Solar-driven direct Z-scheme using hierarchical CdS/SiC Heterostructure for enhanced photocatalytic water splitting

Due to the increasing human need for energy, science is moving towards finding a sustainable and clean alternative to meet the world's energy needs; and among these, Photoelectrochemical and Photocatalytic Water Splitting is the best eco-friendly option! To attain an acceptable performance from overall water splitting, a photocatalyst must have a suitable band structure with sufficient redox power, and also definitely must have high separation efficiency for photo generated charge carriers, and have a sufficient number of active sites. But there are few photocatalyst that have all of these basic properties; However, a suitable and easy solution to achieve the photocatalytic reaction of this is to use the direct Zscheme structured from two semiconductor photocatalysts.When CdS and SiC are in contact, the transfer of free CdS electrons to SiC begins immediately and continues until their Fermi levels are balanced. Therefore, in the interface of these two semiconductors, CdS will have a positive charge, and SiC will have a negative charge. Hence, an internal electric field is created and causes the band edge bending. After excitation by incoming light, both photocatalyst have the ability to create electron-hole pairs. The formation of this internal electric field forms a passage for the recombination of electrons photogenerated in the CdS conduction band and holes photogenerated in the SiC valance band, and a barrier to the transfer of photogenerated electrons from the CdS CB to the SiC CB, as well as the barrier to the transfer of photogenerated holes from SiC VB to CdS VB. Meanwhile, the electrons of the CdS CB and the holes of the SiC VB are conserved and spatially separated and can participate in specific photocatalytic reactions. The photocatalytic performance direct Zscheme photocatalysts depend on their morphology. studies have shown that hierarchical structure photocatalysts have the best form; Large specific surface area, sufficient porous structure, more surface-active sites, and better mass transfer.

Author(s): Mohsen Bayat

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