One‐Pot Synthesis of Cobalt‐Incorporated Nitrogen‐Doped Reduced Graphene Oxide as an Oxygen Reduction Reaction Catalyst in Alkaline Medium

Abstract

Cobalt‐incorporated nitrogen‐doped reduced graphene oxide (Co/NrGO) as a catalyst for the oxygen reduction reaction is prepared in a single step by thermal reduction of graphene oxide to reduced graphene oxide (rGO) in the presence of a cobalt salt and 1,10‐phenanthroline as a nitrogen precursor. Cobalt is identified as cobalt oxide (CoO) in the hybrid. Both the cobalt and nitrogen contents in Co/NrGO are higher than those in cobalt‐ or nitrogen‐free samples; this indicates that cobalt and 1,10‐phenathroline mutually enhance incorporation into the material. An almost four‐electron transfer is observed as the average per oxygen molecule, and Co/NrGO demonstrates highly improved activity in comparison with NrGO and rGO. CoO and nitrogen‐doped moieties may be acting as active centers for oxygen reduction individually or synergistically. With a loading of less than 2 wt % cobalt in Co/NrGO, appreciable activity is already observed. Moreover, the high selectivity for oxygen reduction over methanol oxidation for Co/NrGO is demonstrated, making this hybrid a promising catalyst for direct methanol alkaline fuel cells.

Chitosan Waste‐Derived Co and N Co‐doped Carbon Electrocatalyst for Efficient Oxygen Reduction Reaction

“…M–N–C catalysts show excellent performance for the ORR, owing to their specific metal–nitrogen (M–N) bonds, which play crucial roles in oxygen reduction . Unfortunately, recent research on M–N–C catalysts has mainly been focused on the pyrolysis of the carbon materials with nitrogen sources and metal salts (nitrates or chlorides) . These methods always suffer from complicated preparation methods, uncontrollable generation of the metal oxides, and agglomeration of the metal nitrides in the carbon matrix.…”

A Three‐Dimensionally Structured Electrocatalyst: Cobalt‐Embedded Nitrogen‐Doped Carbon Nanotubes/Nitrogen‐Doped Reduced Graphene Oxide Hybrid for Efficient Oxygen Reduction

“…GO exfoliated from stacked graphite was first confirmed by X‐ray diffraction (XRD; Figure a). The peak observed at around 12° demonstrates the incorporation of oxygen groups and enhanced interlayer spacing . The intermediate Co‐C 3 N 4 /NrGO shows layered morphology, as shown in the transmission electron microscopy (TEM) images (Supporting Information, Figure S1).…”

Cobalt–Nitrogen Co‐doped Carbon Nanotube Cathode Catalyst for Alkaline Membrane Fuel Cells

“…It is believed that the charge delocalization noted above could amend the adsorption behavior of carbon material towards O 2 and thereby effectively weaken the O=O bond to facilitate the ORR . It is worth noting that the total amount of nitrogen in catalyst material does not have such an importance as the distribution of different nitrogen forms on the catalyst surface and that out of all the different nitrogen functionalities, a higher content of pyridinic nitrogen will form defect complexes with carbon vacancies in the graphitic carbon structures such as graphene and carbon nanotubes . Four pyridinic N atoms have been found to form porphyrin‐like defect complexes on the surface of carbon material and it has also been suggested that a rectangular porphyrin‐like defect is well suited for metal ions such as Co to reassemble similar active site to transition metal macrocycles .…”

“…Recently, the addition of transition‐metal salts such as FeCl 3 , FeAc, CoCl 2 and Co(NO 3 ) 2 to nitrogen precursors has been studied to further enhance the electrocatalytic activity of N‐doped carbon materials towards the ORR by increasing the number of nitrogen atoms incorporated into the carbon structure during modification . Furthermore, metal phenanthrolines, phthalocyanines and porphyrins have been used as precursors to create metal‐nitrogen moieties on the carbon support .…”