Highly active subnanometer Rh clusters derived from Rh-doped SrTiO₃ for CO₂ reduction

Sub-nanometer Rh clusters derived from Rh-doped SrTiO₃, demonstrated by in-situ X-ray Diffraction (XRD) and X-ray Absorption Fine Structure (XAFS) measurements, are applied as highly active catalysts for CO₂ reduction. Compared to the supported Rh/SrTiO₃, the catalyst synthesized by a doping-segregation method exhibits a higher space-time yield (STY) to CO with a selectivity of 95% for CO₂ reduction by hydrogen; it also shows a higher activity with a larger turnover frequency (TOF) for CO₂ reduction by ethane. According to the in-situ diffuse reflectance infrared Fourier transformed spectroscopy (DRIFTS) experiments, the higher CO selectivity for CO₂ hydrogenation is attributed to the lower CO binding strength resulted by the strong interactions (e.g., charge transfer) between Rh atoms and the oxide support with surface defects. The superior activity is suggested to be originated from the cooperative effect between the highly dispersed sub-nanometer Rh clusters for efficient dissociation of H₂/C₂H₆ and the reconstructed SrTiO₃ with oxygen vacancies for preferential adsorption/activation of CO₂. The doping-segregation method provides a unique opportunity to tune the size of active metal clusters and the physicochemical properties of the oxide support, offering the potential for applications in a variety of chemical reactions.