Hydrogen evolution over N-doped CoS2 nanosheets enhanced by superaerophobicity and electronic modulation

Doping heteroatoms offers an opportunity to tune the electronic structure and promote hydrogen evolution reaction (HER) activity for an electrocatalyst. Herein, N-doped CoS2 nanosheets (N-CoS2 NSs) were deposited on carbon cloth via a hydrothermal and post-sulfuration process. The N-CoS2 NSs intercrossed with each other, exhibiting promising superaerophobicity without any adhesion to underwater bubbles. XPS analyses revealed the presence of electron transfer from Co to N dopant in N-CoS2, further proved by differential charge density and Bader charge analyses of density functional theory calculations. The electron transfer intrinsically altered the electronic structure of N-CoS2 and decreased the Gibbs adsorption energy of hydrogen over Co sites. The metallicity of CoS2 was remained after N doping, ascertaining a fast charge transfer and favorable HER process. The N-CoS2/CC showed an enhanced electrocatalytic HER activity with a Tafel slope of 60.1 mV dec(-1) and low overpotential of 112 mV at a current density of 10 mA cm(-2). Such promising performance is ascribed to the weak hydrogen adsorption upon N doping as well as the underwater superaerophobicity of N-CoS2/CC electrode. Our work might shed light on designing efficient and inexpensive HER electrocatalysts by tailoring their electronic structure and surface superaerophobicity.