High-performance single-atom M/TiO2 catalysts in the reverse water-gas shift reaction: A comprehensive experimental and theoretical investigation

Single-atom catalysts (SACs) offer high efficiency and selectivity in chemical reactions but face challenges in converting CO2 to CO via the reverse water gas shift (RWGS) reactions. This study addresses these challenges by anchoring three noble metals (Ir, Pd, and Ru) onto titania (TiO2) and analyzing their performance. Comprehensive characterization techniques, including electron microscopy, confirmed the uniform dispersion of metal atoms on TiO2. Among the catalysts, Ir/TiO2 exhibited the best results, achieving an 84 % CO2 conversion rate and ∼98 % CO selectivity, surpassing Pd/TiO2 and Ru/TiO2, which gained 56 % and 52 % conversion, respectively. In-situ gas transmission electron microscopy revealed the catalytic behavior of Ir/TiO2, showing Ir atom mobility and the formation of ∼1 nm nanoclusters. Density functional theory (DFT) and in-situ diffuse reflectance infrared spectroscopy (DRIFTs) further explained that the atomically dispersed Ir sites in Ir/TiO2 follow a hydrogen-assisted mechanism, with the COOH* intermediate desorbing and dissociating into CO. These findings suggest SACs' potential to facilitate greener chemical processes and reduce greenhouse gas emissions. [Display omitted] •Successful and reproducible synthesis of thermally stable M/TiO2 single-atom catalysts with 0.05 % metal loading using modified adsorption method.•Demonstration of exceptional performance, achievement of nearly 100 % CO selectivity with a high conversion rate of 84 % at 700 °C during CO2 hydrogenation.•Nanoscale observations of synthesized M/TiO2 catalysts in gaseous environments and real-time with in-situ gas transmission electron microscopy.•Validation of experimental findings with density functional theory methods.