Ga-Promoted CuCo-Based Catalysts for Efficient CO2 Hydrogenation to Ethanol: The Key Synergistic Role of Cu-CoGaOx Interfacial Sites.

Abstract

Currently, direct catalytic CO2 hydrogenation to produce ethanol is an effective and feasible way for the resource utilization of CO2. However, constructing non-precious metal catalysts with satisfactory activity and desirable ethanol selectivity remains a huge challenge. Herein, we reported gallium-promoted CuCo-based catalysts derived from single-source Cu-Co-Ga-Al layered double hydroxide precursors. It was manifested that the introduction of Ga species could strengthen strong interactions between Cu and Co oxide species, thereby modifying their electronic structures and thus facilitating the formation of abundant metal-oxide interfaces (i.e., Cu0/Cu+-CoGaOx interfaces). Notably, the as-constructed Cu-CoGa catalyst with a Ga:Co molar ratio of 0.4 exhibited a high ethanol selectivity of 23.8% at a 17.8% conversion, along with a high space-time yield of 1.35 mmolEtOH·gcat-1·h-1 for ethanol under mild reaction conditions (i.e., 220 °C, 3 MPa pressure), which outperformed most non-noble metal-based catalysts previously reported. According to the comprehensive structural characterizations and in situ diffuse reflectance infrared Fourier transform spectra of CO2/CO adsorption and CO2 hydrogenation, it was unambiguously revealed that CHx could be formed at oxygen vacancies of defective CoGaOx species, while CO could be stabilized by Cu+ species, and thus the catalytic synergistic role of Cu0/Cu+-CoGaOx interfacial sites promoted the generation of CHx and CO intermediates to participate in the CHx-CO coupling process and simultaneously inhibited alkylation reactions. The present work points out a promising new strategy for constructing CuCo-based catalysts with favorable interfacial sites for highly efficient CO2 hydrogenation to produce ethanol.