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Results for “methanol oxidation reaction”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Mechanistic study of a CO-free pathway in the methanol oxidation reaction over oxygen vacancies in NiOOH

The methanol oxidation reaction is a key reaction in direct methanol fuel cells. Prior research indicates that if oxygen vacancies in NiOOH serve as the active sites, the methanol oxidation mainly proceeds through the formate-involving pathway, which is a CO-free pathway, distinct from the conventional path over transition metal catalysts, though the fundamental reason for this suppressed CO formation is unclear. Herein, we report density functional theory calculations, through which we uncover the underlying reasons for this alternate path of methanol oxidation over the oxygen vacancies in NiOOH. We find that the existence of oxygen vacancies in NiOOH affects the adsorption configuration of adsorbates and that the interfacial charge transfer is minimal for CHO and CO intermediates. In addition, CHO, a key intermediate to form CO, adsorbs at the oxygen vacancy through the oxygen atom, leading to low stability due to the incomplete valence saturation of the carbon atom. This weak electronic interaction and instability effectively inhibit CHO formation and, consequently, CO formation. These insights provide valuable guidance for the development of efficient and CO-tolerant catalysts for methanol oxidation.

Ho, Thy [University of Oklahoma, Norman, OK (Unite↗
DOE OSTI2021

Lanthanum-based double perovskite nanoscale motifs as support media for the methanol oxidation reaction

In this report we have not only analyzed the performance of perovskite oxides as support media for the methanol oxidation reaction (MOR) but also examined the impact and significance of various reaction parameters on their synthesis. Specifically, we have generated (a) La 2 NiMnO 6 , LaMnO 3 , and LaNiO 3 nanocubes with average sizes of ~200 nm, in addition to a series of La 2 NiMnO 6 (b) nanocubes possessing average sizes of ~70 and 400 nm and (c) anisotropic nanorods characterized by average diameters of 40-50 nm. All of these samples, when used as supports for Pt nanoparticles, exhibited activities which were at least twice that measured for Pt/C. We have investigated and correlated the effect of varying perovskite (i) composition, (ii) size, and (iii) morphology upon the measured MOR activity. (i) The Ni-containing perovskites yielded generally higher performance metrics than LaMnO 3 alone, suggesting that the presence of Ni is favorable for MOR, a finding supported by a shift in the Pt d-band in XPS. (ii) MOR activity is enhanced as the perovskite size increases in magnitude, suggesting that a growth in the perovskite particle size enables favorable, synergistic metal–support interactions. (iii) A comparison of the nanorods and nanocubes of a similar diameter implied that the one-dimensional morphology achieved a greater activity, a finding which can be attributed not only to the anisotropic structure but also to a desirable surface structure. Overall, these data yield key insights into the tuning of metal–support interactions via rational control over the composition, size, and morphology of the underlying catalyst support.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Surfactant-Free Synthesis of Three-Dimensional Perovskite Titania-Based Micron-Scale Motifs Used as Catalytic Supports for the Methanol Oxidation Reaction

We synthesized and subsequently rationalized the formation of a series of 3D hierarchical metal oxide spherical motifs. Specifically, we varied the chemical composition within a family of ATiO 3 (wherein “A” = Ca, Sr, and Ba) perovskites, using a two-step, surfactant-free synthesis procedure to generate structures with average diameters of ~3 microns. In terms of demonstrating the practicality of these perovskite materials, we have explored their use as supports for the methanol oxidation reaction (MOR) as a function of their size, morphology, and chemical composition. The MOR activity of our target systems was found to increase with decreasing ionic radius of the “A” site cation, in order of Pt/CaTiO 3 (CTO) > Pt/SrTiO 3 (STO) > Pt/BaTiO 3 (BTO). With respect to morphology, we observed an MOR enhancement of our 3D spherical motifs, as compared with either ultra-small or cubic control samples. Moreover, the Pt/CTO sample yielded not only improved mass and specific activity values but also a greater stability and durability, as compared with both commercial TiO 2 nanoparticle standards and precursor TiO 2 templates.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2022

Experimental Studies of Graphene-Coated Polymer Electrolyte Membranes for Direct Methanol Fuel Cells

The two main technical limitations of direct methanol fuel cells (DMFCs) are the slow kinetic reactions of the methanol oxidation reaction (MOR) in the anode and the crossing over of unreacted methanol through the proton exchange membrane (PEM). It is a common practice to use Nafion membranes as PEMs, which have high ion exchange capacity. However, Nafion-based membranes also have high fuel permeability, decreasing fuel utilization, and reducing the potential power density. This article focuses on using graphene-coated (Gr-coated) PEMs to reduce fuel crossover. Protons can permeate across graphene, and thus, it can be employed in various devices as a proton conductive membrane. Here, we report the efficiency of Gr-coated Nafions. We tested performance and crossover at three different temperatures with four different fuel concentrations and compared it to a Nafion PEM that underwent the same test conditions. We found that the adhesion of Gr on to PEMs is insufficient for prolonging fuel cell operation, resulting in Gr delamination at high temperatures and higher fuel crossover values compared to lower temperature testing. Furthermore, the results for 7.5M methanol fuel show a reduction of up to 25% in methanol crossover, translating to a peak power density that increases from 3.9 to 9.5 mW/cm 2 when using a Gr-coated PEM compared to a Nafion PEM at 30 °C.

25 ENERGY STORAGE↗
DOE OSTI2020

High-Performance Pt–Co Nanoframes for Fuel-Cell Electrocatalysis

Pt-based alloy catalysts are promising candidates for fuel-cell applications, especially for cathodic oxygen reduction reaction (ORR) and anodic methanol oxidation reaction (MOR). The rational design of composition and morphology is crucial to promoting catalytic performances. Here, we report the synthesis of Pt–Co nanoframes via chemical etching of Co from solid rhombic dodecahedra. The obtained Pt–Co nanoframes exhibit excellent ORR mass activity in acidic electrolyte, which is as high as 0.40 A mg Pt –1 initially and 0.34 A mg Pt –1 after 10 000 potential cycles at 0.95 V RHE . Furthermore, their MOR mass activity in alkaline media is up to 4.28 A mg Pt –1 and is 4-fold higher than that of commercial Pt/C catalyst. Furthermore, experimental studies indicate that the weakened binding of intermediate carbonaceous poison contributes to the enhanced MOR behavior. More impressively, the Pt–Co nanoframes also demonstrate remarkable stability under long-term testing, which could be attributed to the negligible electrochemical Co dissolution.

25 ENERGY STORAGE↗
DOE OSTI2022

A single-Pt-atom-on-Ru-nanoparticle electrocatalyst for CO-resilient methanol oxidation

Single Pt atom catalysts are key targets because a high exposure of Pt substantially enhances electrocatalytic activity. In addition, PtRu alloy nanoparticles are the most active catalysts for the methanol oxidation reaction. To combine the exceptional activity of single Pt atom catalysts with an active Ru support we must overcome the synthetic challenge of forming single Pt atoms on noble metal nanoparticles. In this report we demonstrate a process that grows and spreads Pt islands on Ru branched nanoparticles to create single-Pt-atom-on-Ru catalysts. By following the spreading process by in situ TEM, we found that the formation of a stable single atom structure is thermodynamically driven by the formation of strong Pt–Ru bonds and the lowering of the surface energy of the Pt islands. The stability of the single-Pt-atom-on-Ru structure and its resilience to CO poisoning result in a high current density and mass activity for the methanol oxidation reaction over time.

36 MATERIALS SCIENCE↗
DOE OSTI2022

PtRu Catalysts on Nitrogen-Doped Carbon Nanotubes with Conformal Hydrogenated TiO 2 Shells for Methanol Oxidation

The methanol oxidation reaction (MOR) is the limiting factor in direct methanol fuel cells (DMFC). There is an urgent need to improve the catalytic activity and stability of MOR catalysts. This study reports a highly active PtRu catalyst for MOR based on a hybrid multifunctional catalyst support consisting of a conformal amorphous hydrogenated TiO 2 shell wrapped around the oxygenated N-doped carbon nanotube core, denoted as PtRu/TiO 2 / ONCNT-400. Both the TiO 2 shell and the subsequent PtRu nanoparticles are deposited by a rapid microwave-assisted synthesis processes. The hydrogenated TiO 2 shell is found to exhibit a strong interaction with the deposited PtRu catalyst nanoparticles and effectively prevent them from agglomeration during the postdeposition thermal annealing to form more active crystalline PtRu alloy catalysts. In addition, the defective hydrogenated TiO 2 shell enhances the PtRu catalyst activity by the synergistic effects of partial charge transfer from TiO 2 to PtRu and high oxophilicity, which improves the kinetics of oxidation of poisonous CO intermediate to CO 2 . The mass activity for MOR and long-cycling stability of the PtRu/TiO 2 /ONCNT-400 catalyst surpass the two benchmark commercial PtRu/C catalysts from Johnson Matthey (JM) and Tanaka KiKinzoku (TKK), respectively. Furthermore, the results demonstrate that PtRu/TiO 2 /ONCNT-400 can serve as an efficient catalyst for MOR in DMFC.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Pt 3 Sn nanoparticles enriched with SnO 2 /Pt 3 Sn interfaces for highly efficient alcohol electrooxidation

Pt 3 Sn nanoparticles (NPs) enriched with Pt 3 Sn/ultra-small SnO 2 interfaces (Pt 3 Sn@u-SnO 2 /NG) were synthesized through a thermal treatment of Pt 2 Sn/NG in a H 2 atmosphere, followed by annealing under H 2 and air conditions. The unique structure of Pt 3 Sn NPs enriched with Pt 3 Sn/SnO 2 interfaces was observed on the Pt 3 Sn@u-SnO 2 /NG catalyst based on HRTEM. The optimized Pt 3 Sn@u-SnO 2 /NG catalyst achieves high catalytic activity with an ethanol oxidation reaction (EOR) activity of 366 mA mg Pt -1 and a methanol oxidation reaction (MOR) activity of 503 mA mg Pt -1 at the potential of 0.7 V, which are eight-fold and five-fold higher than those for the commercial Pt/C catalyst (44 and 99 mA mg Pt -1 , respectively). The Pt 3 Sn@u-SnO 2 /NG catalyst is found to be 3 times more stable and have higher CO tolerance than Pt/C. The outstanding performance of the Pt 3 Sn@u-SnO 2 /NG catalyst should be ascribed to the synergetic effect induced by the unique structure of Pt 3 Sn NPs enriched with Pt 3 Sn/SnO 2 interfaces. The synergetic effect between Pt 3 Sn NPs and ultra-small SnO 2 increases the performance for alcohol oxidation because the Sn in both Pt 3 Sn and SnO 2 favors the removal of CO ads on the nearby Pt by providing OH ads species at low potentials. The present work suggests that the Pt 3 Sn@u-SnO 2 is indeed a unique kind of efficient electrocatalyst for alcohol electrooxidation.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Platinum/Tantalum Carbide Core–Shell Nanoparticles with Sub‐Monolayer Shells for Methanol and Oxygen Electrocatalysis

Abstract Core–shell architectures provide great opportunities to improve catalytic activity, but achieving nanoparticle stability under electrochemical cycling remains challenging. Herein, core–shell nanoparticles comprising atomically thin Pt shells over earth‐abundant TaC cores are synthesized and used as highly durable electrocatalysts for the methanol oxidation reaction (MOR) and the oxygen reduction reaction (ORR) needed to drive direct methanol fuel cells (DMFCs). Characterization data show that a thin oxidic passivation layer protects the TaC core from undergoing dissolution in the fuel cell‐relevant potential range, enabling the use of partially covered Pt/TaC core–shell nanoparticles for MOR and ORR with high stability and enhanced catalytic performance. Specifically, at the anode the surface‐oxidized TaC further enhances MOR activity compared to conventional Pt nanoparticles. At the cathode, the Pt/TaC catalyst feature increases tolerance to methanol crossover. These results show unique synergistic advantages of the core–shell particles and open opportunities to tailor catalytic properties for electrocatalytic reactions.

Chemistry↗
DOE OSTI2023

Probing the Behavior of Composition‐Tunable Ultrathin PtNi Nanowires for CO Oxidation and Small‐Molecule Electrocatalytic Reactions

We have successfully synthesized ultrathin nanowires of pure Pt, Pt 99 Ni 1 , Pt 9 Ni 1 , and Pt 7 Ni 3 using a modified room-temperature soft-template method. Analysis of both methanol oxidation reaction (MOR) and ethanol oxidation reaction (EOR) results found that the Pt 7 Ni 3 samples yielded the best performance with specific activities of 0.36 and 0.34 mA/cm 2 respectively. Additionally, formic acid oxidation reaction (FAOR) tests noted that both Pt and PtNi nanowires oxidize small organic molecules (SOMs) via an indirect pathway. CO oxidation data suggests little measurable performance without any pre-reduction treatment; however, after annealing in H 2 , we detected significantly improved CO 2 formation for both Pt 9 Ni 1 and Pt 7 Ni 3 motifs. These observations highlight the importance of pre-treating these nanowires under a reducing atmosphere to enhance their performance for CO oxidation. To explain these findings, we collected extended x-ray adsorption fine structure (EXAFS) spectroscopy data, consistent with the presence of partial alloying with a tendency for Pt and Ni to segregate, thereby implying the formation of a Pt-rich shell coupled with a Ni-rich core. Here, we also observed that the degree of alloying within the nanowires increased after annealing in a reducing atmosphere, a finding deduced through analysis of the coordination numbers and calculations of Cowley's short range order parameters.

36 MATERIALS SCIENCE↗
DOE OSTI2024

Platinum and CeO 2-x Occlusion Electrodeposition at Unsupported Vulcan XC-72R for Methanol and Ethanol Oxidation Reactions in Alkaline Media

Abstract Platinum was electrodeposited in a slurry solution of CeO2 and Vulcan XC-72R to produce Pt/CeO2-x/Vulcan XC-72R catalysts by using the Rotating Disk Slurry Electrodeposition (RoDSE) Technique. The activity of the catalysts was measured towards methanol and ethanol oxidation reactions in alkaline conditions by cyclic voltammetry and chronoamperometry. The electrochemical results were compared to those obtained on commercial catalysts. Pt/CeO2-x/Vulcan XC-72R (with ~ 26 wt.% Pt) catalyst was the most active for both alcohol oxidation reactions when compared to commercial 40 wt.% and 20% /Vulcan XC-72R (ETEK) catalysts. The mass activity increases 2.0x and 2.4x for methanol and ethanol oxidation reactions when compare with 40 and 20 Pt wt. % commercial catalysts, respectively. The Pt/CeO2-x/Vulcan XC-72R catalysts contained Pt nanoparticles growth within the cerium oxide through an occlusion electrodeposition method. These effects were systematically investigated using X-ray Diffraction (XRD), High Resolution Transmission Electron Microscopy (HR-TEM), and X-ray Photoelectron Spectroscopy (XPS).

Suleiman Mahmoud, Amal↗
DOE OSTI2024

Oxygen Vacancies Alter Methanol Oxidation Pathways on NiOOH

A thorough comprehension of the mechanism underlying the methanol oxidation reaction (MOR) on Ni-based catalysts is critical for future electrocatalytic design and development. However, the mechanism of MOR on these materials remains a matter of controversy. Herein, we combine in situ surface-enhanced infrared absorption spectroscopy (SEIRAS) and density functional theory (DFT) calculations to identify the active sites and determine the mechanism of MOR on monometallic Ni-based catalysts in alkaline media. The SEIRAS results show that formate and (bi)carbonate are formed after the commencement of the MOR with potential-dependent relative distributions. These spectroscopic results are in good agreement with the DFT-computed reaction profiles over an oxygen vacancy, suggesting that the MOR mainly proceeds through the formate-involving pathway, in which the early consumption of methanol yields formate as the major product, while increasing potential drives further oxidation of formate to (bi)carbonate. We also find a parallel pathway for the generation of (bi)carbonate at high potentials that bypasses the formation of formate. The two main pathways are thermodynamically more feasible than the one predominantly reported in the literature for MOR on NiOOH that involves CHO and/or CO as key intermediates. These DFT results are supported by spectroscopic evidence showing that no band associated with CHO or CO can be detected by SEIRAS, which is attributed to the nature of the oxygen vacancies as the active sites, suppressing deep dehydrogenation of CH 2 O to CHO. Furthermore, this work thus shows the promising role of defect engineering in promoting the electrocatalytic MOR activity and selectivity.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Yttrium-based Double Perovskite Nanorods for Electrocatalysis

In this work, we investigate the effect of chemical composition of double perovskite nanorods on their versatile electrocatalytic activity not only as supports for the oxidation of small organic molecules but also as catalysts for the oxygen evolution reaction. Specifically, Y 2 CoMnO 6 and Y 2 NiMnO 6 nanorods with average diameters of 300 nm were prepared by a two-step hydrothermal method, in which the individual effects of synthetic parameters, such as the pH, annealing temperature, and precursor ratios on both the composition and morphology, were systematically investigated. When used as supports for Pt nanoparticles, Y 2 CoMnO 6 /Pt catalysts exhibited an electrocatalytic activity for the methanol oxidation reaction, which is 2.1 and 1.3 times higher than that measured for commercial Pt/C and Y 2 NiMnO 6 /Pt. Similarly, the Co-based catalyst support material displayed an ethanol oxidation activity, which is 2.3 times higher than both Pt/C and Y 2 NiMnO 6 /Pt. This clear enhancement in the activity for Y 2 CoMnO 6 can largely be attributed to strong metal-support interactions, as evidenced by a downshift in the binding energy of the Pt 4f bands, measured by XPS, which is often correlated not only with a downshift in the d-band center but also to a decreased adsorption of poisoning adsorbates. Moreover, when used as catalysts for the oxygen evolution reaction, Y 2 CoMnO 6 displayed a much greater activity as compared with Y 2 NiMnO 6 . This behavior can largely be attributed not only to a preponderance of comparatively more favorable oxidation states and electronic configurations but also to the formation of an active layer on the surface of the Y 2 CoMnO 6 catalyst, which collectively give rise to improved performance metrics and greater stability as compared with both IrO 2 and Y 2 NiMnO 6 . Overall, these results highlight the importance of both the chemical composition and the electronic structure of double perovskites, especially when utilized in multi-functional roles as either supports or catalysts.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2021

Synthesis of Core@Shell Cu-Ni@Pt-Cu Nano-Octahedra and Their Improved MOR Activity

Fabrication of 3d metal-based core@shell nanocatalysts with engineered Pt-surfaces provides an effective approach for improving the catalytic performance. The challenges in such preparation include shape control of the 3d metallic cores and thickness control of the Pt-based shells. Herein, we report a colloidal seed-mediated method to prepare octahedral CuNi@Pt-Cu core@shell nanocrystals using CuNi octahedral cores as the template. By precisely controlling the synthesis conditions including the deposition rate and diffusion rate of the shell-formation through tuning the capping ligand, reaction temperature, and heating rate, uniform Pt-based shells can be achieved with a thickness of < 1 nm. Furthermore, the resultant carbon-supported CuNi@Pt-Cu core@shell nano-octahedra showed superior activity in electrochemical methanol oxidation reaction (MOR) compared with the commercial Pt/C catalysts and carbon-supported CuNi@Pt-Cu nano-polyhedron counterparts, demonstrating that both the lattice strain and shape effects arising from the as-prepared CuNi@Pt-Cu octahedral nanocatalysts play a crucial role in MOR performance.

36 MATERIALS SCIENCE↗