Ordered Mesoporous Fe-Porphyrin-Like Architectures as Excellent Cathode Materials for the Oxygen Reduction Reaction in Both Alkaline and Acidic Media

Identification of Catalytic Active Sites for Durable Proton Exchange Membrane Fuel Cell: Catalytic Degradation and Poisoning Perspectives

Recent progress in synthetic strategies, analysis techniques, and computational modeling assist researchers to develop more active catalysts including metallic clusters to single-atom active sites (SACs). Metal coordinated N-doped carbons (M-N-C) are the most auspicious, with a large number of atomic sites, markedly performing for a series of electrochemical reactions. This perspective sums up the latest innovative and computational comprehension, while giving credit to earlier/pioneering work in carbonaceous assembly materials towards robust electrocatalytic activity for proton exchange membrane fuel cells via inclusive performance assessment of the oxygen reduction reaction (ORR). M-N_x -C_y are exclusively defined active sites for ORR, so there is a unique possibility to intellectually design the relatively new catalysts with much improved activity, selectivity, and durability. Moreover, some SACs structures provide better performance in fuel cells testing with long-term durability. The efforts to understand the connection in SACs based M-N_x -C_y moieties and how these relate to catalytic ORR performance are also conveyed. Owing to comprehensive practical application in the field, this study has covered very encouraging aspects to the current durability status of M-N-C based catalysts for fuel cells followed by degradation mechanisms such as macro-, microdegradation, catalytic poisoning, and future challenges.

Synthesis of Fe3C@porous carbon nanorods via carbonizing Fe complexes for oxygen reduction reaction and Zn–air battery

The FeCNRs were controlled prepared via carbonizing the Fe complexes and their activities on ORR was found to be suitable for Zn–air battery application.

Porous Carbon Networks Derived From Graphitic Carbon Nitride for Efficient Oxygen Reduction Reaction

Great efforts have been dedicated to finding economic and efficient oxygen reduction reaction (ORR) for fuel cell technology. Among various catalysts, N-doped carbon-based nanomaterials have attracted much attention due to low-cost, noble metal free, and good durability. Herein, we developed a facile and economic strategy to prepare nitrogen-doped carbon networks for efficient ORR application. The g-C₃N₄ is used as the template and N source, and dopamine is used as the carbon source. By simple hydrothermal treatment and sintering, N-doped carbon network structures with high specific surface area, effective ORR activity, and superior durability could be acquired. The present strategy is free of involving generally multistep, poisonous reagents, and complication of removing template for fabrication of 3D carbon structures.

Templating Synthesis of Mesoporous Fe3C-Encapsulated Fe-N-Doped Carbon Hollow Nanospindles for Electrocatalysis

Developing cost-efficient alternatives to the noble metal catalysts toward oxygen reduction reaction (ORR) has attracted much attention. Herein, a kind of mesoporous hollow spindlelike Fe-N-C electrocatalysts with iron carbide nanoparticles encased in the N-doped graphitic layers has been synthesized by a novel "reactive hard template" strategy through the Fe³⁺-assisted polymerization of dopamine on the Fe₂O₃ cores and the following calcinations. The Fe₂O₃ nanospindles not only as the hard template guide the formation of well-defined shape and structure of the catalyst but also as the reactive template provide Fe reservoir to generate Fe₃C nanoparticles in the catalyst during the thermochemical process. The superiority in accessible active sites of Fe-N _x species, Fe₃C nanoparticles in graphenelike layers, and highly mesoporous hollow structure enables the catalysts to exhibit excellent ORR performances including high catalytic activity, outstanding long-term cycling stability, and good tolerance to methanol.

Nanoporous carbon derived from a functionalized metal-organic framework as a highly efficient oxygen reduction electrocatalyst

High levels of iron-nitrogen doped porous carbon materials are obtained from MOF-253 using a step-by-step post-synthetic modification strategy. MOF-253 possessing open 2,2'-bipyridine nitrogen sites not only serves as a precursor but also provides chelate bonding sites for Fe²⁺. Followed by further impregnation of 1,10-phenanthroline, high surface area porous carbon materials are obtained. For comparison, when iron-1,10-phenanthroline species as a whole are incorporated into MOF-253, carbon materials with less active sites and low surface area are obtained. The porous carbon materials derived from MOF-253 by using a step-by-step post-synthetic modification strategy demonstrate excellent ORR activity, high selectivity (direct 4e^- reduction of oxygen to water) and stability under both alkaline and acidic conditions. The onset potential of the porous carbon material under alkaline conditions (980 mV) is the same as that of Pt/C (20 wt%) (980 mV) and the half-wave potential (E_1/2) is 840 mV, which is 20 mV more than that of Pt/C (20 wt%). Under acidic conditions, the onset potential and the half-wave potential are only 20 mV and 30 mV less than those of Pt/C (20 wt%). The developed step-by-step post-synthetic modification route of MOFs has expanded the ways to prepare functionalized porous carbon for energy related applications.

Iron–nitrogen co-doped hierarchically mesoporous carbon spheres as highly efficient electrocatalysts for the oxygen reduction reaction

Iron and nitrogen co-doped hierarchically mesoporous carbon spheres (Fe–N–CS) were successfully prepared by using hierarchically mesoporous silica spheres as hard template.

Fe-Porphyrin functionalized microporous organic nanotube networks and their application for the catalytic olefination of aldehydes and carbene insertion into N–H bonds

Fe-Porphyrin functionalized microporous organic nanotubes networks were synthesized by an in situ hyper-crosslinking reaction between bottlebrush copolymers and meso-tetraphenylporphyrin iron(iii) chloride.

Space-confined synthesis of multilayer Cu–N-doped graphene nanosheets for efficient oxygen electroreduction

Cu–N-doped graphene nanosheets prepared by thermal conversion of montmorillonite-confined Cu(ii) 2,2′-bipyridines exhibit efficient catalytic performance for oxygen electroreduction.

Energy-Related Small Molecule Activation Reactions: Oxygen Reduction and Hydrogen and Oxygen Evolution Reactions Catalyzed by Porphyrin- and Corrole-Based Systems

Globally increasing energy demands and environmental concerns related to the use of fossil fuels have stimulated extensive research to identify new energy systems and economies that are sustainable, clean, low cost, and environmentally benign. Hydrogen generation from solar-driven water splitting is a promising strategy to store solar energy in chemical bonds. The subsequent combustion of hydrogen in fuel cells produces electric energy, and the only exhaust is water. These two reactions compose an ideal process to provide clean and sustainable energy. In such a process, a hydrogen evolution reaction (HER), an oxygen evolution reaction (OER) during water splitting, and an oxygen reduction reaction (ORR) as a fuel cell cathodic reaction are key steps that affect the efficiency of the overall energy conversion. Catalysts play key roles in this process by improving the kinetics of these reactions. Porphyrin-based and corrole-based systems are versatile and can efficiently catalyze the ORR, OER, and HER. Because of the significance of energy-related small molecule activation, this review covers recent progress in hydrogen evolution, oxygen evolution, and oxygen reduction reactions catalyzed by porphyrins and corroles.

Reactive Multifunctional Template-Induced Preparation of Fe-N-Doped Mesoporous Carbon Microspheres Towards Highly Efficient Electrocatalysts for Oxygen Reduction

A novel in situ replication and polymerization strategy is developed for the synthesis of Fe-N-doped mesoporous carbon microspheres (Fe-NMCSs). This material benefits from the synergy between the high catalytic activity of Fe-N-C and the fast mass transport of the mesoporous microsphere structure. Compared to commercial Pt/C catalysts, the Fe-NMCSs show a much better electrocatalytic performance in terms of higher catalytic activity, selectivity, and durability for the oxygen reduction reaction.

Efficient oxygen electroreduction over ordered mesoporous Co–N-doped carbon derived from cobalt porphyrin

High-performance self-supported Co–N-doped carbon electrocatalyst for ORR with comparable activity to Pt/C in both acidic and alkaline media was prepared.

Iron nanoparticles with a square pyramidal structure in mesoporous carbons as an effective catalyst toward oxygen reduction

FeAMC-1273, with more pyridinic-N and pyridinic-N–Fe for the creation of a square pyramidal planar geometry around iron, exhibits the best ORR activity.

MIL-100 derived nitrogen-embodied carbon shells embedded with iron nanoparticles

The use of metal-organic frameworks (MOFs) as templates and precursors to synthesize new carbon materials with controllable morphology and pre-selected heteroatom doping holds promise for applications as efficient non-precious metal catalysts. Here, we report a facile pyrolysis pathway to convert MIL-100 into nitrogen-doped carbon shells encapsulating Fe nanoparticles in a comparative study involving multiple selected nitrogen sources. The hierarchical porous architecture, embedded Fe nanoparticles, and nitrogen decoration endow this composite with a superior oxygen reduction activity. Furthermore, the excellent durability and high methanol tolerance even outperform the commercial Pt-C catalyst.

The role of iron in the preparation and oxygen reduction reaction activity of nitrogen-doped carbon

The exact role of iron in catalyzing oxygen reduction reaction in both alkaline and acidic media is portrayed with unique platelet ordered mesoporous carbon prepared using Fe-phthalocyanine as iron, nitrogen and carbon sources.