No abstract

In this work, La2NiO4+δ-xCe0.55La0.45O2−δ (denoted as LNO-xLDC) with various LDC contents (x = 0, 10, 20, 30, and 40 wt%) were prepared and evaluated as bifunctional oxygen electrodes for reversible solid oxide cells (RSOCs). Compared with the pure LNO, the optimum composition of LNO-30LDC exhibited the lowest polarization resistance (Rp) of 0.53 and 0.12 Ω·cm2 in air at 650 and 750 °C, respectively. The enhanced electrochemical performance of LNO-30LDC oxygen electrode was mainly attributed to the extended triple phase boundary and more oxygen ionic transfer channels. The hydrogen electrode supported single cell with LNO-30LDC oxygen electrode displayed peak power densities of 276, 401, and 521 mW·cm−2 at 700, 750, and 800 °C, respectively. Moreover, the electrolysis current density of the single cell demonstrated 526.39 mA·cm−2 under 1.5 V at 800 °C, and the corresponding hydrogen production rate was 220.03 mL·cm−2·h−1. The encouraging results indicated that LNO-30LDC was a promising bifunctional oxygen electrode material for RSOCs.

Nitrous oxide (N2O) is a potent greenhouse gas, which is produced during nitrifying and denitrifying processes. Some factors and mechanisms affecting N2O emission have been reported in previous literature, but wastewater biological nitrification is accompanied by a dynamic process of dissolved oxygen (DO) consumption and pH reduction, it is more meaningful to study the synergistic effects between DO and pH on N2O production. In this study, the synergistic effects between DO and pH on N2O production were investigated with real domestic wastewater. The results showed that high DO levels and a high pH could improve the oxidation ratio of NH4+-N and the production ratio of NO2--N, while effectively reducing the accumulation ratio of N2O. The NH4+-N was a prerequisite for nitrifier denitrification; when NH4+-N was oxidized completely, there would be no N2O production and an even higher concentration of NO2- The pH factor is shown to directly affect N2O emission, although free ammonia and free nitrous acid which changed with pH had no correlation with N2O emission. There were two reasons: (1) pH can influence the flow direction of electrons afforded by NH2OH oxidation; at high pH, electrons were mainly used for combining H+ and O2 (O2+4H++4e-=2H2O), the accumulation of NO2- cannot be a result of denitrification, and a higher DO can get more electrons to prefer NO2- and (2) NH4+ was the prerequisite for NH2OH oxidation, since NH2OH oxidation process was the way to provide electrons for nitrifier denitrification.

Pr and Ti co-doped strontium ferrite oxide Pr 0.3 Sr 0.7 Ti 0.3 Fe 0.7 O 3−δ (PSTF) has been examined as a hydrogen electrode for solid oxide electrolysis cell (SOEC). X-ray diffraction analysis shows that the PSTF material maintains phase stability during 20 hours of treatment under 5%H 2 /N 2 conditions. An SOEC with a configuration of PSTF||SDC|YSZ||LSM-YSZ operates under various H 2 O concentrations and current