Single‐Atom Barium‐Mediated Hydrogen‐Bonding Interaction via Mortise‐and‐Tenon Interlock for Rechargeable Biomass Electrooxidation in Pure Water

Electrooxidative upgradation of biomass-derived molecules like 5-hydroxymethylfurfural (HMF) offers a carbon-neutral blueprint to produce valuable chemicals, with conversion efficiency highly relying on the strong base and costly membrane use. Herein, we anchor single-atom Ba into nickel-oxyhydroxide as the mortise of sulfate (tenon) to construct a rechargeable anode S-Ba1Ni1- xOOH for decoupling HMF electrooxidation, enabling quantitative 2,5-furandicarboxylic acid (FDCA) production without alkali, potential, and membrane. This decoupling system involves i) active Ni3+-O (re)generation via charging and ii) extraction of H atoms of HMF with Ni3+-O to undergo deprotonation into FDCA (∼100% conversion and selectivity) in pure water without electricity (discharging). Hydrogen-bonding interaction between surficial sulfate and hydroxide of HMF can accelerate the substrate migration toward solid-liquid interface with enhanced conversion. Theoretical calculations expound that hydrogen-bonding interaction decreases the hybridization degree between O-2p and H-1s orbitals in O─H bond of HMF to heighten its H removability, thereby fostering complete HMF oxidation into FDCA. Various biomass derivatives are also amenable to this decoupling system, affording >96.3% yields for acids. Techno-economic analysis illustrates that replacing strong alkali with pure water can reduce the production cost of FDCA by 50.5%, underlining the wide prospect of this decoupling strategy and endowing an attractive route for biomass valorization.