Unusual Formation of CoS0.61Se0.25 Anion Solid Solution with Sulfur Defects to Promote Electrocatalytic Water Reduction

Defects engineering is an effective strategy to promote electrocatalytic performance. Herein, cobalt binary chalcogenide hollow spheres (CBC HSs) with sulfur (S) defects were prepared by selenium (Se) heteroatom substitution to enhance electrocatalytic water reduction. The Se atoms were intentionally introduced into the crystalline lattices of hexagonal CoS HSs, forming an anion solid solution with S vacancies. Due to enhanced intrinsic electroactivity and enlarged surface area, this CBC HS electrocatalyst exhibited low overpotentials of 108 and 372 mV to realize current densities of 10 and 100 mA cm–2, respectively, for hydrogen evolution reaction.