Rationalize the Significantly Enhanced Photocatalytic Efficiency of In3+-doped α′-Ga2S3 by Bond Theory and Local Structural Distortion

Mechanistic understanding on the electronic structure of α′-Ga2S3 unravel that the electrons in nonbonding 3pz orbitals of two-coordinated S2– anions are photoexcited to the adjacent σ-type antibonding orbitals (Ga-4s and S-3p) and migrate thereafter to the surface along the a-axis. By introduction of the In–S antibonding on the one hand and modifying the local dipole moment on the other hand, the light absorption ability and charge separation efficiency can be both enhanced by In3+-to-Ga3+ substitution, and the photocatalytic H2 evolution rate can be significantly promoted. Local geometric distortion is common in solid solutions, but its effect on charge migration behavior has yet been considered in semiconducting photocatalysis. Our case study on In3+-doped Ga2S3 is a good reminder of such the importance.