Early transition metal oxides with oxygen vacancies as new thermodynamically stable materials for electrocatalysis

Currently developed electrocatalysts are difficult to achieve high thermodynamic stability at each active site. Early transition metal oxides are promising electrocatalysts with excellent thermodynamic stability and water dissociation ability for alkaline hydrogen evolution reaction (HER). However, they have not been developed as direct-electrocatalysts for water splitting. Here, we introduce oxygen vacancies (Vo) by electrodeposition to convert early transition metal oxides (scandium oxide (Sc2O3), yttrium oxide (Y2O3), and zirconium oxide (ZrO2)) into active electrocatalysts. By optimizing the metal element species and Vo content, the screened Y2O2.13@GP shows the lowest overpotential (266 mV at 500 mA cm-2. Moreover, Y2O2.13@GP is able to operate stably for over 1000 h at a current density of 500 mA cm-2 under harsh industrial conditions of 6.0 M KOH and 80°C without dissolution and reconstruction. Experimental studies and theoretical calculations indicate that the introduction of Vo can enhance the conductivity of the catalyst, increase the exposure of the active sites, modulate the electronic structure of Y2O2.13@GP, and decrease the *H adsorption and water dissociation energy barriers.