Performance optimization of a commercial Fe-N-C catalyst in direct methanol fuel cells (DMFCs) and long-term durability study

Nowadays, the research for active and stable catalysts for the oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs) and direct methanol fuel cells (DMFCs) still represents a critical aspect for large-scale commercialization. Noble metal catalysts, characterized by suitable activity, present several drawbacks, such as limited earth abundance and, thus, high cost, low tolerance to the presence of alcohols, and instability due to Pt dissolution. Recently, significant attention has been devoted to the development of transition metal -nitrogen -carbon materials (M-N-C where M = Fe, Co, Mn, etc.) derived from abundant and cheap precursors, due to their high activity towards ORR and their extraordinary tolerance to the electrooxidation of alcohols like methanol or ethanol. In particular, the presented analysis is restricted to M-N-C catalysts, firstly, investigated in rotating disk electrode (RDE) configuration for the ORR in the presence of methanol to study alcohol tolerance. The best electrocatalysts were tested in DMFC where important parameters such as catalyst loading, concentration of methanol, ionomer ratio, and operational temperature were optimized for the achievement of highest performance. Furthermore, a long-term durability study in direct methanol fuel cells (DMFCs) of a Fe-N- C cathodic electro-catalyst, commercially available on market, is assessed to analyse the possible causes of performance degradation through different post-mortem physicochemical analyses, such as X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) with X-ray energy dispersive analysis (EDX).