Facile Synthesis of Microsphere-like Co(0.85)Se Structures on Nickel Foam for a Highly Efficient Hydrogen Evolution Reaction

Microsphere-shaped cobalt selenide (Co(0.85)Se) structures were efficiently synthesized via a two-step hydrothermal process. Initially, cobalt hydroxide fluoride (Co(OH)F) microcrystals were prepared using a hydrothermal method. Subsequently, Co(0.85)Se microsphere-like structures were obtained through selenization. Compared to Co(OH)F, the microsphere-like Co(0.85)Se structure exhibited outstanding catalytic activity for the hydrogen evolution reaction (HER) in a 1.0 M KOH solution. Electrocatalytic experiments demonstrated an exceptional HER performance by the Co(0.85)Se microspheres, characterized by a low overpotential of 148 mV and a Tafel slope of 55.7 mV dec(−1). Furthermore, the Co(0.85)Se electrocatalyst displayed remarkable long-term stability, maintaining its activity for over 24 h. This remarkable performance is attributed to the excellent electrical conductivity of selenides and the highly electroactive sites present in the Co(0.85)Se structure compared to Co(OH)F, emphasizing its promise for advanced electrocatalytic applications.