Nitrogen oxide electrochemical reduction characteristics on patterned platinum electrode

Electrochemical reduction performances of NO and O₂ on a patterned Pt electrode were studied by electrochemical impedance spectroscopy and current voltage measurements at different temperatures and gas composition concentrations. The patterned Pt electrode was deposited on single crystalline YSZ electrolyte by an evaporation coating technique. Porous Pt electrode was used for the other electrode. A symmetric porous Pt electrode experiment was performed to eliminate the influence of the porous Pt electrode. Results showed that the porous Pt electrode resistance can be neglected when compared with the patterned electrode. The polarization performances in NO/O₂ were better than in pure O₂ or NO at low temperatures from 500 °C to 550 °C. When the temperature increased to 550 °C and 600 °C, the NO/O₂ electrochemical performance became worse than pure O₂ gas with the voltage over 1 V due to the limited N species diffusion process, N₂ desorption process or the formation of platinum oxide poisoning catalyst by high voltage. The NO/O₂ electrochemical performances increased as the NO concentrations increased from 300 ppm to 900 ppm according to the polarization results and EIS results. EIS results showed that the increase of temperature would give rise to the decrease of the impedances. The increase of O₂ concentrations from 3% to 9% also increased the NO/O₂ polarization performances and the improvement was more significant in the voltage range of 0.3 V to 1.4 V. The NO/O₂ electrochemical reaction mechanisms related to the adsorption/desorption, surface diffusion processes on the Pt surface and charge transfer reactions were proposed according to the experiment results.