Exploring the Photocatalytic Mechanism of BiTi 4 GaO 11 : Insights from the Electronic Structure and Chemical Bonding

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Photocatalytic water splitting and CO 2 reduction offer sustainable solutions to energy and environmental issues, but efficient semiconductor photocatalysts are still limited. Oxide photocatalysts with d 0 and/or d 10 metals often have wide bandgaps, and incorporating d 10 ns 2 metals can raise the valence band maximum (VBM) and narrow the bandgap. Here, we synthesized BiTi 4 GaO 11 (BTGO), a new photocatalyst containing d 10 6s 2, d 0, and d 10 metals. Structural analysis via powder X-ray and neutron diffraction confirmed BTGO crystallizes in the space group Cmcm, with Ga cooccupying all three Ti sites. Density functional theory calculations revealed that the conduction band minimum (CBM) of BTGO is primarily composed of Ti t 2g - O 2p antibonding orbitals. Hybridization between Bi 6s and O 2p orbitals leads to the formation of antibonding orbitals, which further interact with Bi 6p orbitals to form the VBM. This interaction shifts the VBM upward, narrows the bandgap ( E g = 2.82 eV), and enables the visible-light absorption. Experimental results demonstrated that BTGO efficiently catalyzes photocatalytic H 2 production and CO 2 reduction. Furthermore, the incorporation of cocatalysts suppressed the recombination of photogenerated charge carriers, enhancing photocatalytic activity. This work highlights the importance of electronic structure and bonding analysis in understanding the fundamental mechanisms of photocatalysis.