Insight into in situ grown Ru-based integrated electrodes for hydrogen evolution reaction: Boosted mass transfer efficiency and promoted intrinsic activity

The rational design of high-performance electrodes for hydrogen evolution reaction (HER) is crucial for water splitting in industrial applications. Herein, dual regulation of both mass transfer and intrinsic activity for in situ grown integrated electrodes was achieved via 3D electrode design and interfacial regulation. An innovative ruthenium (Ru)-based integrated electrode was constructed through a gravity-guided chemical vapor deposition (CVD) technique, featuring a three-dimensional carbon nanotube (CNT) network structure with embedded Ru clusters. This interlaced CNT structural configuration with high porosity and superhydrophilicity improved bubble transfer efficiency by reducing bubble coverage, bubble departure time, and bubble diameter at the reaction interface. Subsequently, the introduction of appropriate covalent Ru-O bonds on the interface of the integrated electrode boosted its intrinsic HER activity. Furthermore, DFT and AIMD calculations elucidated that the formation of covalent Ru-O bonds could reduce the adsorption and desorption of H*/OH* species, strengthen the hydrogen-bond network, and optimize the orientation of water molecules in the double electric layer (EDL). Consequently, the RuOCNT integrated electrode demonstrated a remarkably low overpotential of 41 mV at 10 mA cm⁻² in a 1.0 M KOH solution and the high durability indicated by a degradation rate of only 140 μV h⁻¹ at 100 mA cm⁻² after 100 h. In addition, an in-depth analysis was carried out to distinguish the contribution of covalent Ru-O sites and electrode's 3D structure to the boosted HER activity. This study highlighted a new approach to fabricating and understanding an efficient electrode by combining electrode engineering and active site modification to enhance HER efficiency in a mutually reinforcing manner.