The metal-support synergistic effects for CO2 hydrogenation to methanol over supported NiGa catalyst: Understanding the role of different active sites

NiGa catalyst is recognized for its effectiveness in CO2 hydrogenation into methanol despite the unavoidable CH4 formation. To address the issue, this study comprehensively investigated the catalytic performance and metal- support synergy of supported NiGa catalyst. ZnO outperformed SiO2, Al2O3 and MgO as NiGa supports in terms of methane suppression and methanol formation. Catalyst characterization revealed that NiZnGa formation on ZnO and ZnGa2O4 identified at the interface between NiZnGa and ZnO played crucial roles in hydrogen activation and CO2 adsorption. The metal-support interaction changes Ni's electronic structure, affecting the catalyst capability of CO adsorption. Changes of Ni:Ga ratio revealed that NiGa(5:3)/ZnO outpaced other two catalysts (3:1, 1:1) to achieve 46.4% methanol selectivity and 53.8 g MeOH /kg cat. /h. The methanol production rate was positively related to the medium CO adsorption. In-situ DRIFTS analysis revealed the reaction mechanism of NiGa(5:3)/ZnO: CO2 adsorption and activation occurred on ZnGa2O4, with methanol formation following the formate and carboxylate pathways.