Inhibiting corrosion ofn-GaAs by cetylpyridinium chloride for stabilised photoelectochemical cell

Abstract

The cationic surfactant cetylpyridinium chloride (CPC) provides photocorrosion inhibition to the GaAs surface when CPC is chemisorbed on the GaAs surface from aqueous acidic electrolytes at concentrations of CPC lower than its critical micelle concentration (CMC). In the presence of CPC, the anodic photogenerated current which is originally due to oxidising the n-GaAS electrode decreases, essentially, due to the adsorption of CPC on the n-GaAs surface. The presence of CPC in the electrolyte also shifts the onset potential of the photocurrent towards more negative values; this is also explained by adsorption of the surfactant molecule on GaAs surface, presumably, via its pyridine aromatic ring. In addition, CPC adsorption not only affects the electrochemical properties of the GaAs electrode but also substantially decreases the rate of photocorroion of GaAs. Photocorrosion is investigated by measuring the quantities of dissolved arsenic and gallium ions into the electrolyte by inductively coupled plasma mass spectroscopy. This dissolution results in an enriching the GaAS surface by gallium due to the referential dissolution of arsenic ions. The maximum inhibition efficiency due to the addition of CPC to the electrolyte is about 80%. Upon addition of cerous nitrate to the acidic solution of CPC the anodic photocurrent is stable and does not exhibit significant change over time though the rate of dissolving the electrode material stays low. It is concluded that in the presence of added Ce 3z the photocurrent is generated due to the oxidation of Ce z3 ions rather than the oxidation of the electrode material itself.