The O <sub> 2 </ Sub> Existence Of The No Electrochemical Solid Electrolyte Battery Depletion Studies

The regularity of the electrochemical removal of NOX in the presence of excess of 62 on the solid electrolyte cell was studied in the dissertation, aiming to eliminate the NOX in the exhaust gas let out from the diesel and lean-burn engines.The properties of RuO2 I Pd I YSZ I Pd cell and Pd | YSZ | Pd cell for NO decomposition in the presence of 62 were investigated in detail. The mechanism of NO decomposition on the solid electrolyte cell was discussed with a new view point in this dissertation, and the rate-determining step of the transport of O2^through the solid electrolyte cell was also proposed. Some important results were obtained as follows:(1) In the presence of excess O2, at 700 ℃, O₂ is preferentially decomposed on the Pd I YSZ I Pd cell than NO; while coating the cathode with RuO2, at 650癈and 700癈, NO can be preferentially decomposed on the RuO2 I Pd I YSZ I Pd cell at a proper DC voltage between1⁴V.(2) ZrO₂ in the solid electrolyte of YSZ could be reduced by the DC voltage, thus provide a new path for O2 to ionize there and enter into the YSZ layer. So, O2 adsorption and ionization are the main reactions on the patially reduced ZrO2 other than NO decomposition. This result is different from that obtained in the He-NO system by Huggins, in which partially reduced ZrO2 was the active site for NO decomposition.(3) NO is decomposed via the electrocatalysis mechanism other than electrolysis mechanism on both the Pd | YSZ | Pd cell and the RuO2 I Pd I YSZ | Pd cell in the range of 1⁴V. Namely, the O2^produced from NO decomposition and ionization of O2 on the surface of the cathode is transported through YSZ to the anode by DC voltage and then given off in the form of O2 so as to maintain the active states of the cathode and the catalyst being coated on the cathode. On the Pd I YSZ | Pd cell, the palladium metal surface is the active site for NO decomposition and on the RuO2 I Pd I YSZ I Pd cell, the partially reduced RuOx(0 at the Pd | YSZ interface is the rate-determining step in theoverall transportation process of O2 from cathode to anode on the cell RuO2 I Pd I YSZ I Pd at 600癈. The rate of O2"" transport decreased as the sequence of Ag > Au > Pd >Pt, and the resistance of the Ag | YSZ is the lowest.(5) RuO2 I Ag I YSZ | Pd cell shows a better result for NO decomposition than Ru02 I Pd | YSZ | Pd for the lower resistance of the O2 transport at the cathode Ag I YSZ interface than at the cathode Pd I YSZ interface. At 500℃, the NO conversion reaches to 15.3% with the NO decomposition parameter a 13.4, which corresponds to the current efficiency 10.0%.As a part of this subject, the surface properties of Zr02 were also investigated in this dissertation. Besides the result of "the partially reduced ZrO2 provide a new path for O2 to ionize and enter into the YSZ layer" as a support of the above result (2), the following important results wen? obtained:(6) Zr + centers detected by ESR in Zr02 sample are the oxygen coordinatively unsaturated Zr sites, which are mainly on the surface of the ZrO2.(7) More Zr3+ centers can be formed as ZrO2 is treated in elevated temperature, which may come from the removal of surface hydroxyl and the desorption of strongly absorbed O2.(8) Zr4+ can not be reduced in H2 at the temperature up to 600 "C, but the surface hydroxyl can be considerably reduced to form F-center at the temperature lower than 300 ℃, and at the temperature above 400 ℃, 02 can be produced from the Zr3+ centers and F-center, and its formation may be concerning with both of H2 and the trace amount of 02 inH2.