Combining heat with light boosts methanol synthesis from CO₂

Annual global production of methanol sits around 100 million-metric-tons and is growing quickly. Used as a precursor to make formaldehyde and other commodity chemicals, methanol is produced industrially via hydrogenation of carbon monoxide with the help of a catalyst consisting of copper, zinc oxide, and alumina. Many studies have shown that CZA catalysts can also produce methanol from carbon dioxide, suggesting a way to control atmospheric levels of the greenhouse gas. But limited understanding of the reaction mechanism and best conditions for converting CO₂ to methanol has hampered development of that technology. Researchers led by Rose Amal and Jason Scott of the University of New South Wales have now shown that the performance of CZA catalysts, normally activated by heat only, can be boosted by combining heat with light, and they have deduced a multistep reaction mechanism explaining the basis of the improvement (Nat. Commun. 2020, DOI: 10.1038/s41467-020-15445-z). The team showed that irradiating the catalyst with ultraviolet and visible light while heating it simultaneously excites copper and zinc oxide, which synergistically activates molecular hydrogen and drives conversion of HCOO reaction intermediates. Compared with thermal catalysis, the photothermal process can raise the methanol yield 30% while running 50 °C cooler.