Attempted preparation of La <sub>0.5</sub>Ba <sub>0.5</sub>MnO <sub>3− <i>δ</i> </sub> leading to an <i>in-situ</i> formation of manganate nanocomposites as a cathode for proton-conducting solid oxide fuel cells
Rui Zhou, Yanru Yin, Hailu Dai, Xuan Yang, Yueyuan Gu, Lei Bi
Abstract
A La<sub>0.5</sub>Ba<sub>0.5</sub>MnO<sub>3−<i>δ</i></sub> oxide was prepared using the sol–gel technique. Instead of a pure phase, La<sub>0.5</sub>Ba<sub>0.5</sub>MnO<sub>3−<i>δ</i></sub> was discovered to be a combination of La<sub>0.7</sub>Ba<sub>0.3</sub>MnO<sub>3−<i>δ</i></sub> and BaMnO<sub>3</sub>. The <i>in-situ</i> production of La<sub>0.7</sub>Ba<sub>0.3</sub>MnO<sub>3−<i>δ</i></sub>+BaMnO<sub>3</sub> nanocomposites enhanced the oxygen vacancy (V<sub>O</sub>) formation compared to single-phase La<sub>0.7</sub>Ba<sub>0.3</sub>MnO<sub>3−<i>δ</i></sub> or BaMnO<sub>3</sub>, providing potential benefits as a cathode for fuel cells. Subsequently, La<sub>0.7</sub>Ba<sub>0.3</sub>MnO<sub>3−<i>δ</i></sub>+BaMnO<sub>3</sub> nanocomposites were utilized as the cathode for proton-conducting solid oxide fuel cells (H-SOFCs), which significantly improved cell performance. At 700 ℃, H-SOFC with a La<sub>0.7</sub>Ba<sub>0.3</sub>MnO<sub>3−<i>δ</i></sub>+BaMnO<sub>3</sub> nanocomposite cathode achieved the highest power density (1504 mW·cm<sup>−2</sup>) yet recorded for H-SOFCs with manganate cathodes. This performance was much greater than that of single-phase La<sub>0.7</sub>Ba<sub>0.3</sub>MnO<sub>3−<i>δ</i></sub> or BaMnO<sub>3</sub> cathode cells. In addition, the cell demonstrated excellent working stability. First-principles calculations indicated that the La<sub>0.7</sub>Ba<sub>0.3</sub>MnO<sub>3−<i>δ</i></sub>/BaMnO<sub>3</sub> interface was crucial for the enhanced cathode performance. The oxygen reduction reaction (ORR) free energy barrier was significantly lower at the La<sub>0.7</sub>Ba<sub>0.3</sub>MnO<sub>3−<i>δ</i></sub>/BaMnO<sub>3</sub> interface than that at the La<sub>0.7</sub>Ba<sub>0.3</sub>MnO<sub>3−<i>δ</i></sub> or BaMnO<sub>3</sub> surfaces, which explained the origin of high performance and gave a guide for the construction of novel cathodes for H-SOFCs.