Pristine carbon nanotube/iron phthalocyanine hybrids with a well-defined nanostructure show excellent efficiency and durability for the oxygen reduction reaction

Abstract

Development of non-platinum electrocatalysts with high performance, durability, and scalability for fuel cells and batteries is a strong social demand for a next-generation eco-friendly energy society. Here, we present a pristine multi-walled carbon nanotube/iron phthalocyanine (MWNT/FePc) hybrid catalyst with a well-defined nanostructure for the oxygen reduction reaction (ORR) in alkaline media that meets this demand. By carefully tuning the microstructure of the FePc stack layer deposited on the highly crystallized graphitic surface of a MWNT support, an ultra-high ORR activity as well as excellent durability are obtained. Moreover, a power density of 185 mW cm⁻² at 0.8 V was obtained for a zinc–air battery using this optimized MWNT/FePc cathode at room temperature. Density functional theory-based calculations of such a well-defined nanostructure of MWNT/FePc have suggested that deposition on the bent graphitic surface of MWNTs significantly changes the geometric and electronic structures of FePc that originated from π–π interactions, leading to such enhanced electrocatalytic activity and durability.