Nanoparticles of\nCoFeZn Supported on N‑Doped\nCarbon as Bifunctional Catalysts for Oxygen Reduction and Oxygen Evolution

Oxygen reduction reaction (ORR) and oxygen evolution\nreaction (OER)\nare two important reactions in clean energy conversion devices. It\nis necessary to develop nonprecious metal-based bifunctional catalysts\nfor ORR and OER. In this work, a multimetal bifunctional catalyst,\nnanoparticles of trimetallic CoFeZn supported on N-doped carbon (CoFeZn/NC),\nis prepared by one-step carbonizing the mixture of M-ZIFs (M = Fe,\nCo, and Zn), carbon black, and melamine. CoFeZn/NC has a more mesoporous\nstructure and a higher specific surface area of 1029.6 m<sup>2</sup>/g compared to FeCo/NC, which is attributed to the easy volatilization\nof Zn at high temperatures. It also has high contents of pyridinic\nN (35.8%) and pyrrolic N (31.1%), abundant metal active sites, and\nexhibits strong synergistic effects between these nanoparticles of\nmetals. Better than the single-metal catalysts (Co/NC, Fe/NC, and\nZn/NC) and bimetallic catalysts (CoFe/NC, FeZn/NC, and CoZn/NC), CoFeZn/NC\nhas an ORR peak potential of 0.90 V (vs. RHE) and a half-wave potential\nof 0.87 V (vs. RHE) in 0.1 M KOH solution, and exhibits excellent\nstability and methanol resistance. For OER, CoFeZn/NC has the lowest\noverpotential of 319.9 mV at a current density of 10 mA/cm<sup>2</sup> and a Tafel slope of 82.47 mV dec<sup>–1</sup>.