Iridium supported on spinal cubic cobalt oxide catalyst for the selective hydrogenation of CO2 to formic acid

Abstract

The utilization of abundantly available CO2 feedstock for the synthesis of high-value compounds and fuels is the main focus of catalysis research. Herein, we report the synthesis of different wt% Ir-Co3O4 oxide as a heterogeneous catalyst prepared by co-precipitation, followed by the hydrothermal method. The P-XRD analysis revealed the formation of a cubic phase with a high intense (3 1 1) plane with a 6 nm crystal size. The synthesized catalyst was used for direct hydrogenation of CO2 assisted by N,N,N',N' tetramethylenylenediamine. Under optimized reaction conditions, the 2.9 wt% Ir-Co3O4 catalyst demonstrated an excellent yield of formic acid (399 mmol). The formic acid yield in N,N,N',N; tetramethylenylenediamine is 25 times better than traditionally used trimethylamine. The outstanding performance of the Ir-Co3O4 catalyst was due to the stoichiometric amount of active Ir content uniformly distributed on Co3O4 support with a mixed Ir+3/4 oxidation state, which readily exchanges electrons between Co3O4 and Ir during the reaction. The catalyst was successfully recycled up to five times with negligible loss in the yield of formic acid.