Hydrogen evolution and oxygen evolution reactions of pristine and alkali metal doped SnSe2 monolayer

Abstract

Many transition metal di-selenides such as MoSe2 and WSe2 show good catalytic activity on their edges with limited active orientations. These metal di-selenides are actively being used as target material for increasing the number of electrocatalytic active sites and in turn to improve the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) activities by increasing the ratio of edges to the basal plane. In present work, we have studied the activity of pristine and alkali atoms (Na, K and Ca) doped-SnSe2 for HER and OER catalyst. The state-of-art density functional theory (DFT) based computations are performed for estimating the catalytic activity of the pristine and doped SnSe2 by means of evaluating the adsorption and Gibbs free energies subjected to hydrogen and oxygen adsorption. Further, to get better prediction of adsorption energy on the individual catalytic surface, we have included the dispersion correction term to exchange-correlation functional. Results show that the pristine SnSe2 is not a good HER catalyst when hydrogen is adsorbed on its basal plane. However, edge-sites show the good hydrogen adsorption and indicates that the edges of SnSe2 are the most preferential site for hydrogen adsorption. As far as the catalytic activity of SnSe2 with dopants is concerned, the Na-doped SnSe2 among all shows the best catalytic activity over its edge-site; whereas K and Ca doped SnSe2 show basal plane as preferred catalytic site. It is interesting to note that the disadvantage of low catalytic activity on basal plane of SnSe2 can be improved by selective doping of alkali metals.