Carbon-doped In 2 O 3 and carbon-doped WO 3 films were produced using a spray pyrolysis methodology with octanoic acid as the carbon dopant source. C-doped and undoped In 2 O 3 films showed a cubic polycrystalline In 2 O 3 structure, and C-doped and undoped WO 3 films displayed a monoclinic polycrystalline WO 3 structure. C-doped In 2 O 3 and WO 3 , compared to their corresponding undoped materials, showed increased absorption in the 350-550 nm range with a red shift in the band gap transition. The presence of carbonate-type species in these C-doped samples was confirmed by XPS. The photoelectrochemical activity was evaluated under near UV-visible light and visible light only irradiation conditions. Under the same irradiation conditions, C-doped In 2 O 3 and C-doped WO 3 electrodes produced greater photocurrent densities than their corresponding undoped electrodes. The C-doped In 2 O 3 electrode exhibited photocurrent densities up to 1 mA/cm 2 , with 40% from visible light irradiation, and the C-doped WO 3 electrode showed photocurrent densities up to 1.3 mA/cm 2 , with 50% from visible light irradiation. These results indicate the potential for further development of In 2 O 3 and WO 3 photocatalysts by simple wet chemical methods, and provide useful information towards understanding the structure and enhanced photoelectrochemical properties of these materials.

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