I use sputtered IrOx electrocatalyst for acid water oxidation. IrOx is sputtered on silicon wafer covered with SiO2 layer and subsequent Ti adhesion layer. After sputtering the IrOx layer is 'activated' by repetitive cycling between 0 and 1.4 V vs RHE in 0.5M H2SO4 for about 1000 cycles at 0.1V/s until surface is blue (Ir4+).
After activation i study OER activity by chronopotentiometry at fixed current (10 mA/cm²) but the potential is not stable and Ir dissolves into the electroyte and loses blue color.
Any suggestions on how to improve this stability?
Iridium oxide after electrochemical activation can be stored dry indefinitely but may require some period of electrolyte immersion to obtain their low impedance state Activated iridium oxide may also be stored wet in distilled water, saline, or buffered saline.
Dear Rhiyaad,
Thank you for your clear answer and the added references.
Indeed the activation procedure is quite harsh and some dissolution does occur but it has proven to be the most effective one yet. For instance, in alkaline solutions the activation does not occur. After activation in acid i do obtain a blue layer of iridium oxide which is very active for OER and this week i noticed that the short-term stability greatly improves when i use 0.1M KOH as an electrolyte for chronopotentiometric studies (i presume because protons were involved in the dissolution reaction of the hydroux oxide layer).
The long-term stability has not yet improved for which your added references are very interesting so thank you!
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