In order to reduce the energy consumption, the ongoing efforts have been focused on seeking oxygenevolving electrocatalysts to suit the diversified application in the past decades. [7,8] Up to now, the noble-metal Ir/Ru oxides have always been the benchmark oxygenevolution electrocatalysts, benefiting from their advisable compatibility with the efficiency, stability, and corrosion-tolerance in various environments relative to the other catalysts. [9][10][11] Nevertheless, the commercial application is extremely hindered by their unsatisfactory overpotential, natural scarcity, and prohibitive cost. [12] Compared with IrO 2 , rutile-structure RuO 2 is cheaper, and also more active for OER in virtue of its desirable ability to bond the oxygen-related intermediates, [13][14][15] which makes Ru-based oxides preferred in catalyzing OER. [16,17] However, the dissolution of high valence Ru generated from the over-oxidation under OER potential is an unavoidable issue. [18,19] Therefore, to enable the practical OER operation, the elaborate design of advanced RuO 2 -based electrocatalysts, integrating the high mass activity, the low usage, and the satisfactory durability under the harsh conditions, is significant.From a fundamental perspective, the intrinsic structure characteristic, especially the electronic structure and the d-band center position (ɛ d ), governs the catalytic ability of materials, because it directly affects the adsorption of oxygen-related intermediates, which is closely associated with the activation energy and the reaction kinetics. [20,21] Plainly, tuning the electronic structure of RuO 2 to obtain suitable adsorption energies (neither too strong nor too weak) is the key to improve OER performance. [17,19,22] Doping foreign metal is recognized as an effective strategy to modulate the intrinsic electronic structure of RuO 2 . [23][24][25][26] For instance, Q. Chen et al. demonstrated Mn doping enhances the intrinsic activity of RuO 2 by tuning the d-band center of Ru active sites. [23] J. Su et al. revealed that Cu doping makes more unsaturated Ru sites exposed on the surface to participate in OER. [15] In these cases, owing to its perceptibly different electronegativity, foreign metal doping can reconfigure the electronic density of RuO x via partial charge Exquisite design of RuO 2 -based catalysts to simultaneously improve activity and stability under harsh conditions and reduce the Ru dosage is crucial for advancing energy conversion involving oxygen evolution reaction (OER). Herein, a distinctive cobalt-dopedRuO x framework is constructed on Co 3 O 4 nanocones (Co 3 O 4 @CoRuO x ) as a promising strategy to realize above urgent desires. Extensive experimental characterization and theoretical analysis demonstrate that cobalt doped in RuO x lattice brings the oxygen vacancies and lattice contraction, which jointly redistribute the electron configuration of RuO x . The optimized d-band center balances the adsorption energies of oxygenated intermediates, lowing the thermodynamical barrier of the rate...

The renewable electricity‐driven hydrogen evolution reaction (HER) coupled with biomass oxidation is a powerful avenue to maximize the energy efficiency and economic feedback, but challenging. Herein, porous Ni‐VN heterojunction nanosheets on nickel foam (Ni‐VN/NF) are constructed as a robust electrocatalyst to simultaneously catalyze HER and 5‐hydroxymethylfurfural electrooxidation reaction (HMF EOR). Benefiting from the surface reconstruction of Ni‐VN heterojunction during the oxidation process, the derived NiOOH‐VN/NF energetically catalyzes HMF into 2,5‐furandicarboxylic acid (FDCA), yielding the high HMF conversion (>99%), FDCA yield (99%), and Faradaic efficiency (>98%) at the lower oxidation potential along with the superior cycling stability. Ni‐VN/NF is also surperactive for HER, exhibiting an onset potential of ≈0 mV and Tafel slope of 45 mV dec−1. The integrated Ni‐VN/NF||Ni‐VN/NF configuration delivers a compelling cell voltage of 1.426 V at 10 mA cm−2 for the H2O‐HMF paired electrolysis, about 100 mV lower than that for water splitting. Theoretically, for Ni‐VN/NF, the superiority in HMF EOR and HER is mainly dominated by the local electronic distribution at the heterogenous interface, which accelerates the charge transfer and optimize the adsorption of reactants/intermediates by modulating the d‐band center, therefore being an advisable thermodynamic and kinetic process.

The renewable-energy-driven integration of hydrogen production and biomass conversion into value-added products is desirable for the current global energy transition, but still a challenge. Herein, carbon-coated CoO–Co heterojunction arrays were built on copper foam (CoO–Co@C/CF) by the carbothermal reduction to catalyze the hydrogen evolution reaction (HER) coupled with a 5-hydroxymethylfurfural electrooxidation reaction (HMFEOR). The electronic modulation induced by the CoO–Co heterojunction endows CoO–Co@C/CF with a powerful catalytic ability. CoO–Co@C/CF is energetic for HER, yielding an overpotential of 69 mV at 10 mA·cm−1 and Tafel slope of 58 mV·dec−1. Meanwhile, CoO–Co@C/CF delivers an excellent electrochemical activity for the selective conversion from HMF into 2,5-furandicarboxylic acid (FDCA), achieving a conversion of 100%, FDCA yield of 99.4% and faradaic efficiency of 99.4% at the lower oxidation potential, along with an excellent cycling stability. The integrated CoO–Co@C/CF||CoO–Co@C/CF configuration actualizes the H2O–HMF-coupled electrolysis at a satisfactory cell voltage of 1.448 V at 10 mA·cm−2. This work highlights the feasibility of engineering double active sites for the coupled electrolytic system.