Simultaneous removal of NOx and propane by solid electrolyte cells with La0.5Pr1.5-xBaxNiO4 bifunctional electrodes.

Solid electrolyte cell is a novel gas purification approach, which has unique superiority in simultaneous nitrogen oxides (NOx) and volatile organic compounds (VOCs) removal. The development of effective electrode materials and the comprehensive understanding of reaction mechanisms are essential to advancing this technology. In this study, La0.5Pr1.5-xBaxNiO4 (x = 0, 0.05, 0.1, 0.2) Ruddlesden-Popper perovskites were successfully synthesized for simultaneous NOx and propane removal. Ba doping led to crystal contraction, increased surface area, and promoted the formation of high-valence Ni ions and oxygen vacancies. Theoretical calculations confirm that Ba-doped samples have a lower oxygen vacancy formation energy and a smaller energy gap, thereby improving surface activity and bulk charge transfer. Without the need for ammonia addition, La0.5Pr1.4Ba0.1NiO4 achieves 38.2 % NOx conversion, 96.2 % propane conversion, 86.9 % N2 selectivity and 91.6 % CO2 selectivity in the presence of oxygen. In-situ electrochemical impedance spectra reveal that gas adsorption, dissociation and diffusion are the rate-limiting steps, and they are promoted by Ba doping. Oxygen decreases NOx conversion but aids propane oxidation. Propane reduces partial NOx, and the reaction products favor surface reaction processes. This study provides valuable theoretical insights into the design of advanced electrode materials and innovative strategies for the efficient and synergistic removal of NOx and VOCs.