Adsorption and splitting of H2S on 2D-ZnO1-xNy: first-principles analysis

We present a thorough analysis of molecular adsorption of a toxic gas, H2S, on pristine, defective and N-substituted 2D-ZnO using first-principles simulations within density functional theory and the parameterized form of van der Waals (vdW) interaction. We find that the binding of H2S with pristine 2D-ZnO is relatively weak (adsorption energy E-A = -29 to -36 kJ mol(-1)) as it is mainly through the vdW interaction. However, substitutional nitrogen doping in 2D-ZnO leads to a drastic increase in the adsorption energy (E-A = -152 kJ mol(-1)) resulting in dissociation of H2S molecules. This originates fundamentally from a strong covalent bonding interaction between an unpaired electron in the p-orbital of nitrogen and an electron in the s-orbital of H. While O-vacancy in 2D-ZnO has little effect on its interaction with H2S at lower coverages, a strong interaction at higher coverages leads to splitting of H2S and formation of H-2 molecules. Our work shows that 2D-ZnO is a promising material to facilitate capturing of toxic H2S from the environment and at the same time converting it to a green source of energy.