Molten-Salt-Synthesized La2CrO6/LaCrO3 Sensing Electrode for Highly Sensitive Impedancemetric NO2 Detection

Flake-like La 2 CrO 6 /LaCrO 3 sensing electrodes (SEs) were synthesized via a one-pot molten-salt method (MSM) for impedancemetric NO 2 sensors based on yttria-stabilized zirconia (YSZ) electrolyte. The MSM-derived La 2 CrO 6 precursor underwent self-phase separation during high-temperature calcination, yielding a La 2 CrO 6 /LaCrO 3 composite SE with abundant heterointerfaces. Structural characterizations confirmed that the molten-salt-derived flakes provide a highly accessible surface and abundant La 2 CrO 6 /LaCrO 3 heterointerfaces after calcination, which effectively amplify the electrode/electrolyte interfacial electrochemical reactions toward NO 2 . Consequently, compared with single-phase LaCrO 3 , the La 2 CrO 6 /LaCrO 3 composite SE exhibits excellent sensitivity, which is attributed to the synergistic coupling effect in the sensing mechanism. La 2 CrO 6 provides strong adsorption sites, while LaCrO 3 ensures thermodynamic stability. By optimizing the temperature and time of the MSM reaction and the calcination parameters, the SE morphology and sensing performance were systematically improved. The optimal La 2 CrO 6 /LaCrO 3 sensing electrode, which was prepared by reacting at 500 °C for 1.5 h and then calcined at 800 °C, exhibited an outstanding sensitivity of 12.51 °/decade to NO 2 (25-700 ppm) at a working temperature of 400 °C. Additionally, the sensor exhibited superior repeatability, humidity resistance, and high anti-interference capabilities against various exhaust gases (H 2 , NH 3 , CH 4 , CO 2 , and NO). This work confirms that the molten salt method is a highly effective strategy for constructing high-performance composite sensing electrodes.