Metal (Mn, Fe, Co, Ni, Cu, and Zn) Phthalocyanine-Immobilized Mesoporous Carbon Nitride Materials as Durable Electrode Modifiers for the Oxygen Reduction Reaction

Abstract

In the search for alternative sources to replace fossil fuels, carbon nitride materials can be used in a variety of ways. In the present work, porosity is introduced to the carbon nitride material using mesoporous silica material, MCM-41, as a hard template, and a mesoporous carbon nitride (MCN) material is synthesized. Further, the MCN is modified by immobilizing metal phthalocyanine (MPc, where M = Mn, Fe, Co, Ni, Cu, and Zn). The resulting MPc-incorporated MCN materials (MPc@MCN) were tested for the electrocatalytic oxygen reduction reaction (ORR) in acidic and basic media. Detailed studies reveal that the FePc@MCN and CoPc@MCN materials exhibit higher ORR activity than the other composites in 0.1 M KOH. FePc@MCN follows a direct four-electron oxygen reduction mechanism and shows ORR onset potential (vs RHE) at 0.93 V (in 0.1 M KOH), which is very close to the onset potential exhibited by the state-of-the-art material, Pt-C (1.0 V), and higher than several similar composites of MPc with carbon supports tested in similar environments. Besides, due to the inherent property of coordination through nitrogen present on the MCN, FePc@MCN shows excellent stability even after 3000 cyclic voltammetry (CV) cycles. FePc@MCN was found to have a better methanol tolerance in comparison to Pt-C in basic medium. CoPc@MCN shows a highly selective two-electron reduction reaction in both acidic and basic media at lower overpotential than many of the reported catalysts for the two-electron oxygen reduction. Therefore, these materials (FePc@MCN and CoPc@MCN) can be used as suitable alternatives to replace Pt and other expensive materials in ORR and related applications.

Steady/transient state spectral researches on the solvent-triggered and photo-induced novel properties of metal-coordinated phthalocyanines

“…The degrees of aggregation depend on various factors, such as solvent, concentration, sidechain substituent, and the coordinated metal. 4 The exploitation of the MPc aggregation and redox mechanism can be beneficial for its applications in the fields of photophysics, 5 photochemistry, 6 materials 7 and catalysis. 8 Transition metal phthalocyanine dual-metal-site catalysts 9 and composite anchoring iron phthalocyanine (FePc)/TiO 2 heterostructure 10 demonstrated good photocatalytic activities for CO reduction or organic contaminant degradation.…”

Porous spinel-type transition metal oxide nanostructures as emergent electrocatalysts for oxygen reduction reactions

“…Mesoporous carbon nitride (MCN)-immobilized metal phthalocyanine (MPc, M = Co, Cu, Fe, Mn, Ni, and Zn) was studied for the ORR in KOH. 123 The study revealed that FePc@MCN had the best ORR and stability because of the strong N-coordination in the Pc of Fe. Integration of Co-doping levels (0-25%) into conductive Fe 3 O 4 grown epitaxially on single-crystal MgO {100} substrates achieved by molecular-beam epitaxy (MBE) growth (at a background pressure 1 × 10 6 Torr; PARADIGM thin-film growth) formed Co-doped Fe 3 O 4 single-crystal thin films with controlled Co content (i.e., 0, 5, 10 and 25%), high conductivity, and exposed active sites.…”

Effect of Support on Oxygen Reduction Reaction Activity of Supported Iron Porphyrins

“…Mesoporous carbon nitride (MCN) has been evaluated as a support for both metal (Mn, Fe, Co, Ni, Cu, and Zn) phthalocyanine and Co porphyrin ORR catalysts by Singh et al , The MCN was synthesized by a hard templating method to improve the surface area and conductivity of the support. The highest E 1/2 (∼0.05 V) is exhibited by CoPc@MCN in these reports, with a limiting current density < 1.5 mA/cm 2 and n ∼ 1.64 in 0.1 M HClO 4 with rotation.…”