Non-precious Metal Catalysts For Oxygen Reduction Reaction Research Articles

Synthesis of NbC@C(Nx) nanoparticles using DC arc discharge plasma for highly efficient oxygen reduction reaction

Development of the low-cost, high-efficiency, and durable non-precious metal electrocatalysts for cathodic oxygen reduction reaction (ORR) is of vital importance for fuel cells and metal-air batteries. Herein, the carbon-coated NbC nanoparticles (NbC@C NPs) were prepared using DC arc discharge plasma under a methane atmosphere. Then, the nitrogen-doping was conducted by heat treatment, resulting in nitrogen-doped carbon-coated NbC nanoparticles (NbC@C(Nx) NPs). Benefiting from the merit of unique core-shell structure and best synergy between the nitrogen-doped carbon shell and the NbC core, the obtained highest nitrogen-doped NbC@C(N1.36) NPs showed an onset potential (Eonset) of 0.89 V (vs. RHE) and a half-wave potential (E1/2) of 0.79 V, which are comparable to those of commercial Pt/C (20 wt%) (Eonset = 0.90 V, E1/2 = 0.80 V), and its diffusion-limited current density (JL) of 5.99 mA·cm−2 is even higher than that of commercial Pt/C (5.43 mA·cm−2). Moreover, it exhibited a remarkable long-term durability and impressive methanol resistance than Pt/C catalyst. In addition, the real-time optical emission spectrum (OES) analysis of arc plasma shows that the electron temperature (Te) is 7562.9 K in local thermal equilibrium (LTE) plasma. Therefore, the use of the DC arc discharge plasma method opens a fast and simple way to develop cost-effective and highly efficient non-precious metal catalysts for ORR.

A lignin–derived N-doped carbon-supported iron-based nanocomposite as high-efficiency oxygen reduction reaction electrocatalyst

Fuel cells are a promising renewable energy technology that depend heavily on noble metal Pt-based catalysts, particularly for the oxygen reduction reaction (ORR). The discovery of new, efficient non-precious metal ORR catalysts is critical for the continued development of cost-effective, high-performance fuel cells. The synthesized carbon material showed excellent electrocatalytic activity for the ORR, with half-wave potential (E1/2) and limiting current density (JL) of 0.88 V and 5.10 mA·cm−2 in alkaline electrolyte, respectively. The material has a Tafel slope of (65 mV dec−1), which is close to commercial Pt/C catalysts (60 mV dec−1). Moreover, the prepared materials exhibited excellent performance when assembled as cathodes for zinc-air batteries. The power density reached 110.02 mW cm−2 and the theoretical specific capacity was 801.21 mAh g−1, which was higher than that of the Pt/C catalyst (751.19 mAh g−1). In this study, with the assistance of Mg5(CO3)4(OH)2·4H2O, we introduce an innovative approach to synthesize advanced carbon materials, achieving precise control over the material's structure and properties. This research bridges a crucial gap in material science, with potential applications in renewable energy technologies, particularly in enhancing catalysts for fuel cells.

Co3Fe7/CoCx nanoparticles encapsulated in nitrogen-doped carbon nanotubes synergistically promote the oxygen reduction reaction in Zn-air batteries

Efficient and stable non-precious metal catalysts (NPMCs) for the oxygen reduction reaction (ORR) are crucial for the advancement of Zn-air batteries. Herein, we report a supramolecular self-scarifying template and confinement pyrolysis strategy to obtain an efficient ORR catalyst of well-dispersed Co3Fe7/CoCx heterostructure nanoparticles encapsulated by nitrogen-doped carbon nanotubes (Co3Fe7/CoCx@N-CNT). The as-synthesized Co3Fe7/CoCx@N-CNT catalyst exhibited outstanding ORR activity, with a half-wave potential of 0.88 V versus a reversible hydrogen electrode, and good stability. The Zn-air battery based on the Co3Fe7/CoCx@N-CNT cathode achieved a peak power density of 265 mW cm−2 and a durability of over 200 h, which is superior to most reported NPMCs and even the Pt/C counterpart. The physical characterization and electrochemical poisoning experiments revealed that the Co3Fe7/CoCx nanoparticles in the core along with pyridine N and Fe–Nx hosted in the carbon nanotube all acted as active sites for the ORR. Further theoretical calculations showed that the charge redistribution between the Co3Fe7/CoCx nanoparticles and the Fe–Nx carbon overlayers downshifted the d-band center of Fe and optimized the adsorption ability, which boosted the ORR kinetics. This work provides an effective strategy to synthesize non-precious metal ORR catalysts with multiple active sites and highlights the synergistic role of encapsulated nanoparticles and carbon support.

Multicore-shell structure CuxCoy-Fe alloy nitrogen doped mesoporous hollow carbon nanotubes composites for oxygen reduction reaction

Carbon-based materials with transition metal modifications are the dominant materials for oxygen reduction reaction (ORR), but the synthesis in a simple and efficient way is still a great challenge. Herein, multicore-shell structure CuxCoy-Fe alloy nitrogen doped mesoporous hollow carbon nanotubes (N-MHCNT/CuxCoy-Fe@C) were designed and synthesized by a facile and environment-friendly method. In the process of pyrolysis, polypyrrole serving as the substrate to form N-doped hollow carbon nanotubes and the polydopamine (PDA) acts as the carbon and nitrogen source to form a shell structure. Additionally, the cubic CuxCoy-Fe MOFs synthesized at room temperature collapses to form multiple alloy cores. Notably, the mesoporous structure of N-MHCNT/CuxCoy-Fe@C enhances the mass transfer process, while the carbon shell protects the metal active sites. Moreover, mesoporous hollow carbon, rich M-Nx (M=Cu, Co, Fe) active sites, the synergistic effects between N-MHCNTs, CuxCoy-Fe alloys and multiple core-shell structures allowed N-MHCNT/Cu2Co1-Fe@C exhibited high activity and long-term durability in ORR. Besides, the RRDE tests confirms the reaction kinetics of N-MHCNT/Cu2Co1-Fe@C as a mainly 4-electron reaction with an electron transfer number of 3.78 (Pt/C is 3.86) and a low hydrogen peroxide yield of 16%. This work provides a new strategy for the development of non-precious metal ORR catalysts by rational structural design and metal ratio adjustment.

The synergistic effect of “soft-hard template” to in situ regulate mass transfer and defective sites of doped-carbon nanostructures for catalysis of oxygen reduction

Nitrogen-doped carbon materials are intensively investigated as electrocatalysts toward oxygen reduction reaction (ORR). The activity of the catalysts can be effectively boosted by regulating the microstructure to construct defective three-phase interface. Herein, an N-doped carbon-based porous catalyst (DT-Fe-N-C) is fabricated by a dual-template strategy with SiO2 and pluronic F127 as the hard and soft templates. Benefited from the modulation, the mesopore-dominated DT-Fe-N-C exhibits remarkable specific surface area (990.19 m2 g-1), high Fe-Nx content and plenty of defects. Resultantly, DT-Fe-N-C shows outstanding catalytic activity to ORR with 0.853 V of half-wave potential, high stability and selectivity to the four-electron ORR mechanism. The Zn-air battery with DT-Fe-N-C outputs 219 mW cm-2 of maximum power density, 861 Wh kgZn−1 of specific energy density at 50 mA cm-2 and runs at a higher voltage than that of Pt/C-based battery. This work provides an avenue for the defect engineering in the design of non-precious metal ORR catalysts.

Si Doping Enables Activity and Stability Enhancement on Atomically Dispersed Fe-Nx /C Electrocatalysts for Oxygen Reduction in Acid.

Fe-N-C represents the most promising non-precious metal catalysts (NPMCs) for the oxygen reduction reaction (ORR) in fuel cells, but often suffers from poor stability in acid due to the dissolution of metal sites and the poor oxidation resistance of carbon substrates. In this work, silicon-doped iron-nitrogen-carbon (Si/Fe-N-C) catalysts were developed by in situ silicon doping and metal-polymer coordination. It was found that Si doping could not only promote the density of Fe-Nx /C active sites but also elevated the content of graphitic carbon through catalytic graphitization. The best-performing Si/Fe-N-C exhibited a half-wave potential of 0.817 V vs. reversible hydrogen electrode in 0.5 m H2 SO4 , outperforming that of undoped Fe-N-C and most of the reported Fe-N-C catalysts. It also exhibited significantly enhanced stability at elevated temperature (≥60 °C). This work provides a new way to develop non-precious metal ORR catalysts with improved activity and stability in acidic media.

ZIF-67-derived Co nanoparticles embedded in N-doped porous carbon composite interconnected by MWCNTs as highly efficient ORR electrocatalysts for a flexible direct formate fuel cell

Non-precious metal materials are considered as the most promising catalysts for oxygen reduction reaction (ORR) due to their high catalytic activity, low cost, superior stability as well as good electrocatalytic selectivity. Here, in situ encapsulation of Co nanoparticles into N-doped porous carbon ([email protected]) nanocages interconnected by carbonized multi-walled carbon nanotubes (C-MWCNTs) are prepared through direct carbonization of the MWCNTs-based ZIF-67 precursor. The obtained hybrid material (denoted as [email protected]/C-MWCNTs) displays an excellent ORR performance with a half-wave potential of 0.79 V, effective four-electron transfer and superior formate-tolerance ability. The superior ORR activity of the [email protected]/C-MWCNTs hybrids is mainly ascribed to the abundant catalytic active sites contributed by the [email protected] nanocages, the high electrical conductivity and large specific surface area rooting in C-MWCNTs, and synergetic effects between [email protected] nanocages and C-MWCNTs. The membraneless flexible direct formate fuel cell (DFFC) using [email protected]/C-MWCNTs as the cathode catalyst delivers a peak power density of 4.32 mW cm−2 stably. Notably, the performance of the flexible DFFC can still maintain 90.9% of its initial value after repeated bending for 1000 times. Moreover, two flexible DFFCs connected in series mode can easily power some low-power electronics. The report not only opens a new door to design high-performance non-precious metal ORR catalysts for DFFCs, but also greatly boosts the development of flexible energy conversion and storage devices.

Designed Synthesis and Catalytic Mechanisms of Non-Precious Metal Single-Atom Catalysts for Oxygen Reduction Reaction.

Oxygen reduction reaction (ORR) is the important half-reaction for metal-air batteries and fuel cells (FCs), which plays the decisive role for the performance of whole devices. Developing high-efficiency non-precious metal ORR catalysts is urgent and still challenging. Single-atom catalysts (SACs) are considered to be one of the promising substitutes for Pt due to their maximum atom utilization efficiency and mass activity. Despite considerable efforts in preparing various SACs, the reaction mechanism and intrinsic activity modulation during the ORR reaction are still not understood in-depth. In this review, the latest advances in the current synthetic strategies for SACs are summarized. The effect of various coordination environments including central metal atoms, coordination atoms, environmental atoms, and guest groups on the intrinsic ORR activity of SACs are discussed. The electrocatalytic mechanisms are clarified by combining density functional theory calculations with in situ advanced characterization technologies. Then, the applications of SACs in FCs and Zn-air batteries are reviewed. Finally, the prospects and challenges for further development of SACs are highlighted.

Co/Co9S8/nitrogen-doping hollow carbon spheres nanocomposite as an efficient and durable electrocatalyst for oxygen reduction reaction

The design of efficient, low-cost, and durable catalysts for oxygen reduction reaction (ORR) is pivotal to fuel cells. Herein, we developed a facile strategy to fabricate a Co/Co9S8/nitrogen-doped hollow carbon spheres (NHCS) nanocomposite via calcining 3-Aminobenzenesulfonic anions within the interlamination of CoAl-layered double hydroxides (CoAl-LDH) at 900 °C in N2 atmosphere. The Co/Co9S8/NHCS nanocomposite with numerous carbon nanosheets possesses large specific surface area and pore volume, and Co/Co9S8 nanoparticles were embedded within the carbon nanosheets. The Co/Co9S8/NHCS nanocomposite exhibits superexcellent ORR activities with an E onset of 0.95 V, an E 1/2 of 0.87 V and a J 1600 rpm of −5.82 mA cm−2 at 0.70 V vs. RHE. Moreover, the Co/Co9S8/NHCS nanocomposite displays prominent methanol tolerance and excellent stability in 0.1 M KOH. This work provides an efficient approach for developing non-precious metal ORR catalysts.

Insights into efficient transition metal-nitrogen/carbon oxygen reduction electrocatalysts

The fundamental understanding of ORR mechanism and active sites in M−N/C catalysts is introduced, and various precursors of M−N/C catalyst with the strategies for design and optimization are reviewed. It is of vital importance to accelerate the sluggish oxygen reduction reaction (ORR) process at the cathode with earth-abundant metal-based catalysts for the commercialization of low-temperature polymer electrolyte membrane fuel cells. In consideration of high catalytic activity, long-term stability and low cost of potential ORR electrocatalysts, transition metal species have attracted much interest and transition metal-nitrogen-carbon (M−N/C, M = Fe, Co, Ni, Mn, etc.) catalysts have been widely considered as the most promising non-precious metal catalysts for ORR. Herein, the fundamental understanding of ORR catalytic mechanism and the identification of active centers are briefly introduced, and then different M−N/C catalysts classified by precursors with the strategies for design and optimization are highlighted. The challenges and possible opportunity for future development of high-performance ORR catalysts are finally proposed.

Defect-controlled Fe-N-doped carbon nanofiber by ball-milling for oxygen reduction reaction

We demonstrate that control of the defect level on carbon materials is effective for enhancing the oxygen reduction reaction (ORR) performance of nonprecious-metal catalysts. Vapor-grown carbon nanofiber (VGCNF) with high crystallinity and high electronic conductivity was chosen as the substrate of our ORR catalysts. To induce defects on the VGCNF, it was subjected to ball-milling for various controlled times, yielding BMx-VGCNF (x represents the ball-milling time, 0-6 h). The defect level introduced on the VGCNF was effectively regulated by controlling the ball-milling time. Although the density of defect sites increased with increasing ball-milling time, the surface area was high-est in BM2-VGCNF. Nonprecious-metal ORR catalysts (BMx-Fe-VGCNF) were prepared by NH3 pyrolysis of Fe-ion-adsorbed BMx-VGCNF. The ball-milling of VGCNF was effective to introduce nitrogen onto the catalyst. In particular, the controlled ball-milling was important to generate highly active sites on the catalyst surface. Among the catalysts studied, BM2-Fe-VGCNF exhibited the best ORR performance, which was 2.5-times greater than that of BMx-Fe-VGCNF (x=4, 6).

Fe/N-doped mesoporous carbons derived from soybeans: A highly efficient and low-cost non-precious metal catalyst for ORR

Oxygen reduction reaction (ORR) plays a crucial role in many energy storage and conversion devices. Currently, the development of inexpensive and high-performance carbon-based non-precious-metal ORR catalysts in alkaline media still gains a wide attention. In this paper, the mesoporous Fe-N/C catalysts were synthesized through SiO2-mediated templating method using biomass soybeans as the nitrogen and carbon sources. The SiO2 templates create a simultaneous optimization of both the surface functionalities and porous structures of Fe-N/C catalysts. Detailed investigations indicate that the Fe-N/C3 catalyst prepared with the mass ratio of SiO2 to soybean being 3:4 exhibits brilliant electrocatalytic performance, excellent long-term stability and methanol tolerance for the ORR, with the onset potential and the half-wave potential of the ORR being about 0.890 V and 0.783 V (vs RHE), respectively. Meanwhile, the desired 4-electron transfer pathway of the ORR on the catalysts can be observed. It is significantly proposed that the high BET specific surface area and the appropriate pore-size, as well as the high pyridinic-N and total nitrogen loadings may play key roles in enhancing the ORR performance for the Fe-N/C3 catalyst. These results suggest a feasible route based on the economical and sustainable soybean biomass to develop inexpensive and highly efficient non-precious metal electrochemical catalysts for the ORR.

Waste wine mash-derived doped carbon materials as an efficient electrocatalyst for oxygen reduction reaction

Oxygen reduction reaction (ORR) is a core reaction of fuel cell and metal-air cell. In recent years, it has been a hot topic to study non-precious metal catalysts for ORR. Herein, we have used waste wine mash-derived carbon, melamine and ferric chloride to prepare a Fe- and N- co-doped carbon catalyst. The specific surface area of the catalyst is up to 1066.6 m2 g−1. And its wave potential is 15 mV higher than that of commercial Pt/C catalyst. The ORR on our catalyst followed a four-electron pathway; and it has high stability and high impressive immunity to methanol. After continuous oxygen reduction of 30,000s, the retention rate is 90%.

Doped porous carbon nanostructure materials as non-precious metal catalysts for oxygen reduction reaction in alkaline and acid media

Various doped porous carbon nanomaterials to replace Pt-based catalysts for oxygen reduction reaction (ORR) in acid and alkaline media have been intensively studied. Herein, doped porous carbon nanostructure materials as non-precious metal catalysts for ORR are synthesized using different weight ratios of polyaniline (PANI) to dicyandiamide (DCDA) as carbon source and dopants with iron salt to control the specific surface area and nitrogen doping content. The as-prepared samples exhibit well-defined porous carbon structure that consists of micro- and meso-pores, high specific surface areas, increased amount of nitrogen dopant, and relative content of graphitic N and pyridinic nitrogen N. Among these doped porous carbon nanostructure catalysts, the catalyst synthesized using a proper ratio of PANI to DCDA exhibits significantly improved electrocatalytic performance for ORR, i.e., high half-wave potential, high specific activity, and enhanced stability in both acid and alkaline media, because of the high graphitic N/pyridinic nitrogen N and micro-pore ratios.

(Invited) Precious Metal-Free Electrocatalysis: Accomplishments and Challenges

In this short presentation, we will concentrate on entirely precious metal-free electrocatalysts as potential alternatives to the incumbent platinum group metal (PGM) materials for electrochemical reactions occurring in acidic, relevant to the energy conversion and storage: (i) oxygen reduction reaction (ORR), (ii) hydrogen evolution reaction (HER) and, time permitted, (iii) hydrogen peroxide generation (“two-electron ORR”). In the first part of this presentation, we will offer a summary of the development of non-precious metal ORR catalysts, emphasizing in particular the approaches that aim at improving the ORR active-site density and understanding of the origins of electrocatalytic activity of non-precious metal catalysts in oxygen reduction as a prerequisite for further development of this class of catalysts. We will focus on metal-nitrogen-carbon (M-N-C) catalysts obtained via the high-temperature treatment of organic precursors of carbon and nitrogen and inorganic precursors of a transition metal, which have been under development at Los Alamos for over a decade and have consistently exhibited the highest ORR activity in both electrochemical-cell and fuel cell testing to date. The second part of this presentation will be devoted to less frequently studied electrocatalysts based on small organic molecules as materials for hydrogen evolution reaction and hydrogen peroxide generation in a two-electron ORR. Unlike the oxygen reduction reaction catalysts in the first part of the talk, these HER/two-electron ORR catalysts are entirely metal-free and have been obtained by a low-temperature synthesis route. In addition to exhibiting a promising activity in electrochemical testing these catalysts show good performance durability over several days of continuous operation. The density functional theory (DFT) calculations have been performed to gain an insight into the reaction mechanisms of HER and two-electron ORR on various conformations of one selected organic molecule. The calculations have revealed thermodynamically favorable reaction pathways and structure-activity relationships, which can guide future synthesis of this new class of electrocatalysts. Acknowledgements Financial support of this research by the U.S. Department of Energy via Fuel Cell Technologies Office (FCTO) and by Los Alamos National Laboratory via Laboratory Directed Research and Development (LDRD) program is gratefully acknowledged.

Hyperporous-Carbon-Supported Nonprecious Metal Electrocatalysts for the Oxygen Reduction Reaction.

Highly porous carbonaceous nonprecious metal catalysts for the oxygen reduction reaction are prepared by carbonization of low-cost metalloporphyrin-based hyper-crosslinked polymers (MPH-X). With high surface area (2768 m2 g-1 ), hierarchical porous structure, and high metal loading (9.97 wt %), the obtained hyperporous carbon MPH-Fe/C catalyst exhibits high oxygen reduction reaction (ORR) activity with a half-wave potential (0.816 V) that is comparable to the 0.819 V of commercial Pt/C. Stability tests reveal that MPH-Fe/C also exhibits outstanding long-term durability and methanol tolerance. Our findings may offer an alternative approach to produce nonprecious metal ORR catalysts on a large scale owing to the low-cost MPH-X precursors with diverse metal types.

Amino acid-derived non-precious catalysts with excellent electrocatalytic performance and methanol tolerance in oxygen reduction reaction

In polymer electrolyte membrane fuel cells (PEMFCs), slow kinetics and high over-potential of oxygen reduction reaction (ORR) can result in a significantly large amount of Pt usage. Thus, non-precious metal (NPM) catalysts, especially, for ORR, that can be utilized instead of Pt-based catalysts, have been intensively studied. Herein, doped carbon nanostructures as NPM catalysts for ORR in an acid medium were synthesized using a template method with nontoxic, eco-friendly cysteine and iron (III) tetramethoxyphenylporphyrin (Fe-TMPP, 5,10,15,20-tetrakis(4-methoxyphenyl)-21H,23H-porphyrin iron(III) chloride) used as carbon and doping sources, respectively. To obtain the doped mesoporous carbon nanostructure, mixtures of cysteine and Fe-TMPP with intended ratios (CysX/FeZ) were heated under an N2 atmosphere at 900 °C for 3 h. In particular, Cys2/Fe0.3/C synthesized with an appropriate ratio of cysteine and Fe-TMPP showed a relatively high specific surface area and fairly high portion of doped species such as pyridinic and pyrrolic N, thiophenic S, and Fe-Nx. Moreover, Cys2/Fe0.3/C exhibited significantly enhanced ORR activity and stability in 0.5 M H2SO4 and superior tolerance of methanol in 0.5 M H2SO4 in the presence of CH3OH.

Highly Efficient Oxygen Reduction Reaction Activity of Graphitic Tube Encapsulating Nitrided CoxFey Alloy

AbstractNonprecious metals are promising catalysts to avoid the sluggish oxygen reduction reaction (ORR) in next‐generation regenerative fuel cells or metal–air batteries. Therefore, development of nonprecious metal catalysts for ORR is highly desirable. Herein, precise tuning of the atomic ratio of Fe and Co encapsulated in melamine‐derived nitrogen‐rich graphitic tube (NGT) is reported. The Co1.08Fe3.34 hybrid with metalnitrogen bonds (1: Co1.08Fe3.34@NGT) shows remarkable ORR catalytic activities (80 mV higher in onset potential and 50 mV higher in half‐wave potential than those of state‐of‐the‐art commercial Pt/C catalysts), high current density, and stability. In acidic solution, 1 also shows compatible performance to commercial Pt/C in terms of ORR activity, current density, stability, and methanol tolerance. The high ORR activity is ascribed to the co‐existence of FeN, CoN, and sufficient metallic FeCo alloys which favor faster electron movement and better adsorption of oxygen molecules on the catalyst surface. In the alkaline anion exchange membrane fuel cell setup, this cell delivers the power density of 117 mW cm−2, demonstrating its potential use for energy conversion and storage applications.

Structure-Activity-Durability Relationships of (CM+PANI)-Me-C PGM-Free Catalysts

The development of durable and highly active platinum group metal-free (PGM-free) electrocatalysts is key to overcoming the greatest barrier in the commercialization of fuel cell electric vehicles: the high cost and limited availability of PGM catalysts utilized in polymer electrolyte fuel cells. While the majority of research on PGM-free catalysts has focused on developing active and selective materials for the sluggish oxygen reduction reaction (ORR), minimal work has been devoted to the understanding of the physical and chemical structure of active PGM-free catalysts and its relationship with the long-term stability of these novel materials. This understanding is imperative for the further development of next-generation PGM-free catalysts with improved activity and durability that could ultimately replace PGM-based ORR catalysts in fuel cells. PGM-free catalysts with high volumetric activity, four-electron selectivity (i.e., low hydrogen peroxide yield), and long-term stability in highly acidic and strongly oxidizing environment of the fuel cell cathode are desired as replacements for PGM-based ORR catalysts. For this presentation, state-of-the-art PGM-free ORR catalysts, developed by our group [1, 2], which are obtained via high-temperature treatment of dual nitrogen precursors, cyanamide (CM) and polyaniline (PANI), different transition metal precursors (Fe, Co, Mn), and with or without carbon support are used as model PGM-free catalyst systems. Depending on the transition metal used, catalysts with different physical and electrochemical characteristic properties are obtained. Specifically, Fe-based catalysts are generally known for their high activity and low peroxide yield generation. However, Co- and Mn-based catalysts generate highly graphitic structures which could improve catalyst long-term stability. In this work, structure-activity-durability relationships are developed based on comprehensive physical, chemical, and electrochemical characterization of highly active (CM+PANI)-Me-C catalysts (Me = Fe, Co, Mn), correlating properties such as carbon structure, elemental speciation, and CO2 generation. Acknowledgement Financial support for this research by DOE-EERE through Fuel Cell Technologies Office is gratefully acknowledged. [1] Chung, H.T., Holby, E.F., Purdy, G.M., Babu, S.K., Litster, S., Cullen, D.A. More, K.L., Zelenay, P. (2015). “Combining Nitrogen Precursors in Synthesis of Non-Precious Metal ORR Catalysts with Improved Fuel Cell Performance.” ECS Meeting s, MA2015-02 (37), 1278. [2] Martinez, U., Holby, E.F., Dumont, J.H., Chung, H.T., Zelenay, P. (2016) “Non-PGM ORR Catalysts Based on Transition Metals Alternative to Iron.” ECS Meeting s, MA2016-01, 1719.

One-pot synthesis of transition metal ion-chelating ordered mesoporous carbon/carbon nanotube composites for active and durable fuel cell catalysts

Development of non-precious metal catalysts for the oxygen reduction reaction (ORR) in proton exchange membrane (PEM) fuel cells with high activity and durability and with optimal water management properties is of outmost technological importance and highly challenging. Here we study the possibilities offered through judicious selection of small molecular precursors used for the formation of ordered mesoporous carbon-based non-precious metal ORR catalysts. By combining two complementary precursors, we present a one-pot synthesis that leads to a composite material consisting of transition metal ion-chelating ordered mesoporous carbon and multi-walled carbon nanotubes (TM-OMC/CNT). The resulting composite materials show high specific surface areas and a carbon structure that exhibits graphitic signatures. The synthesis procedure allows for tuning of the carbon structure, the surface area, the pore volume and the ratio of the two components of the composite. The TM-OMC/CNT composites were processed into membrane electrode assemblies and evaluated in single cell fuel cell measurements where they showed a combination of good ORR activity and very high durability.