Development of In–Cu binary oxide catalysts for hydrogenating CO2via thermocatalytic and electrocatalytic routes

Abstract

Carbon dioxide (CO₂) hydrogenation to obtain valuable chemicals and fuels via thermocatalysis or electrocatalysis is a promising and sustainable method for CO₂ utilization. Here, binary In–Cu oxide co-precipitated materials were investigated to evaluate the catalytic performance in the mentioned conversion processes. The In-rich binary material exhibits remarkable selectivity (>60%) to methanol along with high activity for CO₂ conversion (>2%) at 21 bar and 300 °C, achieving a productivity of about 265 mg_MeOH h⁻¹ g_In2O3⁻¹, which is almost 3 times higher than that of the bare In₂O₃ catalyst. CO₂-temperature programmed desorption revealed that the basicity of the In-rich catalyst remains constant between the calcined and spent samples, so the capacity to adsorb CO₂ does not vary when the catalyst is exposed to the reaction atmosphere. Such a catalyst was demonstrated to be active for formate production in the electrochemical process as the main product. Ex situ characterization after testing proved that the In₂O₃ phase was the active site of methanol synthesis during CO₂ hydrogenation at high temperatures and pressures. In contrast, depending on the cell configuration, different indium interfaces were stabilized at the electrocatalyst surface under ambient conditions. It is envisioned that the co-presence of In⁰, In₂O₃, and In(OH)₃ phases increases the local amount of *CO intermediates, promoting the formation of more reduced products, such as ethanol and 2-propanol, through the *CO dimerization reaction in the electrochemical process. These findings highlight the potential of nonreducible hydroxides as promoters in the electrochemical CO₂ reduction process.