In situ growth of metallic Ag0 intercalated CoAl layered double hydroxides as efficient electrocatalysts for the oxygen reduction reaction in alkaline solutions

Abstract

Metallic Ag⁰ intercalated CoAl-layered double hydroxides (CoAl LDHs) have been successfully synthesized in situ through a simple redox process with ethylene glycol (EG) and triethanolamine (TEOA). The Ag(CN)₂⁻ anion-exchanged precursor was reduced by EG to form metallic Ag⁰. Furthermore, the effect of TEOA on confining the particle size of Ag⁰ was demonstrated. The oxygen reduction reaction (ORR) property of metallic Ag⁰ intercalated CoAl LDHs was examined in alkaline aqueous solution. A typical sample synthesized by the addition of TEOA for 180 min exhibited excellent ORR catalytic activity with a high current density of 5.5 mA cm⁻² at 0.2 V (vs. a reversible hydrogen electrode (RHE)) and good stability. Koutecky–Levich (K–L) calculations and rotating ring-disk electrode (RRDE) measurements further revealed that the ORR of the as-prepared catalyst proceeded mainly via an almost ideal four-electron transfer process. The enhanced electrocatalytic activity was ascribed to the intercalated Ag⁰, confined nanoparticle size and the expanded interlayer space, which effectively facilitate the reactant transfer and electron migration.