Nitrogen‐Doped Inverse Opal Carbons Derived from an Ionic Liquid Precursor for the Oxygen Reduction Reaction

Abstract

Three-dimensionally macroporous nitrogen-doped carbon materials are fabricated via carbonization of an ionic-liquid-based small molecule precursor, 1-ethyl-3-methylimidazolium dicyanamide, using opal silica colloidal crystals as ah ard template. As compared to traditional polymerizable monomer-based precursors such as furfuryl alcohol, the entire process involving ionic liquid does not require any acid catalyst and prepolymerization step. More importantly,n itrogen heteroatomsc an be incorporated into the carbon skeleton in situ. The obtained inverse opal carbonsp ossess large surface areas and pore volumes, and high nitrogen content. When acting as metal-free electrocatalysts, the inverse opal carbonse xhibit high catalytic activity and selectivityt owards the oxygen reduction reaction in alkaline electrolyte, much better than that of the furfuryl-alcohol-derived inverse opal carbon and close to that of commercial Pt/C catalysts.The oxygen reduction reaction( ORR) is ak ey process in fuel cells and metal-air batteries. Platinumn anoparticless upported on high-surface-area carbon materials (Pt/C) are the most widely used electrocatalysts for ORR to date. However,h igh cost, the sluggish kinetics of the ORR process, and an intolerance to fuel crossover have limitedt he scalingu po fc orresponding renewable energy technologiesu sing Pt/C catalysts.[1] Consequently, there have been tremendous efforts on finding replacements for Pt-based catalysts. Amongt hese candidates, N-doped carbon materials as alternative metal-free catalysts are of particular interest.[2] Conjugation between the lone pair of the nitrogen heteroatom and p system of the carbon lattices results in structural irregularities in hexagonal carbon rings, imparting new catalytic sites and ah igh catalytic activity.[3] Despite the high performance of N-doped carbons, their catalytic activities are still far from satisfactory.T his is partly because of their relatively low nitrogen content as well as al ow surface utilization, resulting from randomly formed inaccessible narrow,s mall mesopores. Thus, aw ell-defineda nd continuousp orous structure with ar elativelyl arge surface area, large pore volume, regularp ores, and high nitrogen content is more preferable for high electrocatalytic activity.In this respect, inverse opal carbons (IOCs), which possess cage-like, orderedm acropores and three-dimensionally interconnected windows, could meet these requirements.[4] The large surface area and uniform pore size may facilitate the access of reactants to the active sites and allow ag ood reactant flux, resulting in high catalytic activity.I OC is technologically important for variousa pplicationss uch as photonic crystals, catalysis,s ensing, and separation techniques. For example, it has been previously reported that graphitic carbon nitride supported on three-dimensional interconnected macroporous carbon showed catalytic activity towards ORR comparable to that of commercial Pt/C.[5] Additionally,t he graphitic nature of the macroporous carbon could improve...

Biomass Derived Graphene‐Like Carbons for Electrocatalytic Oxygen Reduction Reaction

“…Take examples, N‐HCH‐900 with the ionic liquid 3‐methyl‐1‐butylpyridine dicyanamide as a precursor and SiO 2 template as a hard temple displays less undesirable ORR performance, likely resulted from the lower surface area . The morphology of Phen‐HS‐900, NMC‐4‐1000 and N‐IOC‐100 present mesoporous massive or inverse opal carbon particles possessing higher surface areas, yet showing lower electrocatalytic activities ,,. In contrast, the GHS‐1000‐2.5 with those unique advantages of effectively in situ nitrogen‐doping, optimization of nitrogen configuration and especially the very desirable graphene‐like two‐dimensional porous structure, displays more outstanding electrochemical activity toward ORR in both acid and alkaline conditions, which are much comparable to the commercial Pt/C catalyst and surpass other silica template‐based electrocatalysts (Table ).…”

Hybrid Spinel Oxides/N‐Doped Reduced Graphene Oxide as Highly‐Active Bifunctional Electrocatalysts for Oxygen Reduction/Evolution Reactions

“…The significant decrease of R ct values indicates the enhanced charge transfer efficiency between the electrodes for the CMO/N‐rGO nanocomposites and active species in KOH electrolyte, which is important for the electrocatalytic activity of the samples . Additionally, the N‐doped rGO not only serves as an enhancer of charge transfer for electrocatalysis, but also provides the doping N as the ORR and OER active species, thus facilitating the ORR and OER processes.…”

Functional Polymer Opals and Porous Materials by Shear‐Induced Assembly of Tailor‐Made Particles

“…Especially hard templating is known to be an excellent technique for the formation of hollow micro‐ and nanostructures. Silica‐based particles as hard templates have been used for nearly 15 years, and it is still one of the major routes for inverse opal or porous structure formation . Especially Ozin and co‐workers reported on tremendous efforts in this field of colloidal crystal templating .…”