Layered double hydroxides (ZnAl-NO3-LDH) to mixed metal oxides: A promising pathway for sustainable NOx abatement

ZnAl layered double hydroxides (LDHs) were explored for their potential transformation into layered double oxides (LDO) through thermal decomposition. LDO have interesting functional properties in photocatalysis. Here, we tested the photodegradation of nitrogen oxides (NOx). This study aimed to develop ZnO[sbnd]ZnAl oxide heterojunctions that demonstrate good selectivity with minimal NO₂ release, addressing critical challenges in NOx abatement. ZnAl-NO₃-LDH was synthesized via a coprecipitation method and then calcined at 600 °C for 3 h to transform LDH into layered double oxides (LDOs). The resulting ZnO-based LDOs were characterized via X-ray diffraction (XRD), Fourier Transform Infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM-EDS), and diffuse reflectance spectroscopy. The photocatalysts demonstrated a conversion efficiency of 27–29 % for NO photocatalytic conversion, with a notable reduction in NO₂ release (3–4 %) and a high selectivity of up to 91 % under light intensities of 20 and 40 W/m². These results highlight the effectiveness of photocatalysts (LDO) in NOx abatement and their potential of forming LDO-NO₃ on reaction thus act as sustainable nanomaterials. Furthermore, this study employs a novel portable photoreactor for rapid NOx abatement evaluation, utilizing a low-volume, continuously stirred continuous-flow photoreactor. This compact, low-volume setup enables rapid onsite measurements, offering significant time and cost advantages for monitoring NOx and completing photocatalytic activity assessment.