Cr_2O_3 nanoparticles boosting Cr-N-C for highly efficient electrocatalysis in acidic oxygen reduction reaction

摘要

Transition metalenitrogenecarbon (M-N-C) catalysts have attracted significant attention for catalyzing oxygen reduction reactions (ORR). In this study, a porous Cr2O3@Cr-N-C catalyst with a small amount of Cr2O3 nanoparticles loaded on the surface of Cr-N-4-C nanomaterials was prepared using synergistic heat treatment (SHT) method with zeolite imidazole frameworks (ZIFs) as precursors. TEM and spherical aberration-corrected TEM results demonstrated the presence of hollow morphologies, Cr2O3 nanoparticles and atomic-level Cr distribution in Cr2O3@Cr-N-C. XPS, XRD and XAFS analysis indicated the coexistence of Cr2O3 nanoparticles and Cr-N-4 sites which were believed to act as active centers for ORR. In 0.1 M HClO4, this material showed outstanding ORR catalytic activity with a half-wave potential of 0.78 V that was 40 mV higher than the traditional heat treatment derived CreNeC. It also revealed relatively low Tafel slope of 52.2 mV dec(-1); 4-electron pathway; remarkable stability and long-term durability. The improved ORR performance is mainly attributed to the synergy between CreN(4) active center and Cr2O3 nanoparticle. The SHT strategy reported here provides a new route to prepare highly efficient non-precious metal M-N-C catalysts with greater ORR activity and stability in acidic environments. (c) 2021 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.