A first-principles study on strain engineering of monolayer stanene for enhanced catalysis of CO reduction.

Using first-principles calculations, we investigated the changes in the lattice structure, electronic structures and catalytic performance for CO reduction reaction (CORR) of stanene under applied strain. Our calculations showed that the initial buckled honeycomb structure of free-standing stanene becomes increasingly flat upon the increase of tensile strain. Stanene remains its gapless semiconductor characteristic within the strain range of -2% and 2%, beyond which a semiconductor-to-metal transition occurs. Under strain, the adsorption of CO is weakened, which can facilitate the desorption of product CO, enabling a strained stanene to be a better catalyst for CORR to CO than strain-free stanene. In particular, the stanene with 4% strain may give rise to the best performance because of the weakest CO adsorption (E= -0.15 eV). The adsorption of intermediate product COOH on stanene is tunable with strain. We also evaluated the overall catalytic performance of the strained stanene based on the adsorption of CO and COOH and the selectivity against HER. If the reduction of COOH is governed by adsorption of the intermediate, a 10% strain may give a stronger COOH adsorption, weaker CO adsorption and better selectivity against HER, leading to an enhanced catalytic performance for CORR to CO. On the other hand, if the reduction of COOH is governed by desorption, a tensile strain higher than 4% may result in an enhanced catalytic performance. Our study here suggests that strain-tuned stanene might serve as an optimal electrocatalyst for CORR to CO with a high activity and selectivity.