Stability of [Ru(II)(tpy)(bpy)(OH(2))](2+)-modified graphite electrodes during indirect electrolyses

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Graphite felt electrodes are utilized in electrochemical applications.
• Ruthenium complexes can be immobilized on electrode surfaces for catalysis.
• Electrochemical oxidation of alcohols requires stable and efficient electrode materials.

Purpose of the Study:

• To investigate the stability of a graphite felt electrode modified with a specific ruthenium complex ([Ru(II)(tpy)(bpy)(OH(2))](2+)).
• To understand the degradation mechanisms during indirect alcohol electrolysis in a flow cell.
• To evaluate the electrode's performance and regeneration potential under varying potentials.

Main Methods:

• Indirect electrolysis of alcohols using a modified graphite felt electrode in a flow cell.
• Electrode potential monitoring and cyclic voltammetry analysis.
• X-ray Photoelectron Spectroscopy (XPS) for elemental analysis of the electrode surface.

Main Results:

• Electrode degradation was indicated by a continuous increase in local potential during electrolysis.
• Cyclic voltammetry showed an 80-90% decrease in the Ru(III/II) couple wave after electrolysis.
• At potentials above 0.95 V(SCE), alcohol concentration increased, and XPS revealed ruthenium loss due to demetalation at high potentials.

Conclusions:

• The modified graphite felt electrode exhibits limited stability during alcohol electrolysis, particularly at higher potentials.
• Electrode degradation is primarily attributed to the demetalation of the oxidized ruthenium complex and subsequent loss of the catalyst.
• While the electrode can be regenerated at low potentials, high potentials lead to irreversible degradation of the electrode material and catalyst.