Nonprecious Bimetallic Sites Coordinated on N‐Doped Carbons with Efficient and Durable Catalytic Activity for Oxygen Reduction

Abstract

Developing efficient, inexpensive, and durable electrocatalysts for the oxygen reduction reaction (ORR) is important for the large‐scale commercialization of fuel cells and metal–air batteries. Herein, a hierarchically porous bimetallic Fe/Co single‐atom‐coordinated N‐doped carbon (Fe/Co‐Nx‐C) electrocatalyst for ORR is synthesized from Fe/Co‐coordinated polyporphyrin using silica template‐assisted and silica‐protection synthetic strategies. In the synthesis, first silica nanoparticles‐embedded, silica‐protected Fe/Co‐polyporphyrin is prepared. It is then pyrolyzed and treated with acidic solution. The resulting Fe/Co‐Nx‐C material has a large specific surface area, large electrochemically active surface area, good conductivity, and catalytically active Fe/Co‐Nx sites. The material exhibits a very good electrocatalytic activity for the ORR in alkaline media, with a half‐wave potential of 0.86 V versus reversible hydrogen electrode, which is better than that of Pt/C (20 wt%). Furthermore, it shows an outstanding operational stability and durability during the reaction. A zinc–air battery (ZAB) assembled using Fe/Co‐Nx‐C as an air‐cathode electrocatalyst gives a high peak power density (152.0 mW cm−2) and shows a good recovery property. Furthermore, the performance of the battery is better than a corresponding ZAB containing Pt/C as an electrocatalyst. The work also demonstrates a synthetic route to a highly active, stable, and scalable single‐atom electrocatalyst for ORR in ZABs.

Optimizing Surface N‐Doping of Fe‐N‐C Catalysts Derived from Fe/Melamine‐Decorated Polyaniline for Oxygen Reduction Electrocatalysis

“…At present, one of the most promising NPMCs is metal and nitrogen co‐doped carbon (M‐N‐C), which is commonly obtained from pyrolysis of a mixture with metal, nitrogen‐containing precursors and carbon supports. [ 19–21 ] When Fe is chosen as the metal, the Fe‐N‐C catalysts always deliver high activity, 4‐electron selectivity and decent stability for ORR. [ 22–24 ] Wu et al.…”

Ion‐Induced Formation of Hierarchical Porous Nitrogen‐Doped Carbon Materials with Enhanced Oxygen Reduction

“…According to the XPS results, the resultant HPNC‐1 and HPNC‐2 possessed similar pyridinic‐N content (33.9 % and 35.4 %), which was obviously larger than the resultant HPNC (26.2 %). Combined with the electrochemical results, we inferred the pyridinic‐N as the catalytic activity sites might play dominant role in the onset potential of the resultant ORR catalysts [49] . On the other hand, previous literature demonstrated that microporous structure facilitated the absorption of reactive substances due to its large specific surface energy and high adsorption capacity, [50] thus speeding up the kinetic process of the catalytic reaction.…”

“…Combined with the electrochemical results, we inferred the pyridinic-N as the catalytic activity sites might play dominant role in the onset potential of the resultant ORR catalysts. [49] On the other hand, previous literature demonstrated that microporous structure facilitated the absorption of reactive substances due to its large specific surface energy and high adsorption capacity, [50] thus speeding up the kinetic process of the catalytic reaction. Meanwhile, the mesoporous structure is beneficial for the diffusion and mass transport process of the catalytic reaction.…”

Fe/Co/N–C/graphene derived from Fe/ZIF-67/graphene oxide three dimensional frameworks as a remarkably efficient and stable catalyst for the oxygen reduction reaction

“…The transition metal-nitrogen-carbon (M-N-C) catalysts could provide more active sites to improve the ORR performance. [19][20][21][22][23][24][25][26][27] Three-dimensional cobalt-nitrogen doubledoped porous carbon (3D Co-N/C) was prepared and exhibited remarkable ORR properties, which were attributed to Co doping and high content of pyridine nitrogen. 28 Co doped N-C (Co/N-C) catalysts were synthesized by direct pyrolysis of glucose doped with cobalt metals, which also showed excellent ORR performance.…”