Tuning the Interface of Co<sub>1–<i>x</i></sub>S/Co(OH)F by Atomic Replacement Strategy toward High-Performance Electrocatalytic Oxygen Evolution
Qian Lin, Daying Guo, Ling Zhou, Lin Yang, Huile Jin, Jun Li, Guoyong Fang, Xi’an Chen, Shun Wang
Abstract
The construction of heterostructures is one of the most promising strategies for engineering interfaces of catalysts to perform high-efficiency oxygen evolution reaction (OER). However, accurately tuning heterostructures’ interface during operation remains a challenge. Herein, we fabricated the needled-like heterostructure Co1–xS/Co(OH)F supported on flexible carbon fiber cloth via an atomic substitution strategy, in which sulfur atoms are simultaneously grafted into F vacancies after the partial removal of F atoms from Co(OH)F during the electrodeposition, thus achieving the growth of cobalt sulfide on the interface of Co(OH)F. This electrocatalyst with such design exhibits the following advantages: (1) The lattice distortion caused by atomic substitution leads to the increase of active sites; (2) Co1–xS constructed on the surface of Co(OH)F by the atomic replacement strategy optimizes the adsorption (OH–) and desorption (O2) energy in the OER process; (3) the needle-like structure possesses the tip-enhanced local electric field effect. As a result, the Co1–xS/Co(OH)F/CC catalyst exhibits very high OER catalytic performance with an overpotential of 269 mV at a current density of 10 mA cm–2 and a Tafel slope of 71 mV dec–1. The asymmetric electrode shows superior catalytic activity and stability in overall water splitting. The catalytic mechanism of these highly efficient Co1–xS/Co(OH)F/CC catalysts was investigated via DFT theoretical calculations and ex situ characterizations. This atomic substitution strategy displays universality for other transition metal sulfides (metal = Ni, Mn, Cu).