Constructing a Triple-Phase Interface in Micropores to Boost Performance of Fe/N/C Catalysts for Direct Methanol Fuel Cells

Abstract

Pyrolyzed Fe/N/C, a promising nonprecious-metal catalyst for oxygen reduction reaction (ORR), usually relies on abundant micropores, which can host a large amount of active sites. However, microporous structure suffers from severe water flooding to break the triple-phase interface where ORR occurs, especially in a direct methanol fuel cell (DMFC) fed with liquid fuel. Current studies about the fabrication of a triple-phase interface are mainly limited on a Pt/C catalyst layer, where mesopores and macropores are concerned. Here, we successfully constructed a triple-phase interface in micropores of Fe/N/C catalysts by controlling the distribution of a hydrophobic additive, dimethyl silicon oil (DMS), just partially penetrating into the micropores. The elaborately constructed Fe/N/C-based DMFC can deliver high power density (102 and 130 mW cm–2 at 60 and 80 °C, respectively) and durability comparable to that of Pt/C-based DMFC. This study presents a new avenue to engineer catalyst microporous channels to boost the performance of nonprecious-metal catalysts for fuel cells.

Iron and nitrogen codoped carbon catalyst with excellent stability and methanol tolerance for oxygen reduction reaction

“…One is assigned to the low-energy spin-orbital (2p 3/2 ) of Fe 2+ (710.9 eV) and Fe 3+ (713.6 eV), and the other corresponds to the higherenergy spin-orbital (2p 1/2 ) of Fe 2+ (722.9 eV) and Fe 3+ (725.2 eV). 11,63,64 Combined with the above N 1s XPS spectra, it can be concluded that a strong Fe 3 N structure was formed in the catalyst during the pyrolysis process, which is also consistent with the results of TEM and XRD.…”

“…And, the E o of Fe 1.5 NC‐900‐2 was 963 mV, which is also much higher than the other two catalysts. Combined with previous TEM, XRD, and XPS results, it can be concluded that different amount of substance of Fe precursor would result in different Fe species in the catalysts and appropriate contents of iron oxide and Fe 3 N active sites play an important role in the process of ORR …”

“…Combined with previous TEM, XRD, and XPS results, it can be concluded that different amount of substance of Fe precursor would result in different Fe species in the catalysts and appropriate contents of iron oxide and Fe 3 N active sites play an important role in the process of ORR. 9,64,66 The influence of the addition amount of melamine on the catalytic performances of Fe 1.5 NC-900-2 sample was also investigated, as can be seen in Figure 4C. The three catalysts did not show significant difference in the catalytic activity.…”

Rational Design and Synthesis of Low-Temperature Fuel Cell Electrocatalysts

“…d Illustration of hydrophobic dimethyl silicon oil (DMS) just partially penetrating into the micropores with masstransport channels open, forming a robust triple-phase interface in micropores [163]. e Polarization curves and power density curves of DMFCs with Fe/N/C-DMS cathodes [163] An ideal electrode structure as proposed by Liu et al [162] should possess micropores with high densities of active sites and reactant/product should transfer directly to and from these active sites through macropores with minimal transport resistance. Based on this, Liu et al [162] prepared an interconnected porous nano-network Fe/N/C catalyst as shown in Fig.…”

“…Rational dispersion of these channels can effectively prevent water flooding. Zhou et al [163] constructed a triple-phase interface in the micropores of Fe/N/C catalysts by controlling the distribution of dimethyl silicon oil (DMS); a hydrophobic additive, so as to partially penetrate the micropores. This elaborately constructed Fe/N/C-based DMFC delivered high power densities (102 and 130 mW cm −2 at 60 and 80 °C, respectively) and durability comparable to that of Pt/C-based DMFCs as illustrated in Fig.…”