Synergistic Amorphous Ni Core–N-Doped Carbon Shell Nanoparticles for Efficient Bifunctional Water Splitting

Amorphous metal-based catalysts are highly promising for water splitting due to their abundance of unsaturated active sites. Herein, we report a one-step, surfactant-free synthesis of amorphous nickel nanoparticles (NPs) encapsulated in nitrogen-doped carbon shells (A-Ni@NC) via pulsed laser ablation in liquid (PLAL). The synergistic integration of the amorphous Ni core and a defect-rich N-doped carbon shell markedly enhanced the catalytic activities for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), with low overpotentials of 182 mV for HER and 288 mV for OER at 10 mA cm⁻² in 1.0 M KOH. Furthermore, the bifunctional catalyst achieved a current density of 10 mA cm⁻² at 1.63 V and retained 98.9% of its initial performance after 100 h of operation. The nitrogen-rich carbon shell not only offered abundant active sites and structural protection but also promoted charge transport. Density functional theory (DFT) calculations revealed that N-doping optimized intermediate adsorption energies, while the amorphous Ni core facilitated efficient electron transfer. This green and scalable synthesis strategy provides a promising platform for developing a wide range of transition metal@N-doped carbon hybrid catalysts for sustainable energy conversion applications.