Achieving Janus Ag@N-doped carbon for oxygen reduction reaction from eccentric encapsulated Ag@polypyrrole

Taking full advantage of both silver and nitrogen-doped carbon (N-C) with finely designed nanostructure is a great challenge in achieving excellent electrocatalysts for oxygen reduction reaction (ORR). The Janus nanostructure composed of Ag nanoparticles (NPs) and N-C with individual exposed surface meets this purpose quite well. This can be achieved via pyrolyzing the core-shell Ag@polypyrrole (Ag@PPy) with eccentric encapsulated structure, where the AgNPs locate away from the center of the PPy spheres. The as-synthesized Janus nanostructured Ag@N-C demonstrates comparable ORR activity to commercial Pt/C catalyst with an onset and half-wave potential of 0.955 V and 0.821 V vs. RHE, respectively, and a limited current density of 4.976 mA cm⁻² at 0.365 V, and it also illustrates better stability and stronger methanol tolerance. The excellent ORR activity is largely attributed to the synergistic effect originating from the interaction between AgNPs and carbonized PPy half-shell, where the former one leads to a higher disordered degree in the carbon layer and the latter results in the positive shift of Ag 3d binding energy to facilitate the active oxygen adsorption and keeps the AgNPs from aggregation to avoid activity losing.