Ru incorporated into Se vacancy-containing CoSe2 as an efficient electrocatalyst for alkaline hydrogen evolution

Abstract

In alkaline media, slow water dissociation leads to poor overall hydrogen evolution performance. However, Ru catalysts have a certain water dissociation performance, thus regulating the Ru–H bond through vacancy engineering and accelerating water dissociation. Herein, an excellent Ru-based electrocatalyst for the alkaline HER has been developed by incorporating Ru into Se vacancy-containing CoSe₂ (Ru–V_Se–CoSe₂). The results from X-ray photoelectron spectroscopy, kinetic isotope effect, and cyanide poisoning experiments for four catalysts (namely Ru–V_Se–CoSe₂, Ru–CoSe₂, V_Se–CoSe₂, and CoSe₂) reveal that Ru is the main active site in Ru–V_Se–CoSe₂ and the presence of Se vacancies greatly facilitates electron transfer from Co to Ru via a bridging Se atom. Thus, electron-rich Ru is formed to optimize the adsorption strength between the active site and H*, and ultimately facilitates the whole alkaline HER process. Consequently, Ru–V_Se–CoSe₂ exhibits an excellent HER activity with an ultrahigh mass activity of 44.2 A mg_Ru⁻¹ (20% PtC exhibits only 3 A mg_Ru⁻¹) and a much lower overpotential (29 mV at 10 mA cm⁻²) compared to Ru–CoSe₂ (75 mV), V_Se–CoSe₂ (167 mV), CoSe₂ (190 mV), and commercial Pt/C (41 mV). In addition, the practical application of Ru–V_Se–CoSe₂ is illustrated by designing a Zn–H₂O alkaline battery with Ru–V_Se–CoSe₂ as the cathode catalyst, and this battery shows its potential application with a maximum power density of 4.9 mW cm⁻² and can work continuously for over 10 h at 10 mA cm⁻² without an obvious decay in voltage.