Controlling selectivities in CO₂ reduction through mechanistic understanding.

Abstract

Catalytic CO₂ conversion to energy carriers and intermediates is of utmost importance to energy and environmental goals. However, the lack of fundamental understanding of the reaction mechanism renders designing a selective catalyst inefficient. Here we show the correlation between the kinetics of product formation and those of surface species conversion during CO₂ reduction over Pd/Al₂O₃ catalysts. The operando transmission FTIR/SSITKA (Fourier transform infrared spectroscopy/steady-state isotopic transient kinetic analysis) experiments demonstrates that the rate-determining step for CO formation is the conversion of adsorbed formate, whereas that for CH₄ formation is the hydrogenation of adsorbed carbonyl. The balance of the hydrogenation kinetics between adsorbed formates and carbonyls governs the selectivities to CH₄ and CO. We apply this knowledge to the catalyst design and achieve high selectivities to desired products.Understanding the mechanism of CO₂ reduction on a catalyst surface is essential for achieving the desired product selectivity. Here, the authors show an operando kinetic analysis of CO₂ hydrogenation over a palladium catalyst in order to address the factors governing the selectivity of the process.