An efficient pH-universal electrocatalyst for oxygen reduction: defect-rich graphitized carbon shell wrapped cobalt within hierarchical porous N-doped carbon aerogel

Abstract

The design and facile synthesis of active, robust, cheap, and earth-abundant electrocatalysts to replace precious Pt catalysts is highly desirable for the cathodic oxygen reduction reaction (ORR) in fuel cells and rechargeable metal batteries. However, maximizing the catalytic activity and stability of the electrocatalysts in catalyzing ORR is significantly important but still remains challenge. To address this issue, we herein reported an effective strategy that fabricate the cobalt nanoparticles encapsulated with defect-rich graphitized carbon shell in the hierarchical porous N-doped carbon aerogel (Co/NCA), which can simultaneously enhance the electrochemical stability while boosting the electrocatalytic activity for ORR. The desirable combination of the Co nanoparticles encapsulated with defect-rich graphitic carbon shells coupling with Co−Nx sites, the large accessible surface-active sites, and the hierarchical porous structure give rise to the superior electrocatalytic activity and stability for ORR in wide pH range. As expect, the as-obtained catalyst exhibits high efficiency for ORR with an onset potential of 0.95 V (versus reversible hydrogen electrode, vs. RHE) and a half-wave potential of 0.83 V in 0.1 M KOH, comparable to the commercial Pt/C. Importantly, the catalyst also provides excellent ORR properties in acidic and neutral media with almost a 4e− pathway and superior durability and methanol tolerance, showing a potential as electrocatalysts for practical applications.