Arsenic Deposition onto a Gold Substrate

Abstract

Arsenic deposition onto a gold substrate was studied as a function of pH, deposition potential, and time. Deposition of less than three monolayers was observed. The rate of deposition decreased as the thickness of the deposit increased. A set of partial reactions leading to arsenic deposition was proposed. The kinetics of deposition at the most cathodic potentials corresponds to a high-field deposition mechanism.Arsenic is a semimetal which has the ability to reduce the grain size in gold electrodeposits (1-3). However, the mechanism by which this occurs is not well understood. An examination of the deposition of arsenic itself upon a gold substrate may serve to help explain the process by which this occurs.Electrodeposited arsenic is usually amorphous (4-6) but becomes crystalline when heated to temperatures greater than 250~ (4, 5). Tammann and Warrentrup (5) claimed that electrodeposited arsenic has an electrical resistance 10 ~3 times greater than crystalline arsenic. Wranglen (7) has also found that electrodeposited arsenic films have a large electrical resistance. Piontelli and Poli (8), however, attributed the behavior of arsenic during electrodeposition to a large overvoltage at the surface. This large resistance, whether due to bulk resistance or overvoltage, prevents arsenic from plating indefinitely upon substrates. It reaches a limiting thickness in most cases. When plated potentiostatically, as has been done in this paper, the deposition current gradually drops. When plated galvanostatically, the current efficiency drops continuously. Kochegarov and Lomakina (4) have noted that after being annealed, arsenic films can be plated upon to form thicker arsenic layers. This indicates that the self-limiting nature of arsenic deposition is connected to the amorphous structure of the electrodeposit.The deposition of arsenic upon gold was studied by using cyclic voltammetry and potentiostatic plating. Cyclic voltammetry was done over a range of pH values in order to determine the potential ranges over which arsenic deposition occurred. The cyclic voltammetry also revealed that there were three cathodic reactions that were taking place before arsenic deposited on the gold substrate. The potentiostatic plating was performed as a function of potential and time in order to determine the amount of arsenic deposited and the type of kinetics that the process exhibited.

Development of a Method for Total Inorganic Arsenic Analysis Using Anodic Stripping Voltammetry and a Au-Coated, Diamond Thin-Film Electrode

“…Therefore, additional Au deposition can only occur at new sites on the surface. 64 Effect of Au Coverage on the As Stripping Peak Current. The effect of the Au coverage on the As stripping peak current was investigated.…”

A study on the evolution of arsine during arsenic electrodeposition: The influence of ammonium citrate

“…Electrochemical deposition should be a promising and convenient method to remove the arsenic from aqueous solution and realize the recycling usage of leaching solution. A lot of efforts [2][3][4][5][6][7][8] have been done to investigate the electrochemical behavior of arsenic in aqueous solution, as well as the deposition rate and current efficiency of elementary As. It has been found that toxic gas arsine will be produced as by-product during the electrodeposition of elementary arsenic [9,10], which has become a very important issue for the study of arsenic deposition.…”

The electrochemical reaction mechanism of arsenic deposition on an Au(111) electrode

“…Relatively good detection capabilities were achieved in the above ASV methods at gold electrodes. However, the mechanism of the electrochemical reaction occurring during the deposition and stripping of arsenic deposited on gold electrodes was seldom studied [39]. Therefore, the study of electrochemical reduction mechanism of arsenic species is of both theoretical and practical significance.…”