Hydroxyl-Bonded Ru on Metallic TiN Surface Catalyzing CO₂ Reduction with H₂O by Infrared Light

Abstract

Synchronized conversion of CO₂ and H₂O into hydrocarbons and oxygen via infrared-ignited photocatalysis remains a challenge. Herein, the hydroxyl-coordinated single-site Ru is anchored precisely on the metallic TiN surface by a NaBH₄/NaOH reforming method to construct an infrared-responsive HO-Ru/TiN photocatalyst. Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (ac-HAADF-STEM) and X-ray absorption spectroscopy (XAS) confirm the atomic distribution of the Ru species. XAS and density functional theory (DFT) calculations unveil the formation of surface HO-RuN₅-Ti Lewis pair sites, which achieves efficient CO₂ polarization/activation via dual coordination with the C and O atoms of CO₂ on HO-Ru/TiN. Also, implanting the Ru species on the TiN surface powerfully boosts the separation and transfer of photoinduced charges. Under infrared irradiation, the HO-Ru/TiN catalyst shows a superior CO₂-to-CO transformation activity coupled with H₂O oxidation to release O₂, and the CO₂ reduction rate can further be promoted by about 3-fold under simulated sunlight. With the key reaction intermediates determined by in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and predicted by DFT simulations, a possible photoredox mechanism of the CO₂ reduction system is proposed.