Aiguo Kong

New heterometallic zirconium metalloporphyrin frameworks and their heteroatom-activated high-surface-area carbon derivatives.

Four cubic zirconium-porphyrin frameworks, CPM-99(H2, Zn, Co, Fe), were synthesized by a molecular-configuration-guided strategy. Augmentation of meso-substituted side arms (with double-torsional biphenyl rings) of tetratopic porphyrin linkers leads to a successful implementation of zirconium-carboxylate frameworks with cubic 2.5 nm cage. The hard-templating effect of Zr6-polyoxo-cluster and uniformly embedded (metallo)porphyrin centers endow CPM-99 with highly desirable properties as precursors for oxygen reduction reaction (ORR) catalysts. The pyrolytic products not only retain the microcubic morphology of the parent CPM-99 but also possess porphyrinic active sites, hierarchical porosity, and highly conducting networks. CPM-99Fe-derived material, denoted CPM-99Fe/C, exhibits the best ORR activity, comparable to benchmark 20% Pt/C in alkaline and acidic media, but CPM-99Fe/C is more durable and methanol-tolerant. This work demonstrates a new route for the development of nonprecious metal ORR catalysts from stable metalloporphyrinic MOFs.

Heterometal‐Embedded Organic Conjugate Frameworks from Alternating Monomeric Iron and Cobalt Metalloporphyrins and Their Application in Design of Porous Carbon Catalysts

DOI: 10.1002/adma.201500727 systems for the development of high-performance electrocatalysts. [ 10 ] The bimetallic catalysts with both Fe and Co can benefi t simultaneously from the unique graphene-rich morphology, enhanced corrosion resistance due to the presence of cobalt, and the intrinsically active FeN x sites, as shown by the earlier studies such as FeCo-EDA/C (EDA = ethylenediamine) by Choi et al., [ 10a ] FeCo-PANI/C (PANI = polyaniline) by Wu et al., [ 10b ] FeCo-OMPC (OMPC = ordered mesoporous porphyrinic carbons) by Cheon et al., [ 10c ] and FeCo-MFR/C (MFR = melamine-formaldehyde resin) by Zhao et al. [ 10d ]

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

Iron ORR: An ordered, mesoporous, Fe-porphyrin-like material was created through the nanocasting and pyrolysis of traditional Fe-N4 porphyrins. The resulting nonprecious metal electrocatalyst was used for the oxygen reduction reaction in both alkaline and acidic media.

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

The demand for directly converting chemical energy generated by exothermal redox reactions into electrical energy has increased markedly in recent years and motivates the development of novel electrochemical power sources. The use of fuel cell technology may be the most promising solution for electrochemical propulsion in electric vehicles. However, at present, the design and synthesis of high-performance and low-cost catalysts for the oxygen reduction reaction (ORR) still remains a significant challenge. Here, a high-performance Co-based carbon electrocatalyst (Co–N–GC) for the ORR is prepared by a simple wet-impregnation nanocasting method using SBA-15 as a hard template and water-soluble cobalt porphyrin as a precursor. The prepared catalysts with Co–Nx moieties have ordered mesoporous channels, and high specific surface area and degree of graphitization. In 0.1 M HClO4 medium, the ORR over Co–N–GC prepared at the optimized heat-treatment temperature (800 °C) exhibits a positive half-wave potential (0.79 V) and higher ORR current density (5.6 mA cm−2 at 0.2 V) compared to commercial Pt/C (20 wt%) catalysts. Moreover, the prepared Co–N–GC materials possess intrinsic long-time stability and the excellent methanol resistance toward the ORR in both acidic and alkaline media, and may serve as a promising alternative to Pt/C materials for the ORR in the widespread implementation of fuel cells.

Low-temperature activation of methane over rare earth metals promoted Zn/HZSM-5 zeolite catalysts in the presence of ethylene

Abstract At low temperature of 723 K, methane can be easily activated in the presence of ethylene in the feed, and converted to higher hydrocarbons (C 2 -C 4 ) and aromatics (C 6 -C 10 ), through its reaction over rare metals modified Zn/HZSM-5 zeolite catalysts without undesirable carbon oxides formation. Methane can get 37.3% conversion over the above catalysts under low temperature, and the catalysts show a longer lifetime than usual metal supported HZSM-5 zeolite catalysts without adding any rare earth metals. The effects of methane activation over various rare earth metal promoted Zn/HZSM-5 catalysts on the products and influences of several reaction conditions such as temperature, catalyst lifetime and molar ratio of CH 4 /C 2 H 4 have been discussed.

Al-coordination polymer-derived nanoporous nitrogen-doped carbon microfibers as metal-free catalysts for oxygen electroreduction and acetalization reactions

Nanoporous nitrogen-doped carbon microfibers were facilely synthesized by the pyrolysis of coordination polymer microfibers of aluminium-diethylenetriamine pentaacetic acid (Al-DTPA). Al-DTPA microfibers could be easily produced at a scale of over 0.25 kilograms by a homogeneous precipitation reaction of DTPA and aluminium nitrate in aqueous solution. After undergoing thermal conversion of Al-DTPA at the optimized temperatures and acid-leaching, the well-defined nitrogen-doped carbon microfibers were obtained at a scale of over 10 g in the laboratory. The interconnected nanoporous textures and plentiful nitrogen-doped functional sites endow such microfibers with not only efficient catalytic activity for the oxygen reduction reaction (ORR) in 0.1 M KOH electrolyte, but also superior durability and methanol-tolerance during ORR. Moreover, Al-DTPA microfibers could be also transferred into carbon-based nanoporous solid acids by the sulfuric acid-solvothermal treatment. Plentiful –SO3H functional groups were grafted on the surfaces of nanoporous nitrogen-dopped carbon microfibers (protonic acid amount, 1.8 mmol g−1). They served as a highly efficient and recyclable solid acid catalyst for the acetalization of benzaldehyde and ethylene glycol in a yield of about 99.0 at%. The thermal conversion of Al-coordination polymers might be a new practically feasible technique for the preparation of functional nanoporous nitrogen-doped carbon microfibers.

Coordination compound-derived ordered mesoporous N-free Fe–Px–C material for efficient oxygen electroreduction

Developing a high-performance non-precious metal electrocatalyst for the oxygen reduction reaction (ORR) is considered the main challenge facing the commercialization of polymer electrolyte fuel cells (PEFCs). Strategies of how to obtain highly active and stable catalysts still need to be studied. Herein, using a specially chosen (Ph3P)2Fe(CO)3 compound, containing Fe–P coordination centers, as the precursor, an ordered mesoporous N-free carbon-based electrocatalyst with embedded Fe–Px active sites was obtained through a wet-impregnation nanocasting method. Through this strategy, the ORR activity of the Fe–P–C material can be remarkably improved in both alkaline and acidic media. This enables Fe–P–C to become a new competitive candidate to substitute Pt-based cathode catalysts for the ORR in fuel cells.

An innovative method for oxidative degradation of chitosan with molecular oxygen catalyzed by metal phthalocyanine in neutral ionic liquid.

A novel aqueous solution-ionic liquid biphasic catalytic system was established for the oxidative degradation of chitosan under mild conditions. In this process, the environmentally acceptable and inexpensive molecular oxygen was first used as oxidant, the metal phthalocyanine was immobilized in ionic liquid as catalyst, and the aqueous solution as medium carried the reactants and the products. Under vigorous stirring and heating, the reactants fully contacted the catalysts in the emulsion and chitosan efficiently degraded into water-soluble materials. At the end of the reaction, the catalytic system could be easily separated by simple decantation and could also be reused in subsequent runs without apparent change in activity. These characters are in favor of the elimination of pollution and the reduction of the economic cost in the large-scale production of the water-soluble chitosan derivatives in chemical industry.

Fluorine and nitrogen co-doped ordered mesoporous carbon as a metal-free electrocatalyst for oxygen reduction reaction

Fluorine and nitrogen co-doped ordered mesoporous carbon (FN-OMC) is synthesized by a hard template method employing inexpensive resorcin as a carbon precursor and ammonium fluoride as a fluorine and nitrogen source. Considerable fluorine and nitrogen atoms (F: 0.35 at%, N: 2.25 at%) are homogeneously implanted in the graphitic carbon matrix with high surface area (671.3 cm2 g−1) and ordered mesoporous channels (6.2 nm). The FN-OMC prepared at the optimized heat-treatment temperature (1000 °C) exhibits a high catalytic activity (Eonset: −0.07 V, E1/2: −0.19 V, current density: 5.83 mA cm−2) for oxygen reduction reaction (ORR) comparable to commercial platinum–carbon (Pt–C, 20 wt%) catalysts, but better stability and methanol-tolerance in alkaline solutions. The synergistic effect of fluorine and nitrogen atoms in carbon frameworks is demonstrated to sharply polarize adjacent carbon atoms and facilitate the formation of defect-induced active sites for ORR.

Hierarchically porous few-layer porphyrinic carbon nanosheets formed by a VOx-templating method for high-efficiency oxygen electroreduction

A new vanadium oxide-templating synthesis strategy is used to synthesize porous few-layer porphyrinic carbon nanosheets (PPCNs) with highly efficient electrocatalytic activity for oxygen reduction reaction (ORR). Fe-porphyrin precursors were intercalated into V2O5 layers and directly transformed to carbon nanosheets after pyrolysis. Highly accessible porphyrinic Fe–N4 moieties embedded within few-layer carbon nanosheets with hierarchical porosity and high surface area (1600 m2 g−1) were obtained. The PPCNs were demonstrated as excellent non-precious metal catalysts for ORR in both alkaline and acidic media. Specifically, the PPCNs exhibited a more positive half-wave potential than commercial Pt/C (20 wt%) in an alkaline medium at a lower catalyst loading. Moreover through further pyrolysis treatment, the catalytic activity and durability of PPCNs for ORR in both media could be further improved. The novel synthesis method presented here opens up a new route to creating novel carbon nanomaterials for various applications.