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

Abstract

The highly efficient energy conversion of the polymer-electrolyte-membrane fuel cell (PEMFC) is extremely limited by the sluggish oxygen reduction reaction (ORR) kinetics and poor electrochemical stability of catalysts. Hitherto, to replace costly Pt-based catalysts, non-noble-metal ORR catalysts are developed, among which transition metal-heteroatoms-carbon (TM-H-C) materials present great potential for industrial applications due to their outstanding catalytic activity and low expense. However, their poor stability during testing in a two-electrode system and their high complexity have become a big barrier for commercial applications. Thus, herein, to simplify the research, the typical Fe-N-C material with the relatively simple constitution and structure, is selected as a model catalyst for TM-H-C to explore and improve the stability of such a kind of catalysts. Then, different types of active sites (centers) and coordination in Fe-N-C are systematically summarized and discussed, and the possible attenuation mechanism and strategies are analyzed. Finally, some challenges faced by such catalysts and their prospects are proposed to shed some light on the future development trend of TM-H-C materials for advanced ORR catalysis.

Wood‐Derived Monolithic Catalysts with the Ability of Activating Water Molecules for Oxygen Electrocatalysis

“…[11,43] Mesopores can increase the exposure degree of active sites and facilitate the construction of more oxygencatalyst-electrolyte three-phase interfaces, thereby enhancing the catalytic activity of the catalysts. [44,45] These aforementioned features facilitate the adsorption and desorption of intermediates to exalt the electrocatalytic activity of the catalysts. [10,46]…”

Coordinated single-molecule micelles: a self-template approach for preparing mesoporous doped carbons

“…6 Macro/mesopores promote mass transfer and the accessibility of chemical mediators, thus avoiding micropore flooding, whereas micropores can markedly enhance the specific surface area due to their high ratio of specific surface area to pore volume. 7–10 Many strategies have been explored to construct the pore structures of carbon. 11,12 Among these, the template approach is one of the significant strategies.…”

Three‐Dimensional Hierarchical Porous Fe, N‐Doped Hollow Carbon Nanospheres as Stable Electrocatalyst for Efficient Oxygen Reduction Reaction in Both Acidic and Alkaline Electrolytes

“…However, the single pore structure is disadvantage to the exposure of active sites, and the excessive ratio of micropores may induce the flooding of micropores and hinder oxygen transport, thus leading to a rapid loss of catalytic performance [10] . Therefore, increasing the proportion of meso‐ and macropores could avoid flooding and filling of micropores and improve mass transfer [17] . Among various carbon nanostructures, three‐dimensional (3D) hierarchical porous hollow nanosphere structure which possess the trimodal pore size distribution of optimal macro‐, meso‐, and micropores is a good choice.…”

“…[10] Therefore, increasing the proportion of meso-and macropores could avoid flooding and filling of micropores and improve mass transfer. [17] Among various carbon nanostructures, three-dimensional (3D) hierarchical porous hollow nanosphere structure which possess the trimodal pore size distribution of optimal macro-, meso-, and micropores is a good choice. On the one hand, 3D hollow carbon nanospheres have a rigid framework and a high surface-to-volume ratio, which facilitates mass transfer and exposes the most active sites.…”