CoNCNTs anchored with Ru/RuO2 heterojunction nanostructures as an electrocatalyst for highly effective water splitting

Abstract

The superior intrinsic activity of electrocatalysts is a key factor in achieving excellent hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) for overall water splitting. Herein, a RuO₂/Ru heterostructure was embedded on the surface of Co-embedded nitrogen-doped bamboo carbon nanotubes (RuO₂/Ru@CoNCNTs) by in situ substitution and thermal oxidation. The designed catalyst displayed excellent bifunctional activity, with an overpotential of only 11 mV and 234 mV for the HER and OER, respectively, at 10 mA cm⁻², and only needed a cell voltage of 1.46 V for water splitting. In particular, both the investigation on the structure–property relationship and the density functional theory (DFT) calculation on key intermediates demonstrated that the unique CoNCNT support and Ru/RuO₂ heterointerfaces induced the redistribution of charge density in Ru sites, balanced the dissociation energy of hydrolysis and free energy of adsorption of intermediates during sorption/desorption, and significantly reduced the reaction energy barrier for the rate-determining steps of HER and OER. Furthermore, the Co₂O₃ and Co_2.1Ru_0.9O₄ formed during the reaction prevented the excessive oxidation of Ru sites, improving the stability of the catalyst. Therefore, this work demonstrates a non-traditional strategy to construct a cost-effective bifunctional catalyst for water splitting that has high activity as well as outstanding stability.