High-Entropy Engineering of Electronic Structure and Oxygen Regulation in LaMnO3 Perovskite for Total NO x Monitoring

Accurate monitoring of total NOx remains challenging because NO2 reduction and NO oxidation involve different interfacial electrochemical processes, often leading to imbalanced responses. Herein, a Sr-assisted B-site high-entropy strategy was proposed to reconstruct the intrinsic electronic structure and surface defect chemistry of LaMnO3 (LMO) perovskite for impedance-metric YSZ based total NOx sensing. Sr doping coupled with Co/Cr/Fe/Mn/Ni high-entropy engineering establishes a coupled multivalent B-site redox network, optimizes the eg occupancy to 0.95, increases the density of states near the Fermi level, and modifies the surface oxygen environment. These electronic and surface-chemical changes enhance NOx adsorption and accelerate interfacial charge transfer at the triple-phase boundary (TPB). As a result, the La0.7Sr0.3(CoCrFeMnNi)0.2O3 (HE-LSMO) sensor exhibits enhanced responses to both NO2 and NO at 400 °C, with a 71% increase for NO2 and 55%/40% increases for NO in the 5-20 ppm and 20-120 ppm ranges, respectively. At 120 ppm, HE-LSMO delivers response values of 17.1° for NO2 and 16.3° for NO. More importantly, the sensor maintains a stable output under varying NO/NO2 ratios, O2 concentrations, humidity levels, and interfering gases, demonstrating its potential for reliable total NOx monitoring in complex exhaust environments.