Anion co-adsorption

The integrated charge would correspond to 0.7 0.1 Cu monolayers. Thus, either a less closely packed Cu layer or an anion co-adsorption that can both lead to a Moire superstructure are probed in the solution investigated [Al2Cl7] is the predominant anion. At h-200 mV vs. Cu/CW the superstructure disappears and a completely closed Cu monolayer is observed, with a charge corresponding to 1.0 0.1 Cu monolayers. 

However, the most interesting feature of anion co-adsorption depicted in Figure 10 is the increase in the adsorption of a neutral solute in the presence of co-adsorbed anions when is used as the independent electrical variable. This is a very peculiar property, because the co-adsorption always leads to a decrease in the adsorption of each co-adsorbed species. Note that although this phenomenon was observed long ago, no satisfactory explanation had been given by the previous adsorption theories. In contrast, the present model gives predictions that are in complete agreement with the experimental... 

Copper electrodeposition on Au(111) Copper is an interesting metal and has been widely investigated in electrodeposition studies from aqueous solutions. There are numerous publications in the literature on this topic. Furthermore, technical processes to produce Cu interconnects on microchips have been established in aqueous solutions. In general, the quality of the deposits is strongly influenced by the bath composition. On the nanometer scale, one finds different superstmctures in the underpotential deposition regime if different counter-ions are used in the solutions. A co-adsorption between the metal atoms and the anions has been reported. In the underpotential regime, before the bulk deposition begins, one Cu mono-layer forms on Au(lll) [66]. 

Angelucci CA, Nart FC, Heirero E, Feliu JM. 2007a. Anion re-adsorption and displacement at platinum single crystal electrodes in CO-containing solutions. Electrochem Commun 9 1113-1119. 

It must be acknowledged, however, that the determination of the number of the different surface species which are formed during an adsorption process is often more difficult by means of calorimetry than by spectroscopic techniques. This may be phrased differently by saying that the resolution of spectra is usually better than the resolution of thermograms. Progress in data correction and analysis should probably improve the calorimetric results in that respect. The complex interactions with surface cations, anions, and defects which occur when carbon monoxide contacts nickel oxide at room temperature are thus revealed by the modifications of the infrared spectrum of the sample (75) but not by the differential heats of the CO-adsorption (76). Any modification of the nickel-oxide surface which alters its defect structure produces, however, a change of its energy spectrum with respect to carbon monoxide that is more clearly shown by heat-flow calorimetry (77) than by IR spectroscopy. 

The electrosorption valency usually increases as the underpotential decreases to approach the ionic charge (total discharge of the cation) close to the Nernst potential, for instance in the case of lead and thallium upd on silver [114]. However, the co-adsorption of anions may contribute to the observed apparent electrosorption valence, as rotating ring disc electrode (RDE) experiments have shown [113]. 

Polivka had investigated the co-adsorption of carotenoid and pheophytin (111) on the surface of TiC>2 electrode and the photophysical properties of pheophytin in this film. The results demonstrated that the fluorescence of 111 was efficiently reductive quenched by carotenoid in this co-assembled film, suggesting similar mechanisms to that in the natural photosynthetic systems. The radical anion of 111 formed during the electron transfer recovered to the neutral state quickly before the charge recombination between carotenoid cation and pheophytin anion took place. It is suspected that the electron injection from the pheophytin anion to the conduction band of Ti02 was responsible for this quick recovery. This result indicated that such a self-assembling strategy may be also considered for novel DSSC constructions [108]. 

Table VII presents a summary of calorimetric measurements of the differential heat of adsorption of ammonia, water, and carbon dioxide on the sodium form of ZSM-5 zeolite. Ammonia adsorption at 416 K (97.147) shows that NaZSM-5 zeolite is weakly acidic, whereas CO adsorption (147) indicates that in addition there are some weak basic sites. It should be noted that of the two samples studied with ammonia adsorption one was 70% H exchanged and the sodium content of the other was not given. Water adsorption on NaZSM-5 displayed unusual behavior, with a steep increase in the differential heat of adsorption at high surface coverages (166). An adsorption mechanism was proposed to explain these findings in which adsorption occurs first on the hydrophilic sites, consisting of sodium cations and framework anions where water molecules are bound by dipole-field interactions. Further adsorption takes place near these sites through weak interaction with zeolite surfaces, and when the number of water molecules close to these sites exceeds a certain value, they tend to reorient by forming clathrate-like struc-...

Direct measurements of adsorption densities of the labelled anions, performed in dilute aqueous solutions of the corresponding acids, enabled to establish the following order of preferential adsorption H2PO4 > HSO4 > Cl" > CIO4. This sequence, based upon the results of co-adsorption experiments, refers to equilibrium adsorption conditions in the range of pH lower than the PZC of Ti02-... 

Typically, the rate of simple (outer-sphere) electron-transfer reactions, such as Fe(CN)e + e - Fe(CN)6 , is much slower at titanium dioxide than at metallic electrodes . This is consistent both with the flat shape of the voltammetric peaks in Fig. 2 and their shift to more negative potentials with increasing the sweep rate. The kinetics of the cathodic reactions at Ti02 appear to be markedly affected by the co-adsorption of some anions from the supporting electrolyte. The phosphate ions are not unique to cause such effects arsenate, fluoride and certainly other anions are expected to act in a similar way. 

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