Synthesis of Bimetallic Conductive 2D Metal–Organic Framework (CoxNiy‐CAT) and Its Mass Production: Enhanced Electrochemical Oxygen Reduction Activity

The development of new electrocatalysts for electrochemical oxygen reduction to replace expensive and rare platinum‐based catalysts is an important issue in energy storage and conversion research. In this context, conductive and porous metal–organic frameworks (MOFs) are considered promising materials for the oxygen reduction reaction (ORR) due to not only their high surface area and well‐developed pores but also versatile structural features and chemical compositions. Herein, the preparation of bimetallic conductive 2D MOFs (CoxNiy‐CATs) are reported for use as catalysts in the ORR. The ratio of the two metal ions (Co2+ and Ni2+) in the bimetallic CoxNiy‐CATs is rationally controlled to determine the optimal composition of CoxNiy‐CAT for efficient performance in the ORR. Indeed, bimetallic MOFs display enhanced ORR activity compared to their monometallic counterparts (Co‐CAT or Ni‐CAT). During the ORR, bimetallic CoxNiy‐CATs retain an advantageous characteristic of Co‐CAT in relation to its high diffusion‐limiting current density, as well as a key advantage of Ni‐CAT in relation to its high onset potential. Moreover, the ORR‐active bimetallic CoxNiy‐CAT with excellent ORR activity is prepared at a large scale via a convenient method using a ball‐mill reactor. Bimetallic conductive 2D MOFs of CoxNiy‐CAT with varied ratios of Co2+ and Ni2+ are successfully synthesized and display enhanced oxygen reduction reaction (ORR) activities compared to monometallic counterparts, Co‐CAT and Ni‐CAT. In addition, mass production of ORR‐active CoxNiy‐CAT was demonstrated using a ball‐mill reactor.