Facile Synthesis of Microsphere-like Co_0.85Se Structures on Nickel Foam for a Highly Efficient Hydrogen Evolution...

Microsphere-shaped cobalt selenide (Co_0.85Se) 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_0.85Se microsphere-like structures were obtained through selenization. Compared to Co(OH)F, the microsphere-like Co_0.85Se 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_0.85Se microspheres, characterized by a low overpotential of 148 mV and a Tafel slope of 55.7 mV dec^-1. Furthermore, the Co_0.85Se 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_0.85Se structure compared to Co(OH)F, emphasizing its promise for advanced electrocatalytic applications.