Ru/TiO2 catalyst modified by phosphate anion: Realizing specific transformation of CO2 hydrogenation products

Regulation of the CO2 hydrogenation process to obtain highly selective target products is a challenging and important research topic. In this study, we report the key role of PO43- anions modified on the Ru/TiO2 catalyst surface in regulating the CO2 hydrogenation process. Ion chromatography, X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy confirmed the successful preparation of the Ru/TiO2 catalyst modified by PO43- anions. The original Ru/TiO2 catalyst showed poor catalytic activity in CO2 hydrogenation, and the main hydrogenation product was CO. With the PO43- anion-modified Ru/TiO2 catalysts, the conversion of CO2 was clearly improved, and the hydrogenation product changed from CO to CH4. XPS characterization and DFT theoretical calculations confirmed that the modified PO43- anions interacted mainly with the Ru metal site on the Ru/TiO2 catalyst surface, effectively regulating the surface electronic properties of the Ru metal, which affected the conversion efficiency of CO2. In addition, CO temperature-programmed desorption and diffuse reflectance infrared Fourier transform spectroscopy characterization revealed that the adsorption of CO intermediates improved after the Ru metal surface was modified with PO43- anions, which was beneficial for further CO hydrogenation and the formation of CH4 products. Our work expands the research strategies of anion-modified metal-based catalysts that regulate the hydrogenation performance of CO2 and provides a new direction for further understanding the influence mechanism of the catalyst surface structure on hydrogenation performance.