Enhancing CO selectivity in the reverse water gas shift reaction using PdIr/TiO2 dual atoms catalysts: A combined experimental and computational approach

This study addresses the challenge of selective CO₂-to-CO conversion via the reverse water-gas shift (RWGS) reaction using atomically dispersed dual-atom catalysts (DACs). Three PdIr/TiO₂ compositions with varying Pd-to-Ir ratios (10:90, 25:75, and 40:60) were synthesized and characterized. Among them, PdIr/TiO₂ (10% Pd, 90% Ir) demonstrated the highest CO₂ conversion (74.77%) and 99% CO selectivity. In contrast, higher Pd loadings (>25%) led to a decline in both activity and selectivity. Advanced characterization, including in-situ gas-phase transmission electron microscopy (TEM) and Electron energy loss spectroscopy (EELS), revealed atom mobility and nanocluster formation under reaction conditions, along with enhanced Ti–O hybridization, oxygen vacancies, and partial Ti⁴⁺ reduction due to hydrogen spillover from PdIr sites. Complementarily, density functional theory (DFT) and in situ diffuse reflectance infrared spectroscopy (DRIFTs) studies revealed a hydrogen-assisted reaction pathway involving *COOH intermediates that dissociate to form CO. These insights highlight the role of dual-metal synergy and support interactions in stabilizing active sites and guiding selective reaction pathways. Overall, this work demonstrates the potential of DACs to overcome current limitations in CO₂ hydrogenation and contributes to the development of more sustainable catalytic processes for greenhouse gas mitigation. • Tunable PdIr/TiO₂ DACs designed for optimal CO₂ hydrogenation performance. • Achieved ~99% CO selectivity and 74.77% CO₂ conversion at 650 °C. • In-situ STEM/EELS revealed stable nanocluster formation from Pd–Ir single sites. • DFT and DRIFTS unveiled Pd–Ir synergy via the COOH* intermediate pathway. • Catalyst exhibited >100 hours of stability under industrial RWGS conditions.