Arsenopyrite-powder modified carbon paste electrode
The bare carbon paste (CP) was prepared in the usual way by
handmixing graphite powder and silicone oil to form homogeneous
mixture using a pestle and mortar. The ratio of graphite
powder to silicone oil was 4:1. The arsenopyrite used to prepare
the FeAsS-CPE was obtained from pure crystals ground in an agate
mortar and dry sieved using a standard Tyler sieve, until a particle
size of less than 0.1 mm was obtained. The arsenopyrite-powder
modified carbon paste electrode was prepared by mixing 0.5 g
freshly made CP with 0.1 g arsenopyrite powder. The resulting
paste was packed tightly into a PTFE sleeve and the electrode surface
was polished to a smooth finish on a piece of weighing paper.
After polishing, the electrode was ready to use, without any further
mechanical, chemical or electrochemical pretreatment. Electrical
contact was established with a stainless steel screw. The constructed
electrode was washed with distilled water and then was
transferred to the supporting electrolyte solution. Ultra pure argon
was bubbled through the solutions to remove dissolved oxygen.
Initially the solution was bubbled with argon for 5 min and then
again for 1 min before each measurement.