Mechanisms of CO2 reduction into CO and formic acid on Fe (100): a DFT study
Caroline R. Kwawu, Albert Aniagyei, Destiny Konadu, Boniface Yeboah Antwi
Abstract
Abstract Understanding the mechanism of CO 2 reduction on iron is crucial for the design of more efficient and cheaper iron electrocatalyst for CO 2 conversion. In the present study, we have employed spin-polarized density functional theory calculations within the generalized gradient approximation (DFT-GGA) to elucidate the mechanism of CO 2 reduction into carbon monoxide and formic acid on the Fe (100) facet. We also sort to understand the transformations of the other isomers of adsorbed CO 2 on iron as earlier mechanistic studies are centred on the transformations of the C 2v geometry alone and not the other possible conformations i.e., flip-C 2v and Cs modes. Two alternative reduction routes were considered i.e., the direct CO 2 dissociation against the hydrogen-assisted CO 2 transformation through formate and carboxylate into CO and formic acid. Our results show that CO 2 in the C 2v mode is the precursor to the formation of both products i.e., CO and formic acid. Both the formation and transformation of CO 2 in the Cs and flip-C 2v is challenging kinetically and thermodynamically compared to the C 2v mode. The formic acid formation is favoured over CO via the reverse water gas shift reaction mechanism on Fe (100). Both formic acid formation and CO formation will proceed via the carboxylate intermediate since formate is a stable intermediate whose transformation into formic acid is challenging both kinetically and thermodynamically. Graphic abstract