Development of highly active and stable non-precious oxygen reduction catalysts for PEM fuel cells using polypyrrole and a chelating agent

High oxygen reduction activity of few-walled carbon nanotubes with low nitrogen content

“…Research on metal-free catalysts for ORR has thus become a very active topic in catalysis, especially with the emergence of nitrogen-doped carbon nanomaterials as one of the promising electrocatalysts. Recent research has investigated nitrogen doping of different carbon nanomaterials (CNM) such as carbon nanotubes (CNTs) [5][6][7][8][9][10][11][12][13][14], carbon nanofibers (CNFs) [15,16], graphene [17,18], mesoporous carbon [19], carbon nanocages [20], and hollow carbon nanoparticles [21]. The studies are particularly numerous for Nitrogen-doped CNTs (N-CNTs) among these materials.…”

“…However, any acid leaching to remove metals may damage nitrogen functionalities. Post-treatment methods typically avoid this difficulty by treating already purified CNTs with nitrogen precursors; such as ammonia [11], urea [14], dicyandiamide [30], or polymers including polyaniline (PANI) [13] and polypyrrole [16].…”

Nitrogen-doped carbon xerogel as high active oxygen reduction catalyst for direct methanol alkaline fuel cell

“…Although this catalyst is with low graphitic degree, they present some defects, which can also cause the formation of pyridine-N [47]. Besides, graphite-N considered to be more stable than pyridine-N in acid media, may be also contribute to the high ORR [48]. However, about which one plays a predominant role in the ORR, more work is still needed.…”

Nitrogen-doped graphene with enhanced oxygen reduction activity produced by pyrolysis of graphene functionalized with imidazole derivatives

“…Moreover, addition of nitrogen varies the charge distribution of the carbon network so that the C atoms adjacent to N become more positively charged, resulting in an enhanced interaction with the adsorbing molecule and thus lower activation barrier for its decomposition [96]. 41 Recently, a variety of metal-free nitrogen doped CNMs have been synthesized in the form of CNTs [97][98][99][100][101][102], CNFs [103,104], graphene [105,106], mesoporous carbon [107], carbon nanocages [108], carbon spheres, hollow carbon nanoparticles [109], etc. In this thesis the synthesis and electrocatalytic activity of N-FWCNTs and N-GNPs for the ORR have been investigated.…”

“…In this regard, an efficient N-CNT should be obtained by incorporating accessible N-atoms at the surface while preserving the inner CNT structure for an efficient electron transfer and conductivity. In the post-treatment doping techniques, purified CNTs are treated with different nitrogen precursors such as NH 3 [115], urea [116], dicyandiamide [117] or polymers including polyaniline (PANI) [55] and polypyrrole [104], then followed by a thermal annealing at high temperatures to form graphitized N-doped layer around the intact CNT walls.…”