Electrocatalytic Activity of Nafion‐Impregnated Pyrolyzed Cobalt Phthalocyanine: A Correlative Study Between Rotating Disk and Solid Polymer Electrolyte Fuel‐Cell Electrodes

Abstract

Carbon supported electrocatalysts for the reduction of oxygen can be screened quickly by using a rotating disk electrode (RDE) when an appropriate material is used as a binder to hold the catalyst on the disk electrode. The results obtained with the RDE in an oxygen-saturated H2SO4 solution mimic those measured for a full-cell H2/O2 solid polymer electrolyte setup. This result is demonstrated with a cobalt phthalocyanine-on-carbon black catalyst pyrolyzed at various temperatures ranging from 400 to ll00~ When the catalyst is held on the disk electrode with electropolymerized pyrrole, a broad maximum of activity for the reduction of oxygen is observed for pyrolysis temperatures ranging between 600 and 900~ When the catalyst is dispersed in a Nation film on the disk electrode, a sharp maximum in its activity is observed at the pyrolysis temperature of 600~ in agreement with its behavior in a full-cell setup.

Effect of Preparation Conditions of Sol–Gel-Derived Co–N–C-Based Catalysts on ORR Activity in Acidic Solutions

“…However, a varying catalyst layer porosity may also be influencing these measured Tafel slopes. 50 Optimization of heat-treatment temperature of ORR catalysts.-Based on earlier work with catalysts derived from Co-and Fe-based macrocyles, 13,[15][16][17]22,25,27,31,51 heat-treatment in an inert atmosphere was expected to improve both the ORR activity and the stability of our catalysts. As has been shown in our previous work, 40 this is true for our sol-derived catalysts as well.…”

“…27 For CoPc, the ORR activity increased with heat-treatment to 600°C, with similar activities obtained at 700 and 900°C, and then decreased with heat treatment to 1000°C. 16 CoPcTc ͑Co tetra carboxylic phthalocyanine͒ catalysts heat-treated from 100 to 1100°C demonstrated optimum activity between 500 and 700°C, with a significant decrease in activity seen for samples heat-treated at 400 and 800°C. 19 CoTCPP ͓Co 5,10,15,20-tetrakis͑4-carboxyphenyl͒porphyrin͔ and CoTMPyP ͓5,10,15,20-tetrakis͑1-methyl-4-pyridinio͒porphyrin͔, heat-treated together at 200-1200°C, demonstrated maximum ORR activity at 600 and 800°C.…”

Pyrolyzed phthalocyanines as surrogate carbon catalysts: Initial insights into oxygen-transfer mechanisms

“…On the other hand, heat-treated phthalocyanines (Pcs) [2] have been of interest since the pioneering, but largely ignored, studies of Souma [3][4][5]. Their intriguing properties have attracted much attention after the discovery that Co-Pc might replace platinum as an electrocatalyst in the ORR [6,7]; in extensive follow-up studies [8][9][10][11][12][13][14][15][16][17][18][19][20] it was reported that a pyrolyzed transition-metal Pc can be even more effective. In addition, pyrolyzed phthalocyanines have been used more recently as raw materials in the production of carbon nanotubes [21][22][23][24][25][26][27][28][29][30].…”

Accurate Assessment of the Oxygen Reduction Electrocatalytic Activity of Mn/Polypyrrole Nanocomposites Based on Rotating Disk Electrode Measurements, Complemented with Multitechnique Structural Characterizations

“…With the increasing of the rotation speed, the diffusion limited current plateau becomes inclined and this slope increases. This behaviour is quite common in the literature for carbon-based catalysts (pyrolyzed Mn, Co, Fe/PPy [47], Ag–MnO 2 [82], pyrolyzed Fe(III)-tetramethoxyphenyl porphyrin [21], pyrolyzed cobalt [83] and iron phthalocyanine [84], and N-doped carbon nanotubes [85]) and has been attributed to the a heterogeneous distribution of the active sites on the surface catalyst [86, 87]. The ORR performance of our PPy60/G film is superior to that of PPy prepared by a polymerization process via chemical oxidation with FeCl 3 [88]: both the onset ( E onset ) and half-wave ( E 1/2 ) potentials shift to more positive values, from 0.72 to 0.85 V/RHE and from 0.34 to 0.69 V/RHE, respectively.…”