scholarly journals Trivalent ion overcharging on electrified graphene

2022 ◽  
Author(s):  
Amanda J. Carr ◽  
Sang Soo Lee ◽  
Ahmet Uysal
Keyword(s):  
Co Adsorption ◽  
Aqueous System ◽  
Ion Distribution ◽  
X Ray ◽  
Molecular Scale ◽  
Graphene Interface ◽  
Controlled Potential ◽  
Excess Positive Charge ◽  
Electron Density Profiles ◽  
Controlled Adsorption

Abstract The structure of the electrical double layer (EDL) formed near graphene in aqueous environments strongly impacts its performance for a plethora of applications, including capacitive deionization. In particular, adsorption and organization of multivalent counterions near the graphene interface can promote nonclassical behaviors of EDL including overcharging followed by co-ion adsorption. In this paper, we characterize the EDL formed near an electrified graphene interface in dilute aqueous YCl3 solution using in situ high resolution x-ray reflectivity (also known as crystal truncation rod (CTR)) and resonant anomalous x-ray reflectivity (RAXR). These interface-specific techniques reveal the electron density profiles with molecular-scale resolution. We find that yttrium ions (Y3+) readily adsorb to the negatively charged graphene surface to form an extended ion profile. This ion distribution resembles a classical diffuse layer but with a significantly high ion coverage, i.e., 1 Y3+ per 11.4 ± 1.6 Å2, compared to the value calculated from the capacitance measured by cyclic voltammetry (1 Y3+ per ~240 Å2). Such overcharging can be explained by co-adsorption of chloride that effectively screens the excess positive charge. The adsorbed Y3+ profile also shows a molecular-scale gap (≥5 Å) from the top graphene surfaces, which is attributed to the presence of intervening water molecules between the adsorbents and adsorbates as well as the lack of inner-sphere surface complexation on chemically inert graphene. We also demonstrate controlled adsorption by varying the applied potential and reveal consistent Y3+ ion position with respect to the surface and increasing cation coverage with increasing the magnitude of the negative potential. This is the first experimental description of a model graphene-aqueous system with controlled potential and provides important insights into the application of graphene-based systems for enhanced and selective ion separations.

X-ray Microanalysis of Ion Distribution inAbutilonNectary Hairs

1986 ◽  
Vol 37 (7) ◽  
pp. 940-946 ◽  
Author(s):  
A. W. ROBARDS ◽  
K. OATES
Keyword(s):  
Ion Distribution ◽  
X Ray

scholarly journals In-situ/operando X-ray absorption spectroscopic investigation of the electrode/electrolyte interface on the molecular scale

2020 ◽  
Vol 702 ◽  
pp. 121720
Author(s):  
Li Cheng Kao ◽  
Xuefei Feng ◽  
Yang Ha ◽  
Feipeng Yang ◽  
Yi-Sheng Liu ◽  
...  
Keyword(s):  
Spectroscopic Investigation ◽  
X Ray ◽  
Electrolyte Interface ◽  
Molecular Scale ◽  
X Ray Absorption

scholarly journals Case study of the mesospheric and lower thermospheric effects of solar X-ray flares: coupled ion-neutral modelling and comparison with EISCAT and riometer measurements

2008 ◽  
Vol 26 (8) ◽  
pp. 2311-2321 ◽  
Author(s):  
C.-F. Enell ◽  
P. T. Verronen ◽  
M. J. Beharrell ◽  
J. P. Vierinen ◽  
A. Kero ◽  
...  
Keyword(s):  
Solar Proton ◽  
Spectral Irradiance ◽  
Cluster Ions ◽  
Ion Chemistry ◽  
Density Profiles ◽  
X Ray ◽  
Noise Absorption ◽  
D Region ◽  
Electron Density Profiles ◽  
Cosmic Noise

Abstract. Two case studies of upper mesospheric and lower thermospheric (UMLT) high-latitude effects of solar X-ray flares are presented. Sodankylä Ion-neutral Chemistry Model (SIC) electron density profiles agree with D-region EISCAT and riometer observations, provided that the profiles of the most variable ionisable component, nitric oxide, are adjusted to compensate for NOx production during preceding geomagnetically active periods. For the M6-class flare of 27 April 2006, following a quiet period, the agreement with cosmic noise absorption observed by the Sodankylä riometers was within reasonable limits without adjustment of the [NO] profile. For the major (X17-class) event of 28 October 2003, following high auroral activity and solar proton events, the NO concentration had to be increased up to on the order of 108 cm−3 at the D-region minimum. Thus [NO] can in principle be measured by combining SIC with observations, if the solar spectral irradiance and particle precipitation are adequately known. As the two case events were short and modelled for high latitudes, the resulting neutral chemical changes are insignificant. However, changes in the model ion chemistry occur, including enhancements of water cluster ions.

scholarly journals Kaolinite-Magnesite or Kaolinite–Talc-Based Ceramics. Part II: Microstructure and the Final Properties Related Sintered Tapes

Minerals ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1080
Author(s):  
Aghiles Hammas ◽  
Gisèle Lecomte-Nana ◽  
Imane Daou ◽  
Nicolas Tessier-Doyen ◽  
Claire Peyratout ◽  
...  
Keyword(s):  
Flexural Strength ◽  
Ceramic Industry ◽  
Raw Materials ◽  
Tape Casting ◽  
Casting Process ◽  
Aqueous System ◽  
Mechanical And Thermal Properties ◽  
X Ray Diffraction ◽  
X Ray ◽  
Kaolinitic Clay

In recent decades, talc and kaolinite have been widely used as raw materials for the ceramic industry. In this study, the final characteristics of kaolinitic clay mixed with 6 mass% of magnesite obtained in our previous work were compared with those obtained with mixtures of kaolin (kaolin BIP) and talc (as the source of magnesium oxide). However, different amounts of talc in the kaolin powder were studied, namely 10, 30, and 50 mass% of added talc (with respect to kaolin + talc). The tape casting process was used during this work in order to manufacture the green tapes in an aqueous system with 0.2 mass% of dispersant. Subsequently, the green tapes were heated to 1000 and 1100 °C with a dwelling time of 12 min. The green and sintering tapes were characterized using the following techniques: DTA/TG, X-ray diffraction, porosity, and flexural strength analyses. The results obtained from our previous work indicate that the specimen with 6 mass% of MgCO3 sintered at 1200 °C for 3 h exhibited the best performances, with high flexural strength and weak porosity value—117 MPa and 27%—respectively. As results from this study, the optimal mechanical and thermal properties of sintering tapes were obtained for the specimen with 10 mass% of added talc sintered at 1100 °C. Indeed, this specimen exhibited 50 MPa and 43% of stress to rupture and apparent porosity, respectively.

Molecular-scale friction at a water–graphene interface and its relationship with slip behavior

2020 ◽  
Vol 32 (9) ◽  
pp. 092001
Author(s):  
Linyang Zhang ◽  
Keliu Wu ◽  
Zhangxin Chen ◽  
Jing Li ◽  
Xinran Yu ◽  
...  
Keyword(s):  
Molecular Scale ◽  
Graphene Interface

scholarly journals Factors Influencing the Surface Functionalization of Citrate Stabilized Gold Nanoparticles with Cysteamine, 3-Mercaptopropionic Acid or l-Selenocystine for Sensor Applications

Chemosensors ◽  
2020 ◽  
Vol 8 (3) ◽  
pp. 80
Author(s):  
Georgia I. Sakellari ◽  
Nicole Hondow ◽  
Philip H.E. Gardiner
Keyword(s):  
Gold Nanoparticles ◽  
Co Adsorption ◽  
Limiting Factor ◽  
Experimental Conditions ◽  
Mercaptopropionic Acid ◽  
X Ray ◽  
Sensor Applications ◽  
Factors Influencing ◽  
Electrostatic Repulsions ◽  
Functionalized Aunps

Thiols and selenides bind to the surface of gold nanoparticles (AuNPs) and thus provide suitable platforms for the fabrication of sensors. However, the co-existence of adsorbed citrate on the surface of the nanoparticles can influence their functionalization behavior and potentially their sensing performance measured by the extent of particle aggregation. In this study, the functionalization of purchased (7.3 ± 1.2 nm) and in-house prepared AuNPs (13.8 ± 1.2 nm), under the same experimental conditions with either cysteamine (Cys), 3-mercaptopropionic acid (3-MPA), or l-selenocystine (SeCyst) was investigated. 1H-NMR measurements showed distinct citrate signatures on the in-house synthesized citrate-stabilized AuNPs, while no citrate signals were detected on the purchased AuNPs other than evidence of the presence of α-ketoglutaric acid. Carboxylate-containing species attributed to either citrate or α-ketoglutaric acid were identified in all functionalized AuNPs. ATR-FTIR spectroscopy confirmed the functionalization of AuNPs with Cys and 3-MPA, and energy dispersive X-ray (EDX) spectroscopy measurements suggested the formation of SeCyst functionalized AuNPs. Co-adsorption rather than displacement by the functionalizing agents and carboxylate-containing molecules was indicated, which for Cys and SeCyst functionalized AuNPs was also the aggregation limiting factor. In contrast, the behavior of 3-MPA functionalized AuNPs could be attributed to electrostatic repulsions between the functionalized groups.

scholarly journals Catalytic Behaviour of Flame-Made CuO-CeO2 Nanocatalysts in Efficient CO Oxidation

Catalysts ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 256 ◽  
Author(s):  
Feng Zhao ◽  
Shuangde Li ◽  
Xiaofeng Wu ◽  
Renliang Yue ◽  
Weiman Li ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Water Vapor ◽  
Co Oxidation ◽  
Photoelectron Spectroscopy ◽  
Co Adsorption ◽  
Synergistic Interaction ◽  
Flame Spray ◽  
Oxidation Activity ◽  
X Ray

CuO-CeO2 nanocatalysts with varying CuO contents (1, 5, 9, 14 and 17 wt %) were prepared by one-step flame spray pyrolysis (FSP) and applied to CO oxidation. The influences of CuO content on the as-prepared catalysts were systematically characterized by X-ray diffraction (XRD), N2 adsorption-desorption at −196 °C, field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and hydrogen-temperature programmed reduction (H2-TPR). A superior CO oxidation activity was observed for the 14 wt % CuO-CeO2 catalyst, with 90% CO conversion at 98 °C at space velocity (60,000 mL × g−1 × h−1), which was attributed to abundant surface defects (lattice distortion, Ce3+, and oxygen vacancies) and high reducibility supported by strong synergistic interaction. In addition, the catalyst also displayed excellent stability and resistance to water vapor. Significantly, in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS) showed that in the CO catalytic oxidation process, the strong synergistic interaction led readily to dehydroxylation and CO adsorption on Cu+ at low temperature. Furthermore, in the feed of water vapor, although there was an adverse effect on the access of CO adsorption, there was also a positive effect on the formation of fewer carbon intermediates. All these results showed the potential of highly active and water vapor-resistive CuO-CeO2 catalysts prepared by FSP.

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