Nickel–Copper Alloy Encapsulated in Graphitic Carbon Shells as Electrocatalysts for Hydrogen Evolution Reaction

Searching for cost-effective and high-performance electrocatalysts for hydrogen production is of paramount importance. Herein, nickel-copper (NiCu) alloy nanoparticles are encapsulated into graphitic shells via an ambient-pressure chemical vapor deposition process. The resulting carbon-encapsulated NiCu (denoted as NiCu@C) composite possesses a well-defined core–shell structure with tunable thicknesses of the shells and is examined as electrocatalysts for the hydrogen evolution reaction (HER) in acidic, neutral, and alkaline solutions. Electrochemical measurements indicate that the activity of the NiCu@C highly depends on the thickness of the shell. Single-layered graphene encapsulated NiCu nanoparticles show remarkable HER activity and durability. To obtain a current density of 10 mA cm⁻², overpotentials of 48, 164, and 74 mV are needed in electrolyte solutions with pH = 0, 7, and 14, respectively. Such low overpotentials render the composite as one of the most active nonprecious electrocatalysts. Accelerated durability tests demonstrate that the NiCu@C catalysts exhibit excellent stability. Density function theory calculations are conducted to investigate the electronic structures of the NiCu@C. It is found that the representative Ni₄₃Cu₁₂@C₂₄₀ model shows an ideal adsorption energy of hydrogen (−0.03 eV), manifesting its high HER activity.