Transition　metal-based　electrocatalysts　are　a　promising　alternative　to　noble　metal　catalysts　for　electrochemical　upgrading　of　biomass-derived　5-hydroxymethylfurfural　(HMF)　into　high-value　2,5-furandicarboxylic　acid　(FDCA).　However,　the　rational　design　of　efficient　electrocatalysts　with　precisely　tailored　structure–activity　correlations　remains　a　critical　challenge.　Herein,　we　report　a　hierarchically　structured　self-supporting　electrode　(Vo-NiCo(OH)2-NF)　synthesized　through　in　situ　electrochemical　reconstruction　of　NiCo-Prussian　blue　analogue　(NiCo-PBA)　precursor,　in　which　oxygen　vacancy　(Vo)-rich　Co-doped　Ni(OH)2　nanosheet　arrays　are　vertically　aligned　on　nickel　foam　(NF),　creating　an　interconnected　conductive　network.　When　evaluated　for　the　HMF　oxidation　reaction　(HMFOR),　Vo-NiCo(OH)2-NF　exhibits　exceptional　electrochemical　performance,　achieving　near-complete　HMF　conversion　(99%),　ultrahigh　FDCA　Faradaic　efficiency　(97.5%),　and　remarkable　product　yield　(96.2%)　at　1.45　V,　outperforming　conventional　Co-doped　Ni(OH)2　(NiCo(OH)2-NF)　and　pristine　Ni(OH)2　(Ni(OH)2-NF)　electrodes.　By　combining　in　situ　spectroscopic　characterization　and　theoretical　calculations,　we　elucidate　that　the　synergistic　effects　of　Co-doping　and　oxygen　vacancy　engineering　effectively　modulate　the　electronic　structure　of　Ni　active　centers,　favor　the　formation　of　high-valent　Ni3+　species,　and　optimize　HMF　adsorption,　thereby　improving　the　HMFOR　performance.　This　work　provides　valuable　mechanistic　insights　for　catalyst　design　and　may　inspire　the　development　of　advanced　transition　metal-based　electrodes　for　efficient　biomass　conversion　systems.　©　2025　Science　Press　and　Dalian　Institute　of　Chemical　Physics,　Chinese　Academy　of　Sciences.