Liquid phase hydrogenation of CO2 to formate using palladium and ruthenium nanoparticles supported on molybdenum carbide

We report the development of palladium nanoparticles supported on Mo2C as an active catalyst for the liquid-phase hydrogenation of CO2 to formate under mild reaction conditions (100 °C and 2.0 MPa of a 1 : 1 CO2 : H2 mixture). A series of Pd/Mo2C catalysts were synthesised via the modified wet-impregnation (MIm) and sol-immobilization (SIm) techniques and evaluated for CO2 hydrogenation, in an aqueous 1 M NaOH solution. MIm catalysts synthesised using PdCl2 dissolved in a 2 M HCl solution gave the highest formate yield with turnover numbers of up to 109 after 19 h. We further report the crucial role of base and the pH of the reaction medium for the hydrogenation of CO2 to formate. Based on stability studies, electron microscopic characterisation and density functional theory calculations we found that Ru has a stronger affinity than Pd to Mo2C resulting in the development of a stable bimetallic RuPd/Mo2C catalyst for the hydrogenation of CO2 to formate.