W18O49 with isolated Ni sites promotes sustainable electro-oxidation of 5-hydroxymethylfurfural with high yield rate

W 18 O 49 with separately dispersed Ni sites was prepared as the electrocatalyst for electro-oxidation reaction of 5-hydroxymethylfurfural (HMFOR). • Ni 0.33 &W 18 O 49 promotes efficient HMFOR to 2,5-furandicarboxylic acid (FDCA) with a high yield rate (YR FDCA ) of ⁓3.37 mmol cm -2 h -1 . • Experimental and computational results reveal an indirect pathway for HMFOR, where the in-situ formed NiO(OH) acts as the proton acceptor. • A nickel foam‖Ni 0.33 &W 18 O 49 pair enables continuous production of FDCA with a high YR FDCA of ca. 0.279 g cm -2 h -1 . The electro-oxidation reaction of 5-hydroxymethylfurfural (HMFOR) provides an ideal solution for addressing the sustainable production of 2,5-furandicarboxylic acid (FDCA), a critical precursor for biodegradable polymer synthesis. However, HMFOR over non-precious catalysts may suffer from low current density and hence insufficient FDCA yield rate (YR FDCA ). In this work, a series of W 18 O 49 nanostructures with interstitially doped Ni 2+ sites (Ni x &W 18 O 49 ) are employed as the model catalyst for HMFOR. Among them, the optimal candidate Ni 0.33 &W 18 O 49 exhibits a superior performance in terms of an impressive YR FDCA of 2.88 mmol cm −2  h −1 and good durability, outperforming that of α-Ni(OH) 2 with continuously dispersed Ni-(μ 2 -OH)-Ni species. Experimental and theoretical studies reveal that the Ni&W 18 O 49 with an isolated Ni 2+ site follows an indirect pathway, where the in-situ formed NiO(OH) serves as a proton acceptor during HMFOR. It also surpasses α -Ni(OH) 2 in terms of remarkably reduced reaction barrier. Finally, an electrode pair of NF‖Ni 0.33 &W 18 O 49 is constructed to enable continuous productions of H 2 and FDCA with a high YR FDCA of 1.79 mmol cm −2  h −1 in a flowing single cell. This work thus provides fundamental insights into the design of Ni-based catalysts for highly efficient electro-oxidation of HMF to FDCA.