Fe3O4 nano-octahedra and SnO2 nanorods modifying low-Pd amount electrocatalysts for alkaline direct ethanol fuel cells

Author(s)

Gentil, Tuani C. ; Lucchetti, Lanna E. B. ; Moura, Joa Paulo C. ; Silva, Julio Cesar M. ; Minichova, Maria ; Briega-Martos, Valentin ; Trench, Aline B. ; Batista, Bruno L. ; Cherevko, Serhiy ; Santos, Mauro C.

• Document type: Journal article
• Source: Electrochimica Acta; v. 535, p. 16-pg., 2025-09-20.

Abstract

This work describes the ethanol oxidation reaction (EOR) in alkaline medium using low-palladium nanoparticle electrocatalysts modified by Fe3O4 nano-octahedra and SnO2 nanorods. Operation studies on an alkaline direct ethanol fuel cell (ADEFC) were conducted using the developed electrocatalysts, and stability studies were performed using the advanced scanning flow cell (SFC) technique combined to inductively coupled plasma mass spectrometry (online SFC-ICP-MS). The EOR was catalyzed by single (Pd/C and commercial Pd/C Alfa Aesar) and by synthesized binary/ternary electrocatalysts, in which Fe3O4 and SnO2 nanostructures partially replaced the high-cost noble metal. The PdFe3O4/C was identified as the most promising synthesized material in the electrochemical studies, exhibiting the highest mass activity (1426 mA mg-1 Pd) by cyclic voltammetry (CV), followed by the binary PdSnO2/C (1135 mA mg-1 Pd), and by the ternary (1074 mA mg-1 Pd). This enhancement was attributed to the bifunctional mechanism enabled by Fe3O4 and SnO2, therefore reducing poisoning and improving the EOR. Moreover, the operating results revealed that PdFe3O4/C showed the highest power density among the synthesized materials (31 mW cm-2 at 70 degrees C), even with a-45 % reduction in Pd content compared to the commercial. The XPS results showed that the Pd 3d5/2and 3d3/2peaks for PdFe3O4/C, PdSnO2/C, and PdFe3O4SnO2/C were shifted by-0.5 eV to higher binding energies compared to Pd/C, indicating a loss of electron density in Pd due to strong metal-oxide interactions. These interactions led to a downward shift in the Dband center of Pd, weakening the Pd-adsorbed bonds, facilitating the desorption of intermediates, and improving the catalyst tolerance to toxic species. Furthermore, the higher proportion of Pd oxides in the binary and ternary materials appeared to contribute to the supply of oxygenated species required for the oxidation of EOR intermediates. Thus, the observed enhancement resulted from synergistic bifunctional and electronic effects. Finally, online SFC-ICP-MS studies showed that Fe3O4 nano-octahedra contributed to the enhanced stability of the electrocatalyst, as PdFe3O4/C exhibited less Pd dissolution and no Fe dissolution. (AU)

• FAPESP's process: 18/18675-8 - Nanostructured electrocatalysts based on PT, PD and oxides of low cost for applications in energy and environment
• Grantee: Tuani Carla Gentil
• Support Opportunities: Scholarships in Brazil - Doctorate
• FAPESP's process: 17/22976-0 - Development of palladium and niobium nanoelectrocatalysts for alkaline direct ethanol fuel cells
• Grantee: Felipe de Moura Souza
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)
• FAPESP's process: 17/10118-0 - Study and application of electrochemical technology for the analysis and degradation of endocrine interferents: materials, sensors, processes and scientific dissemination
• Grantee: Marcos Roberto de Vasconcelos Lanza
• Support Opportunities: Research Projects - Thematic Grants
• FAPESP's process: 22/12895-1 - Advanced processes for the degradation of emerging pollutants: catalytic materials, electroanalytical sensors and scientific dissemination
• Grantee: Marcos Roberto de Vasconcelos Lanza
• Support Opportunities: Research Projects - Thematic Grants
• FAPESP's process: 17/26288-1 - Hybrid electrocatalysts based on Pd, Pt and Sn nanoparticles, and on ceria nanorods for application in fuel cells
• Grantee: Victor dos Santos Pinheiro
• Support Opportunities: Scholarships in Brazil - Doctorate
• FAPESP's process: 21/05364-7 - Nanostructured electrocatalysts based on manganese and tungsten oxides supported on carbon for electrogeneration of hydrogen peroxide and electrochemical degradation of ciprofloxacino
• Grantee: João Paulo Carvalho Moura
• Support Opportunities: Scholarships in Brazil - Doctorate
• FAPESP's process: 22/15252-4 - Nanostructured electrocatalysts for application in direct alkaline-acid fuel cells of glycerol
• Grantee: Mauro Coelho dos Santos
• Support Opportunities: Program for Research on Bioenergy (BIOEN) - Regular Program Grants
• FAPESP's process: 21/14394-7 - Use of Vulcan XC-72 carbon modified with fluorine and/or cerium doped niobium nanostructures in the electrogeneration of H2O2 for degradation of endocrine disruptors by advanced electrochemical oxidative processes
• Grantee: Aline Barrios Trench
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 21/10033-0 - Online analysis of the dissolution of palladium-based electrocatalysts in alkaline medium
• Grantee: Tuani Carla Gentil
• Support Opportunities: Scholarships abroad - Research Internship - Doctorate
• FAPESP's process: 20/14100-0 - Sodium niobate electrodes decorated with WO3 and CeO2 for degradation of the organophosphate pesticide acephate by advanced oxidative electrochemical processes
• Grantee: Felipe de Moura Souza
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 17/21846-6 - Nanostructures for environmental remediation and power generation from renewable sources
• Grantee: Mauro Coelho dos Santos
• Support Opportunities: Program for Research on Bioenergy (BIOEN) - Regular Program Grants