To improve the photoelectrochemical activity of ${\mathrm{TiO}}_2$ for hydrogen production through water splitting, the band edges of ${\mathrm{TiO}}_2$ should be tailored to match with visible light absorption and the hydrogen or oxygen production levels. By analyzing the band structure of ${\mathrm{TiO}}_2$ and the chemical potentials of the dopants, we propose that the band edges of ${\mathrm{TiO}}_2$ can be modified by passivated codopants such as ($\mathrm{Mo}+\mathrm{C}$) to shift the valence band edge up significantly, while leaving the conduction band edge almost unchanged, thus satisfying the stringent requirements. The design principle for the band-edge modification should be applicable to other wide-band-gap semiconductors.

• Received 31 October 2008

DOI:https://doi.org/10.1103/PhysRevLett.102.036402