Functional customization of two-dimensional materials for photocatalytic activation and conversion of inert small molecules in the air

Air has the advantage of abundance and easy availability, so it is suitable to be used as a synthetic raw material and energy source. However, the triggering of inert small molecules in the air, like O2, N2, and CO2, is a kinetically complex and energetically challenging multistep reaction. Photocatalysis brings hope for this challenge, but obstacles remain in many aspects. Here, aiming at the key difficulties of the photocatalytic activation and conversion of these three inert small molecules, i.e., regulating electronic structure, active sites, charge carrier separation and mobility, and reaction energy barrier, we propose the concept of functional customization strategy of ultrathin two-dimensional materials for achieving more efficient activation and better performance, including thickness control, vacancy engineering, doping operation, single-atom site fabrication, and composite construction. The in-depth understanding of the functional customization will provide more profound guidance for designing photocatalysts that specialize in activating and converting inert small molecules.