Nanowires-based MnO2-Ru/rGO: An efficient oxygen reduction reaction electrocatalyst

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Ferreira, Rayse Machado ; de Lima, Scarllett Lalesca Santos ; Pereira, Fellipe dos Santos ; Mouchrek, Charbel Nagib ; Takana, Auro Atsushi ; Domingues, Sergio Humberto ; Fonsaca, Jessica Eliza Silva ; Liu, Liying ; Yatsuzuka, Rebeca ; da Silva, Anderson Gabriel Marques ; Aquino, Flavia de Medeiros ; Garoia, Marco Aurelio Suller

• Document type: Journal article
• Source: Applied Surface Science; v. 651, p. 11-pg., 2024-01-03.

Abstract

Oxygen Reduction Reaction (ORR) for clean energy is hindered by expensive Pt -based electrocatalysts, prompting efforts to replace it with alternative electrocatalysts. Thus, we started by synthesizing MnO2 nanowires through a hydrothermal approach, followed by the growth of ruthenium nanoparticles (Ru NPs) without surface modification, using just 2.0 wt% of the noble metal (MnO2-Ru). However, to further enhance the electrocatalyst's performance and reduce costs, we combined different ratios of reduced graphene oxide (rGO) with the electrocatalyst. X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, and energy dispersive X-ray spectroscopy were employed to characterize the chemical composition and morphological properties of MnO2-Ru. These analyses identified the presence of the compounds during synthesis and confirmed the deposition of Ru NPs on the surface of MnO2 nanowires. The optimized MnO2-Ru/rGO demonstrated superior ORR activity than rGO, MnO2 , and MnO2-Ru individually, with more positive onset potential (-0.054 V) and half -wave potential of -0.173 V. Notably, MnO2-Ru/rGO reduced oxygen via the fourelectron transfer pathway. Furthermore, the higher stability and excellent methanol tolerance of MnO2-Ru/ rGO compared to the commercial 20 wt% Pt/C indicates its suitability for fuel cells, maintaining approximately 70 % of its initial current after 8000 s. (AU)

• FAPESP's process: 20/13288-6 - Two-dimensional materials and their derivatives in photonic biosensoring of pathogens
• Grantee: Jéssica Eliza Silva Fonsaca
• Support Opportunities: Scholarships in Brazil - Post-Doctoral