Electrolyte accessibility of non-precious-metal catalysts with different spherical particle sizes under alkaline conditions for oxygen reduction reaction

Pore Modification and Phosphorus Doping Effect on Phosphoric Acid-Activated Fe-N-C for Alkaline Oxygen Reduction Reaction

“…This suggested that the change in pore structure caused by PA was suppressed by the carbon structure graphitization effect by Fe [57]. In addition, there was no byproduct of large Fe particles, which indicated that silica excluded iron particles and composites by inhibiting the growth of Fe particles [58], as mentioned in the Section 1.…”

Boosting activity toward oxygen reduction reaction of a mesoporous FeCuNC catalyst via heteroatom doping-induced electronic state modulation

“…This nding indicated the absence of nanoparticles and suggested that their growth was hindered by the ability of the silica template and nitrogen species to anchor Fe atoms. 15,49,68 Similarly, metal nanoparticles were not observed in the STEM image of FeNC (Fig. S5 †).…”

“…However, as the sluggish kinetics of the ORR necessitate the use of large amounts of Pt and thus increase the fuel cell cost, affordable alternatives, such as alloys, transition metals, and carbon-based materials, are highly sought aer. [12][13][14][15][16] Transition metal-, N-, and C-based catalysts (MNCs) exhibit remarkable activity (compared to that of Pt) under alkaline conditions and remain highly active in acidic media, thus drawing much attention. [17][18][19][20][21] When such MNCs were applied as anion-exchange membrane fuel cell (AEMFC) cathodes, their performances were signicantly lower than that of Pt/C; consequently, there were concerns about the commercialization of MNC cathodes.…”

“…47,49 For example, silica was reported to effectively inhibit the growth of metal particles during MNC synthesis. 15,47,49 Calcined ordered mesoporous silica (OMS, e.g., SBA-15 and KIT-6) does not deform even during high-temperature treatment up to 1100 C, maintaining the ordered pore structure of the catalyst and preventing the agglomeration of metal particles. [49][50][51] The formation of catalytic active sites with non-porous silica spheres could be inhibited due to insufficient micropores and small mesopores, which means that additional porogens are needed for the micropores.…”

“…Meanwhile, in the case of OMS, since sufficient mesopores are developed and this approach efficiently exposes the catalyst active site, the strong interaction between silica and Fe prevents the agglomeration of Fe and improves the accessibility of the active site. 15 Although silica templating requires additional processes, such as HF etching, which are not eco-friendly and require further processing costs, it bears the advantages of preventing Fe agglomeration and achieving nanoporosity of the catalysts simultaneously. Moreover, it was noted that this method reduces the specic surface area due to the carbon graphitization effect of Fe, making it impossible to form more than a certain number of active sites.…”