Ru incorporated into Se vacancy-containing CoSe ₂ as an efficient electrocatalyst for alkaline hydrogen evolution

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.