Effects of Pyrrole Polymerizing Oxidant on the Properties of Pyrolysed Carbon-Supported Cobalt-Polypyrrole as Electrocatalysts for Oxygen Reduction Reaction

Abstract

A series of pyrolysed carbon-supported polypyrrole-cobalt, Co-PPy-TsOH/C, have been synthesized as electrocatalysts for oxygen reduction reaction (ORR) with chemically polymerized polypyrrole using different oxidants. The effects of pyrrole polymerizing oxidants on electrocatalytic performance of the final catalysts toward ORR have been comparatively investigated, and the results have been discussed and analyzed with the help of physicochemical characterizations. It's shown that the pyrrole polymerizing oxidants have essential influence on the structure, morphology as well as chemical states of cobalt and nitrogen in the Co-PPy-TsOH/C catalysts, leading to distinct catalytic performance for ORR. In addition, the role of cobalt and nitrogen in catalytic active sites in the catalysts has also been discussed.

Cobalt and Iron Complexes with N-heterocyclic Ligands as Pyrolysis Precursors for Oxygen Reduction Catalysts

“…After pyrolysis at 700 C sharp patterns were observed. They were assigned to CoO and Co phases, no other components were detected, particularly Co 3 O 4 [43]. From the signal intensities, it was possible to conclude that catalysts obtained from six membered ring ligands, i.e.…”

Transition Metal–Nitrogen–Carbon (M–N–C) Catalysts for Oxygen Reduction Reaction. Insights on Synthesis and Performance in Polymer Electrolyte Fuel Cells

“…For the synthesis of PPY and PANI (the two most common N-containing electroconductive polymers), the most used oxidants are H 2 O 2 , FeCl 3 , and ammonium persulfate ((NH 4 ) 2 S 2 O 8 , APS). Their use in the pyrrole polymerization for the synthesis of a pyrolyzed Co-PPY catalyst supported on carbon has been comparatively explored by Sha et al, showing that the best ORR activity was obtained by using FeCl 3 [107]. This could be attributed either to its best properties as polymerizing agent, or to an additional Fe incorporation in the catalyst during the pyrolysis.…”

Effects of cobalt precursor on pyrolyzed carbon-supported cobalt-polypyrrole as electrocatalyst toward oxygen reduction reaction

“…Figure 6 demonstrates Raman spectra of the Co-PPy-TsOH/C catalysts prepared from various cobalt precursors. As in our previous work [ 10 , 23 ], the characteristic peaks generally observed in the wavenumber range from about 900 to 1,150 cm −1 for PPy and 1,370 cm −1 for antisymmetric in-ring C-N stretching [ 31 , 32 ] disappeared in all the obtained catalysts, while only two peaks representing the disorder-induced band ( D band, 1,327 cm −1 ) and the graphite band ( G band, 1,595 cm −1 ) for carbon can be found, indicating the decomposition of PPy and insertion of nitrogen into the carbon layers during high-temperature pyrolysis. Usually, the graphitization degree of carbon materials can be estimated with the ratio of the G band and D band intensities ( I G / I D ), the higher the ratio, the larger the graphitization degree [ 33 ].…”

“…The Co-PPy-TsOH/C catalysts were synthesized from various cobalt precursors with a procedure previously reported [ 23 ]. Specifically, 0.6 g BP2000 carbon powder (Cabot company, Boston, MA, USA), previously treated with 6 M HNO 3 for 8 h at 100°C, was ultrasonically dispersed in 100 ml isopropyl alcohol for 30 min, followed by an addition of 3 mmol of freshly distilled pyrrole and 100 ml double-distilled water and stirring for another 30 min.…”