Temperature effects on CO adsorption/desorption at Pt film electrodes: an electrochemical in situ infrared spectroscopic study

Geng, Bo; Cai, Jun; Liang, Sangzi; Liu, Shao Xiong; Li, Ming Fang; Chen, Yan‐Xia

doi:10.1039/c002665d

Cited by 24 publications

(14 citation statements)

References 31 publications

(53 reference statements)

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“…This may be due to hydrogen chemisorption and spillover blocking the reverse effect for CO. During the experiment, the signal of m/z = 32 (indicative of oxygen) remained at the background level. The CO desorption at 353 K in He for nanocrystalline Pt observed here is in line with the reported observation of no CO desorption up to 343 K on a Pt film (Geng et al, 2010).…”

Section: Chemisorption Of Co and No On Pt Nanocrystalssupporting

confidence: 92%

Powder diffraction in studies of nanocrystal surfaces: chemisorption on Pt

2014

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Atoms at the surface of nanocrystals contribute appreciably to the X‐ray diffraction pattern. Phenomena like chemisorption, affecting the displacement of surface atoms with respect to their positions in the perfect crystallographic structure, cause diffraction peak shifts and intensity changes. These effects are easily measurable for small nanocrystals up to 10 nm size. This article reports diffraction effects of chemisorption of adsorbing gases H2, O2, CO and NO for a series of in situ powder diffraction experiments on nanocrystalline Pt supported on silica. On the basis of previous diffraction observation of Pt surface reconstruction during hydrogen desorption, it was possible to quantify this effect versus crystallite size and rationalize the observed diffraction peak shift for the other adsorbing species. This enabled the surface reconstruction to be distinguished from the surface relaxation effect, the latter depending monotonically on the adsorption energy. Even if no phase transition occurs, monitoring of a peak's position, intensity, width and gas composition (via mass spectrometry) during a carefully designed physicochemical process (including surface chemical reaction) enables insight into and understanding of the surface structure evolution (e.g. amorphization, relaxation, reconstruction or changes in the overall morphology). The proposed technique can be used as a surface science tool, allowing studies of nanocrystals under high pressure.

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Section: Chemisorption Of Co and No On Pt Nanocrystalssupporting

confidence: 92%

Powder diffraction in studies of nanocrystal surfaces: chemisorption on Pt

2014

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“…This may be an indication that the COad pathway (r13) becomes more prevalent in the oscillatory regime, 37 since Eapp values around 100 kJ mol -1 have been estimated for this reaction on Pt. 94 However, to distinguish the contributions of each reaction step for the oscillatory frequency and their respective dependencies with the temperature requires the use of in situ and on line techniques to evaluate the coverage of reaction intermediates, with temporal resolution high enough to contemplate the oscillatory period.…”

Section: Electrochemical Impedance Spectroscopymentioning

confidence: 99%

Direct Liquid Fuel Cells – The Influence of Temperature and Dynamic Instabilities

Nogueira¹,

Varela²

2020

Preprint

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The interconversion between chemical and electrical energies plays a pivotal role in the challenge for a sustainable future. Proton exchange membrane (PEMFC) based on the electro-oxidation of hydrogen and reduction of oxygen comprise a relatively mature technology of indisputable relevance. Alternatively, some open questions concerning the use of Direct Liquid Fuel Cells (DLFC) call for further experimental investigations on these systems. In this paper we evaluate the temperature effect on DLFCs under conventional and oscillatory conditions. We studied four molecules: methanol, formic acid, ethanol, and dimethyl ether. The use of identical experimental conditions allowed at studying the role of the fuel on the DLFC performance, providing thus reference values for future investigations. Under regular, non-oscillatory regime, we observed for all cases that the overpotential decreases as the temperature increases mainly because water activation on the catalyst surface is facilitated at high temperatures. By mapping the conditions where oscillatory kinetics manifest itself under galvanostatic mode, only the electro-oxidation of dimethyl ether did not exhibit potential oscillations. The relationship between oscillatory frequency and temperature during the methanol and formic acid electro-oxidation followed a conventional Arrhenius dependence, whereas with ethanol there was no straightforward trend, and temperature compensation prevails. The atypical behavior found for ethanol was addressed in terms of its main electrocatalytic poisons: adsorbed CO and acetate. The absence of oscillations during dimethyl ether electro-oxidation was attributed to its weak interaction with the catalyst surface.<br>

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“…49 However, CO adsorbs more strongly at lower temperature. 50 The contradictory increase in mass transfer resistance indicates that the CO adsorption resistance is more dominant than the diffusion resistance over this temperature range.…”

Section: Effects Of Catalytic Loading-mentioning

confidence: 99%

Analysis of an Electrochemical Filter for Removing Carbon Monoxide from Reformate Hydrogen

Balasubramanian

Weidner

2015

J. Electrochem. Soc.

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We studied the operation of a twin-cell electrochemical filter for removing carbon monoxide (CO) from reformate hydrogen by periodically adsorbing and then electrochemically oxidizing CO on the electrode. During the adsorption step, we studied the effects of feed CO concentration, flow rate, electrode catalyst loading, type of feeder gas, and temperature on CO breakthrough. We then applied a fixed bed adsorber model to show that the breakthrough time could be accurately correlated to the adsorption-step operating parameters. Since the oxidation step was found to be much faster than that for CO breakthrough, adsorption time should dictate switching time. This insight was used to predict steady-state filter performance, and the prediction was validated for an electrochemical filter operated with CO contaminated hydrogen to decrease the CO concentration from 10,000 to 10 ppm. The model was also used to explore the employability of an electrochemical filter over a range of operating conditions by considering the comparative electrode area of a filter with that of a fuel cell. Proton exchange membrane fuel cells (PEMFC) efficiently convert chemical energy in hydrogen (H 2 ) to electrical energy. However, the low volumetric energy density of H 2 makes the fuel storage and transport cumbersome. Alternatively, H 2 can be generated at the point-ofuse from hydrocarbons via catalytic steam reforming.1 The reformate gas has carbon monoxide (CO) concentrations as high as 10,000 ppm, 2 whereas the platinum (Pt) anode, typically used in PEMFC, is susceptible to poisoning at concentrations as low as 10 ppm.3-4 In water-gas shift catalysis, typically used for removing CO from H 2 , improving the selectivity of oxidation of CO over H 2 faces thermodynamic limitations below a CO concentration of 1,000 ppm.5 Mitigation strategies such as operating fuel cells at elevated temperatures, 6 air-bleeding, [7][8] anode alloying 9-11 and in situ potential pulsing 4,12-13 have been explored to minimize the impact of CO poisoning. But the tolerance level of PEMFC has been improved only to a CO concentration of 100 ppm. 9,[14][15][16][17][18][19][20] In general, CO contamination in H 2 is handled by employment of CO removal techniques such as pressure swing adsorption (PSA), [21][22] or membrane separation, 23 or conversion of CO into methane in catalytic methanation [24][25][26] or carbon dioxide (CO 2 ) in preferential oxidation (PrOx) with air bleed. [7][8]14,[27][28][29][30][31][32][33][34][35][36][37][38][39] However, the consequent increase in cost due to fuel loss, 7 power loss, 40 components and space requirements 41 hampers the utilization of aforementioned techniques for commercially viable systems, especially in portable power applications. Balasubramanian et al. proposed an electrochemical filtering technique in which CO in reformate is concentrated by preferentially adsorbing on an electrocatalyst bed. Instead of purging as done in PSA, the adsorbed CO is electrochemically oxidized to CO 2 .42 Also, the ambient-pressure operation...

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Temperature effects on CO adsorption/desorption at Pt film electrodes: an electrochemical in situ infrared spectroscopic study

Cited by 24 publications

References 31 publications

Powder diffraction in studies of nanocrystal surfaces: chemisorption on Pt

Powder diffraction in studies of nanocrystal surfaces: chemisorption on Pt

Direct Liquid Fuel Cells – The Influence of Temperature and Dynamic Instabilities

Analysis of an Electrochemical Filter for Removing Carbon Monoxide from Reformate Hydrogen

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