Low-temperature-synthesized RuO2 from acidic chloride solution for the electrode coating applications

For the preparation of RuO2 coatings on Ti substrate, the RuO2 was synthesized in acidic aqueous medium by simple one-step low temperature-controlled microwave (MW) irradiation. The physical composition of synthesized solid phase was analysed through particle size distribution (PSD), whereas the coating was investigated for its capacitive response and activity in oxygen evolution reaction (OER). The oxide phase was found highly polydisperse, with overlapped fractions within rather narrow particle size range and clear tendency toward agglomeration. The smallest particles and their best resolved fractions were synthesized at the temperature just above the boiling point of the reaction medium, and quite below the chloride-to-oxide conversion temperature. Consequently, the highest OER activity was registered for RuO2/Ti anodes prepared from this sample, with strong indication of different oxide structure, with respect to the electrodes prepared from samples synthesized at higher temperatures. However, the coatings from high temperature samples have considerably higher capacitance than those synthesized at lower temperatures. These findings can be rather correlated to the MW temperature-dependent oxide structure than to different morphology analysed through PSD.