Boosting the activity of nitrogen-doped carbon catalyst by the guided formation of active sites and enhanced scavenging on reactive oxygen species under the regulation of cerium

Abstract

The design of nitrogen-doped carbon materials with high density of active sites is of paramount importance for catalysis of the oxygen reduction reaction (ORR). Herein, an efficient oxygen reduction electrocatalyst (CL-Fe/(Fe,Ce)xOy-NC) is developed by planting carbon nanotubes with encapsulated Fe/(Fe,Ce)xOy particles on porous carbon polyhedron particles derived from calcinated ZIF-8 framework. The introduction of Ce evidently promotes the formation of pyridinic nitrogen, graphitic nitrogen and metal nitrogen species in carbon matrix, enhancing the catalytic activity towards the ORR. The Ce oxide in the catalyst effectively scavenges the active oxygen species in ORR process. Under the synergistic effect of high specific surface area with Ce species, the CL-Fe/(Fe,Ce)xOy-NC has a better half-wave potential (0.861 V vs. RHE), faster kinetics (44.13 mV dec−1) and is more stable than the commercial Pt/C catalyst. The zinc-air battery assembled with CL-Fe/(Fe,Ce)xOy-NC has the highest power density of 195 mW cm−2, energy density of 858 Wh kg−1, and better durability. This work presents a novel approach to enhance the efficacy of nitrogen-doped carbon-based catalysts, paving a possible way to substitute the precious platinum catalysts for a variety of electrochemical energy devices.