Rational design of 2D/2D CS/SiC van der Waals type-II heterojunctions: a visible-light-driven photocatalyst for hydrogen production

Abstract

A hotspot in renewable energy research is visible-light-driven photocatalytic water splitting for hydrogen production. Monolayer stacking in the form of van der Waals heterojunctions (vdWHs) can be used for band gap engineering and the control of exciton dynamics for prospective nano-electronic devices. Using state-of-the-art hybrid dispersion-corrected density functional theory calculations (DFT-D3(BJ)), 2D/2D CS/SiC vdWHs are designed and investigated for the feasibility of using them as a potential photocatalyst for visible-light-driven H₂ generation. It has been established that the most favourable stacking pattern of CS/SiC vdWHs is mechanically, dynamically, and energetically stable, paving the way for their experimental synthesis. Furthermore, the charge transfer at the interface area generates a built-in electric field that may be used to prevent electron–hole recombination, which is favourable for achieving increased carrier mobility and prolonged lifetimes. Additionally, the CS/SiC vdWHs show a maximum optical absorption intensity for visible light, reaching 10⁵ cm⁻¹, and a suitable band gap (1.96 eV) that crosses the redox potentials of photocatalytic water splitting at pH = 7. A positive electric field (+0.6 to +0.8 V Å⁻¹) and a negative electric field (−0.2 to −0.6 V Å⁻¹) can be used to tune the band alignment of CS/SiC vdWHs to type I, offering theoretical guidance for their experimental synthesis for applying them in next-generation optoelectronics and solar energy devices. These results provide comprehensive knowledge of the enhanced photocatalytic mechanism of 2D/2D CS/SiC vdWHs, and they also offer a rational method for developing very effective CS/SiC photocatalysts for H₂ production.