Publications by authors named "Young Jin Sa"

17 Publications

  • Page 1 of 1

Catalyst-electrolyte interface chemistry for electrochemical CO reduction.

Chem Soc Rev 2020 Sep;49(18):6632-6665

Clean Energy Research Center, Korea Institute of Science and Technology (KIST), Seoul 02792, Republic of Korea. and Division of Energy and Environmental Technology, KIST School, Korea University of Science and Technology (UST), Seoul 02792, Republic of Korea and Department of Chemical and Biomolecular Engineering and Yonsei-KIST Convergence Research Institute, Yonsei University, Seoul 03722, Republic of Korea.

The electrochemical reduction of CO2 stores intermittent renewable energy in valuable raw materials, such as chemicals and transportation fuels, while minimizing carbon emissions and promoting carbon-neutral cycles. Recent technoeconomic reports suggested economically feasible target products of CO2 electroreduction and the relative influence of key performance parameters such as faradaic efficiency (FE), current density, and overpotential in the practical industrial-scale applications. Furthermore, fundamental factors, such as available reaction pathways, shared intermediates, competing hydrogen evolution reaction, scaling relations of the intermediate binding energies, and CO2 mass transport limitations, should be considered in relation to the electrochemical CO2 reduction performance. Intensive research efforts have been devoted to designing and developing advanced electrocatalysts and improving mechanistic understanding. More recently, the research focus was extended to the catalyst environment, because the interfacial region can delicately modulate the catalytic activity and provide effective solutions to challenges that were not fully addressed in the material development studies. Herein, we discuss the importance of catalyst-electrolyte interfaces in improving key operational parameters based on kinetic equations. Furthermore, we extensively review previous studies on controlling organic modulators, electrolyte ions, electrode structures, as well as the three-phase boundary at the catalyst-electrolyte interface. The interfacial region modulates the electrocatalytic properties via electronic modification, intermediate stabilization, proton delivery regulation, catalyst structure modification, reactant concentration control, and mass transport regulation. We discuss the current understanding of the catalyst-electrolyte interface and its effect on the CO2 electroreduction activity.
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http://dx.doi.org/10.1039/d0cs00030bDOI Listing
September 2020

Unassisted solar lignin valorisation using a compartmented photo-electro-biochemical cell.

Nat Commun 2019 11 12;10(1):5123. Epub 2019 Nov 12.

School of Energy and Chemical Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan, 44919, Republic of Korea.

Lignin is a major component of lignocellulosic biomass. Although it is highly recalcitrant to break down, it is a very abundant natural source of valuable aromatic carbons. Thus, the effective valorisation of lignin is crucial for realising a sustainable biorefinery chain. Here, we report a compartmented photo-electro-biochemical system for unassisted, selective, and stable lignin valorisation, in which a TiO photocatalyst, an atomically dispersed Co-based electrocatalyst, and a biocatalyst (lignin peroxidase isozyme H8, horseradish peroxidase) are integrated, such that each system is separated using Nafion and cellulose membranes. This cell design enables lignin valorisation upon irradiation with sunlight without the need for any additional bias or sacrificial agent and allows the protection of the biocatalyst from enzyme-damaging elements, such as reactive radicals, gas bubbles, and light. The photo-electro-biochemical system is able to catalyse lignin depolymerisation with a 98.7% selectivity and polymerisation with a 73.3% yield using coniferyl alcohol, a lignin monomer.
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http://dx.doi.org/10.1038/s41467-019-13022-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6851146PMC
November 2019

Active Edge-Site-Rich Carbon Nanocatalysts with Enhanced Electron Transfer for Efficient Electrochemical Hydrogen Peroxide Production.

Angew Chem Int Ed Engl 2019 Jan 21;58(4):1100-1105. Epub 2018 Dec 21.

Department of Energy Engineering and School of Energy and Chemical Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan, 44919, Republic of Korea.

A highly efficient, metal-free carbon nanocatalyst is presented that possesses abundant active, oxygenated graphitic edge sites. The edge site-rich nanocarbon catalyst exhibits about 28 times higher activity for H O production than a basal plane-rich carbon nanotube with a H O selectivity over 90 %. The oxidative treatment further promotes the H O generation activity to reach close to the thermodynamic limit. The optimized nanocarbon catalyst shows a very high H O production activity, surpassing previously reported catalysts in alkaline media. Moreover, it can stably produce H O for 16 h with Faradaic efficiency reaching 99 % and accumulated H O concentration of 24±2 mm. Importantly, we find that the heterogeneous electron transfer kinetics of the carbon-based catalyst is closely related to the electrocatalytic activity, suggesting that first outer-sphere electron transfer to O is an important step governing the H O production rate.
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http://dx.doi.org/10.1002/anie.201812435DOI Listing
January 2019

Oxygen-deficient triple perovskites as highly active and durable bifunctional electrocatalysts for oxygen electrode reactions.

Sci Adv 2018 06 15;4(6):eaap9360. Epub 2018 Jun 15.

Hybrid Materials Center, Department of Nanotechnology and Advanced Materials Engineering, Sejong University, Seoul 05006, Republic of Korea.

Highly active and durable bifunctional oxygen electrocatalysts have been of pivotal importance for renewable energy conversion and storage devices, such as unitized regenerative fuel cells and metal-air batteries. Perovskite-based oxygen electrocatalysts have emerged as promising nonprecious metal bifunctional electrocatalysts, yet their catalytic activity and stability still remain to be improved. We report a high-performance oxygen electrocatalyst based on a triple perovskite, NdBaCoFeMnO (NBCFM), which shows superior activity and durability for oxygen electrode reactions to single and double perovskites. When hybridized with nitrogen-doped reduced graphene oxide (N-rGO), the resulting NBCFM/N-rGO catalyst shows further boosted bifunctional oxygen electrode activity (0.698 V), which surpasses that of Pt/C (0.801 V) and Ir/C (0.769 V) catalysts and which, among the perovskite-based electrocatalysts, is the best activity reported to date. The superior catalytic performances of NBCFM could be correlated to its oxygen defect-rich structure, lower charge transfer resistance, and smaller hybridization strength between O 2p and Co 3d orbitals.
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http://dx.doi.org/10.1126/sciadv.aap9360DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6018999PMC
June 2018

Iridium-Based Multimetallic [email protected] Structure: An Efficient and Robust Electrocatalyst toward Oxygen Evolution Reaction.

ACS Nano 2017 06 14;11(6):5500-5509. Epub 2017 Jun 14.

Center for Molecular Spectroscopy and Dynamics, Institute for Basic Science (IBS) , Seoul 02841, Korea.

Nanoframe electrocatalysts have attracted great interest due to their inherently high active surface area per a given mass. Although recent progress has enabled the preparation of single nanoframe structures with a variety of morphologies, more complex nanoframe structures such as a double-layered nanoframe have not yet been realized. Herein, we report a rational synthetic strategy for a structurally robust Ir-based multimetallic double-layered nanoframe (DNF) structure, [email protected] By leveraging the differing kinetics of dual Ir precursors and dual transition metal (Ni and Cu) precursors, a core-shell-type [email protected] structure could be generated in a simple one-step synthesis, which was subsequently transformed into a multimetallic IrNiCu DNF with a rhombic dodecahedral morphology via selective etching. The use of single Ir precursor yielded single nanoframe structures, highlighting the importance of employing dual Ir precursors. In addition, the structure of Ir-based nanocrystals could be further controlled to DNF with octahedral morphology and [email protected] core-shell structures via a simple tuning of experimental factors. The IrNiCu DNF exhibited high electrocatalytic activity for oxygen evolution reaction (OER) in acidic media, which is better than Ir/C catalyst. Furthermore, IrNiCu DNF demonstrated excellent durability for OER, which could be attributed to the frame structure that prevents the growth and agglomeration of particles as well as in situ formation of robust rutile IrO phase during prolonged operation.
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http://dx.doi.org/10.1021/acsnano.7b00233DOI Listing
June 2017

Roles of Fe-N and [email protected] Species in Fe-N/C Electrocatalysts for Oxygen Reduction Reaction.

ACS Appl Mater Interfaces 2017 Mar 10;9(11):9567-9575. Epub 2017 Mar 10.

School of Energy and Chemical Engineering, Ulsan National Institute of Science and Technology (UNIST) , 50 UNIST-gil, Ulsan 44919, Republic of Korea.

Iron and nitrogen codoped carbons (Fe-N/C) have emerged as promising nonprecious metal catalysts for the oxygen reduction reaction (ORR). While Fe-N sites have been widely considered as active species for Fe-N/C catalysts, very recently, iron and/or iron carbide encased with carbon shells ([email protected]) has been suggested as a new active site for the ORR. However, most of synthetic routes to Fe-N/C catalysts involve high-temperature pyrolysis, which unavoidably yield both Fe-N and [email protected] species, hampering the identification of exclusive role of each species. Herein, in order to establish the respective roles of Fe-N and [email protected] sites we rationally designed model catalysts via the phase conversion reactions of FeO nanoparticles supported on carbon nanotubes. The resulting catalysts selectively contained Fe-N, [email protected], and N-doped carbon (C-N) sites. It was revealed that Fe-N sites dominantly catalyze ORR via 4-electron (4 e) pathway, exerting a major role for high ORR activity, whereas [email protected] sites mainly promote 2 e reduction of oxygen followed by 2 e peroxide reduction, playing an auxiliary role.
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http://dx.doi.org/10.1021/acsami.6b13417DOI Listing
March 2017

A General Approach to Preferential Formation of Active Fe-N Sites in Fe-N/C Electrocatalysts for Efficient Oxygen Reduction Reaction.

J Am Chem Soc 2016 11 1;138(45):15046-15056. Epub 2016 Nov 1.

Hydrogen and Fuel Cell Center, Korea Institute of Energy Research (KIER) , Jellabuk-do 56332, Republic of Korea.

Iron-nitrogen on carbon (Fe-N/C) catalysts have emerged as promising nonprecious metal catalysts (NPMCs) for oxygen reduction reaction (ORR) in energy conversion and storage devices. It has been widely suggested that an active site structure for Fe-N/C catalysts contains Fe-N coordination. However, the preparation of high-performance Fe-N/C catalysts mostly involves a high-temperature pyrolysis step, which generates not only catalytically active Fe-N sites, but also less active large iron-based particles. Herein, we report a general "silica-protective-layer-assisted" approach that can preferentially generate the catalytically active Fe-N sites in Fe-N/C catalysts while suppressing the formation of large Fe-based particles. The catalyst preparation consisted of an adsorption of iron porphyrin precursor on carbon nanotube (CNT), silica layer overcoating, high-temperature pyrolysis, and silica layer etching, which yielded CNTs coated with thin layer of porphyrinic carbon (CNT/PC) catalysts. Temperature-controlled in situ X-ray absorption spectroscopy during the preparation of CNT/PC catalyst revealed the coordination of silica layer to stabilize the Fe-N sites. The CNT/PC catalyst contained higher density of active Fe-N sites compared to the CNT/PC prepared without silica coating. The CNT/PC showed very high ORR activity and excellent stability in alkaline media. Importantly, an alkaline anion exchange membrane fuel cell (AEMFC) with a CNT/PC-based cathode exhibited record high current and power densities among NPMC-based AEMFCs. In addition, a CNT/PC-based cathode exhibited a high volumetric current density of 320 A cm in acidic proton exchange membrane fuel cell. We further demonstrated the generality of this synthetic strategy to other carbon supports.
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http://dx.doi.org/10.1021/jacs.6b09470DOI Listing
November 2016

Rational design of Pt-Ni-Co ternary alloy nanoframe crystals as highly efficient catalysts toward the alkaline hydrogen evolution reaction.

Nanoscale 2016 Sep;8(36):16379-16386

Center for Molecular Spectroscopy and Dynamics, Institute for Basic Science (IBS), Seoul 02841, Korea and Department of Chemistry and Research Institute for Natural Sciences, Korea University, Seoul 02841, Republic of Korea.

The rational design of highly efficient electrocatalysts for the hydrogen evolution reaction (HER) is of prime importance for establishing renewable and sustainable energy systems. The alkaline HER is particularly challenging as it involves a two-step reaction of water dissociation and hydrogen recombination, for which platinum-based binary catalysts have shown promising activity. In this work, we synthesized high performance platinum-nickel-cobalt alloy nanocatalysts for the alkaline HER through a simple synthetic route. This ternary nanostructure with a Cartesian-coordinate-like hexapod shape could be prepared by a one-step formation of core-dual shell [email protected]@Co nanostructures followed by a selective removal of the [email protected] shell. The cobalt precursor brings about a significant impact on the control of size and shape of the nanostructure. The PtNiCo nanohexapods showed a superior alkaline HER activity to Pt/C and binary PtNi hexapods, with 10 times greater specific activity than Pt/C. In addition, the PtNiCo nanohexapods demonstrated excellent activity and durability for the oxygen reduction reaction in acidic media.
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http://dx.doi.org/10.1039/c6nr04572cDOI Listing
September 2016

Self-Supported Mesostructured Pt-Based Bimetallic Nanospheres Containing an Intermetallic Phase as Ultrastable Oxygen Reduction Electrocatalysts.

Small 2016 Oct 12;12(38):5347-5353. Epub 2016 Aug 12.

School of Energy and Chemical Engineering, Ulsan National Institute of Science and Technology (UNIST), 50 UNIST-gil, Ulsan, 44919, Republic of Korea.

Developing highly active and stable cathode catalysts is of pivotal importance for proton exchange membrane fuel cells (PEMFCs). While carbon-supported nanostructured Pt-based catalysts have so far been the most active cathode catalysts, their durability and single-cell performance are yet to be improved. Herein, self-supported mesostructured Pt-based bimetallic (Meso-PtM; M = Ni, Fe, Co, Cu) nanospheres containing an intermetallic phase are reported, which can combine the beneficial effects of transition metals (M), an intermetallic phase, a 3D interconnected framework, and a mesoporous structure. Meso-PtM nanospheres show enhanced oxygen reduction reaction (ORR) activity, compared to Pt black and Pt/C catalysts. Notably, Meso-PtNi containing an intermetallic phase exhibits ultrahigh stability, showing enhanced ORR activity even after 50 000 potential cycles, whereas Pt black and Pt/C undergo dramatic degradation. Importantly, Meso-PtNi with an intermetallic phase also demonstrated superior activity and durability when used in a PEMFC single-cell, with record-high initial mass and specific activities.
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http://dx.doi.org/10.1002/smll.201601825DOI Listing
October 2016

Coordination Chemistry of [Co(acac)2 ] with N-Doped Graphene: Implications for Oxygen Reduction Reaction Reactivity of Organometallic Co-O4 -N Species.

Angew Chem Int Ed Engl 2015 Oct 2;54(43):12622-6. Epub 2015 Sep 2.

Department of Chemistry and Chemical Engineering, Inha University, 100 Inha-ro, Nam-gu, Incheon 402-751 (Republic of Korea).

Hybridization of organometallic complexes with graphene-based materials can give rise to enhanced catalytic performance. Understanding the chemical structures within hybrid materials is of primary importance. In this work, archetypical hybrid materials are synthesized by the reaction of an organometallic complex, [Co(II) (acac)2 ] (acac=acetylacetonate), with N-doped graphene-based materials at room temperature. Experimental characterization of the hybrid materials and theoretical calculations reveal that the organometallic cobalt-containing species is coordinated to heterocyclic groups in N-doped graphene as well as to its parental acac ligands. The hybrid material shows high electrocatalytic activity for the oxygen reduction reaction (ORR) in alkaline media, and superior durability and methanol tolerance to a Pt/C catalyst. Based on the chemical structures and ORR experiments, the catalytically active species is identified as a Co-O4 -N structure.
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http://dx.doi.org/10.1002/anie.201504707DOI Listing
October 2015

Monolayer-precision synthesis of molybdenum sulfide nanoparticles and their nanoscale size effects in the hydrogen evolution reaction.

ACS Nano 2015 Apr 26;9(4):3728-39. Epub 2015 Mar 26.

†Department of Chemistry, ‡School of Energy and Chemical Engineering, and §UNIST Central Research Facilities (UCRF), Ulsan National Institute of Science and Technology (UNIST), 50 UNIST-gil, Ulsan 689-798, Republic of Korea.

Metal sulfide-based nanostructured materials have emerged as promising catalysts for hydrogen evolution reaction (HER), and significant progress has been achieved in enhancing their activity and durability for the HER. The understanding of nanoscale size-dependent catalytic activities can suggest critical information regarding catalytic reactivity, providing the scientific basis for the design of advanced catalysts. However, nanoscale size effects in metal sulfide-based HER catalysts have not yet been established fully, due to the synthetic difficulty in precisely size-controlled metal sulfide nanoparticles. Here we report the preparation of molybdenum sulfide (MoS2) nanoparticles with monolayer precision from one to four layers with the nearly constant basal plane size of 5 nm, and their size-dependent catalytic activity in the HER. Using density functional theory (DFT) calculations, we identified the most favorable single-, double-, and triple-layer MoS2 model structures for the HER, and calculated elementary step energetics of the HER over these three model structures. Combining HER activity measurements and the DFT calculation results, we establish that the turnover frequency of MoS2 nanoparticles in the HER increases in a quasi-linear manner with decreased layer numbers. Cobalt-promoted MoS2 nanoparticles also exhibited similar HER activity trend. We attribute the higher HER activity of smaller metal sulfide nanoparticles to the higher degree of oxidation, higher Mo-S coordination number, formation of the 1T phase, and lower activation energy required to overcome transition state. This insight into the nanoscale size-dependent HER activity trend will facilitate the design of advanced HER catalysts as well as other hydrotreating catalysts.
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http://dx.doi.org/10.1021/acsnano.5b00786DOI Listing
April 2015

Simple coordination complex-derived three-dimensional mesoporous graphene as an efficient bifunctional oxygen electrocatalyst.

Chem Commun (Camb) 2015 Apr;51(31):6773-6

Department of Chemistry, Ulsan National Institute of Science and Technology (UNIST), UNIST-gil 50, Ulsan 689-798, Republic of Korea.

3D mesoporous graphene (mesoG) was synthesized from [Ni2(EDTA)] (EDTA = ethylenediaminetetraacetate). The material is comprised of interconnected 4 nm-sized hollow carbon shells composed of 3-4 layers of graphene and exhibits high bifunctional electrocatalytic activity as well as high durability for use in oxygen evolution and reduction reactions.
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http://dx.doi.org/10.1039/c5cc01123jDOI Listing
April 2015

An ice-templated, pH-tunable self-assembly route to hierarchically porous graphene nanoscroll networks.

Nanoscale 2014 Aug 7;6(16):9734-41. Epub 2014 Jul 7.

School of Energy and Chemical Engineering, KIER-UNIST Advanced Center for Energy, Ulsan National Institute of Science and Technology (UNIST), Ulsan Metropolitan City, 689-798, Republic of Korea.

Porous graphene nanostructures are of great interest for applications in catalysis and energy storage. However, the fabrication of three-dimensional (3D) macroporous graphene nanostructures with controlled morphology, porosity and surface area still presents significant challenges. Here we introduce an ice-templated self-assembly approach for the integration of two-dimensional graphene nanosheets into hierarchically porous graphene nanoscroll networks, where the morphology of porous structures can be easily controlled by varying the pH conditions during the ice-templated self-assembly process. We show that freeze-casting of reduced graphene oxide (rGO) solution results in the formation of 3D porous graphene microfoam below pH 8 and hierarchically porous graphene nanoscroll networks at pH 10. In addition, we demonstrate that graphene nanoscroll networks show promising electrocatalytic activity for the oxygen reduction reaction (ORR).
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http://dx.doi.org/10.1039/c4nr01988aDOI Listing
August 2014

Carbon nanotubes/heteroatom-doped carbon core-sheath nanostructures as highly active, metal-free oxygen reduction electrocatalysts for alkaline fuel cells.

Angew Chem Int Ed Engl 2014 Apr 19;53(16):4102-6. Epub 2014 Feb 19.

Department of Chemistry and School of Nano-Bioscience and Chemical Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 689-798 (Republic of Korea) http://shjoo.unist.ac.kr/; KIER-UNIST Advanced Center for Energy, UNIST, Ulsan 689-798 (Republic of Korea).

A facile, scalable route to new nanocomposites that are based on carbon nanotubes/heteroatom-doped carbon (CNT/HDC) core-sheath nanostructures is reported. These nanostructures were prepared by the adsorption of heteroatom-containing ionic liquids on the walls of CNTs, followed by carbonization. The design of the CNT/HDC composite allows for combining the electrical conductivity of the CNTs with the catalytic activity of the heteroatom-containing HDC sheath layers. The CNT/HDC nanostructures are highly active electrocatalysts for the oxygen reduction reaction and displayed one of the best performances among heteroatom-doped nanocarbon catalysts in terms of half-wave potential and kinetic current density. The four-electron selectivity and the exchange current density of the CNT/HDC nanostructures are comparable with those of a Pt/C catalyst, and the CNT/HDC composites were superior to Pt/C in terms of long-term durability and poison tolerance. Furthermore, an alkaline fuel cell that employs a CNT/HDC nanostructure as the cathode catalyst shows very high current and power densities, which sheds light on the practical applicability of these new nanocomposites.
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http://dx.doi.org/10.1002/anie.201307203DOI Listing
April 2014

Catalytic conversion of Undaria Pinnatifida over nanoporous materials using Py-GC/MS.

J Nanosci Nanotechnol 2013 Dec;13(12):7794-800

Graduate School of Energy and Environmental System Engineering, University of Seoul, Seoul 130-743, Korea.

Catalytic pyrolysis of Undaria Pinnatifida was carried out over a nanoporous Al-SBA-15 catalyst for the first time. Pt nanoparticles were added to Al-SBA-15 to generate a Pt/Al-SBA-15 catalyst. The effect of the addition of the Pt nanoparticles on the catalytic pyrolysis was investigated. For rapid product analysis and catalyst evaluation, a pyrolysis-gas chromatography/mass spectrometry was used. The characteristics of the catalysts were analyzed using X-ray diffraction, nitrogen adsorption-desorption, transmission electron microscope, NH3 temperature programmed desorption, and inductively coupled plasma optical emission spectrometer. Compared to the non-catalytic pyrolysis, catalytic pyrolysis over Al-SBA-15 produced a higher-quality bio-oil with a high stability and a low oxygen content. When Pt/Al-SBA-15 was used, compared to Al-SBA-15, the improvement of bio-oil quality was more profound; the yield of high-value-added aromatics increased, while the yields of acids and oxygenates decreased.
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http://dx.doi.org/10.1166/jnn.2013.8125DOI Listing
December 2013

Ordered mesoporous porphyrinic carbons with very high electrocatalytic activity for the oxygen reduction reaction.

Sci Rep 2013 ;3:2715

Department of Chemistry, School of Nano-Bioscience and Chemical Engineering, KIER-UNIST Advanced Center for Energy, and Low-Dimensional Carbon Materials Center, Ulsan National Institute of Science and Technology (UNIST), 50 UNIST-gil, Ulsan 689-798, Republic of Korea.

The high cost of the platinum-based cathode catalysts for the oxygen reduction reaction (ORR) has impeded the widespread application of polymer electrolyte fuel cells. We report on a new family of non-precious metal catalysts based on ordered mesoporous porphyrinic carbons (M-OMPC; M = Fe, Co, or FeCo) with high surface areas and tunable pore structures, which were prepared by nanocasting mesoporous silica templates with metalloporphyrin precursors. The FeCo-OMPC catalyst exhibited an excellent ORR activity in an acidic medium, higher than other non-precious metal catalysts. It showed higher kinetic current at 0.9 V than Pt/C catalysts, as well as superior long-term durability and MeOH-tolerance. Density functional theory calculations in combination with extended X-ray absorption fine structure analysis revealed a weakening of the interaction between oxygen atom and FeCo-OMPC compared to Pt/C. This effect and high surface area of FeCo-OMPC appear responsible for its significantly high ORR activity.
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http://dx.doi.org/10.1038/srep02715DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3779849PMC
April 2014

Ordered mesoporous carbon nitrides with graphitic frameworks as metal-free, highly durable, methanol-tolerant oxygen reduction catalysts in an acidic medium.

Langmuir 2012 Jan 13;28(1):991-6. Epub 2011 Dec 13.

Department of Energy & Mineral Resources Engineering, Sejong University, Seoul 143-747, Republic of Korea.

Developments of high-performance cost-effective electrocatalyts that can replace Pt catalysts have been a central theme in polymer electrolyte membrane fuel cells (PEMFCs) and direct methanol fuel cells (DMFCs). In this direction, nitrogen-doped carbon nanostructures free of metallic components have attracted particular attention. Here we show that directing graphitic carbon nitride frameworks into mesoporous architecture can generate a highly promising metal-free electrocatalyst for an oxygen reduction reaction (ORR) in an acidic medium. The ordered mesoporous carbon nitride (OMCN) was synthesized with a nanocasting strategy using ordered mesoporous silica as a template. A variety of characterizations revealed that the OMCN is constructed with graphitic carbon nitride frameworks and ordered arrays of uniform mesopores. The OMCN showed significantly enhanced electrocatalytic activity for ORR compared to bulk carbon nitride and ordered mesoporous carbon in terms of the current density and onset potential. A high surface area and an increased density of catalytically active nitrogen groups in the OMCN appear to contribute concomitantly to the enhanced performance of the OMCN. Furthermore, the OMCN exhibited superior durability and methanol tolerance to a Pt/C catalyst, suggesting its widespread utilization as an electrocatalyst for PEMFCs and DMFCs.
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http://dx.doi.org/10.1021/la204130eDOI Listing
January 2012
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