Co-based catalysts are promising alternatives to precious metals for the selective and effective oxidation of 5-hydroxymethylfurfural (HMF) to the higher value-added 2,5-furandicarboxylic acid (FDCA). However, these catalysts still suffer from unsatisfactory activity and poor selectivity. A series of N-doped carbon-supported Co-based dual-metal nanoparticles (NPs) have been designed, among which the Co-Cu_1.4-CN_x exhibits enhanced HMF oxidative activity, achieving FDCA formation rates 4 times higher than that of pristine Co-CN_x, with 100% FDCA selectivity. Density functional theory (DFT) calculations evidenced that the increased electron density on Co sites induced by Cu can mediate the positive electronegativity offset to downshift the d-band center of Co-Cu_1.4-CN_x, thus reducing the energy barriers for the conversion of HMF to FDCA. Such findings will support the development of superior non-precious metal catalysts for HMF oxidation.

Manipulating the oxidation state of Cu catalysts can significantly affect the selectivity and activity of electrocatalytic carbon dioxide reduction (CO₂RR). However, the thermodynamically favorable cathodic reduction to metallic states typically leads to catalytic deactivation. Herein, a defect construction strategy is employed to prepare crystalline/amorphous Cu₂₊₁O/CuO_x heterostructures (c/a-CuO_x) with abundant Cu⁰ and Cu^δ+ (0 < δ < 1) sites for CO₂RR. The C₂₊ Faradaic efficiency of the heterostructured Cu catalyst is up to 81.3%, with partial current densities of 406.7 mA·cm⁻². Significantly, real-time monitoring of the Cu oxidation state evolution by in-situ Raman spectroscopy confirms the stability of Cu^δ+ species under long-term high current density operation. Density functional theory (DFT) calculations further reveal that the adjacent Cu⁰ and Cu^δ+ sites in heterostructured c/a-CuO_x can efficiently reduce the energy barrier of CO coupling for C₂₊ products.

The high unoccupied d band energy of Ni₃N basically results in weak orbital coupling with water molecule, consequently leading to slow water dissociation kinetics. Herein, we demonstrate Cr doping can downshift the unoccupied d orbitals and strengthen the interfacial orbital coupling to boost the water dissociation kinetics. The prepared Cr-Ni₃N/Ni displays an impressive overpotential of 37 mV at 10 mA·cm_geo^-2, close to the benchmark Pt/C in 1.0 M KOH solution. Refined structural analysis reveals the Cr dopant exists as the Cr-N₆ states and the average d band energy of Ni₃N is also lowered. Density functional theory calculation further confirms the downshifted d band energy can strengthen the orbital coupling between the unpaired electrons in O 2p and the unoccupied state of Ni 3d, which thus facilitates the water adsorption and dissociation. The work provides a new concept to achieve on-demand functions for hydrogen evolution catalysis and beyond, by regulating the interfacial orbital coupling.