Electrochemical techniques provide a possible alternative to allow
a rough characterization of the surface state of arsenopyrite.
Several publications report the electrochemical characterization
of the arsenopyrite surface in alkaline media [3,4], while fewer
document characterization in acidic media [5]. The majority of
these studies utilized a crystal sample as the arsenopyrite electrode.
However, due to the polishing conditions and the intrinsic
characteristics of the crystal material, this type of electrode presents
the problem of poor reproducibility of the electrochemical
response. For a carbon paste electrode (CPE) with a non-conducting
binder, the sensitivity is high and its residual currents are low, due
to the small double layer capacitance at the electrode–electrolyte
interface. The hydrophobic binder used in the CPE lowers the double
layer capacitance, and consequently the residual current decreases.
Therefore, penetration of the electrolyte into the CPE is
unlikely, due to its hydrophobic nature; thus, electrochemical reactions
take place entirely at the interface [10,11]. The concept of
percolation is the probability that any given region of the CPE is
sufficiently well connected to the rest to be available for conduction
[12,13], playing an important role in the electroactive