Zn‐MOF‐74 Derived N‐Doped Mesoporous Carbon as pH‐Universal Electrocatalyst for Oxygen Reduction Reaction

Abstract

It is of increasing importance to explore new low‐cost and high‐activity electrocatalysts for oxygen reduction reaction (ORR), which have had a substantial impact across a diverse range of energy conversion system, including various fuel cell and metal–air batteries. Although engineering carbon nanostructures have been widely explored as a candidate class of Pt‐based ORR electrocatalysts owing to their proved high activity, outstanding stability, and ease of use, there still remains a daunting challenge to develop high activity metal‐free electrocatalysts in pH‐universal electrolyte system. Here, a reliable and controllable route amenable to prepare nitrogen‐doped porous carbon (NPC) with high yields and exceptional quality is described. The as‐prepared NPC shows advantages of high activity, high durability, and methanol‐tolerant as an efficient pH‐universal electrocatalyst for ORR, showing comparable or even better activity as compared with the commercial Pt/C catalysts not only in alkaline media but also in acidic and neutral electrolyte. Systematic electrochemical studies, combining with density functional theory calculation, demonstrate the unique nitrogen‐doping species and favorable pores in the as‐designed NPC synergistically contribute to the significantly improved catalytic activity in pH‐universal medium. The present work potentially presents an important breakthrough in developing ORR electrocatalysts for various fuel cells.

Highly Efficient Porous Carbon Electrocatalyst with Controllable N‐Species Content for Selective CO2 Reduction

“…Meanwhile, nitrogen element was proven to be uniformly doped in the NPC‐1000, which can be evidenced by the elemental mapping images as shown in Figure b. TEM image further proved the highly porous structure of NPC‐1000, which showed well distributed large pores with diameters around 10 nm (Figure c). The pore size of the NPC‐1000 was comparable with the previously reported Zn‐MOF‐74 derived NPC and larger than most of the previously reported MOFs‐derived carbon materials, which can mainly be attributed to the high percentage of oxygen in the Zn‐MOF‐74 . The large pores would promote the fast mass transport and are highly beneficial to the exposure of the active sites to the electrolyte for catalytic reactions.…”

“…N‐doped porous carbon (NPC) with large pores and controllable doped N species could be an ideal candidate for CO 2 RR. The large pores not only provide good pathways for fast mass transport, but also more importantly, expose a large amount of active N sites to the electrolyte for efficient CO 2 RR . Metal–organic frameworks (MOFs) have been widely used as hard templates for casting of porous carbons owing to their highly porous nature, the ability to immobilize active functional materials, and highly controllable nanostructures .…”

“…Xu's group developed an effective approach to the fabrication of one‐dimensional carbon nanorods by thermal transformation of MOF‐74‐Rod, which exhibit excellent supercapacitor performance . Wen and co‐workers reported recently that the use of oxygen‐rich MOFs as a precursor can help the formation of carbon materials with large pores . Their NPC obtained from Zn‐MOF‐74 shows excellent oxygen reduction reaction (ORR) performance under a wide pH range from acidic to basic conditions …”

“…Wen and co‐workers reported recently that the use of oxygen‐rich MOFs as a precursor can help the formation of carbon materials with large pores . Their NPC obtained from Zn‐MOF‐74 shows excellent oxygen reduction reaction (ORR) performance under a wide pH range from acidic to basic conditions …”

Synthesis of Bimetallic Conductive 2D Metal–Organic Framework (CoxNiy‐CAT) and Its Mass Production: Enhanced Electrochemical Oxygen Reduction Activity

“…However, the majority of MOFs cannot be used directly in electrocatalytic applications because they are usually nonconductive. And so, many MOFs are used indirectly in electrocatalytic applications as precursor materials for the production of porous carbon‐based ORR catalysts through the pyrolysis . Fortunately, some conductive MOFs have recently been developed, which can be directly used in electrocatalytic applications.…”