Effect of Acid-Leaching on the Electrochemical Performance of Carbon-Supported Copper Phthalocyanine Tetrasulfonic Acid Tetrasodium Salt (CuTSPc/C) Catalys

Abstract

Since the strong O=O bond (498kJ mol-1) with very slow oxygen reduction reaction (ORR) rate at the cathode has a much larger overpotential (or polarization) than that of hydrogen oxidation reaction (HOR) at the anode, the cathodic ORR has become the most challenging step in a fuel cell1. Up to now, Pt is still the best catalyst candidate for the ORR due to its high catalytic activity. As yet, there are still two major challenges for the Pt-based catalysts, one is high cost, and the other is insufficient electrochemical durability2-3. Therefore, the major effort in fuel cell research and development have been put on reducing Pt loading by exploring more effective synthesis technologies, and/or replacing Pt metal using other non-precious metals such as Fe, Co and Cu. In this regard, carbon-based transition metal macrocycle complexes catalysts have become one of the most promising candidates to replace Pt/C catalyst, especially these catalysts synthesized after thermal treatment show high catalytic activity3,4. For revealing the mechanism of ORR and improving the ORR activity, one should know the active site in these catalysts. So far, there is a consensus that carbon, nitrogen and transition metals are all considered to be indispensable elements for the ORR activity5. However, for the transition metals, there is few report clearly point out whether it is a part of the active sites in these macrocycle complexes. In this work, with carbon-supported copper phthalocyanine tetrasulfonic acid tetrasodium salt, CuTSPc/C, as a target, the role of transition metal in macrocycle complexe was investigated by acid-leaching procedures.