A first principles investigation of electron transfer between Fe(II) and U(VI) on insulating Al- vs. semiconducting Fe-oxide surfaces via the proximity effect

2017 ◽  
Vol 197 ◽  
pp. 305-322 ◽  
Author(s):  
S.D. Taylor ◽  
M.C. Marcano ◽  
U. Becker
Keyword(s):  
Electron Transfer ◽  
First Principles ◽  
Proximity Effect ◽  
Oxide Surfaces ◽  
Fe Oxide

scholarly journals Stability and morphology of cerium oxide surfaces in an oxidizing environment: A first-principles investigation

2009 ◽  
Vol 131 (10) ◽  
pp. 104701 ◽  
Author(s):  
Marco Fronzi ◽  
Aloysius Soon ◽  
Bernard Delley ◽  
Enrico Traversa ◽  
Catherine Stampfl
Keyword(s):  
Cerium Oxide ◽  
First Principles ◽  
Oxide Surfaces

scholarly journals Energetics of Mg and B adsorption on polar zinc oxide surfaces from first principles

2008 ◽  
Vol 77 (3) ◽  
Author(s):  
Kazume Nishidate ◽  
Masahito Yoshizawa ◽  
Masayuki Hasegawa
Keyword(s):  
Zinc Oxide ◽  
First Principles ◽  
Oxide Surfaces

scholarly journals On the Mechanism of Carbon Dioxide Reduction on Sn-Based Electrodes: Insights into the Role of Oxide Surfaces

Catalysts ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 636 ◽  
Author(s):  
Giane B. Damas ◽  
Caetano R. Miranda ◽  
Ricardo Sgarbi ◽  
James M. Portela ◽  
Mariana R. Camilo ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Electron Transfer ◽  
Formic Acid ◽  
Oxide Layer ◽  
Co2 Reduction ◽  
Carbon Dioxide Reduction ◽  
Oxide Surfaces ◽  
In Situ Conditions

The electrochemical reduction of carbon dioxide into carbon monoxide, hydrocarbons and formic acid has offered an interesting alternative for a sustainable energy scenario. In this context, Sn-based electrodes have attracted a great deal of attention because they present low price and toxicity, as well as high faradaic efficiency (FE) for formic acid (or formate) production at relatively low overpotentials. In this work, we investigate the role of tin oxide surfaces on Sn-based electrodes for carbon dioxide reduction into formate by means of experimental and theoretical methods. Cyclic voltammetry measurements of Sn-based electrodes, with different initial degree of oxidation, result in similar onset potentials for the CO2 reduction to formate, ca. −0.8 to −0.9 V vs. reversible hydrogen electrode (RHE), with faradaic efficiencies of about 90–92% at −1.25 V (vs. RHE). These results indicate that under in-situ conditions, the electrode surfaces might converge to very similar structures, with partially reduced or metastable Sn oxides, which serve as active sites for the CO2 reduction. The high faradaic efficiencies of the Sn electrodes brought by the etching/air exposition procedure is ascribed to the formation of a Sn oxide layer with optimized thickness, which is persistent under in situ conditions. Such oxide layer enables the CO2 “activation”, also favoring the electron transfer during the CO2 reduction reaction due to its better electric conductivity. In order to elucidate the reaction mechanism, we have performed density functional theory calculations on different slab models starting from the bulk SnO and Sn6O4(OH)4 compounds with focus on the formation of -OH groups at the water-oxide interface. We have found that the insertion of CO2 into the Sn-OH bond is thermodynamically favorable, leading to the stabilization of the tin-carbonate species, which is subsequently reduced to produce formic acid through a proton-coupled electron transfer process. The calculated potential for CO2 reduction (E = −1.09 V vs. RHE) displays good agreement with the experimental findings and, therefore, support the CO2 insertion onto Sn-oxide as a plausible mechanism for the CO2 reduction in the potential domain where metastable oxides are still present on the Sn surface. These results not only rationalize a number of literature divergent reports but also provide a guideline for the design of efficient CO2 reduction electrocatalysts.

First principles study on the adsorption of Au dimer on metal-oxide surfaces: The implications for Au growing

2017 ◽  
Vol 426 ◽  
pp. 554-561 ◽  
Author(s):  
Shan Dong ◽  
Yanxing Zhang ◽  
Xilin Zhang ◽  
Jianjun Mao ◽  
Zongxian Yang
Keyword(s):  
Metal Oxide ◽  
First Principles ◽  
Oxide Surfaces ◽  
Metal Oxide Surfaces ◽  
First Principles Study

Interactive effects of iron oxides and organic matter on charge properties of red soils in Thailand

Soil Research ◽  
2013 ◽  
Vol 51 (3) ◽  
pp. 222 ◽  
Author(s):  
D. Ketrot ◽  
A. Suddhiprakarn ◽  
I. Kheoruenromne ◽  
B. Singh
Keyword(s):  
Organic Matter ◽  
Humic Acid ◽  
Clay Fraction ◽  
Interactive Effects ◽  
Soil Conditions ◽  
Oxide Surfaces ◽  
Fe Oxide ◽  
Fe Oxides ◽  
Red Soils ◽  
Variable Surface

Iron (Fe) oxides and organic matter (OM) play important roles in maintaining the fertility of highly weathered soils. The main objective of this study was to investigate the interactive effects of variable surface charge minerals, particularly Fe oxide minerals, and OM on the charge properties of red soils from Thailand. We also evaluated the effect of the 5 m NaOH procedure, used to concentrate Fe oxides from soils, on the charge characteristics of Fe oxide concentrates. Fourteen clay fractions (untreated and OM-free clay fractions), and Fe oxide concentrates of these clays, were used in the study. Cation exchange capacity (CEC) and electrophoretic mobility (EM) were measured for the soil clays, artificial mixtures, and goethite adsorbed with humic acid (HA) and phosphate (P). Kaolinite and Fe oxides (predominantly a mixture of hematite and goethite) were the main minerals in the clay fraction. Results indicated that OM or metal–OM complexes may have blocked or neutralised negatively charged sites on clay minerals. After OM removal these sites became accessible, inducing an increase in CEC and shifting the EM values towards more negative values and the isoelectric point (IEP) towards lower pH for many samples. The CEC values of Fe oxide concentrates prepared by 5 m NaOH treatment were overestimated and their EM and IEP shifted towards more negative values. It is possible that the amorphous phase from clay dissolution was still present in the Fe oxide concentrates, or the adsorption of silicate ions modified the surfaces of Fe oxides concentrates. Humic acid and P adsorbed on Fe oxide surfaces caused the IEP to shift to lower values. In natural soil conditions, a variety of anions can be adsorbed on Fe oxide surfaces, which might lead to higher values of negative charge and lower IEP than observed for pure synthetic minerals.

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