Calorimetric Effects Accompanying Ion Adsorption at the Charged Metal Oxide/Electrolyte Interfaces:  Effects of Oxide Surface Energetic Heterogeneity

Langmuir ◽  
1998 ◽  
Vol 14 (18) ◽  
pp. 5210-5225 ◽  
Author(s):  
W. Rudziński ◽  
R. Charmas ◽  
W. Piasecki ◽  
F. Thomas ◽  
F. Villieras ◽  
...  
Keyword(s):  
Metal Oxide ◽  
Oxide Surface ◽  
Ion Adsorption ◽  
Energetic Heterogeneity ◽  
Oxide Electrolyte

scholarly journals On the Nature of the Energetic Surface Heterogeneity in Ion Adsorption at an Electrolyte/Oxide Interface. Theoretical Studies of the Correlations between Binding-to-Surface Energies of Various Surface Complexes

1996 ◽  
Vol 14 (1) ◽  
pp. 25-38 ◽  
Author(s):  
Wladyslaw Rudziński ◽  
Robert Charmas ◽  
Wojciech Piasecki
Keyword(s):  
Surface Heterogeneity ◽  
Ion Adsorption ◽  
Surface Oxygen ◽  
Oxide Interface ◽  
Surface Complexes ◽  
Surface Energies ◽  
Outermost Surface ◽  
Energetic Heterogeneity ◽  
Total Lack ◽  
Oxide Electrolyte

When a metal oxide is brought into contact with an electrolyte, the outermost surface oxygens adsorb one or two protons, a cation or an aggregate composed of two protons and an anion. In this way, various surface complexes are formed. The actual surfaces are, as a rule, geometrically distorted. This causes a variation of the binding-to-surface energy from one surface oxygen to another for each of these complexes. This energetic heterogeneity of the actual oxide surfaces strongly affects the adsorption of ions within the electrical double layer formed at the oxide/electrolyte interface. The way in which the surface heterogeneity affects the adsorption of ions depends on the correlations between the binding-to-surface energies of the various surface complexes. To date, two extreme models have been considered by us; one assuming the existence of very high correlations, and the other one assuming a total lack of correlation between binding-to-surface energies in going from one surface oxygen to another. This paper presents a theoretical study of ion adsorption based on the assumption of a partial correlation between the binding-to-surface energies.

scholarly journals Rhodium Oxide Surface-Loaded Gas Sensors

Nanomaterials ◽  
2018 ◽  
Vol 8 (11) ◽  
pp. 892 ◽  
Author(s):  
Anna Staerz ◽  
Inci Boehme ◽  
David Degler ◽  
Mounib Bahri ◽  
Dmitry Doronkin ◽  
...  
Keyword(s):  
Metal Oxide ◽  
Noble Metal ◽  
Noble Metals ◽  
Metal Cluster ◽  
Empirical Work ◽  
Oxide Surface ◽  
Metallic State ◽  
X Ray ◽  
Rhodium Clusters ◽  
Sensing Characteristics

In order to increase their stability and tune-sensing characteristics, metal oxides are often surface-loaded with noble metals. Although a great deal of empirical work shows that surface-loading with noble metals drastically changes sensing characteristics, little information exists on the mechanism. Here, a systematic study of sensors based on rhodium-loaded WO3, SnO2, and In2O3—examined using X-ray diffraction, high-resolution scanning transmission electron microscopy, direct current (DC) resistance measurements, operando diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, and operando X-ray absorption spectroscopy—is presented. Under normal sensing conditions, the rhodium clusters were oxidized. Significant evidence is provided that, in this case, the sensing is dominated by a Fermi-level pinning mechanism, i.e., the reaction with the target gas takes place on the noble-metal cluster, changing its oxidation state. As a result, the heterojunction between the oxidized rhodium clusters and the base metal oxide was altered and a change in the resistance was detected. Through measurements done in low-oxygen background, it was possible to induce a mechanism switch by reducing the clusters to their metallic state. At this point, there was a significant drop in the overall resistance, and the reaction between the target gas and the base material was again visible. For decades, noble metal loading was used to change the characteristics of metal-oxide-based sensors. The study presented here is an attempt to clarify the mechanism responsible for the change. Generalities are shown between the sensing mechanisms of different supporting materials loaded with rhodium, and sample-specific aspects that must be considered are identified.

scholarly journals Effects of metal oxide surface doping with phosphonic acid monolayers on alcohol dehydration activity and selectivity

2019 ◽  
Vol 571 ◽  
pp. 102-106 ◽  
Author(s):  
Lucas D. Ellis ◽  
Jordi Ballesteros-Soberanas ◽  
Daniel K. Schwartz ◽  
J. Will Medlin
Keyword(s):  
Metal Oxide ◽  
Phosphonic Acid ◽  
Oxide Surface ◽  
Alcohol Dehydration ◽  
Metal Oxide Surface ◽  
Surface Doping
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