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

TL;DR

This study develops low-Pd electrocatalysts modified with Fe3O4 and SnO2 nanostructures for alkaline ethanol fuel cells, achieving high activity and stability with reduced noble metal content.

Contribution

It introduces novel Fe3O4 and SnO2 nanostructure modifications to low-Pd catalysts, enhancing ethanol oxidation performance and stability in alkaline fuel cells.

Findings

PdFe3O4/C showed the highest mass activity (1426 mA mg-1 Pd).

PdFe3O4/C achieved the highest power density (31 mW cm-2 at 70°C).

Modified catalysts exhibited strong metal-oxide interactions indicated by XPS.

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 coupled 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 and 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 C), even with an approximately 45 percent reduction in Pd content compared to the commercial catalyst. XPS results showed that the Pd 3d5/2 and 3d3/2 peaks for PdFe3O4/C, PdSnO2/C, and PdFe3O4SnO2/C were shifted by approximately 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.