Second harmonic generation studies of polycrystalline platinum electrodes in sulfuric and perchloric acid solutions

Campbell, Deborah J.; Corn, Robert M.

doi:10.1021/j100331a050

Cited by 37 publications

(21 citation statements)

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“…This increase is similarly also observed by the same group on polycrystalline platinum electrodes. 21,22 They also report a rotational anisotropy of the second harmonic ͑SH͒ signal for ps and sp polarization in accordance with the expected C 3v symmetry of this surface. Interestingly, the CO-covered Pt͑111͒ electrode featured an additional isotropic contribution for ps polarization at variance with the C 3v symmetry.…”

Section: Introductionsupporting

confidence: 64%

Potential-dependence of CO adlayer structures on Pt(111) electrodes in acid solution: Evidence for a site selective charge transfer

Akemann¹,

Friedrich²,

Stimming³

2000

The Journal of Chemical Physics

100

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Simultaneous in situ monitoring of surface and gas species and surface properties by modulation excitation polarization-modulation infrared reflection-absorption spectroscopy: CO oxidation over Pt filmThe oxidation of carbon monoxide on a Pt͑111͒ electrode surface is studied under transient and stationary reaction conditions in a 0.1 M HClO 4 aqueous solution as a function of the applied electrode potential. The optical response is investigated by optical second harmonic generation ͑SHG͒ at 280 nm and infrared absorption spectroscopy ͑IRAS͒ starting at low potentials where the electrode is not reactive ͓e.g., 0.1 V vs the reversible hydrogen electrode ͑RHE͔͒ towards more positive potentials where CO oxidation is initiated. For transient reaction conditions, in the absence of CO dissolved in solution, the oxidation starts at about 0.5 V vs. RHE and consists of a fast oxidation of about 10% of the adlayer and of a second reaction with slower kinetics involving the removal of the complete CO layer ͑overlayer stripping͒. Under steady-state conditions in CO-saturated solution the CO adlayer is stable up to 0.9 V vs RHE. At 0.63 V an overlayer phase transition is indicated by a 20% increase of the isotropic component of the second harmonic ͑SH͒ intensity ͑pp-polarization͒. The same potential region for this phase transition in the adlayer structure is derived from IRAS spectra after correcting for the effect of the thin layer electrolyte in IRAS measurements. The disappearance of hollow sites, the appearance of bridge sites, as well as an increased occupation of on-top sites at 0.63 V is interpreted as corresponding to the adlayer phase transition. The observations are consistent with a transition from the c(2ϫ2) to the (ͱ19ϫͱ19) adlayer structure of CO. The high sensitivity of SHG with regard to structural phase transitions of the CO adlayer is explained by distinct charge transfer contributions to the second-order surface susceptibility at different coordination sites.

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Section: Introductionsupporting

confidence: 64%

Potential-dependence of CO adlayer structures on Pt(111) electrodes in acid solution: Evidence for a site selective charge transfer

Akemann¹,

Friedrich²,

Stimming³

2000

The Journal of Chemical Physics

100

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“…The surface adsorption of sulfate anions on polycrystalline Pt electrode have been previously studied with Fourier transform infrared (FTIR), , sum frequency generation (SFG), or second harmonic generation (SHG) , spectroscopy in the double layer region at relatively higher concentrations (usually introduced as 0.5 M H 2 SO 4 ). The use of high concentration sulfate ions was probably due to the relatively weak signals of surface sulfate under the testing conditions.…”

Section: Resultsmentioning

confidence: 99%

On-Chip in Situ Monitoring of Competitive Interfacial Anionic Chemisorption as a Descriptor for Oxygen Reduction Kinetics

et al. 2018

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The development of future sustainable energy technologies relies critically on our understanding of electrocatalytic reactions occurring at the electrode–electrolyte interfaces, and the identification of key reaction promoters and inhibitors. Here we present a systematic in situ nanoelectronic measurement of anionic surface adsorptions (sulfates, halides, and cyanides) on ultrathin platinum nanowires during active electrochemical processes, probing their competitive adsorption behavior with oxygenated species and correlating them to the electrokinetics of the oxygen reduction reaction (ORR). The competitive anionic adsorption features obtained from our studies provide fundamental insight into the surface poisoning of Pt-catalyzed ORR kinetics by various anionic species. Particularly, the unique nanoelectronic approach enables highly sensitive characterization of anionic adsorption and opens an efficient pathway to address the practical poisoning issue (at trace level contaminations) from a fundamental perspective. Through the identified nanoelectronic indicators, we further demonstrate that rationally designed competitive anionic adsorption may provide improved poisoning resistance, leading to performance (activity and lifetime) enhancement of energy conversion devices.

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“…According to the pseudophase separation model for micelles,128 the Gibbs-Duhem equation can be expressed as l>idu,m = 0 (1) where n¡ and uim are the molar number and the chemical potential of the z'th component in the micelle phase, respectively. From the equilibrium condition we have «,• d In a¡ = 0…”

Section: Resultsmentioning

confidence: 99%

“…A number of research groups are currently exploring the use of the nonlinear optical process of second harmonic generation (SHG) as an in situ probe of chemisorption and structure at metal electrodes. [1][2][3][4][5][6][7][8][9] The sensitivity of SHG to the interfacial region…”

Section: Introductionmentioning

confidence: 99%

Physicochemical properties of aqueous mixtures of tetrabutylammonium bromide and anionic surfactants. 3. Effects of surfactant chain length and salinity

Yu¹,

Zhang²,

Xu³

et al. 1990

J. Phys. Chem.

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The solution behaviors of equimolar mixtures of tetrabutylammonium bromide and sodium alkyl sulfate (B,NC,,S, n = 8-18) have been studied. The surface tension measurement shows that the ratios of tetrabutylammonium to alkyl sulfate both in micelles at the cmc and in surface adsorption layers obtained by using the Gibbs-Duhem equation are less than unity and decrease with increasing surfactant chain length. The Krafft point of B4NC$ in 0.2 M NaBr decreases with increasing surfactant concentration and is considerably lower than that of the corresponding alkyl sulfate salt without tetrabutylammonium. The cloud point phenomenon is observed in all surfactant systems. The cloud point increases with increasing surfactant chain length except for n > 16 below 56 mM surfactant concentration. This behavior is interpreted in terms of the variation of tetrabutylammonium content in the micelles by using our previously proposed model for the cloud point phenomenon. The addition of NaBr increases the cloud point initially, passing through a maximum, and then decreases again. The possible causes for the phenomenon of a maximum in the cloud point are discussed. B4NC18S may form a stable homogeneous micellar solution at room temperature, the micellar size of which increases with temperature in the presence of a comparable amount of NaBr to the surfactant or in the absence of NaBr and decreases in excess NaBr. An Arrhenius type of equation cannot be used in calculating the activation energy of viscous flow of micellar solutions without considering the effect of micellar size change with temperature.

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Second harmonic generation studies of polycrystalline platinum electrodes in sulfuric and perchloric acid solutions

Cited by 37 publications

References 0 publications

Potential-dependence of CO adlayer structures on Pt(111) electrodes in acid solution: Evidence for a site selective charge transfer

Potential-dependence of CO adlayer structures on Pt(111) electrodes in acid solution: Evidence for a site selective charge transfer

On-Chip in Situ Monitoring of Competitive Interfacial Anionic Chemisorption as a Descriptor for Oxygen Reduction Kinetics

Physicochemical properties of aqueous mixtures of tetrabutylammonium bromide and anionic surfactants. 3. Effects of surfactant chain length and salinity

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