Methanol-tolerant Oxygen Reduction Reaction Research Articles

Substituent effect in determining the total structure of an all-alkynyl-protected Ag98 nanocluster for methanol tolerant oxygen reduction reaction.

Metal nanoclusters (NCs) with atomically precise structures are desirable models for truly understanding their structure-property relationship. This study reports the synthesis and structural anatomy of a Ag98 NC protected solely by an alkynyl ligand, 2-(trifluoromethyl)phenylacetylene (2-CF3PhC[triple bond, length as m-dash]CH), which features a -CF3 substituent at the ortho position (ortho-CF3). 2-CF3PhC[triple bond, length as m-dash]CH ligands are so exquisitely arranged on the surface of Ag98 that the steric hindrance caused by ortho-CF3 is minimized but its function as a hydrogen-bond (H-bond) acceptor (H⋯F) is maximized. Such a rule also applies to inter-cluster interactions which define the stacking sequence of Ag98 NCs. When supported on carbon black, Ag98 NCs demonstrate desirable oxygen reduction activity with robust long-term durability and excellent methanol tolerance, outperforming the commercial Pt/C catalyst.

Methanol Tolerant Oxygen Reduction Reaction Electrocatalysis using Size‐Specific Triphenylphosphine‐Ligated Gold Nanoclusters

AbstractThe development of a stable and efficient Oxygen Reduction Reaction (ORR) electrocatalysts with high methanol tolerance is crucial for Direct Methanol Fuel Cells (DMFCs). Herein, triphenylphosphine (PPh3)‐ligated gold nanoclusters and complexes (AuNCs), Au101(PPh3)21Cl5, Au9(PPh3)8(NO3)3, and Au1(PPh3)Cl supported on reduced graphene oxide (rGO) have been explored as methanol tolerant ORR electrocatalysts. Electrocatalytic performance of each AuNCs‐rGO was determined through linear sweep voltammograms (LSV) and cyclic voltammetry (CV) and compared with Pt/C. Size‐dependent ORR activity was observed which followed the size trend of Au101NC‐rGO>Au9NC‐rGO>Au1NC‐rGO. Repeated LSV and chronoamperometry measurements revealed that the long‐term stability over 24 hours followed the trend Au101NC‐rGO>Au9NC‐rGO∼Au1NC‐rGO and all were more stable than Pt/C. The methanol tolerance of each AuNCs‐rGO was also evaluated via LSV and CV. Size‐independent methanol tolerance with no noticeable change in ORR performance of AuNCs‐rGO was observed in the presence of methanol. AuNCs‐rGO nanocomposites are promising cathode electrocatalysts for DMFCs.

Diluted silicon promoting Pd/Pt catalysts for oxygen reduction reaction with strong anti-poisoning effect

Poisoning species, such as methanol and air pollutants, degrade the electrocatalytic activity for oxygen reduction reaction (ORR). Here, via taking advantage of the varied electronic property of nano-silicon, a versatile strategy is reported for enhancing the catalytic activity and anti-poisoning ability toward ORR by decorating noble metal catalysts with the size-controlled silicon nanoclusters (DS). Consequently, DS-Pd exhibits the enhanced ORR performance with a large halfwave potential of 0.892 V and an onset potential of 1.010 V. More importantly, it also shows enhanced anti-poisoning performance in methanol, NaNO2 and NaHSO3 electrolytes, compared to those of commercial Pt/C and Pd/C catalysts. Mechanism studies reveal that the synergistic effect between Pd and more oxygen-philic and less poison-philic Si nanoclusters largely abbreviate the absorption of poisoning species on the active sites. This strategy also improves the methanol-tolerant performance of Pt based catalysts, providing a versatile strategy for the fabrication of methanol-tolerant ORR catalysts.

Silk‐Derived N‐Doped Fe@NPC as Efficient Bifunctional Electrocatalyst for Direct Methanol Fuel Cell (DMFC)

AbstractThe development of economic and efficient bifunctional electrocatalysts, which can boost both the oxygen reduction reaction (ORR) and methanol oxidation reaction (MOR) is quite necessary for the evolution of direct methanol fuel cell (DMFC). Herein, a novelty of precious metal‐free, iron, nitrogen and phosphorus‐doped porous carbon (Fe@NPC) was prepared by using cheap and renewable biomass silk as basic nitrogen sources, as an efficient ORR and MOR electrocatalyst with its high nitrogen content (8.16 wt%). The Fe@NPC catalyst exhibits extremely high onset potential (1.125 V vs RHE), current density (−6.089 mA cm−2) and methanol tolerance for ORR, even exceeds the corresponding values of Pt/C (1.007 V vs RHE, 5.068 mA cm−2). Furthermore, it also served as a good carrier for Pt nanoparticles (NPs). Pt/Fe@NPC shows high catalytic activity and stability for MOR in acidic condition.

Highly stable and methanol tolerant oxygen reduction reaction electrocatalyst Co/CoO/SnO@N-C nanocubes by one-step introduction of functional components

To develop high-performance non-precious metal-based electrocatalysts for oxygen reduction reaction (ORR) is an urgent demand. We herein report an ingenious strategy to develop highly selective and competitive precious metal-free ORR electrocatalyst Co/CoO/SnO encapsulated in N-rich mesoporous carbon (CCS@NPC) nanocubes, via a simple one-step introduction of all functional components. Atomically mixed composites with significantly enhanced catalytic activity were obtained by adopting amorphous mesoporous ternary metal oxides CoSnO3 nanocubes as precursor and template. The synergistic effect of the triphase nanohybrids (Co, CoO & SnO) anchored in nitrogen-doped mesoporous carbon nanocubes promoted the catalytic reactions, owning to the anisotropic morphology, great heterojunction interfaces, and structural stability. The large-scale prepared CCS@NPC exhibited excellent electrocatalytic activity toward ORR with an admirable onset potential (1.01 V) and diffusion-limited current density (5.88 mA cm−2). The CCS@NPC showed stronger stability (20 h) and higher methanol tolerance with the concentration up to 8.0 M, compared to that of commercial Pt/C.

Interconnected porous nitrogen-doped carbon framework: Recoverable template fabrication and excellent electrocatalytic performance for oxygen reduction reaction

The development of efficient metal-free catalysts for oxygen reduction reaction (ORR) is of great importance for accelerating the commercial application of fuel cell. Here, a 3D interconnected N-doped porous carbon skeleton (PC) was prepared by one-step pyrolysis strategy with the help of recyclable NaCl. Combining the advantages of template and pyrolysis, the obtained N-PC-900 product showed a large specific surface area (470.9 m2 g−1), porous structure and high N contents (pyridinic N 30.2% and graphitic N 40.2%). The high ID1/IG value of 1.76 suggested that N-PC-900 had more defects which could be produced at 900 °C. In alkaline condition, the prepared N-PC-900 exhibited positive onset potential (0.90 V), half-wave potential (0.75 V) and high current density (5.38 mA/cm2 at 0.2 V), which was close to the 20% Pt/C. The number of transferred electrons was 3.87–3.98 at a potential of 0.055–0.9 V, meaning a 4e− pathway towards the ORR. Meanwhile, the N-PC-900 displayed better durability and methanol tolerance for ORR in both acid and alkaline conditions than 20%Pt/C. This study provided a convenient and low-cost method to prepare high-performance metal-free ORR catalysts, and the product may have great potentials in ORR catalysis.

A precious-metal-free Fe-intercalated carbon nitride porous-network with enhanced activity for the oxygen reduction reaction and methanol-tolerant oxygen reduction reaction

The economical cost of the catalyst material has remained a challenging task in traditional fuel cells (FCs) and in direct methanol fuel cells (DMFCs).

Graphene wrapped Fe7C3 nanoparticles supported on N-doped graphene nanosheets for efficient and highly methanol-tolerant oxygen reduction reaction

Green and efficient non-precious metal electrocatalysts for oxygen reduction reaction (ORR) are prepared to meet the increasing demand for clean, secure and sustainable energy. Herein, we report a novel and environmentally friendly strategy for synthesis of graphene-wrapped iron carbide (Fe7C3) nanoparticles supported on hierarchical fibrous N-doped graphene with open-mesoporous structures (Fe7C3/NG) by simply annealing the mixture of melamine, iron (II) phthalocyanine (FePc) and Fe2O3. The effects of the pyrolysis temperature and the molar ratio of FePc to melamine were critically examined in the controls. Remarkably, the Fe7C3/NG obtained at 800 °C (i.e. Fe7C3/NG-800) manifested the forward shifts in the onset potential (0.98 V) and half-wave potential (0.85 V) with respective to commercial Pt/C (50 wt%) in 0.1 M KOH, coupled with the great enhancement in the durability (still remained 92.11% of its initial current density even after 40,000 s) and strong methanol tolerance. This research presents a promising strategy for developing Pt-free non-precious efficient ORR electrocatalysts in fuel cells.

Amorphous Rhenium Disulfide Nanosheets: A Methanol-Tolerant Transition Metal Dichalcogenide Catalyst for Oxygen Reduction Reaction

A methanol tolerant catalyst for the reduction of oxygen is important for the effective utilization of direct methanol fuel cells (DMFCs). Herein, the synthesis of a layered transition metal dichalcogenide rhenium disulfide (ReS2) and its utilization as an effective novel precious metal free, methanol tolerant oxygen reduction catalyst is reported. A single step wet chemical synthesis procedure is used to synthesize ReS2, and morphological analysis revealed the formation of ultrathin nanosheets of thickness 1.6 nm. The catalytic activity of ReS2 toward the oxygen reduction reaction (ORR) was monitored in 0.1 M H2SO4, which showed higher current density and excellent stability comparable with the commercially available carbon supported platinum catalyst. The catalyst exhibited selective 4 electron transfer kinetics (n = 3.9) and has remarkable tolerance to methanol in contrast to platinum supported on carbon, which makes it promising as a Pt-free methanol tolerant ORR catalyst.

N, F-Codoped Microporous Carbon Nanofibers as Efficient Metal-Free Electrocatalysts for ORR

HighlightsA new and facile method to synthesize N, F-codoped microporous carbon nanofiber (N, F-MCF) electrocatalysts via electrospinning, hydrothermal process, and thermal treatment.Polyvinylidene fluoride is applied as a fluorine source in oxygen reduction reaction (ORR) catalysis for the first time in literature.N, F-MCFs exhibit distinguished electrocatalytic activity, stability, and methanol tolerance for ORR in alkaline media.

One-pot synthesis of unprotected PtPd nanoclusters with enhanced catalytic activity, durability, and methanol-tolerance for oxygen reduction reaction

Bimetallic PtPd alloys are regarded as promising high performance oxygen reduction reaction (ORR) catalysts. However, the application of a subnanometer scale PtPd bimetallic nanoclusters (NCs) is rarely studied. In this work, ordered mesoporous carbon (OMC) supported PtPd NCs with the constant metal loading of 10 wt% and various Pt:Pd atomic ratios were synthesized by a modified polyol reduction route. The PtPd NCs show a maximum activity at Pt:Pd molar ratio close to 3:1 with a mean size of ∼2.35 nm. The specific activity (SA) and mass activity (MA) of Pt3Pd1 NCs/OMC (PtPd loading: 10 wt%) is 2.5 and 4.1 times higher than those of the commercial Pt/C (Pt loading: 20 wt%) in 0.1 M HClO4. Meanwhile, the Pt3Pd1 NCs/OMC exhibits improved methanol tolerance and durability for ORR. Therefore, the Pt3Pd1 NCs/OMC is excellent candidate that may become a practical cathode catalyst for fuel cells.

Effect of Small Nb‐doping Amount on the Performance of BaCoO3‐δ‐based Perovskite as Bifunctional Oxygen Catalysts

AbstractPerovskite oxides are of great interest as cost‐effective replacements for noble metals and oxides employed in bifunctional electrocatalysts including the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). In this work, a series of Bi/Nb co‐doped BaCoO3‐δ‐based perovskite oxides BaBi0.05Co0.95‐xNbxO3‐δ (BBC0.95‐xNx, x=0.1, 0.15, 0.2) were synthesized and evaluated as oxygen electrocatalysts for ORR and OER. It is interesting to note that Nb‐doping amount is related to the contents of surface oxygen vacancies and oxidation states of cobalt, subsequently inducing performance differences among BBC0.95‐xNx. Results show that BBC0.95‐xNx have bifunctional electrocatalytic activities toward both ORR and OER in alkaline media. Compared with the BBC0.85N0.1 and BBC0.8N0.15, BBC0.75N0.2 with the highest Nb‐doping rate delivered a lowest total overpotential between the ORR and the OER. Moreover, the BBC0.95‐xNx catalysts deliver outstanding durability and methanol tolerance for ORR, better than Pt/C. BBC0.95‐xNx holding promising application as nonprecious bifunctional catalysts.

Platinum‐Decorated Si Nanowires as Methanol‐Tolerant Oxygen Reduction Electrocatalysts

AbstractPlatinum decorated Si nanowire (Pt/SiNW) catalysts were prepared by directly reducing Pt ions with Si−H bonds and exhibited excellent electrocatalytic behavior in the methanol tolerant oxygen reduction reaction. The onset potential and half wave potential of Pt/SiNW catalysts were positively shifted about 29 and 9 mV respectively compared with Pt/C commercial catalysts. Furthermore, the methanol tolerant capacity of Pt/SiNW catalysts is much higher than that of Pt/C commercial catalysts since the current density of Pt/C for methanol oxidation is 13.45 (or 20.56) folds higher when 0.1 (or 1) M methanol was added into the electrolyte. The outstanding catalytic performance of Pt/SiNW catalysts is due to the synergistic effect of Pt nanoparticles and SiNWs: Pt nanoparticles are tightly anchored SiNWs, avoiding the aggregation during the electrochemical process. Meanwhile, SiNWs may hinder the methanol oxidation and improve the tolerant capacity. The results presented here confirm the Pt/SiNW catalyst is efficient and ecologically friendly catalysts for direct methanol fuel cell technology.

Astragali Radix-derived nitrogen-doped porous carbon: An efficient electrocatalyst for the oxygen reduction reaction

The development of biomass-derived nitrogen-doped porous carbons (NPCs) for the oxygen reduction reaction (ORR) is important for sustainable energy systems. Herein, NPCs derived from Astragali Radix (AR) via a cost-effective strategy are reported for the first time. The as-prepared AR-950-5 catalyst shows a stacked layer-like structure and porosity. Notably, the optimized AR-950-5 delivers catalytic activity comparable to that of commercial Pt/C (C-Pt/C), with high onset potential, positive half-wave potential and large limiting current density. It also displays superior long-term stability and methanol tolerance for ORR. This work will pave the way for a new approach in the development of highly active and low-cost NPCs for fuel cells.

Catalysis for Low-Temperature Fuel Cells

Today, the development of active and stable catalysts still represents a challenge to be overcome in the research field of low-temperature fuel cells.[...]

Nano-Porous Electro-Catalyst with Textured Surface Active Pd-Pt Islands for Efficient Methanol Tolerant Oxygen Reduction Reaction

Herein, we report a simple and elegant aqueous synthesis of Pd100-xPtx (x=5, 10, 15 and 20) nano-porous structures (NPoS) derived from Pd100-xMn2x (x=5, 10, 15 and 20) nano-alloys. Pd100-xPtx/C NPoS exhibit enhanced oxygen reduction reaction (ORR) activity along with higher retention of figure of merit in the presence of methanol compared to HiSPEC Pt/C catalyst. The ORR mass and specific activity values of Pd100-xPtx/C NPoS are high and exceed the U.S. department of energy (DOE) 2017–2020 targets. The enhanced methanol tolerance and ORR activity of Pd100-xPtx/C NPoS is attributed to their unique surface active Pd−Pt islands on nano-porous Pd. Direct methanol fuel cell performance studies employed using Pd85Pt15/C NPoS as cathode material (0.4 mgPt/cm2) and HiSPEC PtRu/C NPs as anode material (0.2 mgPt/cm2) shows improved direct methanol fuel cell (DMFC) single cell activity at low Pt loading and the results are presented.

Pyrite-Type Nanomaterials for Advanced Electrocatalysis.

Since being proposed by John Bockris in 1970, hydrogen economy has emerged as a very promising alternative to the current hydrocarbon economy. Access to reliable and affordable hydrogen economy, however, requires cost-effective and highly efficient electrocatalytic materials that replace noble metals (e.g., Pt, Ir, Ru) to negotiate electrode processes such as oxygen evolution reaction (OER), hydrogen evolution reaction (HER), and oxygen reduction reaction (ORR). Although substantial advances in the development of inexpensive catalysts, successful deployment of these materials in fuel cells and electrolyzers will depend on their improved activity and robustness. Recent research has demonstrated that the nanostructuring of Earth-abundant minerals provides access to newly advanced energy materials, particularly for nanostructured pyrites, which are attracting great interest. Crystalline pyrites commonly contain the characteristic dianion units and have cations occurring in octahedral coordination-whose generalized formula is MX2, where M can be transition metal of groups 8-12 and X is a chalcogen. The diversity of pyrites that are accessible and their versatile and tunable properties make them attractive for a wide range of applications from photovoltaics to energy storage and electrocatalysis. Pyrite-type structures can be further extended to their ternary analogues, for example, CoAsS (cobaltite), NiAsS (gersdorffite), NiSbS (ullmannite), CoPS, and many others. Moreover, improved properties of pyrites can be realized through grafting them with promoter objects (e.g., metal oxides, metal chalcogenides, noble metals, and carbons), which bring favorable interfaces and structural and electronic modulations, thus leading to performance gains. In recent years, research on the synthesis of pyrite nanomaterials and on related structure understanding has dramatically advanced their applications, which offers new perspectives in the search for efficient and robust electrocatalysts, yet a focused review that concentrates the critical developments is still missing. In this Account, we describe our recent progress on the discoveries and applications of nanostructured pyrite-type materials in the area of electrocatalysis. We first briefly highlight some interesting properties of pyrite-type materials and why they are attractive for modern electrocatalysis. Some recent advances on their synthesis that allows access to highly nanostructured pyrite-type materials are reviewed, along with the grafting of resultant pyrites with foreign materials (e.g., metal oxides, metal chalcogenides, noble metals, and carbons) to enable improved catalytic performances. We finally spotlight the exciting examples where pyrite nanostructures were used as efficient electrocatalysts to drive the OER, HER, and methanol-tolerant ORR. It is reasonable to assume that, with significant efforts and focus, the next few years will bring new advances on the pyrites and other minerals for electrocatalysis.

Reduced graphene oxide-supported Pd@Au bimetallic nano electrocatalyst for enhanced oxygen reduction reaction in alkaline media

Rational design and synthesis of core-shell bimetallic nanoparticles with tailored structural and functional properties is highly sought to realize clean and energy-efficient fuel cell systems. Herein, PdAu bimetallic nanoparticles (NPs) with core-shell morphology (PdCore–AuShell) were fabricated on the surface of reduced graphene oxide (RGO) support by a facile two-step protocol. In the first step, PdCore–AgShell bimetallic NPs were synthesized on RGO support by reducing Pd2+and Ag+ ions with methyl ammonia borane (MeAB). Later, PdCore–AuShell bimetallic NPs were conveniently fabricated on RGO support via a galvanic replacement strategy involving sacrificial oxidation of metallic silver and reduction of gold ions. The resulting core/shell bimetallic NPs were characterized by X-ray diffraction (XRD), High-resolution transmission electron microscopy (HR-TEM), Energy dispersive X-ray spectroscopy (EDS), Fourier-Transform Infrared Spectroscopy (FT-IR) and cyclic voltrammetry (CV). The electrocatalytic performance of core/shell nanostructures for the room temperature oxygen reduction reaction (ORR) in alkaline media were systematically performed by CV. The electrode-area-normalized ORR activity of RGO-supported PdCore–AuShell NPs was higher than the corresponding commercially available carbon-supported Pt nanoparticles (Pt/C) at −0.8 V vs Ag/AgCl (satd. KCl) (6.24 vs 5.34 mA cm−2, respectively). Further, methanol-tolerant ORR activities of as-synthesized catalysts were also studied. The Au-on-Pd/RGO bimetallic NPs presented enhanced ORR activity both in presence and in the absence of methanol in comparison with a commercial Pt/C catalyst and as-synthesized Pd/RGO and Au/RGO catalysts. The enhanced catalytic activities of core/shell structures might be resulted owing to the optimized core/shell structure comprising of a small Pd core and a thin Au shell and synergistic effects offered by Pd and Au. The present synthesis protocol demonstrated for two-layer structure can be extended to multi-layered structures with desired functions and activities.

Electrochemical study of methanol tolerant oxygen reduction reaction PdxCoy/C-catalysts from organometallic molecular precursors

In this work, we study the mechanism and kinetics of the oxygen reduction reaction (ORR) over Pd/C, Pd2Co/C and PdCo2/C electrocatalysts synthesized by thermal reduction of organometallic precursors, such as [Pd3(μ-3-Ph-pz)6], [Et4N]2[Pd2Co(μ-4-I-3,5-Me2-pz)4Cl4], and [Et4N]2[PdCo2(μ-4-I-3,5-Me2-pz)4Cl4]. The methanol tolerance and formation of peroxide under oxygen reduction reaction conditions were determined using a rotating disk electrode (RDE) and a rotating ring disk electrode (RRDE). The Pd2Co/C catalysts prepared from [Et4N]2[PdCo2(4-I-3,5-Me2-pz)4Cl4] showed the best ORR activity and higher methanol tolerance, compared with commercial platinum catalysts. The ORR electron transfer number for Pd2Co/C was 3.7, similar to the Pd/C commercial catalysts. Compared to the commercial catalysts, Pd2Co/C and PdCo2/C showed the highest hydrogen peroxide formation (%H2O2), 16 and 24%, respectively. Electrogeneration of hydrogen peroxide has potential application in advanced oxidation processes.

A pulsed laser synthesis of nanostructured bi-layer platinum-silver catalyst for methanol-tolerant oxygen reduction reaction

In the present work, we report the synthesis by pulsed laser deposition technique of binder-free platinum layer coated with silver layer, with each layer having a thickness of about 25 nm. The resulting Pt/Ag material exhibits clear electrocatalytic activity for oxygen reduction reaction (ORR) in alkaline solution. More interestingly, it shows no activity for methanol oxidation reaction (MOR), in contrast to Pt. Furthermore, the Pt/Ag catalyst demonstrates selective activity for ORR even in the presence of concentration of methanol as high as 5 M. Such high methanol tolerance indicates good perspectives for the application of Pt/Ag catalysts in alcohol fuel cell cathodes. For portable electronic applications, the binder-free structure of the Pt/Ag catalyst with its planar deposition make it very attractive as a cathode for membrane-type DMFCs or for membraneless fuel cells such as mixed reactant microfluidic fuel cell that depends on the characteristics of the electrodes to separate the oxidation and reduction reactions.