Ni Nanoparticles Encapsulated in N-doped Carbon Derived from Metal-Organic Frameworks as Bifunctional Electrocatalysts for Energy-Efficient Hydrogen Production

The development of bifunctional electrocatalysts for energy-saving hydrogen production coupled with alcohol upgrading is highly desirable yet challenging. Herein, we report Ni nanoparticles encapsulated in N-doped carbon shells (Ni@NC-450) as a bifunctional electrocatalyst for hydrogen evolution reaction (HER) and ethanol oxidation reaction (EOR). The catalyst is derived from pyrolysis of Ni-based zeolitic imidazolate framework (Ni-ZIF) at 450 °C, a temperature that enables effective regulation of nitrogen configurations and affords a high proportion of pyridinic N. The resulting Ni@NC‑450 requires only 85 mV for HER and 1.38 V for EOR to reach 10 mA cm−2 in alkaline media. When employed in ethanol-water electrolyzer, Ni@NC-450 delivers 1.58 V at 10 mA cm−2 (162 mV below conventional water splitting), producing acetate as the major product confirmed by nuclear magnetic resonance. Furthermore, Ni@NC-450 exhibits excellent long‑term stability, retaining its catalytic activity after 1000 cyclic voltammetry cycles and 15 h of continuous operation. Systematic poisoning and acid‑etching experiments reveal that the enhanced bifunctional activity originates from the joint contribution of metallic Ni and pyridinic N. This work provides a rational design strategy for metal-organic framework (MOF)‑derived N‑doped carbon encapsulated Ni catalysts and clarifies the roles of metallic Ni and pyridinic N for hybrid water electrolysis.