Ordered mesoporous FeNx-doped carbon: a class of highly active and stable catalysts in acids, bases and polymer electrolyte membrane fuel cells

Abstract

The high cost and scarcity of platinum (Pt) materials have considerably hindered their use as catalysts for the oxygen reduction reaction (ORR) and thus wide-scale implementation in fuel cells for practical applications. Here we describe a class of non-noble metal catalysts, i.e., an ordered mesoporous FeN_x-doped carbon (OMFeNC) that shows both performance activity and stability approaching or even greater than those of traditional Pt catalysts in acidic and basic solutions, as well as promising performances in operating polymer electrolyte membrane fuel cells (PEMFCs). The OMFeNC was synthesized by pyrolysis of metalloproteins in combination with an ordered mesoporous silica template. The remaining silica from the template in the OMFeNC material was removed during the synthesis process, and required no post-synthesis HF acid treatment. In addition, multiple heat-treatments were explored and it was found that the OMFeNC catalyst obtained after pyrolysis at 800 °C possessed the best catalytic activity and stability for the ORR. The activity and stability of OMFeNC were further evaluated in a single membrane electrode assembled PEMFC, whereby a 355 mW cm⁻² peak power was achieved with pure H₂/O₂ feed streams, the OMFeNC material utilized as the cathode catalyst and a cell operating temperature of 60 °C. After 60 hours of durability testing, 73% of the initial activity remained for the PEMFC, whereas 86% of the initial activity remained after 120 hours of durability testing with a neutralized ionomer binder in the cathode layer.