In situ Control of the Adsorption Species in CO2 Hydrogenation: Determination of Intermediates and Byproducts

CO2 hydrogenation over catalysts is a potentially exciting method to produce fuels while closing the CO2 cycle and mitigating global warming. The mechanism of this process has been controversial due to the difficulty in clearly identifying the species present and distinguishing which are reaction intermediates and which are byproducts. We in situ manipulated the independent formation and hydrogenation of each adsorption species produced in CO2 hydrogenation reaction over Ru/Al2O3 using operando diffuse reflectance infrared Fourier transformation spectroscopy (DRIFTS) and executed a novel iterative Gaussian fitting procedure. The adsorption species and their role in CO2 hydrogenation reaction have been clearly identified. The adsorbed carbon monoxide (CO*) of four reactive structures was the key intermediate of methane (CH4) production. Bicarbonate (HCO3-*), formed on the metal-support interface, appeared to be not only the primary product of CO2 chemisorption, but also a reservoir of CO*, and consisted th...