Cation induced electrostatic adsorption driven self-assembly sandwich-like α-MnO2/MXene for efficient self-heating photothermal synergistic catalytic decomposition of carcinogenic gaseous formaldehyde

Realizing self-assembly between different nanoparticles is an important strategy for constructing novel nanostructures or excellent functional composites. Formaldehyde is the primary gaseous pollutant in indoor air, and achieving its ambient temperature decomposition is of great significance for improving indoor air quality. This research reports an electrostatic adsorption driven self-assembly strategy, constructing a sandwich structure alpha-MnO2/MXene for self-heating photothermal synergistic catalytic decomposition of formaldehyde. The selfassembly process and electrostatic adsorption driven mechanism were detailed. A comparative study was conducted on the performance and mechanisms of the self-assembled sandwich structure and mechanically mixed alpha-MnO2/MXene in the self-heating photothermal catalytic decomposition of formaldehyde. The sandwich structure alpha-MnO2/MXene with built-in electric field and Schottky barrier exhibited excellent self-heating photothermal catalytic activity for formaldehyde decomposition, realizing the 100% mineralization of formaldehyde under simulated solar-light irradiation at room temperature; even with the irradiation of visible light, the sandwich structure alpha-MnO2/MXene can still maintain 82.6% HCHO conversion. Furthermore, we elucidated the self-heating photothermal catalytic mechanism, shedding light on the distinct roles and contributions of photocatalysis and thermalcatalysis. It was found that the photothermal catalytic mechanism of the sandwich structure alpha-MnO2/MXene-S composite involved a thermal-assisted photocatalytic process. The advantages of the self-assembled sandwich structure and its mechanism for enhancing photothermal performance were fully revealed. This study reports an effective strategy for electrostatic adsorption self-assembly, offering a fresh perspective on developing non-noble metal catalysts for ambient-temperature formaldehyde decomposition.