Interplay of hetero-MN4 catalytic sites on graphene for efficient oxygen reduction reaction

Author(s)

Kumar, Abhishek ; Goncalves, Josue M. ; Luder, Johann ; Nakamura, Marcelo ; Angnes, Lucio ; Bouvet, Marcel ; Bertotti, Mauro ; Araki, Koiti

• Document type: Journal article
• Source: Electrochimica Acta; v. 419, p. 12-pg., 2022-07-01.

Abstract

Noble-metal-free macrocycles dispersed on a carbonaceous support are a promising alternative to expensive Ptbased electrocatalysts to revolutionize the market outreach of low-cost clean energies technologies like fuel cells. Herein, a new composite material made of two transition metal phthalocyanines (MPc; M: Co, Fe) immobilized on a graphene support is presented as efficient and stable electrocatalyst for the oxygen reduction reaction (ORR). Electrochemical activation breaks the microparticles of MPcs into nanoclusters, facilitating their homogeneous dispersion on the support. The catalytic performance of the composite examined in oxygen-saturated KNO3 revealed tetra-electronic behavior and superior ORR activity compared to the similar loading of Pt/C catalyst. Moreover, high stability and negligible interference from methanol on the ORR response of the composite make it an ideal catalyst for direct methanol fuel cell. Density Functional Theory (DFT) calculations provide insights into the composite structure, revealing preferred arrangements in which two MPc sandwich graphene, and into the ORR mechanism in such configurations. The simulations revealed intricate interplay of interaction strengths between the composite's metal ions and ORR intermediates and O2, demonstrating that mixture of MPc facilitates higher ORR efficiency. Such enhancement is attributed to charge redistribution in sandwiched configurations, causing localization of dipoles on MPc. (AU)

• FAPESP's process: 17/13137-5 - Formation and properties of hemiesters of carbonic acid in aqueous medium
• Grantee: Claudimir Lucio Do Lago
• Support Opportunities: Research Projects - Thematic Grants
• FAPESP's process: 19/14418-3 - Electrochemical sensors for water quality monitoring
• Grantee: Gilberto Jose Silva Junior
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)