摘要
Using first-principles calculations,hydrogen evolution reaction(HER) activity on two-dimensional(2 D) gallium chalcogenides monolayers GaX(X=O,S,Se,and Te) as well as the derived Janus monolayers Ga_(2) XY(X≠Y,X/Y=O,S,Se,and Te) were systematically examined.It was found that Ga_(2) OSe Janus monolayer with a 0.3% strain has the lowest ΔG_(H)*of 0.19 eV(modified to-0.01 eV including the solvation effect) because(ⅰ) O is the most electronegative among X/Y atoms,(ⅱ) the Ga_(2) OSe monolayer has a larger lattice parameter with respect to GaO monolayer,and(ⅲ) the built-in electric field is enhanced after H adsorption.The enhanced H adsorption with the lattice stretching is a result of the weaker Ga-O bond strength before H adsorption and the reduced electron fillings of anti-bonding molecular orbital formed by H 1 s and O2 p_(z) orbitals after H adsorption.The O-p_(z) band center can be served as a descriptor to describe the HER activity trend for these p-block materials.Moreover,Ga_(2) OSe monolayer has appropriate band alignment,distinguished optical absorption coefficient(10~5 cm^(-1)),low exciton binding energy(0.71 eV),and the spontaneous HER process,indicating that it is a highly potential candidate for near-infrared photocatalyst for hydrogen production.Our research provides a novel paradigm that forming Janus structure can effectively tune the HER activity,which would guide the searching for excellent HER photocatalysts for clean hydrogen production.
基金
supported byNational Natural Science Foundation of China no. 21573002 (HY)
Natural Science Funds for Distinguished Young Scholar of Anhui Province (1908085J08)。