Enhanced photostability and ice-nucleation catalytic activity in two-dimensional silver iodide

Abstract

Silver iodide (AgI) serves as one of the most successful and widely used rainfall catalysts. This study investigates the structural, mechanical, electronic, and optical properties of two-dimensional (2D) AgI using first-principles calculations. The interlayer binding energy is comparable to graphene, suggesting that monolayer and few-layer AgI can be obtained via mechanical exfoliation. Phonon spectra confirm the dynamical stability of monolayer, bilayer, and trilayer AgI. Mechanically, 1 L AgI shows reduced in-plane stiffness compared to thicker layers and bulk, enhancing its flexibility for lattice matching with ice during heterogeneous nucleation. Electronically, AgI remains a direct bandgap semiconductor with the bandgap increasing from bulk to monolayer. This widening bandgap suppresses absorption in the blue‑violet region of sunlight, potentially improving photostability and reducing photodecomposition under solar irradiation. The binding energy of AgI/H₂O heterostructure is close to that of graphene. Our calculations show that 2D AgI exhibits favorable lattice matching and interfacial binding with ice, suggesting that it is a promising candidate for efficient heterogeneous ice nucleation. However, according to recent reports, lattice matching and interfacial interaction strength alone are not sufficient to determine heterogeneous ice-nucleation behavior. Direct evaluations of nucleation barriers or rates, as well as experimental validation, are needed to quantify the ice-nucleation efficiency of 2D AgI.