Single-metal catalytic sites via high-throughput mechanochemistry enable selective and efficient CO2 photoreduction

In this work, we first report synthesizing a series of single-atom metals (covering main-group, transition, precious, and rare earth metals) photocatalysts M-SA/TiO2 using a simple, efficient, and high-yield mechanochemistry (high-energy ball milling) and evaluate their efficiency towards CO2 photoreduction. In the synthesized single-atom catalyst (SAC), the CH4 yield from CO2 photoreduction using PdsA/TiO2 reaches as high as 271.6 mu mol.g(-1).h(-1) with the selectivity of similar to 98.0%, far surpassing those of conventional Pd clusters and nanoparticles. The experimental results and density functional theory (DFT) calculations reveal that the strong adsorption at single-atom catalytic sites (Pd) leads to significant bending of O=C=O bond angle from 180.0 to 151.0 degrees and length from 1.16 to 1.20 angstrom. The induced deformation greatly 'energizes' the CO2, thus reducing the kinetic energy barrier significantly and offering high catalytic activity. Meanwhile, combined with in-situ Fourier-transform infrared (FT-IR), a rational reaction pathway of CO(2)( )photoreduction over efficient SACs is proposed.