Zn _<i>x</i> Co _{1– <i>x</i>} /N-Doped Carbon Nanotube Composites as Electrocatalysts for Hydrogen and Oxygen Evolution

The development of cost-effective bifunctional electrocatalysts with atomic precision for both hydrogen and oxygen evolution reactions (HER/OER) remains critical for sustainable water electrolysis. Herein, we designed a series of two-dimensional (4,4)-networked ZnxCo1–x-MOFs through controlled Zn2+/Co2+ coordination. These were subsequently transformed into metallic Co nanoparticles embedded within N-doped carbon nanotube heterostructures via a simple carbonization process, labeled ZnxCo1–x-NCNT. Benefiting from the nanoscale synergistic effects between highly active metallic Co- and N-doped CNTs, as well as the pore-forming role of Zn that generates a hierarchical nanoscale porous architecture, the catalysts exhibit increased specific surface area and abundant exposed active sites. Among these, Zn0.33Co0.67-NCNT-1000 demonstrates exceptional electrocatalytic performance, achieving low overpotentials of 147 mV for the HER and 281 mV for the OER at 10 mA cm–2. Density functional theory calculations reveal near-ideal hydrogen adsorption free energy (ΔGH* ≈ 0) and reduced OER energy barriers. This work provides a nanostructural engineering strategy for the design of efficient bifunctional electrocatalysts derived from bimetallic MOFs.