Oxygen vacancy engineering and interfacial proton capture: Constructing asymmetric Co/I dual-sites on TiO2 for enhanced photocatalytic hydrogen evolution activity

Integrating dual functional sites in the crystal lattice is a promising strategy to fabricate novel hetero nuclear-hetero polar dual-atom catalyst. However, the synergy between the dual active sites is governed by the local coordination environment, shaped by doping configuration of hetero atoms in the crystal lattice. Herein, engineering cobalt–iodine dual-site on anatase-TiO2 (Co-I-a-TiO2) was conducted by coupling in-situ cross-linking-assisted hydrothermal synthesis with electrostatic self-assembly. The optimal Co-I-a-TiO2 exhibits a H2 production rate of 20.8 mmol g−1 h−1, approximately 8.32 fold higher than that of pristine a-TiO2. Experimental and theoretical analysis reveal that the Co3+-for-Ti4+ substitution and vacancy-doped I ions in the lattice alter the electron density distribution, establishing a built-in electric field oriented from bulk to surface in the near-surface region. This redistribution empowers Co atom to function as an electron-rich center and I atom as a proton-trapping site. These findings emphasize the importance of constructing asymmetric coordination via anion-cation dual-site modification to promote photogenerated charge separation, as well as the enhanced probability of electron-proton binding.