Ruthenium/Ruthenium oxide hybrid nanoparticles anchored on hollow spherical Copper-Cobalt Nitride/Nitrogen doped carbon nanostructures to promote alkaline water splitting: Boosting catalytic performance via synergy between morphology engineering, electron transfer tuning and electronic behavior modulation

Exploring bi-functional electrocatalysts with excellent activity, good durability, and cost-effectiveness for electrochemical hydrogen and oxygen evolution reactions (HER and OER) in the same electrolyte is a critical step towards a sustainable hydrogen economy. Three main features such as high density of active sites, improved charge transfer, and optimized electronic configuration have positive effects on the electrocatalyst activity. In this context, understanding structure-composition-property relationships and catalyst activity is very important and highly desirable. Herein, for the first time, we present the design and fabrication of novel MOF-derived ultra-small Ru/RuO2 nanoparticles doped in copper/cobalt nitride (CuCoN) encapsulated in nitrogen-doped nanoporous carbon framework (NC) (Ru/RuO2/CuCoN@NC). For the synthesize of this nanocomposite, firstly bimetallic Cu-Co/MOF hollow nanospheres are prepared via a facile emulsion-based interfacial reaction method and used as the template for Ru ion doping (Ru-doped Cu-Co/MOF). Then, Ru-doped Cu-Co/MOF precursor during the carbonization/nitridation/cooling process converted to the Ru/RuO2/CuCoN@NC nanocomposite. Benefiting from the desirable compositional and structural advantages of more exposed active sites, optimized electronic structure, and interfacial synergy effect, Ru/RuO2/CuCoN@NC hollow nanosphere electrocatalyst demonstrates striking catalytic performances under alkaline conditions with a current density of 10 mA cm-2at low overpotentials of 41 mV for HER and 231 mV for OER, respectively. Moreover, as a bifunctional electrocatalyst for overall water splitting, a two-electrode device needs a voltage of 1.51 V to reach a current density of 10 mA cm-2. Comprehensive electrochemical studies show that the excellent electrocatalytic performance of the Ru/RuO2/CuCoN@NC hollow nanosphere could be attributed to the improved physical and chemical properties such as desirable compositional, catalysts uniform dispersion, structural advantages of more exposed active sites, optimized electronic structure, high electrical conductivity, and interfacial synergy effect. This work paves a novel avenue for constructing robust bifunctional electrocatalyst for overall water splitting.