Role of Graphene Oxide Aerogel Support on the CuZnO Catalytic Activity: Enhancing Methanol Selectivity in the Hydrogenation Reaction of CO2

A novel CuZnO multicomponent catalyst, involving reduced graphene oxide (rGO) as a support, was synthesized to be applied in the catalytic hydrogenation of CO2 to methanol. The CuZnO@rGO composite was prepared as a 3D aerogel by a two-step process involving supercritical CO2 for macrostructuration and H2 treatment for reduction. Electron microscopy was applied to visualize the meso/macroporous morphology formed by the supercritical drying. The elemental mapping depicted a homogenous distribution of CuZnO nanoparticles deposited on the rGO flakes. It was demonstrated that methanol production increases for the CuZnO@rGO composite in comparison to unsupported similar CuZnO nanoparticles. This behavior was ascribed to a different interaction established between the Cu0 and ZnO nanoparticles used as synthetized or deposited on rGO. It is shown that the highly reduced rGO component stimulates H2O desorption produced during the hydrogenation reaction, thus it serves as a support hindering the sintering of Cu0 nanoparticles. The formation of a diluted surface alloy of Zn into Cu0 was determined for the unsupported CuZnO NPs, while for the CuZnO@rGO aerogel composite, the absence of any additional phase, e. g., a surface alloy or reduced ZnO, was confirmed. The composite aerogels show excellent MeOH selectivity at high temperature (up to 260 °C) and low pressure (10 bar).This work was supported by the Spanish Ministry of Science and Innovation MICINN through the Severo Ochoa Program for Centers of Excellence (CEX2019-000917-S) and the Spanish National Plan of Research with project PID2020-115631GB-I00. Catalytic experiments were funded by the Ramón Areces foundation, in the hallmark of the META2NOL project granted in the XIX national contest of life and matter sciences projects. Márta Kubovics acknowledge the financial support from the European Union's Horizon 2020 research and innovation program under the Marie Sklodowska-Curie Cofund grant (agreement no MSCA-COFUND-DP/0320-754397). This work has been done in the framework of the doctoral program “Chemistry” of the Universitat Autònoma de Barcelona by Márta Kubovics.With funding from the Spanish government through the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000917-S).Peer reviewe