Exploring the heterointerface of silver nanoparticles and cobalt oxide nanorings toward the oxygen reduction reaction

Abstract

The low performance of silver toward the electrocatalytic oxygen reduction reaction (ORR) can be enhanced significantly by combining it with other metals via synergistic interaction. In this study, we have synthesized a highly efficient and cost-effective silver based electrocatalyst for the ORR. The cobalt in the catalyst is uniquely designed as nanorings, a morphology achieved through the templating effect of alpha naphthol. Furthermore, silver nanoparticles serve a dual function by not only acting as a catalyst for the ORR but also unzipping multiwalled nitrogen-doped carbon nanotubes (MW-NCNTs) to form ultrathin nitrogen-doped carbon nanosheets (NCNS). These nanosheets enhance conductivity and charge transport, thus improving overall catalytic efficiency. Many studies have reported the formation of CNTs containing metallic cobalt or cobalt oxide (CoO_x) from ZIF materials, but our novel synthetic process uniquely produces Co₃O₄ nanorings, paving the way for further advancements in catalyst design. The Ag_0.9–Co₃O₄/NCNS catalyst exhibits high efficiency due to the formation of an Ag/Co₃O₄ heterointerface and the facile switching of cobalt's oxidation state. The catalyst demonstrates a half-wave potential (E_1/2) of ≈0.85 V_RHE, mass activity ≈ 84 mA mg_Ag⁻¹, and enhanced durability over an extended period comparable to state-of-the-art catalysts, highlighting its practical applicability and cost-effectiveness. Furthermore, density functional theory (DFT) calculations revealed the origin of greatly enhanced ORR catalytic activity of the Ag/Co₃O₄ heterointerface.