Hierarchically porous carbons with optimized nitrogen doping as highly active electrocatalysts for oxygen reduction

Abstract

Development of efficient, low-cost and stable electrocatalysts as the alternative to platinum for the oxygen reduction reaction is of significance for many important electrochemical devices, such as fuel cells, metal-air batteries and chlor-alkali electrolysers. Here we report a highly active nitrogen-doped, carbon-based, metal-free oxygen reduction reaction electrocatalyst, prepared by a hard-templating synthesis, for which nitrogen-enriched aromatic polymers and colloidal silica are used as precursor and template, respectively, followed by ammonia activation. Our protocol allows for the simultaneous optimization of both porous structures and surface functionalities of nitrogen-doped carbons. Accordingly, the prepared catalysts show the highest oxygen reduction reaction activity (half-wave potential of 0.85 V versus reversible hydrogen electrode with a low loading of 0.1 mg cm À 2 ) in alkaline media among all reported metal-free catalysts. Significantly, when used for constructing the air electrode of zinc-air battery, our metal-free catalyst outperforms the state-of the-art platinum-based catalyst.

Advanced Architectures and Relatives of Air Electrodes in Zn–Air Batteries

“…For example, Liang and his colleague reported a kind of hierarchical porous N‐doped carbon material with ultrahigh ORR catalytic activity even better than that of Pt/C ( Figure 2 a) 130. When assembled to Zn–air battery, this material behaved better than Pt/C especially at a high current density of 100 mA cm −2 (Figure 2b) 130. Besides, N‐doped porous nanocarbons/graphene composite also exhibited a similar 4e ORR pathways as Pt/C (Figure 2c,d) 131.…”

Cobalt Oxide and Cobalt‐Graphitic Carbon Core–Shell Based Catalysts with Remarkably High Oxygen Reduction Reaction Activity

“…Moreover, the presence of meso and/or macroporosity have been demonstrated to promote the transport of ORR‐related species (O 2 , H + , OH − , and H 2 O). [[qv: 8c]],12 …”

Graphene based metal and metal oxide nanocomposites: synthesis, properties and their applications

“…However, these and other methods mentioned before are not suitable for the synthesis of graphene needed for the preparation of graphene-based nanocomposites that usually require large amounts of graphene sheets preferably with modified surface structure. 5,9,58,59 While mechanical exfoliation using scotch-tape is a laborious procedure and rarely leads to a good quality of individual graphene sheets, epitaxial growth requires highvacuum conditions and specialized, expensive fabrication system to generate films on small areas. Still, the production of graphene monolayers with large surface areas has been attainable due to the more recent advances in CVD techniques, the uniform growth of single layers of graphene is still a challenge and indeed suitable methods have yet to be fully developed.…”

“…[6][7][8] For nearly three decades, the carbonaceous materials such as fullerenes and carbon nanotubes (CNTs) have drawn considerable attention due to their exceptional electronic and mechanical properties. 9 Specifically, after the discoveries of zero-dimensional (0D) buckminsterfullerene 10 and shortly later one-dimensional 1D CNTs, 11 enthusiasm in the research of carbon based nanomaterials have increased further. 12 Both fullerenes and CNTs have been proposed to be derived from the 2D graphene sheet that is viewed as key building block of all other graphitic carbon allotropes (cf.…”