Nitrogen-Doped Carbon Derived from Metal Organic Frameworks (ZIF67) Modified Electrochemically with Non-precious Metal Nanoparticles: Synthesis and Application for Oxygen Evolution Reaction

Here, a general method for fabricating active electrocatalysts is introduced for oxygen evolution reaction (OER) based on multimetallic (ternary alloy) structures formed on the N-doped nanoporous carbon platform without using ruthenium or iridium. Accordingly, three different sizes, small, medium, and large, of cobalt zeolitic imidazolate framework-67 (ZIF67X, X: S, M, L) are synthesized. Then, the product is carbonized via direct pyrolysis at 800 °C in an argon atmosphere to yield nitrogen-doped nanoporous carbon composited with cobalt nanoparticles (PZIF67X₈₀₀). To improve the activity, the most active nanoporous system for OER (PZIF67L₈₀₀) is further modified by electrochemical deposition of Co, Ni, and Fe (PZIF67L₈₀₀-CoNiFe). The electrochemical results revealed a large electrocatalytic activity for the GC-PZIF67L₈₀₀-CoNiFe toward the OER in alkaline media, Tafel slopes of 72 mV dec⁻¹ and overpotentials of 314 mV at 30 mA cm⁻² (η₃₀), compared with those obtained under the same conditions on GC-RuO₂ (99 mV dec⁻¹ and 499 mV). The improved activity is attributed to (i) the increase in active surface area and simultaneous formation of Co nanoparticles and nitrogen-doped porous carbon, causing uniformly dispersed metal nanoparticles in the composite, and (ii) synergistic effect between the ingredients of ternary alloy nanoparticles (CoNiFe-NPs) and nitrogen-doped carbon nanoporous platform.

Graphical Abstract