Recent innovation on heterogeneous ZnO-based catalysts for enhanced CO2 hydrogenation

Global warming has gotten worse recently as a result of significant CO2 emissions, making the development of technologies to lower greenhouse gas emissions of CO2 a necessity. Thermo-catalytic hydrogenation of CO2 into methanol, methane, carbon monoxide and olefin is a promising technique to overcome this problem, as it not only uses CO2 as feedstock but also yields valuable chemicals. Presently, most catalytic studies reported on the development of new catalysts to overcome the limitations of conventional catalysts. ZnO is one of the metal oxides that has been frequently utilized as a support or promoter catalyst in CO2 hydrogenation for the production of high value-added chemicals. However, the preparation of ZnO influenced the morphology and structure design of the fabricated catalysts. Recently, the tremendous inverse catalyst design involving ZnO has also been reported. The involvement of ZnO in CO2 hydrogenation is very important as it provides sufficient surface area for metal dispersion, oxygen vacancies for the generation of active sites, basic/acid properties for adsorption-desorption of molecules as well as stability for long-term usage in the reaction process. Therefore, in this review, ZnO-based catalysts used in CO2 hydrogenation and strategies to design ZnO-based catalysts were highlighted. Then, the mechanism involving ZnO-based catalysts in CO2 hydrogenation was summarized. Finally, challenges and the future of the ZnO-based catalysts are provided, emphasizing the great potential for the efficient synthesis of high value-added chemicals by CO2 conversion.