Enhancing the performance of traditional La2NiO4+x cathode for proton-conducting solid oxide fuel cells with Zn-doping

A Zn-doping strategy was employed to modify the Ruddlesden-Popper (R–P) structure oxide La2NiO4+x to improve hydration and proton diffusion ability. First-principles calculations indicated the formation of interstitial oxygen instead of oxygen vacancy is favorable for Zn-modified and Zn-free La2NiO4+x. The doping of Zn significantly lowered the hydration energy for La2NiO4+x and decreased the proton migration barrier. The electrical conductivity relaxation confirmed that the Zn-modified La2NiO4+x sample had a higher proton diffusion rate than the Zn-free sample. Furthermore, the Zn-doping strategy did not alter the thermal expansion behavior of the material, and both Zn-modified and Zn-free La2NiO4+x samples showed a similar thermal expansion coefficient value, which was also close with the electrolyte materials. As a result, the Zn-modified La2NiO4+x exhibited suitability as the cathode for proton-conducting solid oxide fuel cells (H–SOFCs). An H–SOFC using the Zn-modified La2NiO4+x showed a relatively high peak power density of 1070 mW cm-2 at 700 °C, significantly larger than that La2NiO4+x-based H–SOFCs reported previously.