A one-pot carbon-coating-ex-solution route to efficient Ru-MnO@C nanowire electrocatalysts with enhanced interfacial interactions

The immobilization of metal nanoclusters in an inorganic matrix has attracted intense research interest because of its usefulness in exploring highly efficient electrocatalyst materials. In this study, a novel one-pot carbon-coating-ex-solution route to robust high-performance electrocatalysts of metal-nanocluster-embedded carbon-coated inorganic nanostructures was developed by the C₂H₂ treatment of metal-substituted MnO₂ nanowires at elevated temperatures. The calcination of Ru-substituted Mn_1-xRu_xO₂ nanowires under a flow of C₂H₂/Ar led not only to the simultaneous carbon coating and reductive formation of MnO, but also to the ex-solution embedding of Ru nanoclusters between the MnO substrate and the coated carbon layers. The resulting Ru-embedded Ru-MnO@C nanowires showed a promising electrocatalytic performance with an improved stability for the hydrogen evolution reaction (HER), and this performance was superior to those of Ru-deposited Ru-MnO@C nanowires, Ru-free MnO@C nanowires, and Mn_1-xRu_xO₂ nanowires. The Ru-MnO@C nanowires possessed an excellent electrochemical stability due to the formation of strong interfacial Ru⁴⁺-O-Mn²⁺ bonding and the promoted crystallization of the tight graphitic carbon layer by Ru anchoring. Furthermore, in situ surface-enhanced Raman scattering and electron paramagnetic resonance analyses provided strong evidence for the improved interfacial charge transfer kinetics and enhanced electron injection from MnO to the Ru nanoclusters. This is responsible for the beneficial effect of the simultaneous carbon-coating-ex-solution process on the HER electrocatalyst functionality.