First-principles discovery of stable two-dimensional AlInX2 (X=N, P, As) with high carrier mobility for photocatalytic water splitting

Using First-principles calculations and the CALYPSO program, we predicted the stable structural configuration of the AlInX₂ (X = N, P, As) monolayer upon Indium substitution for Aluminum element. The stability, mechanical, electronic, carrier mobility, optical properties and the photocatalytic water splitting of AlInX₂ monolayer were investigated. The AlInX₂ monolayer exhibits semiconducting behavior, with band gaps of 2.46 eV for AlInN₂, 1.87 eV for AlInP₂, and 0.94 eV for AlInAs₂. Additionally, these monolayers possess high carrier mobility exceeding 1.0 × 10³ cm²V⁻¹s⁻¹, with the exception of the hole mobility along the armchair direction of AlInN₂ monolayer. AlInX₂ monolayer also show excellent light absorption from visible to ultraviolet region and absorption coefficients reaching 10⁵ cm⁻¹. The outstanding electronic and optical properties render AlInX₂ monolayers highly promising for optoelectronic and nanoelectronic device applications. Significantly, our calculations reveal that band edges of the AlInP₂ monolayer fully encompass the redox potentials of water, coupled with a theoretically predicted solar-to-hydrogen conversion efficiency of 14.53 %. The catalytic activity of redox reaction on the surface of AlInP₂ monolayer is elucidated by analyzing the Gibbs free energy. The hydrogen and oxidation evolution reaction can proceed concurrently when exposed to light irradiation. These findings demonstrate its exceptional promise as a high-performance photocatalyst for water splitting applications.