Engineering spatially proximate redox sites in Pd-In/TiO2 photocatalyst for selective CO2 photoreduction

The synergistic integration of redox reactions in the photocatalyst poses a significant challenge for CO 2 photoreduction. Addressing this issue requires the design of spatially proximate redox sites while effectively suppressing charge recombination at these sites. This work offers a pioneering tactic that exploits synergistic redox reactions in close atomic proximity. The deliberate incorporation of palladium and indium into TiO 2 , where the Pd site assists in hole accumulation, accelerates water dissociation, and generates highly active H* species. Meanwhile, adjacent In sites capture photogenerated electrons from TiO 2 , producing reactive intermediates by activating CO 2 . The synergistic incorporation of Pd and In accelerates redox functionality, boosts charge carrier separation, and mitigates recombination at closely situated redox sites. Comprehensive characterizations, including in-situ XPS and FTIR, strengthen these innovative outcomes. The optimized Pd 0.5 -In 1 /TiO 2 photocatalyst achieves nearly 100 % selectivity of CH 4 with a production rate of 30.5 µmol g -1 h −1 without the use of any sacrificial reagent, demonstrating a 25-fold improvement compared to pristine TiO 2 . In-situ infrared spectroscopy further validates that the synergistic doping of metal ions promotes the formation of *CH 3 O and *CHO, key intermediates in the production of CH 4 . This investigation provides valuable insight into the intricate design of coupled redox active sites.