Heat-Treated Nonprecious Catalyst Using Fe and Nitrogen-Rich 2,3,7,8-Tetra(pyridin-2-yl)pyrazino[2,3-g]quinoxaline Coordinated Complex for Oxygen Reduction Reaction in PEM Fuel Cells

Abstract

Polymer electrolyte membrane (PEM) fuel cells have garnered widespread attention due to their potential application as stationary, mobile, and transportation power devices. The sluggish oxygen reduction reaction (ORR) kinetics occurring at the cathode is considered the primary limiting factor facing the performance of these devices. As of now, platinum-based catalysts are the only commercially available option that show the best performance and stability under the harsh acidic conditions encountered at the cathode. The excessive cost and limited supply of platinum hinders the economical feasibility of these devices. Two approaches can be taken to offset the high cost of platinum; (1) increase platinum utilization at the cathode in order to reduce the overall platinum requirement, 1,2 or (2) completely replace platinum by nonprecious metal alternatives. 3À5 In the long term, due to limited supply of platinum, it is more desirable to develop non-platinum, nonprecious catalysts.Research in transition metal organic complexes as nonprecious ORR catalyst alternatives began in the 1960s 3 with the investigation of transition metal macrocyclic complexes. Later studies indicated that the pyrolysis of these transition metal macrocycles could lead to significant improvement in both activity and stability. 4À10 Drawing on this, a significant breakthrough was achieved years later when researchers demonstrated the potential of creating active catalyst materials by pyrolysis methods without the use of expensive macrocyclic precursors. 10À12 These active catalysts were synthesized through the pyrolysis of separate nitrogen, carbon, and transition metal precursors, resulting in a promising class of MÀN/C catalysts (M = Fe, Co). Although the

Iron-tetracyanobenzene complex derived non-precious catalyst for oxygen reduction reaction

“…Fe 3 C was also shown to be present in the catalyst structure with characteristic peaks observed at 38, 43 and 78 . The presence of these iron-based crystallites indicate that iron migration and coalescence occurs during the high temperature heat treatment process and is consistent with results of previous reports on M-N-C catalyst development [16,34,35].…”

“…Owing to the heterogeneous complexity of the resulting catalyst structures, there still remains debate in the literature over the exact identity and nature of the catalytically active sites, with contrasting opinions over whether the transition metal species comprises the active site, or merely plays an integral role in active site formation [3]. Regardless, it has been well established that the structure, properties and resulting ORR activity of heat treated M-N-C complexes is directly governed by the particular precursor materials employed and synthetic processes utilized [10][11][12][13][14][15][16].…”

Nonprecious Bimetallic (Fe,Mo)–N/C Catalyst for Efficient Oxygen Reduction Reaction

“…The XRD patterns of (Fe,Mo)−N/C catalysts before acid leaching showed in Figure 1b show the emergence of three peaks at 44°, 45°, and 51°when the initial FeCl 2 /MoCl 5 molar ratio reaches 1.0, and with further increases in the molar ratio, the peaks become more obvious, indicating the formation of iron particles, similar to that observed in Fe−N/C catalyst ( Figure S1a in the Supporting Information). 26 In contrast, the XRD pattern of the Mo−N/C catalyst ( Figure S1b in the Supporting Information) shows no Mo species, demonstrating that Mo ions do not aggregate into metallic particles under our pyrolysis conditions. The transmission electron microscopy (TEM) images ( Figure S2 in the Supporting Information) of (Fe,Mo)−N/C samples before acid leaching show some metallic particles, even when the Fe/Mo ratio is <1.0, but the amount of metallic phases is too low to be detected by XRD measurements.…”

New non-platinum Ir–V–Mo electro-catalyst, catalytic activity and CO tolerance in hydrogen oxidation reaction

“…Some Pt-free catalysts have shown remarkable catalytic activity toward O 2 reduction [2], such as carbonized catalase [3], Co-or Fe-based catalysts [4,5], and macrocyclic [6] or pyrolyzed macrocyclic compounds [7]. Nevertheless, few efforts have been devoted toward materials that can replace Pt as the anode catalyst in PEMFCs, since the requirements for good resistance to both CO and acid are difficult to achieve for normal alloy catalysts.…”