*3.4. Maximum Output Performance at a Given pO*<sup>2</sup>

The influence of oxygen intake pressure on *Pmax* and *ηmax* of HT-PEMFC is shown in Figure 6. It can be seen from several figures that *Pmax* and *ηmax* raise with the increase of *pO*<sup>2</sup> , but from a numerical point of view the improvement is not large. The increase in pressure improves the mass transfer of the reaction gas and reduces the influence of concentration polarization on the reversible potential.

**Figure 6.** Effect of operating temperature on *Pmax* and *ηmax* of HT-PEMFC under different parameters. (**a**) Different *lm*; (**b**) different *X*; (**c**) different T; (**d**) different *pH*<sup>2</sup> .

Figure 6a reflects the effect of *pO*<sup>2</sup> on *Pmax* and *ηmax* of HT-PEMFC under different *lm*. It can be seen that as the thickness of the proton film decreases, *Pmax* and *ηmax* will increase. As shown in Figure 6b, *pO*<sup>2</sup> has a significant effect on *Pmax* and *ηmax* of HT-PEMFC under different *X*. It is obvious that as the doping level of phosphoric acid raises, *Pmax* and *ηmax* will improve.

Figure 6c shows the impact of *pO*<sup>2</sup> on *Pmax* and *ηmax* of HT-PEMFC under different *T*. Obviously, as the temperature increases, *Pmax* and *ηmax* will increase and the increase is relatively large.

Figure 6d reveals the effect of *pO*<sup>2</sup> on *Pmax* and *ηmax* of HT-PEMFC under different *pH*<sup>2</sup> . It is obvious that with the increase of *pH*<sup>2</sup> , *Pmax* and *ηmax* will enhance. It is clear that *pH*<sup>2</sup> has little effect on the maximum output power *Pmax*.
