Methanol oxidation on sputter-coated platinum oxide catalysts

Rednyk, Andrii; Johánek, Viktor; Khalakhan, Ivan; Dubau, Martin; Vorokhta, Mykhailo; Matolín, Vladimı́r

doi:10.1016/j.ijhydene.2015.09.147

Cited by 22 publications

(7 citation statements)

References 51 publications

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“…Similar observations have been made in prior studies of silicon oxide supported Pt nanoparticle electrocatalysts, with the improved performance most commonly attributed to hydroxyl-facilitated removal of CO intermediates through the aforementioned bifunctional mechanism. − , In order to design catalysts that are more CO tolerant, it is important to understand the source of the hydroxyl groups that are responsible for aiding in the removal of adsorbed CO intermediates on Pt (Pt–CO ad ). As expressed in eqs and , CO oxidation may be achieved through reactions with silanol groups attached to SiO x (SiO x –OH) or hydroxyls on Pt (Pt–OH) ,,, where, in both cases, hydroxyls must be regenerated through an additional oxidation step. …”

Section: Discussionmentioning

confidence: 99%

“…Small alcohol fuels, such as methanol and ethanol, are attractive energy carriers for a sustainable energy future because of their high energy densities, ease of storage as liquids, and the ability to produce them electrochemically from carbon dioxide (CO 2 ) and water (H 2 O) using electricity from renewable resources. − These alcohol fuels can be converted back into electricity for various applications using direct alcohol fuel cells (DAFCs), where alcohol oxidation at the anode is coupled with the oxygen reduction reaction (ORR) at the cathode. , Despite recent advances in the performance of DAFCs, their power densities (≈0.01–10 W cm –2 ) are still significantly lower than hydrogen fuel cells (HFCs), which typically achieve power densities of ≈10–100 W cm –2 . Major reasons for the performance gap between DAFCs and HFCs are voltage losses that originate from (i) fuel crossover to the cathode and (ii) sluggish reaction kinetics associated with alcohol oxidation at the DAFC anode. , The state-of-the-art anode catalysts in acidic medium are based on nanoparticles of platinum (Pt) or Pt alloys that are supported on high surface area carbon (Pt/C). − The performance of DAFC anodes can also suffer from degradation of the electrocatalyst and carbon support, which can lead to dissolution, detachment, migration, and/or agglomeration of the catalytic nanoparticles. − …”

Section: Introductionmentioning

confidence: 99%

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Silicon Oxide-Encapsulated Platinum Thin Films as Highly Active Electrocatalysts for Carbon Monoxide and Methanol Oxidation

et al. 2018

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Direct alcohol fuel cells (DAFCs) have the potential to provide high power densities for transportation and portable applications. However, widespread use of DAFCs is greatly hindered by the lack of anode electrocatalysts that are inexpensive, stable, resistant to CO poisoning, and highly active toward alcohol oxidation. One promising approach to overcoming these challenges is to combine transition metal catalysts with oxide supports, such as SiO2, which are known to enhance alcohol oxidation by promoting CO oxidation at oxide|metal interfacial regions through the so-called bifunctional mechanism. Herein, we report on a membrane-coated electrocatalyst (MCEC) architecture for alcohol oxidation, in which a thin, permeable silicon oxide (SiO x ) nanomembrane encapsulates a well-defined Pt thin film (SiO x |Pt). A key advantage of the MCEC design compared to oxide-supported nanoparticles is that the oxide encapsulation maximizes the density of oxide|metal interfacial sites between the SiO x and Pt catalyst. A series of electroanalytical measurements indicates that the SiO x overlayers provide proximal hydroxyls, in the form of silanol groups, which can enhance alcohol oxidation by interacting with adsorbed intermediates at SiO x |Pt interfaces. Thanks to these interactions, the SiO x |Pt electrocatalysts exhibit significantly enhanced CO oxidation activity and roughly a 2-fold increase in the maximum methanol oxidation current density compared to bare Pt. Overall, these demonstrations highlight the potential of using SiO x -based MCECs for CO tolerant and highly active methanol oxidation electrocatalysts.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Silicon Oxide-Encapsulated Platinum Thin Films as Highly Active Electrocatalysts for Carbon Monoxide and Methanol Oxidation

et al. 2018

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“…On the basis of microanalysis data for the nonreduced and reduced anodes, we assumed that PtO x was reduced and active Pt species dispersed into the whole cermet anode layer by fast diffusion through the grain boundaries of Ni particles (i.e., classical interdiffusion through the grain boundaries of Ni particles) and/or diffusion on the surface of the connection of Ni particles after activation of the anode in the hydrogen atmosphere at 1073 K.…”

Section: Resultsmentioning

confidence: 99%

Design of Active Sites on Nickel in the Anode of Intermediate‐Temperature Solid Oxide Fuel Cells using Trace Amount of Platinum Oxides

et al. 2018

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In recent years, the lowering of the operation temperature of solid oxide fuel cells (SOFCs) has attracted much attention owing to the trade‐off between the best performance and the life span of SOFCs. For this challenge, new active sites on the Ni surfaces in a Nickel–Yttria‐Stabilized Zirconia (Ni‐YSZ) cermet anode of SOFCs have been created by deposition of trace amounts of platinum oxide (PtOx) followed by an activation step of the anode at 1073 K in a hydrogen flow. The internal resistance (IR) free value (185 mA cm−2 at 0.8 V) observed for the single cell with an anode sputtered with a trace amount of PtOx (Pt content in anode: from 9 to 91 ppm) at 973 K is conspicuously higher than that of a similar single cell with a nonsputtered cermet anode (85 mA cm−2) at 0.8 V and 1073 K. Transmission electron microscopy microanalysis shows that the defect structure is formed on a partially oxidized Ni surface by active Pt species. Also, surface atomistic simulation on NiO (111) predicts the formation of Frenkel defect clusters with Pt cations, which partially cover the Ni surface. The formation of Frenkel defect clusters on the partially oxidized Ni surface (i.e., creation of new active sites for formation of water molecules) promotes the anode reaction, resulting in improvements in the anode performance of SOFC single cells at 973 K. Design of the aforementioned new active sites on Ni through sputtering of trace amounts of PtOx provides a great opportunity for “radical innovation” in the design of intermediate‐temperature SOFCs.

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“…The magnetron sputtering technique proved to be a very versatile and relatively simple means of deposition of multicomponent thin films on almost any type of substrate. − On the other hand, layers sputter-deposited at room temperature are generally thermodynamically unstable, and therefore, they typically undergo morphological and chemical changes during the initial reaction cycle. In this section, we demonstrate this stabilization process, but in the situations where we make comparisons of different samples, only the results of the second TPR cycle measurements will be presented to provide relevant comparisons with respect to real long-term operating conditions.…”

Section: Resultsmentioning

confidence: 99%

Efficient Ceria–Platinum Inverse Catalyst for Partial Oxidation of Methanol

et al. 2016

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Ceria-platinum-based bilayered thin films deposited by magnetron sputtering were developed and tested in regard to their catalytic activity for methanol oxidation by employing a temperature-programmed reaction (TPR) technique. The composition and structure of the samples were characterized by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Both conventional (oxide-supported metal nanoparticles [NPs]) and inverse configurations (metal with oxide overlayer) were analyzed to uncover the structural dependence of activity and selectivity of these catalysts with respect to different pathways of methanol oxidation. We clearly demonstrate that the amount of cerium oxide (ceria) loading has a profound influence on methanol oxidation reaction characteristics. Adding a noncontinuous adlayer of ceria greatly enhances the catalytic performance of platinum (Pt) in favor of partial oxidation of methanol (POM), gaining an order of magnitude in the absolute yield of hydrogen. Moreover, the undesired by-production of carbon monoxide (CO) is strongly suppressed, making the ceria-platinum inverse catalyst a great candidate for clean hydrogen production. It is suggested that the methanol oxidation process is facilitated by the synergistic effect between both components of the inverse catalyst (involving oxygen from ceria and providing a reaction site on the adjacent Pt surface) as well as by the fact that the ability of ceria to exchange oxygen (i.e., to alter the oxidation state of Ce between 3+ and 4+) during the reaction is inversely proportional to its thickness. The increased redox capability of the discontinuous ceria adlayer shifts the preferred reaction pathway from dehydrogenation of hydroxymethyl intermediate to CO in favor of its oxidation to formate.

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Methanol oxidation on sputter-coated platinum oxide catalysts

Cited by 22 publications

References 51 publications

Silicon Oxide-Encapsulated Platinum Thin Films as Highly Active Electrocatalysts for Carbon Monoxide and Methanol Oxidation

Silicon Oxide-Encapsulated Platinum Thin Films as Highly Active Electrocatalysts for Carbon Monoxide and Methanol Oxidation

Design of Active Sites on Nickel in the Anode of Intermediate‐Temperature Solid Oxide Fuel Cells using Trace Amount of Platinum Oxides

Efficient Ceria–Platinum Inverse Catalyst for Partial Oxidation of Methanol

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