Tailoring the Electrochemical Interface for 5-Hydroxymethylfurfural Hydrodimerization Using Single and Gemini Quaternary Ammonium Surfactants

The electrochemical pinacol coupling of 5-hydroxymethylfurfural (HMF) offers a sustainable route to value-added chemicals, yet optimizing selectivity and conversion remains a challenge. Therefore, we employed surfactants as electrode–electrolyte interface modifiers to enhance the electro-hydrodimerization of HMF to 5,5′-bis(hydroxymethyl)hydrofuroin (BHH) on carbon electrodes. By applying 10 mM long-chain quaternary trimethylammonium surfactants, we successfully enhanced the product selectivity toward BHH from 37% to almost 60%. Replacing single-charged surfactants with analogous Gemini surfactants lowers the required modifier concentration to only 0.2 mM while maintaining the same results. Furthermore, substituting planar glassy carbon electrodes with reticulated vitreous carbon (RVC) enables a significant increase in HMF conversion, exceeding 96% within 2 h, with no performance loss. This study provides new insights into surfactant-mediated electrocatalysis and establishes a scalable strategy for enhancing electrochemical biomass valorization.