Abstract: First principle calculation was carried out to study the electronic structures of photocatalysts K4Ce2Ta10O30, K4Ce2Nb10O30, and their solid solution compounds, which were all capable of responding to visible light, based on density functional theory (DFT) within plane-wave pesudopotential (PWP) and generalized gradient approximation (GGA) method. The calculation results indicated that conduction bands of K4Ce2Ta10O30 and K4Ce2Nb10O30 were mainly attributable to the Ta 5d and Nb 4d orbitals, respectively. Although the unoccupied Ce 4f orbitals had overlapped at the bottom of the conduction band, they were less effective in transferring electrons and photocatalytic activities for their high localized nature, while their valence bands were composed of hybridization with the bonding of O 2p+Ta 5d (or Nb 4d) and occupied Ce 4f orbitals. The contribution of these orbitals to the energy bands affected the electronic structure of photocatalysts and gave rise to their differences in light absorption and photocatalytic activities. As for the solid solutions compounds of K4Ce2Ta10-xNbxO30 (x=2, 5, 8), their band gaps decreased with an increase of the x value resulting in a corresponding lower reducing ability to evolve H2. The valence band edges in solid solution compounds were lower than that of K4Ce2Ta10O30 and K4Ce2Nb10O30 for the little contribution from occupied Ce 4f. This consequently led to the higher oxidize ability. The results of the analysis of electronic structures were in good accordance with their experimental photocatalytic activities for water decomposition.

Key words: Visible-light driven, Photocatalyst, K4Ce2Ta10O30, K4Ce2Nb10O30, Density functional theory, Electronic structure, First principle