Optimizing Nickel Orbital Occupancy via Co-Modulation of Core and Shell Structures to Accelerate Alkaline Hydrogen Electro-Oxidation Reaction

Nickel-based catalysts are recognized as a promising alternative to platinum-based catalysts for the alkaline hydrogen oxidation reaction (HOR) yet suffer from poor stability and relatively low activity. Herein, a nitrogen ligand-assisted approach is reported to encapsulate nickel-copper nanoparticles within few carbon layers, and by modulating the core and shell components/structure, the charge distribution in the nanostructures can be finely regulated. The optimized Ni93Cu7@NC catalyst exhibits outstanding HOR activity with an intrinsic activity of 61.0 mu A cm-2 and excellent stability, which is among the most advanced Ni-based HOR catalysts. Notably, an alkaline exchange membrane fuel cell utilizing this catalyst achieves a peak power density of 381 mW cm-2 and maintains stability at 100 mA cm-2 for over 24 h. Experimental and theoretical investigations unveil that the electron re-distribution at the interface of NiCu core and nitrogen-doped carbon reduces the electron occupancy in Ni 4s-H 1s bonding orbitals and Ni 3dz2/yz-O 2p antibonding orbitals, leading to a weakened hydrogen binding energy and enhance hydroxide binding energy. Consequently, the limiting energy for the HOR is reduced following a bifunctional mechanism on the Ni93Cu7@NC. This work provides a core-shell co-modulation strategy to accurately regulate the electronic structure of transition metals to design robust catalysts. A novel nitrogen ligand-assisted method is introduced for the encapsulation of nickel-copper nanoparticles within a limited number of carbon layers. This innovative approach enables precise control of the charge distribution in nanostructures by modulating the core and shell components/structure. The resulting Ni93Cu7@NC catalyst demonstrates outstanding activity and stability for the hydrogen oxidation reaction, presenting a promising advancement for alkaline exchange membrane fuel cells. image