Bimetal Phthalocyanine‐Modified Carbon Nanotube‐Based Bifunctional Catalysts for Zinc‐Air Batteries

Abstract A series of non‐precious bifunctional electrocatalysts composed of first‐row transition metal phthalocyanine (MPc, M=Mn, Ni, Co) modified multi‐walled carbon nanotubes (CNTs) was prepared and examined for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in alkaline media. The use of MPc in carbon matrix is attractive due to the formation of M‐N x sites, which are responsible for ORR electrocatalysis and transition metal oxides that are OER‐active. Physical characterisation of the prepared catalysts was carried out by scanning electron microscopy/energy dispersive X‐ray spectroscopy, scanning transmission electron microscopy, N 2 physisorption analysis, X‐ray diffraction and X‐ray photoelectron spectroscopy. The highest ORR activity among bimetallic catalysts was shown by a MnCoN‐CNT catalyst with half‐wave potential of 0.84 V. The electrochemical results of the prepared bimetallic catalysts revealed superior OER activity of NiCoN‐CNT with E OER of 1.61 V at 10 mA cm −2 and also good ORR activity ( E 1/2 =0.83 V). Furthermore, NiCoN‐CNT exhibited excellent stability for both, ORR and OER, with only 5 mV change in half‐wave potential and only 14 mV loss in E OER , respectively. For checking bifunctionality, the NiCoN‐CNT catalyst was used as an air electrode and tested for zinc‐air battery (ZAB). Good ZAB performance was obtained, with open circuit voltage (OCV) of 1.338 V.