"Tantalum oxynitride for PEFC new cathode"Figure 1 XRD patterns of samples (a) Ta2O5 prepared under NH3 flow of 20 cm−3 min−1 (b) sample and (c) sample prepared under 1000 cm−3 min−1 NH3 flow Figure 2 Potential-current curve of TaON (nitrogen: 7.0 wt%) under N2 atmosphere
Potentials were cycled in the 0.05–1.2 V range with a scan rate of 50 mV s−1. 3A and 3B show the potential-current curves of Ta3N5 and TaO0.92N1.05 (nitrogen: 7.0 wt%), respectively. Under O2 condition, the reduction current of Ta3N5 increases more than that under N2 condition, about 0.4 V. This indicates that Ta3N5 has lower catalytic activity for ORR. However, as shown in Figure 3B, the reduction current for 0.92N1.05 (nitrogen: 7.0 wt%) under O2 starts at 0.8 V. Since no such reduction current was observed under N2 atmosphere, the reduction current may be due to the reduction of oxygen. TaO0.92N1.05 (nitrogen: 7.0 wt%) has obvious catalytic activity. The reduction current of platinum in 0.1 mol/dm3 sulfuric acid occurs below 0.95 V, indicating that the cathodic activity of TaO of 0.92N1.05 is currently much lower than that of platinum. The activity can be further enhanced by optimizing the catalyst composition and electrochemical interface. Figure 3 Potential-current curves of (A) Ta3N5 and (B) TaO0.92N1.05 in 0.1 mol/dm3 sulfuric acid under N2 and O2 atmosphere. Potential sweep range from 1.2 V to RHE to 0.2 V at a sweep rate of 5 mV s-1 Figure 4 Dependence of onset potential Es on reduction current at several constant potentials (A) TaO0.92N1.05 and (B) platinum black |
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