Using auxiliary electrochemical working electrodes as probe during contact glow discharge electrolysis: A proof of concept study

Abstract

Plasma in-liquid by means of anodic contact glow discharge electrolysis (aCGDE) is a growing research field allowing the selective modification of the electrode and the electrolyte. The aim of this proof of concept study is to demonstrate that auxiliary electrochemical electrodes placed in the vicinity of the plasma electrode can be modified by aCGDE (ignited at the anode by applying a DC voltage between the driving electrodes). Furthermore, we illustrate in how far such auxiliary electrodes can be used as a probe to detect products (in particular, [Formula: see text], [Formula: see text], and [Formula: see text]) formed in the solution by aCGDE via electrochemical techniques. In this work, aCGDE is achieved by applying a voltage of 580 V to a small Pt wire (plasma electrode) versus a large stainless steel counter electrode. An auxiliary Pt electrochemical working electrode, operated in a three electrode configuration, is placed at different distances from the plasma working electrode. Depending on the distance, we find small changes in the working electrode structure. More importantly, we will show that, in principle, the local [Formula: see text] concentration in the electrolyte can be monitored operando. After aCGDE, the concentration changes with time and depends on the distance from the plasma electrode.

Nanoporous Au Formation on Au Substrates via High Voltage Electrolysis**

“…We suggested that the Au oxide is reduced by H 2 O 2 which forms during anodic contact glow discharge electrolysis (aCGDE). [37][38][39][40] Our results also indicate that H 2 O 2 might also form at lower voltages (still in the range of a few 100 V) in the normal electrolysis region, as suggested previously. [41] This approach allows preparing samples within a few minutes.…”

“…As described above, the Au oxide formed during HV electrolysis is reduced when the electrode is kept in the electrolysis solution after HV electrolysis. It was suggested that the reduction process is caused by H 2 O 2 in the electrolyte [36,40], which forms during HV electrolysis. [38,39,41] The general ability of H 2 O 2 to reduce Au cations is already known in literature and can be explained by using the standard electrochemical potentials.…”

“…Possible reasons for this discrepancy are that after HV electrolysis, the H 2 O 2 concentration will be high in the region around the electrode and will decrease with increasing time, as shown elsewhere. [40] Furthermore, during HV electrolysis, the temperature of the electrolyte will increase, [39,41,52,53] which could also be a decisive factor for the structure formation.…”

“…Overall, these results show that the H 2 O 2 concentration and temperature play a major role in structure formation. This is an important aspect since these parameters change dynamically and in an uncontrolled way when the electrodes are kept in the electrolysis solution after HV electrolysis, i. e., the H 2 O 2 concentration will probably decrease due to dissipation in the electrolyte, [40] and the local temperature will also decrease due to heat dissipation into the surrounding electrolyte.…”

Cyclic Voltammetry Method for Analysis of Phosphate Concentration in Water

“…The material usually used as an auxiliary electrode is inert. Platinum (Pt) is an electrochemical electrode material widely used due to the optimal benchmark system [17].…”