Herrmann, I. ; Kramm, U.I. ; Fiechter, S. ; Bogdanoff, P.: Oxalate supported pyrolysis of CoTMPP as electrocatalysts for the oxygen reduction reaction. Electrochimica Acta 54 (2009), p. 4275-4287
10.1016/j.electacta.2009.02.056
Abstract:
The utilisation of different metal oxalates in the pyrolysis of cobalt-tetramethoxyphenylporphyrin (CoTMPP) has been investigated as a structure forming agent to obtain highly active electrocatalysts for the oxygen reduction reaction (ORR). Decomposition products of the metal oxalates provide a nano-scaled template for the carbonisation of CoTMPP. After the pyrolysis this template is removed by an etching step so that highly porous carbon-based particles with different morphologies are attained. Thermogravimetric measurements, gas sorption isotherms (BET and pore size distribution), neutron activation analysis (NAA), SEM and XRD analysis examine the pyrolysis process of CoTMPP in the presence of the metal oxalates and the subsequent conditioning step. Thereby, the degree of graphitisation and the morphology of the formed carbon matrix are influenced by the decomposition products of the metal oxalates. Furthermore the solubility of the decomposition products in the etching step is a crucial factor for the porosity of the final obtained product. Electrochemical analysis (CV and RDE) shows that the catalysts exhibit high kinetic current densities towards the ORR in acidic electrolyte which is correlated to the contribution of mesopores within the catalyst. Among the investigated metal oxalates, the utilisation of tin oxalate reveals the most beneficial characteristics for the preparation.