Preparation of catalytic materials for efficient indoor air treatment at mild temperatures

Indoor air quality has gained attention due to the dangerous effects on human health. This thesis targets the catalytic oxidation of carbon monoxide (CO) and volatile organic compounds (VOCs) over manganese-oxide catalysts engineered for high conversion at mild temperatures. Two polymorph supports, MnO&#8322; and Mn&#8322;O&#8323;, are prepared by Solution Combustion Synthesis (SCS) and Nanocasting (NC) and then modified with either Au or bimetallic Au–Cu nanoparticles to create metal–oxide interfaces that can enhance redox properties and activity. A comprehensive investigation links structure to performance: N&#8322; physisorption at &#8722;196 °C quantifies surface area and porosity, X-ray diffraction resolves phases and crystallite size, H&#8322;-TPR probes reducibility, O&#8322;-TPD assesses the lability and mobility of surface and bulk oxygen and EDX provides elemental mapping to verify Au dispersion across MnO&#8339;. The catalysts were subsequently tested for CO and C&#8322;H&#8324;, simulating real concentrations in confined spaces (100 ppm). Across the series, MnO&#8322;-functionalized catalysts systematically outperform Mn&#8322;O&#8323; analogues; adding Au or Au&#8323;Cu enables measurable CO conversion near room temperature compared to the bare supports. The nanocast Au sample AuPVA_MnO&#8322;_NC is the best performer, combining high specific surface area (95.2 m² g&#8315;¹) with the smallest crystallites (7 nm) and exhibiting a marked low-temperature O&#8322;-TPD desorption, a feature attributable to labile surface oxygen, consistent with fast redox cycling and early light-off. Concerning the catalytic tests, the addition of Au NPs, for CO, improves catalytic performances in terms of T&#8321;&#8320;/T&#8325;&#8320;/T&#8329;&#8320;, passing from 61/97/125 °C (MnO&#8322;_NC) to 27/60/89 °C (AuPVA_MnO&#8322;_NC), achieving full conversion at 100 °C. For ethylene, values improve from 154/203/236 °C to 106/153/184 °C. To reduce Au loading, bimetallic Au&#8323;Cu was also evaluated: on MnO&#8322;_NC, it gives T&#8321;&#8320;/T&#8325;&#8320;/T&#8329;&#8320; of <25/67/96 °C (CO) and 116/163/192 °C (C&#8322;H&#8324;), better than the bare support at low temperature yet behind the Au-only analogue. Conversion rates also demonstrated the superior performance of AuPVA_MnO&#8322;_NC. In fact, for CO at 50 °C, the specific rates are 2.1×10&#8315;² µmol g&#8315;¹ s&#8315;¹ and 2×10&#8315;&#8308; µmol m&#8315;² s&#8315;¹, while for ethylene at 125 °C, it reaches 1.5×10&#8315;² µmol g&#8315;¹ s&#8315;¹ and 2×10&#8315;&#8308; µmol m&#8315;² s&#8315;¹. Stability tests further support applicability: under time-on-stream, the catalyst maintains activity over 6 h with negligible activity loose and heating–cooling cycles yield virtually overlapping conversion–temperature profiles, indicating the stability of the sample. From a materials-design standpoint, three conclusions emerge: (i) support oxidation state/reducibility governs low-T activity, MnO&#8322; (Mn&#8308;&#8314;-rich) outperforms Mn&#8322;O&#8323;; (ii) interfacial Au (and Au–Cu) nanoparticles accelerate CO/O&#8322; activation at mild temperature; (iii) microstructure matters, nanocasting maximizes accessible site density and compresses light-off even when per-m² intrinsic rates are similar. Overall, AuPVA MnO&#8322; NC emerges as a promising candidate for indoor air remediation at mild temperatures, coupling low light-off, high accessible site density and robust stability.