Direct hydrogenation of CO2 to formic acid using Ru supported Co3O4 oxide as an efficient heterogeneous catalyst

The concentration of CO2 in the atmosphere is rapidly increasing, posing serious environmental concerns. It is preferable to use CO2 as a feedstock for fine chemicals and fuel synthesis to address this challenge successfully. Herein, we report the synthesis of bimetallic oxide composite with significantly lower wt.% of active Ru loaded on spinel cubic phase Co3O4 oxide support. The synthesized catalyst formed cubic Ru-Co3O4 (Ruthenium and Cobalt oxide) nanocrystalline surface morphology with active Ru+3/+4 and Co+2/+3 oxidation states under hydrothermal conditions. The synthesized Ru-Co3O4 oxide catalyst facilitated the reduction of CO2 to formic acid under tailored conditions. The 2.9 wt.% Ru-Co3O4 catalyst exhibited highest formic acid yield (250 mmol) with a high turnover number of 182 under the mild reaction conditions, 1:1 CO2 and H2 (62 bar) gas pressure, 120 °C in 6 h. Ru-supported Co3O4 catalyst captures CO2 through the base. The activated CO2 is then hydrogenated to formic acid. The catalyst can be reused for multiple cycles without losing any activity due to its alkali tolerant properties. The study offers a simple synthesis and efficient industrially viable heterogeneous catalyst for CO2 hydrogenation.