Hydrogen evolution reaction and electronic structure calculation of two dimensional bismuth and its alloys

We present a systematic ab initio study of atomic hydrogen and oxygen adsorption on bismuthene monolayer and its alloys with arsenic and antimony through electronic structure calculations based on density functional theory within generalized gradient approximation. We systematically investigated the preferable adsorption site for hydrogen and oxygen atom on 2D Bi, BiAs and BiSb. It was found that the hydrogen atom prefers top site of bismuth atom and oxygen atom prefers to reside in the hexagonal ring of these 2D bismuth alloys. The free energy calculated from the individual adsorption energy for each monolayer subsequently guides us to predict the best suitable catalyst among the considered 2D monolayers. The 2D BiSb serves better for hydrogen evolution reaction (HER) with hydrogen adsorption energy as ?1.384 eV while 2D BiAs is suitable for oxygen evolution reaction (OER) with oxygen adsorption energy as ?1.092 eV. We further investigated the effects of the adsorbate atom on the electronic properties of 2D Bi, BiAs and BiSb. The adsorption of oxygen on 2D BiAs and BiSb was shown to reduce the bulk band gap by 40.56 and 67.79% respectively which will be advantageous for the observation of Quantum Spin Hall effect at ambient conditions.