Low-Crystalline Cobalt Iron Oxide-Supported Single Ru Atoms and Ru Clusters for 2,5-Hydroxymethylfurfural Electro-Oxidation Coupled with Hydrogen Evolution

Producing hydrogen at the cathode coupled with biomass electro-oxidation to generate high-value chemicals at the anode in an electrolytic cell is expected to alleviate the energy crisis and meet the people’s demand for chemicals. It would result in simple construction and cost savings if a catalyst had the function of both electrochemical hydrogen evolution reaction (HER) and biomass electro-oxidation in the same electrolyte. Herein, we used low-crystalline cobalt iron oxide as a substrate to anchor Ru species. The Ru was mainly in the form of single Ru atoms and Ru nanoclusters. After the introduction of Ru, the electronic structure of the oxide substrate was effectively regulated, which had a tendency to accept electrons from Ru species. With the redistributed charge density, the electrochemical ability of the catalyst was greatly improved, which needed only 37 mV to reach 10 mA cm–2 for HER. Moreover, the electrocatalyst also exhibited outstanding catalytic performance for 2,5-hydroxymethylfurfural (HMF) oxidation with fast reaction kinetics and high yield rate and Faraday efficiency. When the electrolytic cell was constructed with this electrocatalyst as both cathode and anode, it needed only 1.16 V to reach 10 mA cm–2, which was 408 mV smaller than that of a traditional water-splitting system. Theoretical calculation demonstrated that the free energy barrier had been decreased, and the adsorption of active sites toward intermediates had been strengthened after the loading of Ru, leading to improved electrocatalytic ability. This work provides a new idea for the development of an advanced bifunctional electrocatalyst.