Visible-light-driven photocatalysts: (La/Bi + N)-codoped NaNbO3 by first principles

To improve the photocatalytic activity of NaNbO3 for water splitting, the bandgap and the band edges of NaNbO3 should be tailored to match the visible part of the solar spectrum and hydrogen and oxygen redox potentials. By analyzing the band structures of La/Bi-doped and (La/Bi vertical bar N)- codoped NaNbO3, we found that the pseudointermediate band (PIB) was formed in the bandgap in all the doped systems because of the orbital splitting of the Nb 4d induced by the dramatically enlarged O-Nb-O angles. The PIB could make the wide bandgap semiconductors absorb visible-light photons as long as it was degenerate or partially degenerate. Considering that the appropriate band edges and absorption properties, we believe that (La/Bi vertical bar N)-codoped NaNbO3 materials are promising photocatalysts for hydrogen production through water splitting under visible-light irradiation without other modifications. (C) 2011 American Institute of Physics. [doi:10.1063/1.3554697]