Operando Raman interrogation of the synthesis and activation of a CoSe HER catalyst

Abstract

A highly active cobalt selenide electrocatalyst for the hydrogen-evolution reaction (HER) in acidic media was electrochem. synthesized using a two-step process consisting of potentiostatic electrodeposition from aq. soln. followed by galvanostatic conditioning in the HER potential regime. Ex-situ Raman spectroscopy and energy-dispersive X-Ray spectroscopy indicated that the initial deposition step generated a material contg. CoSe as well as Se in multiple phases. Operando Raman anal. during the initial galvanostatic operation indicated a structural evolution of the Se phases including the partial elimination of one phase. Despite operating in the HER regime, the faradaic efficiency towards hydrogen evolution was low until this structural change was complete, demonstrating the in situ realization of the active catalytic material. This resulting catalyst required an overpotential (η) < 150 mV to drive the benchmark c.d. of -10 mA cm^(-2) in 0.5 M H_2SO_4. Stability anal. including continuous galvnostatic operation as well as simulated intermittent operation indicated significant electrochem. robustness in the acidic operating environment.