Galvanic replacement assisted in situ solution combustion synthesis of copper-cobalt oxide heterointerface catalyst for electrocatalytic oxidation of 5-hydroxymethylfurfural

Developing electrocatalysts with heterointerface for biomass valorization represents a promising strategy to achieve better performance. Unfortunately, despite significant advances in the heterointerface catalyst for 5-hydroxymethylfurfural (HMF) oxidation, these catalysts still suffer from complex and multistep fabrication techniques and low activity, particularly in the low-bias region. Furthermore, the majority of these catalysts are synthesized as powders and require an additional procedure to passivate on the electrode substrates (current collector) via directly adding polymeric binders. Herein, we report the synthesis of a Cu_xO/CoO_x catalyst, synthesized on a raw Cu foam via galvanic replacement assisted in situ solution combustion method (ISCS). Interestingly, the two approaches work synergistically to engineer a self-standing Cu_xO/CoO_x heterointerface catalyst for the efficient oxidation of HMF to furanedicarboxylic acid (FDCA). Physicochemical and electrochemical characterizations, along with density functional theory (DFT) calculations, reveal strong electronic coupling between Cu_xO and CoO_x, facilitating accelerated HMFOR kinetics through enhanced charge transfer and adsorption of HMF and OH^–. Specifically, Cu_xO/CoO_x catalyst demonstrates low onset potential (∼1.0 V_RHE) and high current density (j), reaching 46.6, 172.8 and 361.9 mA cm⁻² at small voltages of 1.2, 1.3 and 1.4 V_RHE, respectively, with excellent selectivity and Faradaic efficiency for FDCA (∼98 % and ∼ 96.7 %, respectively). This study presents a novel synthesis route and offers valuable insights for designing efficient heterointerface electrocatalysts for value-added biomass conversion.