One-pot synthesis of Co/N-doped mesoporous graphene with embedded Co/CoO_x nanoparticles for efficient oxygen reduction reaction

Abstract

Exploration of sustainable electrocatalysts toward oxygen reduction reaction (ORR) with high catalytic activity remains a key challenge in the development of metal-air batteries and fuel cells. In this work, a hybrid electrocatalyst composed of cobalt (Co/CoO) nanoparticles encapsulated in Co/N-doped mesoporous graphene (Co/CoO@Co/N-graphene) is reported for efficient ORR catalysis. The catalyst is rationally designed and synthesized via a facile combination of spontaneous one-pot polymerization of dopamine in the presence of graphene oxide (GO) and Co ions and the subsequent carbonization process. The morphology, doping nature and ORR activity of the as-prepared catalyst are systematically investigated. It is found that there are abundant Co/N active sites and Co/CoO nanoparticles in this hybrid catalyst, leading to a synergistic enhancement effect for improved ORR activity. In an alkaline environment, this Co/CoO@Co/N-graphene catalyst displays Pt/C-comparable ORR activity in terms of half-wave potential and four-electron reduction selectivity, and higher limiting current density, better methanol tolerant ability and long-term durability. When being evaluated in a Zn-air battery, it demonstrates superior performance to the commercial Pt/C catalyst.

Nitrogen‐Doped Carbon Nanosheets Encapsulating Cobalt Nanoparticle Hybrids as High‐Performance Bifunctional Electrocatalysts

“…For the Co 2p XPS spectrum (Figure d), the peaks centered at 781.5 and 797.2 eV correspond to the binding energy of Co 2p 3/2 and the Co 2p 1/2 , which are consistent with the binding energy of Co species in CoO, indicating the presence of Co 2+ . Meanwhile, two satellite peaks of Co 2p are observed at the binding energy of 785.6 and 801.6 eV ,. The peak at 774.5 eV is attributed to Auger peak of cobalt .…”

Unusual Effect of Trace Water on the Structure and Activity of NixCo1−x Electrocatalysts for the Methanol Oxidation Reaction

“…[30] The peaks observed at 777.8 and 793.3 eV correspond to Co 2p 3/2 and Co 2p 1/2 and reflect that the chemical valence of Co is zero. The bindinge nergies of 780.9 and7 96.5 eV are assigned to Co 2 + , and the satellite peaks are at 785.5 [47] and 802.3 eV. [10] These peaks of Ni 2 + andC o 2 + indicate the existence of some oxides on the surface.…”

Fe/Co-based nanoparticles encapsulated in heteroatom-doped carbon electrocatalysts for oxygen reduction reaction

“…Cobalt ions were confined in polydopamine via polymerization of dopamine (Figs 10, 11), and the obtained complex was annealed successively under N 2 and air atmosphere. Metal NPs treated under air atmosphere formed metal/metal oxide core-shell structure easily [90,91]. In addition, there was the case that metal particles formed together with oxide NPs inevitably during an annealing process.…”