ZnxCo1–x/N-Doped Carbon Nanotube Composites as Electrocatalysts for Hydrogen and Oxygen Evolution

Abstract

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 Zn_xCo_1–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 Zn_xCo_1–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, Zn_0.33Co_0.67-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 (ΔG_H* ≈ 0) and reduced OER energy barriers. This work provides a nanostructural engineering strategy for the design of efficient bifunctional electrocatalysts derived from bimetallic MOFs.