Methanol-tolerant Electrocatalyst Research Articles

Synergistic Effect of Oxygen Vacancy-Rich SnO2 and AgCl in the Augmentation of Sustained Oxygen Reduction Reaction.

Developing a stable and methanol-tolerant electrocatalyst for a sustained oxygen reduction reaction (ORR) is of great importance for advancing direct methanol fuel cell applications. The silver-based electrocatalysts are particularly interesting among the promising non-Pt-based electrocatalysts for ORR. Herein, we report a single-step synthesis of a composite of AgCl and SnO2 with oxygen vacancy (AgCl-SnO2(VO)), which exhibits sustained and selective catalytic activity for the ORR along with excellent durability. Hydrothermal synthesis generates oxygen vacancies within the material and facilitates a strong interaction between AgCl and SnO2(VO), which effectively augments the ORR activity and the long-term stability of the composite. The composite exhibits remarkable methanol tolerance, as evidenced by a meager shift of only 0.002 V in the half-wave potential. Furthermore, the composite demonstrates excellent durability, with no noticeable changes in onset and half-wave potential even after 2500 cycles. The cost-effectiveness, durability, and ORR selectivity of this composite hold great promise toward contributing to the advancement of clean energy technology.

Carbon nanobowl supported chemically functionalized PtRh nanocrystals: a highly active and methanol tolerant electrocatalyst towards the oxygen reduction reaction

Pt1Rh1@BmimBF4/CNBs reveal significantly enhanced ORR electroactivity and fascinating ORR selectivity in the presence of methanol compared to Pt1Rh1/CNBs nanohybrids without BmimBF4 due to particular metal–organic interface engineering.

Au Nanowires@Pd-Polyethylenimine Nanohybrids as Highly Active and Methanol-Tolerant Electrocatalysts toward Oxygen Reduction Reaction in Alkaline Media

Optimizing the shape, structure, and interface of noble metal bimetallic nanostructures significantly improves their catalytic properties. Recently, Au@Pd core–shell bimetallic nanostructures have ...

Facile Synthesis of Polyhedral Pd Nanocrystals as a Highly Active and Methanol-Tolerant Electrocatalyst for Oxygen Reduction

The polyhedral Pd nanocrystals are synthesized by a facile conventional hydrothermal method, in which the cetyltrimethylammonium bromide, Fe3+ and formaldehyde are designed as structural orientation, etching and reduction agents, respectively. The crystal and morphological characteristics show that the crystal facets of (111) and (220) planes are exposed on the surface of face-centered cubic crystal structure of Pd polyhedron. Electrochemical analyses indicate that the polyhedral Pd/XC-72 catalyst shows the highest electrochemically active surface area (57.6 m2 g−1), similar half-wave potential and diffusion-limiting current density (-4.79 mA cm−2) with state-of-the-art commercial Pd/C in alkaline electrolytes. The excellent electrocatalytic activity supports a four-electron-transfer pathway and smaller Tafel slope (67.2 mV dec−1) reveals a higher intrinsic activity for ORR. Additionally, the polyhedral Pd/XC-72 catalyst also exhibits much better methanol tolerance crossover effects and long-term stability than commercial Pd/C. All these excellent electrocatalytic performances are considered to be the coaction of the exposed high surface energy facets and more of active sites on the polyhedral crystals surface, which could significantly improve the adsorption and activation energies with oxygenated intermediates in alkaline solution. This work provides a new prospect in designing high active, non-easy tolerance and more stable Pd-based catalyst in alkaline fuel cells.

Tungsten diselenide/porous carbon with sufficient active edge-sites as a co-catalyst/Pt-support favoring excellent tolerance to methanol-crossover for oxygen reduction reaction in acidic medium

Developing an acid-stable, highly active and methanol-tolerant electrocatalyst towards the oxygen reduction reaction (ORR) is crucial for commercialization of direct methanol fuel cells (DMFCs). In this study, via a simultaneous synthesis method, tungsten diselenide/porous carbon (WSe2/C) composites are prepared as the supports/ORR co-catalysts to support Pt with a low loading of 5wt.%. Varied WSe2/C supports are obtained by tuning the carbonization temperature (600–1000°C) to investigate the relationships between structural characteristics and ORR performance. Pt-WSe2/C (800°C) exhibits a considerably higher specific activity (4.57mAcm−2) for ORR than those of WSe2/C (2.45mAcm−2) and commercial Pt/C (10wt.%, 2.69mAcm−2), owing to the high ORR co-catalytic activity of WSe2/C for Pt. The robust contacts among Pt, WSe2 and porous carbon with high surface area can significantly improve the exposure of Pt active sites, which correspondingly promote the charge transfer efficiency and the fast adsorption, activation and reduction of oxygen molecules. Moreover, Pt-WSe2/C (800°C) catalyst exclusively exhibits a four-electron pathway for ORR. With the intimate cooperation among Pt, WSe2 and porous carbon skeleton, more available Pt active sites are exposed to improve the ORR kinetics and durability. The tolerance to methanol-crossover on Pt-WSe2/C are remarkably enhanced, which should be attributed to the synergistic effects between the exposed edge sites of embedded WSe2 and the porous carbon skeleton with abundant oxygen-containing functional groups. The use of WSe2/C supports with low-cost, high co-catalytic/catalytic activity and strong methanol-tolerance provides a promising way to enhance ORR activity in DMFCs.

Shape controlled synthesis of porous tetrametallic PtAgBiCo nanoplates as highly active and methanol-tolerant electrocatalyst for oxygen reduction reaction.

Mechanistic control is a powerful means for manufacturing specific shapes of metal nanostructures and optimizing their performance in a variety of applications. Thus, we successfully synthesized multimetallic nanoplates (PtAgBiCo and PtAgBi) by combining the concepts of crystal symmetry, oxidative etching and seed ratio, and tuned their activity, stability and methanol tolerance, as well as Pt utilization, for the oxygen reduction reaction in direct methanol fuel cells. Systematic studies reveal that the formation of PtAgBiCo triangular nanoplates with a high morphological yield (>90%) can be achieved by crystallinity alteration, while electrochemical measurements indicate that the PtAgBiCo nanoplates have superior electrocatalytic activity towards the oxygen reduction reaction. The specific and mass activity of the PtAgBiCo nanoplates are 8 and 5 times greater than that of the commercial Pt/C catalyst, respectively. In addition, the tetrametallic PtAgBiCo nanoplates exhibit a more positive half-wave potential for the oxygen reduction reaction and possess an excellent methanol tolerance limit compared with the commercial Pt/C catalyst.

Highly methanol-tolerant platinum electrocatalyst derived from poly(vinylpoyrrolidone) coating

The design and fabrication of a methanol-tolerant electrocatalyst is still one of the most important issues in direct methanol fuel cells (DMFCs). Here, we focus on the design of a cathodic electrocatalyst in DMFCs and describe a new methanol-tolerant electrocatalyst fabricated from poly(vinylpyrrolidone) (PVP) coating on platinum nanoparticles assisted by hydrogen bonding between PVP and polybenzimidazole (PBI). The PVP layer has a negligible effect on the oxygen reduction reaction (ORR) activity, while the methanol oxidation reaction is retarded by the PVP layer. The PVP-coated electrocatalyst shows higher ORR activity under various methanol concentrations in the electrolyte, suggesting that the PVP-coated electrocatalyst has a higher methanol tolerance. Also, the PVP-coated electrocatalyst loses only 14% of the electrochemical surface area after 5000 potential cycles from 0.6–1.0 V versus the reversible hydrogen electrode, indicating better Pt stability than non-coated (27%) and commercial (38%) electrocatalysts due to the unique sandwich structure formed by the PVP and PBI. The power density of the PVP-coated electrocatalyst is four to five times higher compared to non-coated and commercial electrocatalysts with 12 M methanol feeding to the anode side, respectively. PVP coating is important for the enhancement of Pt stability and methanol tolerance. This study offers a new method for preparing a low-cost and high-methanol-tolerant Pt electrocatalyst, and useful information for real DMFC application to eliminate the methanol crossover problem in the cathode side.

Multicomponent platinum-free nanoporous Pd-based alloy as an active and methanol-tolerant electrocatalyst for the oxygen reduction reaction

Development of high-performance oxygen reduction reaction (ORR) catalysts is crucial to improve proton exchange membrane fuel cells. Herein, a multicomponent nanoporous PdCuTiAl (np-PdCuTiAl) electrocatalyst has been synthesized by a facile one-step dealloying strategy. The np-PdCuTiAl catalyst exhibits a three-dimensional bicontinuous interpenetrating ligament/channel structure with an ultrafine length scale of ~3.7 nm. The half-wave potential of np PdCuTiAl is 0.873 V vs. RHE, more positive than those of PdC (0.756 V vs. RHE) and PtC (0.864 V vs. RHE) catalysts. The np-PdCuTiAl alloy shows a 4-electron reaction pathway with similar Tafel slopes to PtC. Remarkably, the half-wave potential shows a negative shift of only 12 mV for np-PdCuTiAl in the presence of methanol, and this negative shift is much lower than those of the PdC (50 mV) and PtC (165 mV) catalysts. The enhanced ORR activity of np-PdCuTiAl has been further rationalized through density functional theory calculations.

Ultra-small Fe2N nanocrystals embedded into mesoporous nitrogen-doped graphitic carbon spheres as a highly active, stable, and methanol-tolerant electrocatalyst for the oxygen reduction reaction

A low-cost, highly active, stable, and methanol tolerant electrocatalyst towards the oxygen reduction reaction (ORR) is extremely desirable for promoting the commercialization of fuel cells. Herein, we reported a facile two-step pyrolysis and acid leaching process to synthesize a high performance ORR electrocatalyst, where ultra-small Fe2N nanocrystals were incorporated into mesoporous nitrogen-doped graphitic carbon spheres (MNGCS). The Fe2N/MNGCS electrocatalysts with difference Fe2N contents and BET surface areas were obtained via altering the acid leaching time, and all exhibited the apparent electrocatalytic activity. The optimized ORR activity was achieved over (Fe2N/MNGCS)4 with the positive half-wave potentials (0.881V vs RHE), high selectivity (4 e− process), excellent long-term stability (95.2% of the initial current remaining after 60,000s of continuous operation) and good tolerance against methanol-crossover effect (94.9% of the current retained prior to 4.0M methanol injection) in alkaline media, which even was more superior to that of commercial Pt/C catalyst. The remarkable ORR activity was originated from the cooperative effect of ultra-small Fe2N nanocrystals and MNGCS, where the balance of catalytic active site density, mesoporous structure, BET specific surface area, and electron conductivity played a key role in determining the ORR performance.

Nano ceria supported nitrogen doped graphene as a highly stable and methanol tolerant electrocatalyst for oxygen reduction

Ceria (CeO2) nanoparticles with ellipsoid shape are coupled on a nitrogen doped reduced graphene oxide sheet through a single step solvothermal procedure.

Investigation of PtNi/C as methanol tolerant electrocatalyst for the oxygen reduction reaction

Platinum–nickel electrocatalysts prepared by a simple and cost-effective procedure have been investigated for the oxygen reduction reaction (ORR) in direct methanol fuel cells (DMFCs). The formic acid method was used to deposit well-dispersed PtxNiy nanoparticles (x:y=3:2) on the surface of a carbon black support (Ketjenblack). Carbothermal reduction of the as-prepared catalyst in an inert gas (Ar) at 900°C produced an alloy and a partial modification of the crystalline structure from the face centered cubic, typical of Pt, to a tetragonal structure of PtNi alloy. An acid leaching treatment was carried out to partially remove unalloyed surface nickel atoms in the outermost layers, leading to an enrichment of Pt concentration (x:y=2:1). Cyclic voltammetry analysis in acidic medium indicated a relatively high electrochemical active surface area (>70m2g−1) for both untreated and thermally treated PtxNiy catalysts. The activity towards the ORR was evaluated in half-cell configuration (0.5M H2SO4) using the rotating disk electrode technique. Similar behavior towards the ORR was found for the untreated and thermally treated PtNi/C catalysts, with an increase in activity compared to a commercial Pt/C catalyst. A remarkably better tolerance to methanol was observed for both PtNi/C cathode catalysts compared to the commercial Pt/C catalyst.

Synthesis of highly stable and methanol-tolerant electrocatalyst for oxygen reduction: Co supporting on N-doped-C hybridized TiO2

The currently used carbon supported Pt or Pt alloy catalysts for cathodic oxygen reduction reaction (ORR) suffer from prohibitive cost as well as limited productivity of Pt, carbon-support corrosion, and methanol poisoning. Here we report a one-pot heat treatment for synthesis of Co supporting on N-doped-C (C-N) hybridized TiO2 catalyst. For the first time, TiO2 is used as the predominant content in C-based ORR catalyst. Fiber-like polyaniline (PANI) is introduced as a C-N precursor and also acts as a good template for growing TiO2 crystals. During the following one-pot heat treatment, the metallic Co particles are in situ growing on the carbonized TiO2/PANI support. The influences of PANI proportion, calcination temperature, and Co incorporation on the ORR catalytic performance are systematically investigated. The optimal Co/TiO2/C-N catalyst shows higher stability and methanol-tolerance than commercial Pt/C or Co/C-N catalyst with comparable activity. The remarkable enhancement of stability is mainly ascribed to the following two reasons: (1) the excellent chemical stability of rutile TiO2; (2) the strong interactions of “TiO2-PANI coupling” and “metal-support coupling”. Thus, TiO2/C-N appears to be a promising substitute for carbon materials when supporting metal or metal oxide catalyst for PEMFC application in terms of electrochemical stability.

A simple preparation of very high methanol tolerant cathode electrocatalyst for direct methanol fuel cell based on polymer-coated carbon nanotube/platinum

The development of a durable and methanol tolerant electrocatalyst with a high oxygen reduction reaction activity is highly important for the cathode side of direct methanol fuel cells. Here, we describe a simple and novel methodology to fabricate a practically applicable electrocatalyst with a high methanol tolerance based on poly[2,2′-(2,6-pyridine)-5,5′-bibenzimidazole]-wrapped multi-walled carbon nanotubes, on which Pt nanoparticles have been deposited, then coated with poly(vinylphosphonic acid) (PVPA). The polymer coated electrocatalyst showed an ~3.3 times higher oxygen reduction reaction activity compared to that of the commercial CB/Pt and methanol tolerance in the presence of methanol to the electrolyte due to a 50% decreased methanol adsorption on the Pt after coating with the PVPA. Meanwhile, the peroxide generation of the PVPA coated electrocatalyst was as low as 0.8% with 2 M methanol added to the electrolyte, which was much lower than those of the non-PVPA-coated electrocatalyst (7.5%) and conventional CB/Pt (20.5%). Such a high methanol tolerance is very important for the design of a direct methanol fuel cell cathode electrocatalyst with a high performance.

Methanol tolerant electrocatalysts for the oxygen reduction reaction

Direct methanol fuel cells (DMFCs) represent an interesting alternative in obtaining electricity in a clean and efficient way. Portable power sources are one of the most promising applications of passive DMFCs. One of the requirements in these devices is to use high alcohol concentration, which due to methanol crossover causes a considerable loss of fuel cell efficiency. In order to develop methanol tolerant cathodes with suitable activity, different supported catalysts namely PtCo/C and PtCoRu/C, were prepared either via ethylene glycol reduction (EG) with or without microwave heating assistance (MW) or via the alloy method, the latter followed by a thermal treatment in a reducing atmosphere (N2/H2). All cathode-catalysts were tested to determine the role of the components in simultaneously enhancing the oxygen reduction reaction (ORR) and discouraging the methanol oxidation reaction. According to the synthesis methodology, X-ray photoelectron spectra showed that the amount of metal oxides on the surface varies, being higher on the PtCo/C EG and PtCoRu/C EG catalysts. The electrochemical characterization of the catalysts was accomplished in a three electrodes electrochemical cell with a glassy carbon rotating disk electrode covered with a thin catalytic film as working electrode. To study the ORR and the influence of different methanol concentrations, linear sweep voltammetry and cyclic voltammetry were employed. The PtCo/C EG, with an important metal oxide amount on the surface, and the PtCoRu/C MW and EG electrodes, both with RuO2 on their surfaces, were the most tolerant to methanol presence.

Tungsten carbide promoted Au–Pd–Pt as methanol-tolerant electrocatalysts for oxygen reduction reaction

Au–Pd–Pt nanotrimetallic particles supported on nanocrystaline tungsten carbide as a cathodic electrocatalyst for oxygen reduction reaction (ORR) were prepared by an intermittent microwave heating (IMH) method. XRD measurement revealed that Au–Pd–Pt alloy formed during the IMH process. These novel electrocatalysts could offer the activities which surpass that of the state-of-the-art Pt-based electrocatalysts for oxygen reduction reaction. The AuPdPt-WC/C electrocatalyst showed better performance for oxygen reduction in alkaline solution than that of Pt/C catalyst. The results revealed that an over 90 mV shift towards more positive potentials compared to Pt/C electrode for ORR. The methanol tolerance and selectivity of the AuPdPt-WC/C electrocatalyst are favourable for the ORR in the presence of methanol which makes it a promising cathodic electrocatalyst in direct methanol fuel cells (DMFCs). The ORR is hardly affected in the methanol-containing solutions up to 1·0 mol L−1 methanol. The advantage seemed to come from the novel support of tungsten carbide which itself has the catalytic activity to enhance the catalytic activity of the metal electrocatalysts.

Polypyrrole-Modified-Carbon-Supported Ru-Pt Nanoparticles as Highly Methanol-Tolerant Electrocatalysts for the Oxygen-Reduction Reaction

With ORR without you: A carbon-supported Ru-Pt electrocatalyst exhibits superior methanol tolerance than Pt/C during the oxygen-reduction reaction, thus leading to more active and durable direct methanol fuel cells. Modification of the carbon support with polypyrrole allows for better dispersion of the Ru-Pt nanoparticles.

Nanoporous PdNi alloys as highly active and methanol-tolerant electrocatalysts towards oxygen reduction reaction

A nanoporous PdNi (NP-PdNi) alloy with uniform structure dimension is easily fabricated by one-step mild dealloying of a PdNiAl precursor alloy. NP-PdNi consists of an interconnected nanoscaled network backbone and bicontinuous hollow channels in all three dimensions with a typical ligament size of around 5 nm. Electrochemical measurements indicated that the NP-PdNi alloy has superior electrocatalytic activity towards oxygen reduction reaction (ORR) with much higher specific and mass activities as well as higher methanol tolerance compared with Pt/C catalysts. Importantly, NP-PdNi suffers less loss of the ORR activity and the electrochemical surface area of metal upon 5000 potential cycles in acid solution than Pt/C, indicating a better catalytic durability. The NP-PdNi alloy holds great application potential as a cathode electrocatalyst in the fuel cell related technology with unique ORR performance, high structure stability, and easy preparation.

Cornered silver and silver[sbnd]platinum nanodisks: Preparation and promising activity for alkaline oxygen reduction catalysis

A simple method for the efficient synthesis of cornered Ag and AgPt nanodisks by using triangular Ag nanoplates as reactants has been developed. The triangular Ag nanoplates are heated and reshaped to spherical nanodisks; in turn, through the introduction of PtCl42− ions, the spherical nanodisks undergo sculpturing and a subsequent displacement reaction to form cornered Ag nanodisks and AgPt nanodisks with pores. The selected-area electron diffraction pattern shows that the cornered Ag nanodisks are composed of two basal Ag (111) planes, thus indicating the occurrence of selective etching on the spherical nanodisks by this method. The analyses provided by X-ray diffraction spectroscopy and line-scanned energy-dispersive spectroscopy confirm the compositions of these cornered nanodisks and the mixed alloy in the Ag–Pt nanodisks. For the investigation of the practical feasibility of the application of the proposed method, these cornered Ag and AgPt nanodisks were then used as methanol-tolerant electrocatalysts in the alkaline oxygen reduction reaction (ORR). Electrochemical measurements were performed using an ultrathin-film rotating ring-disk electrode. The two types of nanodisks are found to have high stabilities and improved activities in 1M NaOH electrolyte. In the electrolyte with free methanol, the mass activities at −0.1V (vs. Ag/AgCl; within kinetic control region) in terms of the currents normalized to Ag mass for the Ag nanodisks and AgPt nanodisks are 6.98×10−4 and 2.01×10−3mAμg−1, respectively, which are greater than the value of 2.09×10−4mAμg−1 for Ag nanoparticles. The order in terms of the ORR activity is found to be as follows: cornered AgPt nanodisks>cornered Ag nanodisks>Ag nanoparticles. Additionally, in the presence of methanol, all the cornered nanodisk catalysts experience cathodic currents, indicating that the ORR occurs despite the use of a methanol solution.

Nitrogen-doped carbon black as methanol tolerant electrocatalyst for oxygen reduction reaction in direct methanol fuel cells

Nitrogen-doped metal free carbon catalysts were prepared via pyrolysis of polyaniline-coated carbon in different ratios with varying nitrogen content. The surface states and surface composition were investigated using XPS (X-ray photoelectron spectroscopy). XPS analysis confirms the presence of pyridinic and pyrollic nitrogen in the carbon network that is responsible for the oxygen reduction activity. The shift in onset potential of oxygen reduction on C:N (1:1) is ∼0.3V more positive compared to Vulcan carbon, shows improved activity toward oxygen reduction reaction in acidic electrolyte. Hydrodynamic voltammetric studies confirm that the reduction of oxygen follows the 4e− pathway which leads to the formation of water.

Ordered Mesoporous Platinum@Graphitic Carbon Embedded Nanophase as a Highly Active, Stable, and Methanol-Tolerant Oxygen Reduction Electrocatalyst

Highly ordered mesoporous platinum@graphitic carbon (Pt@GC) composites with well-graphitized carbon frameworks and uniformly dispersed Pt nanoparticles embedded within the carbon pore walls have been rationally designed and synthesized. In this facile method, ordered mesoporous silica impregnated with a variable amount of Pt precursor is adopted as the hard template, followed by carbon deposition through a chemical vapor deposition (CVD) process with methane as a carbon precursor. During the CVD process, in situ reduction of Pt precursor, deposition of carbon, and graphitization can be integrated into a single step. The mesostructure, porosity and Pt content in the final mesoporous Pt@GC composites can be conveniently adjusted over a wide range by controlling the initial loading amount of Pt precursor and the CVD temperature and duration. The integration of high surface area, regular mesopores, graphitic nature of the carbon walls as well as highly dispersed and spatially embedded Pt nanoparticles in the mesoporous Pt@GC composites make them excellent as highly active, extremely stable, and methanol-tolerant electrocatalysts toward the oxygen reduction reaction (ORR). A systematic study by comparing the ORR performance among several carbon supported Pt electrocatalysts suggests the overwhelmingly better performance of the mesoporous Pt@GC composites. The structural, textural, and framework properties of the mesoporous Pt@GC composites are extensively studied and strongly related to their excellent ORR performance. These materials are highly promising for fuel cell applications and the synthesis method is quite applicable for constructing mesoporous graphitized carbon materials with various embedded nanophases.