A combined diffuse reflectance infrared Fourier transform spectroscopy–mass spectroscopy–gas chromatography for the operando study of the heterogeneously catalyzed CO2 hydrogenation over transition metal-based catalysts

We built an inline diffuse reflectance infrared Fourier transform spectroscopy–mass spectroscopy–gas chromatography (DRIFTS–MS–GC) apparatus aiming at an operando mechanistic study of the heterogeneously catalyzed CO2 hydrogenation reaction. The multifunctional and accurate system enabled the simultaneous utilization of IR, MS, GC, and nuclear magnetic resonance techniques in one single device to analyze the surface, gas, and liquid products formed during the reaction process. To assess the potential of the system, we compared the activity of pristine metal (Fe, Co, Ni, and Cu), metal alloy (LaNi4Cu), and metal–metal oxide (Co—CoO) catalysts with respect to the interactions between gaseous CO2 and the catalyst surfaces. For the quantitative comparison, the rate constants and activation energies of CO2 hydrogenation were determined. The results showed a composition dependent reactivity of the metals. The metal oxide mixed with the metal is essentially important for the formation of observable of the surface species deriving from CO2 adsorption and for the enhancement of the CO2 conversion to CH4.