Computational design of enhanced photocatalytic activity of two-dimensional cadmium iodide

Abstract

The recent synthesis of two-dimensional cadmium iodide (CdI₂) opens up the questions of its properties and potential applications in optoelectronic and photovoltaic devices. Using a first-principles design approach, the electronic structure of 2D CdI₂ is determined. The calculated results of the band gaps and band edges demonstrated that CdI₂ is a suitable photocatalyst for water splitting. Monolayer CdI₂ should exhibit a relatively low photocatalytic activity due to its large band gap (about 3.0 eV). Some favourable doping can introduce extra bands to its band gap with the redox potentials of water straddled in its band gap, which can lead to improved photocatalytic performance. Multilayer CdI₂ with a narrower band gap may absorb a finite amount of visible light, making it a more suitable photocatalyst. Furthermore, multilayer CdI₂ exhibits significant modulation of its band gap and band alignment by applying normal strain and a vertical electric field. A reduced band gap with the CBM and VBM approaching the H⁺/H₂ and the H₂O/O₂ potentials, respectively, can result in an enhanced photocatalytic activity by applying normal strain and a vertical electric field.