Electronic Structure Engineering of RuNi Alloys Decrypts Hydrogen and Hydroxyl Active Site Separation and Enhancement for Efficient Alkaline Hydrogen Evolution

Abstract

Rational design of the active sites of hydrolysis dissociation intermediates to weaken their active site competition and toxicity is a key challenge to achieve efficient and stable hydrogen evolution reaction (HER) in ruthenium-containing alloys. Density Functional Theory (DFT) simulations reveal that the transfer of the d-band electrons from Ru to Ni in RuNi alloys results in a Gibbs free energy of −0.12 eV for the Ru0.250Ni Fcc-site H*. In addition, the high spin state of the electrons outside the Ru nucleus strengthens the adsorption of OH* on the Ru─Ni bond, which weakens the active-site competition and toxicity successfully. This theoretical prediction is confirmed by electrodeposition of prepared aRuxNi, and the RuNi alloys obtained by Ru atom doping have excellent HER properties. aRu0.250Ni has overpotentials of 38 and 162.4 mV at −10 and −100 mA cm−2, respectively, and can be stably operated at −100 mA cm−2 Dual-electrode system aRu0.250Ni//bRu0Ni demonstrates an ultra-low battery voltage (1.86 V @500 mA cm−2) and excellent stability (24 h@300 mA cm−2). This holistic work resolves the mechanism of active site separation and strengthening in RuNi alloys, and provides a new design idea for the preparation of highly efficient alkaline HER electrodes.