N-Doped Graphene Quantum Dots Incorporated into NiCo Bimetallic-Organic Framework as an Electrocatalyst for Alkaline Water Splitting

Rational tuning of the electronic structure is one of the feasible routes to enhance the electrical conductivity of electrocatalysts based on metal–organic frameworks (MOFs). Herein, a composite of NiCo-MOF and N-doped graphene quantum dots (NGQDs) with a hierarchical structure was synthesized via a controlled electrodeposition strategy as an exemplary non-noble metal catalyst for alkaline water splitting. The increased active sites by synergy effect between Ni and Co ions and the enhanced local electrical conductivity through uniform incorporation of NGQDs into porous NiCo-MOF matrix offer a catalyst that only demanded overpotentials of 218 and 359 mV to deliver a current density of 100 mA·cm–2 toward the HER and OER, respectively, and also exhibited drastically enhanced electrochemical stability for over 150 h in alkaline media. In particular, the assembled two-electrode setup for overall water electrolysis yields a current density of 10 mA·cm–2 at a low cell voltage of 1.62 V. This facile strategy can provide a creative avenue to design efficient and conductive MOF-based electrocatalysts for large-scale practical applications.