Ab Initio Study of CO2 Activation on Pristine and Fe-Decorated WS2 Nanoflakes

There is an intense race by the scientific community to identify materials with potential applications for the conversion of carbon dioxide (CO2) into new products. To extend the range of possibilities and explore new effects, in this work, we employ density functional theory calculations to investigate the presence of edge effects in the adsorption and activation of CO2 on pristine and Fe-decorated (WS2) 16 nanoflakes. We found that Fe has an energetic preference for hollow sites on pristine nanoflakes, binding with at least two two-fold edge S atoms and one or two three-fold core S atoms. Fe adsorption on the bridge sites occurs only at the edges, which is accompanied by the breaking of W-S bonds in most cases (higher energy configurations). CO2 activates on (WS2)(16) with an OCO angle of about 129 degrees only at higher energy configurations, while CO2 binds via a physisorption mechanism, linear structure, in the lowest energy configuration. For CO2 on Fe/(WS2)(16), the activation occurs at lower energies only by the direct interaction of CO2 with Fe sites located near to the nanoflake edges, which clearly indicates the enhancement of the catalytic activity of (WS2)(16) nanoflakes by Fe decoration. Thus, our study indicates that decorating WS2 nanoflakes with TM atoms could be an interesting strategy to explore alternative catalysts based on two-dimensional materials.