Hydrogenation of CO2 to formic acid over efficient heterogeneous ruthenium oxide supported on cubic phase zirconium oxide catalyst

The development of active, cost-effective heterogeneous catalysts for the hydrogenation of CO2 to chemicals is currently progressing rapidly. In this study, we have demonstrated a significantly lower weight percentage (wt.%) RuO2/ZrO2 oxide catalyst that is effective for CO2 hydrogenation to formic acid (FA) synthesis. RuO2/ZrO2 was synthesized using a co-precipitation followed by a hydrothermal method. The X-ray diffraction pattern exhibits the cubic phase of ZrO2 with an average crystal size of 80.7 nm and tetragonal Ru oxide. Scanning electron microscopy and transmission electron microscopy confirmed that RuO2 was uniformly dispersed on the ZrO2 surface, with fringes measuring 0.22 and 0.25 nm corresponding to tetragonal Ru, which were incorporated in the ZrO2 oxide. XPS analysis showed that the Ru3/4+ chemical state strongly interacts with the ZrO2 facet, as confirmed via the Ru (1 1 0) and (2 1 1) planes. The outstanding performance of the 2.7 wt% RuO2/ZrO2 catalyst for CO2 hydrogenation yielded 40 mmol of FA with 39.7 TON. Based on the above investigations, we proposed a plausible mechanistic pathway for the hydrogenation of CO2 to FA over a RuO2/ZrO2 catalyst.