Atomic equidistribution enhanced RuIr electrocatalysts for overall water splitting in the whole pH range

Developing bifunctional electrocatalysts with high activity and long-term stability over the whole pH range is still a great challenge. Herein, the unsupported RuIr alloys are reported as robust electrocatalysts for pH-universal overall water splitting. The as-synthesized Ru0.5Ir0.5 alloy exhibits unexpected low overpotentials of 4, 28, 16 mV for hydrogen evolution reaction (HER) and 160, 176, 248 mV for oxygen evolution reaction (OER) at 10 mA cm−2 in 0.5 M H2SO4, 1.0 M KOH and 1.0 M PBS solutions, respectively. Especially, the Ru0.5Ir0.5||Ru0.5Ir0.5 cell only needs voltages of 1.44, 1.48 and 1.51 V in the three environments to reach the same current density for overall water splitting and can continuously operate for more than 400, 100 and 100 h. Comprehensive studies verify that the excellent electrocatalytic performance of Ru0.5Ir0.5 originates from the uniform arrangement of Ru and Ir atoms in the alloy, which leads to the leaching of an appropriate amount of Ru atoms and thus produces a protective skeleton composed of high valence Ir (IV) to prevent further dissolution of Ru. In addition, the weak coupling between Ru and Ir makes electron transfer from Ir to adjacent Ru as active sites, resulting in optimal adsorption strength for key intermediates.