Bimetallic catalysts for green methanol production via CO2 and renewable hydrogen: a mini-review and prospects

Recently, the increasing level of atmospheric CO2 has been well noted due to its association with global warming, provoking growth in environmental concerns toward the continued use of fossil fuels. To mitigate the concentration of atmospheric CO2, various strategies have been implemented. Carbon capture and utilisation along with renewable hydrogen production to generate raw materials for methanol production are one of the options to turn waste CO2 into useful fuels and chemicals. In the 1960s, the highly active and cost-effective Cu/ZnO/Al2O3 catalyst was developed for the synthesis of methanol from carbon oxides and hydrogen derived from natural gas. Since then, metal nanoparticles and nanocomposites have been extensively investigated and applied to CO2 hydrogenation to methanol. Particularly, bimetallic catalysts have emerged as an important class of catalysts due to their unique properties and enhanced catalytic performances compared to their monometallic counterparts. In this mini review, after giving the introduction of the main motivation for the development of green methanol production via CO2 hydrogenation, we first summarise the recent promising research activities in the fields of generating renewable CO2/H2 sources from carbon capture technologies, green hydrogen production, and biomass-derived CO2/H2 mixtures. Then we provide an overview of the developments in the preparation of some new bimetallic catalysts for CO2 hydrogenation to methanol with emphasis on the synergistic effects and the enhancement of catalytic performances compared to their monometallic counterparts. Finally, the main conclusions are summarised and an outlook is presented for future development in this research area.