Tin oxide (SnO2) is an efficient catalyst
for the CO2 reduction reaction (CO2RR) to formic
acid; however,
the understanding of the SnO2 surface structure under working
electrocatalytic conditions and the nature of catalytically active
sites is a current matter of debate. Here, we employ ab initio density functional theory calculations to investigate how the selectivity
and reactivity of SnO2 surfaces toward the CO2RR change at varying surface stoichiometry (i.e., reduction degree).
Our results show that SnO2(110) surfaces are not catalytically
active for the CO2RR or hydrogen evolution reaction, but
rather they reduce under an applied external bias, originating surface
structures exposing few metal tin layers, which are responsible for
formic acid selectivity.
Mineral surfaces have been demonstrated to play a central role in prebiotic reactions, which are understood to be at the basis of the origin of life. Among the various molecules proposed as precursors for these reactions, one of the most interesting is formamide. Formamide has been shown to be a pluripotent molecule, generating a wide distribution of relevant prebiotic products. In particular, the outcomes of its reactivity are strongly related to the presence of mineral phases acting as catalysts toward specific reaction pathways. While the mineral–products relationship has been deeply studied for a large pool of materials, the fundamental description of formamide reactivity over mineral surfaces at a microscopic level is missing in the literature. In particular, a key step of formamide chemistry at surfaces is adsorption on available interaction sites. This report aims to investigate the adsorption of formamide over a well-defined amorphous silica, chosen as a model mineral surface. An experimental IR investigation of formamide adsorption was carried out and its outcomes were interpreted on the basis of first principles simulation of the process, adopting a realistic model of amorphous silica.
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