La-RuO2 nanocrystals with efficient electrocatalytic activity for overall water splitting in acidic media: Synergistic effect of La doping and oxygen vacancy

Abstract

The development of high-performance and durable Ru-based electrocatalysts in proton exchange membrane (PEM) water electrolyzers for both the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) remains a huge challenge due to the severe catalyst’s corrosion and high reaction overpotential in acid media. Herein, we reported a synergistic strategy of effectively combining hetero-atom doping and oxygen vacancy in the La-doped RuO2 nanocrystals, successfully realized by a hydrothermal and followed annealing process aiming for efficiently overall water splitting. The as-obtained La-doped RuO2 nanocrystals demonstrate superior electrocatalytic performances with ultra-low overpotential of 208 mV for OER and 71 mV for HER at the current density of 10 mA/cm2 together with robust long-term stability in 0.5 M H2SO4 electrolyte, which are 222 and 15 mV lower in overpotentials than that of bare RuO2 electrocatalyst. Moreover, the La-doped RuO2 nanocrystals only require a cell voltage of 1.53 V to drive the overall water splitting reaction and exhibit a remarkable stability. Density functional theory (DFT) calculations further reveal that the synergistic effect of La doping and oxygen vacancy engineering could tune the d-band center of Ru active sites and optimize the Gibbs free energy of intermediate state, thus enhancing the activity of RuO2. Such synergistic strategy of aliovalent doping and vacancy engineering for much enhanced acid electrocatalysis may offer important referential values for exploring efficient electrocatalysts towards overall water splitting in acidic media.