Cobalt tetramethoxyphenyl porphyrin-emission Mossbauer spectroscopy and O₂ reduction electrochemical studies

Cobalt tetramethoxyphenyl porphyrin (Co-TMPP) on a high area carbon support after thermal treatment at 450-900°C has been found to be an effective catalyst for O₂ reduction in alkaline electrolytes. The effect of the heat treatment at 850°C on this catalyst has been examine with emission Mössbauer spectroscopy using Co-57 enriched Co-TMPP. The spectra indicate the presence of cobaltous oxides with no evidence of Co-N₄ centers or any other form of cobalt. The metal-free complex H₂TMPP, given similar thermal treatment on a mineral-free carbon support does not show catalytic activity beyond that of the carbon support, thus confirming the importance of the transition metal to the catalysis.