Exploring the photocatalytic performance of (CH3NH3)2AgInBr6, a Pb-free perovskite, and the composite with a MgAlTi layered double hydroxide for air purification purposes

Pb-free metal halide perovskites (MHPs) have lately been employed in different types of photocatalytic applications due to their high absorption in the visible region and excellent electrochemical properties. In this work, the In-based (CH₃NH₃)₂AgInBr₆ (MAIB) perovskite has been synthesized using a solvent-free mechanochemical method and the photocatalytic activity has been assessed in the NO removal reaction. The ball milling approach has been employed to obtain microcrystals with a high degree of crystallinity. The diffuse reflectance spectroscopy reveals a band gap energy of 3.44 eV but with an absorption tail covering the visible region. The photocatalytic experiments reveal a high NO abatement of 92 % and 32 % under UV-Vis and visible irradiation, respectively. The cyclability of the MAIB material was investigated during six cycles obtaining an almost nearly constant performance. In a novel approach, the low selectivity showed by the MAIB perovskite in the DeNOx process was circumvented by the preparation of a composite with the MgAlTi layered double hydroxide (LDH). The presence of MgAlTi-LDH avoids the release of NO₂ during the photochemical oxidation of the NO gas. Under visible light, the MAIB perovskite is the active species leading to the production of superoxide radicals, which initiate the photochemical process. The MAIB/LDH composite exhibited good efficiency and outstanding selectivity to remove NO gas, together with long-term stability when irradiated under visible light.