Compositional and morphological engineering of in-situ‐grown Ag nanoparticles on Cu substrate for enhancing oxygen reduction reaction activity: A novel electrochemical redox tuning approach.

• Well-dispersed Ag NPs developed on Cu support assisted with in-situ electrochemical redox are fabricated. • The as-synthesized Ag NPs-based material shows superior catalytic activity and stability towards ORR. • The synergistic effect of electrochemical redox activation and NiII ions-mediation is discussed. • A novel activation path to boost the ORR catalytic activity of Ag-based electrocatalysts is proposed. • This work provides a general way to anchor metal NPs on supports uniformly and stably. Silver nanoparticles (NPs) developed on a copper substrate, Ag NPs/Cu, are synthesized by a novel and facile galvanic replacement method performed in Ethaline deep eutectic solvent (DES). It reveals that the Ag NPs could be well dispersed on the Cu support via an in-situ electrochemical oxidation-reduction (ECO-ECR) activation process, which deliver significantly enhanced activity and stability for the oxygen reduction reaction (ORR) in alkaline media. The in-situ redox tuning triggers a reversible phase transformation of the formed initially Ag NPs, Ag ↔ Ag 2 O, with surface reconstruction and gives rise to a strong metal-support interaction with tailored atomic/electronic structures, resulting in enhanced ORR activity. Impressively, the introduction of NiII ions can regulate the galvanic replacement kinetics by mediating the diffusion of AgI ions and subsequent growth of Ag on the Cu surface in Ethaline, leading to the formation of uniformly distributed Ag NPs. Coupled with redox activation, the optimal Ag-Ni 1 NPs/Cu_ECO-ECR exhibits ORR activity similar to that of the commercial state-of-the-art Pt/C catalyst, and better long-term durability (95% activity retention after 30,000 s), cyclic stability performance, and anti-poisoning capacity for methanol (96% after 3300 s), suggesting it a promising ORR electrocatalyst for practical application. [ABSTRACT FROM AUTHOR]