MOF-derived N-doped CoNi@C as bifunctional catalysts for efficient water splitting†

Abstract

The development of efficient and stable bifunctional non-noble metal catalysts for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is essential for electrochemical water splitting. In this study, CoNi@C core–shell structure catalysts derived from ZIF-67 were synthesized through high-temperature calcination. The hydrophilic carbon shell inhibits the oxidation of Co and Ni and enhances the activity and stability of the water splitting reaction. CoNi serves as the active site of the reaction, while the doped nitrogen further promotes the electrocatalytic reaction. The synthesized Ni₁Co₁₀/C catalyst exhibits high bifunctional performance, with low overpotentials at 100 mA cm⁻² for the OER (380 mV) and HER (357 mV), and a high double-layer capacitance (54 mF cm⁻²). Moreover, the Ni₁Co₁₀/C catalyst serves as an effective cathode for water splitting in a two-electrode system, demonstrating a stable cell voltage of 2.05 V and maintaining a constant catalytic current of 100 mA cm⁻² over 24 hours. DFT calculation showed that the active site of the OER and HER was Co.