Efficient Nanoclay-Based Composite Photocatalyst: The Role of Nanoclay in Photogenerated Charge Separation

Natural clay mineral is a low-cost support for photocatalytic materials, but it exhibits insulating properties determined by intrinsic compositions of aluminosilicate, which normally makes it difficult to participate in the charge carrier separation and transfer of the photocatalytic system. Herein, natural iron-rich kaolinite clay with photoresponse is used as a multifunctional support to construct a CdS composite photocatalyst, and we find that the natural kaolinite nanosheets exhibit strong oxygen adsorption capacity by hydroxyl groups and could enhance the charge carrier separation. Density functional theory calculations show that the hydroxyl groups of kaolinite could effectively adsorb oxygen via hydrogen bonding, and the absorbed water further promotes the adsorption of oxygen. Because of these special properties, the kaolinite nanosheets not only directly improved photogenerated charge separation efficiency by a type II staggered band structure of heterostructures but also promoted the production of superoxide radicals via providing an oxygen-rich microenvironment, which resulted in the greatly enhanced photocatalytic performance of CdS nanoparticles. This work could provide a deeper understanding of the role of the iron-rich natural clay mineral as a photocatalytic support and shed light on the design of clay-based composite photocatalysts.