A General Carboxylate‐Assisted Approach to Boost the ORR Performance of ZIF‐Derived Fe/N/C Catalysts for Proton Exchange Membrane Fuel Cells

Abstract

An Fe/N/C catalyst derived from the pyrolysis of metal–organic frameworks, for example, a zeolitic‐imidazolate‐framework‐8 (ZIF‐8), has been regarded as one of the most promising non‐precious metal catalysts toward oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs). However, its ORR mass activity is still much inferior to that of Pt, partly because of the lack of general and efficient synthetic strategies. Herein, a general carboxylate‐assisted strategy that dramatically enhances the ORR mass activity of ZIF‐derived Fe/N/C catalysts is reported. The carboxylate is found to promote the formation of Fe/N/C catalysts with denser accessible active sites and entangled carbon nanotubes, as well as a higher mesoporosity. These structural advantages make the carboxylate‐assisted Fe/N/C catalysts show a 2–10 fold higher ORR mass activity than the common carboxylate‐free one in various cases. When applied in H2–O2 PEMFCs, the active acetate‐assisted Fe/N/C catalyst generates a peak power density of 1.33 W cm−2, a new record of peak power density for a H2–O2 PEMFC with non‐Pt ORR catalysts.

Stabilizing Fe–N–C Catalysts as Model for Oxygen Reduction Reaction

“…[ 104 ] As shown in Figure 14 a , Sun's team proposed a carboxylate‐assisted strategy to increase the density of active sites. [ 105 ] In the ordinary way, Fe doping into ZIF‐8 is achieved by replacing Zn 2+ with Fe 3+ . After adding acetate (OAc), Fe 3+ can also enter the ZIF‐8 structure in the form of Fe 3+ –OAC–Zn 2+ (Figure 14c ).…”

Atomically dispersed Co–N–C electrocatalysts synthesized by a low-speed ball milling method for proton exchange membrane fuel cells

“…considered to have great application prospects in proton exchange membrane fuel cells. Peak power density is an important index to evaluate electrocatalysts in PEMFCs 7 . Therefore, the membrane electrode assembly (MEA) of Co-120 and Co-40 catalysts were prepared, and the fuel cell polarization curve was tested to characterize the maximum power density of the PEMFCs.…”

“…Metal-organic frameworks (MOFs), such as ZIF-8, are a kind of utility porous material characterized with massive porous structure, great tunable functionality and constitutive property, which was expected as promising sacrificial templates of metal-nitrogen-carbon for ORR electrocatalysts 6 . In recent years, significant progress have been made in the synthesis of atomic-dispersed catalysts using ZIF-8 as template for ORR, which have become the most promising material to replace commercial Ptbased electrocatalysts [7][8][9] . However, traditional methods for the synthesis of metal atomic-dispersed ZIF-8 template, such as liquid phase synthesis, have a lot of shortcomings.…”

Recovery of High Purity Chlorine by Cu‐Doped Fe2O3 in Nitrogen Containing Carbon Matrix: A Bifunctional Electrocatalyst for HCl Electrolysis

“…Nevertheless, only few reports are available as bifunctional catalyst on non‐noble metals viz ., Fe−N−C [20] and recently we have reported molecular catalyst [21] and Co‐NSC [22] as a catalyst towards ODC and chlorine production. On the other hand Fe‐based catalysts specially iron oxide [23–25] have shown remarkable potential applications in electrocatalysis [26] water oxidation (OER) [27] and batteries [28] but, the stability and activity is low [29] . One can improve the activity along with the stability of iron oxides by doping with transition metals such as Fe, Cu, Co and Mn due to possible synergistic effect between metal and metal oxide [30] .…”