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  Bär, M.; Weinhardt, L.; Marsen, B.; Cole, B.; Gaillard, N.; Miller, E.L.; Heske, C.: Mo incorporation in WO₃ thin film photoanodes: Tailoring the electronic structure for photoelectrochemical hydrogen production. Applied Physics Letters 96 (2010), p. 032107/1-3

10.1063/1.3291689

Abstract:
The electronic surface structure of Mo-incorporated WO3 (“WO3 :Mo”) is investigated using direct and inverse photoemission and compared to that of pure (Mo-free) WO3. The films are found to be n-type with an electronic surface band gap of 3.27 (+/- 0.15) eV. The conduction band minimum (valence band maximum) is 0.64 (+/- 0.10) eV above [2.63 (+/- 0.10) eV below] the Fermi level andat most 0.38 (+/- 0.11) eV above the H+ /H2 reduction potential [at least 1.66 (+/- 0.11) eV below the H2O/O2 oxidation potential]. The findings suggest an explanation why WO3:Mo/WO3 bilayer structures show improved photoelectrochemical performance compared to respective single layer photoanodes.