage larger than U{sub VB}, most 3-oxygen terminated substrates are stable. These results thus suggest that the surface, hydroxylated in the dark, should release protons undermore » illumination. Considering the surface free energy of all the possible terminations shows that O{sub 3}–S{sub 5} and O{sub 3}–S{sub 1} are the most thermodynamically stable. While water oxidation process on the former requires an overpotential of 1.22 V, only 0.84 V is needed on the latter.« less
Authors:
;  [1] ;  [2] ;  [3]
  1. The Abdus Salam International Centre for Theoretical Physics, Strada Costiera 11, 34151 Trieste (Italy)
  2. CNR-IOM DEMOCRITOS, c/o SISSA, via Bonomea 265, 34136 Trieste (Italy)
  3. The Abdus Salam International Centre for Theoretical Physics, Strada Costiera 11, 34151 Trieste, Italy and CNR-IOM DEMOCRITOS Simulation Center, 34136 Trieste (Italy)
Publication Date:
OSTI Identifier:
22255114
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 140; Journal Issue: 6; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; DENSITY FUNCTIONAL METHOD; ELECTRIC POTENTIAL; FERRITES; FREE ENERGY; HEMATITE; IRON; IRON OXIDES; OXIDATION; PROTONS; REDOX POTENTIAL; SUBSTRATES; SURFACES; WATER