Electrodeposition and Electrochemical Behaviour of Arsenic Film in Aqueous Solution

Electrodeposition of arsenic has been studied in acidic and alkaline solutions containing As2O3. The current efficiency from the electrodeposition of arsenic was approximately 90% in initial 3 hours but it gradually falled down below 50% after 20 hours. The cathode deposits were metallic grey arsenic at low current densities but was less-conductive powdery arsenic at high current densities. An X-ray analysis indicated that the deposits were non-crystalline. Cathodic hydrogen evolution on the electrodeposited arsenic in an acidic solution obeyed the Tafel relation with a slope of 0.12V/decade in a limited range of current densities and the exchange current density for hydrogen was in the order of 10-3 A m-2. It was also found that the arsenic electrode was slowly reduced to arsine (AsH3) during the cathodic polarization experiment. The anodic polarization curves for the arsenic exhibited a Tafel line with a slope of 0.06V/decade.