Graphene quantum dots induce hexagonal CdS prism formation and interparticle Z-scheme heterojunctions for efficient Hg0 removal under visible light

Graphene has recently emerged as a nano-functional material with great potential in the field of photocatalysts. Doping graphene quantum dots (GQDs) into CdS by a simple hydrothermal method led to a unique hexagonal CdS prism structure that assembled into nanospheres, simultaneously inducing intergranular Z -Scheme heterojunctions of the (001) and (100) plane families in CdS. As a result, the CdS-GQDs composite exhibited excellent removal efficiencies for gaseous mercury (Hg 0 ), exceeding 95% under visible light and 90% over photocatalytic cycles. Experimental and optical characterization results indicated that the photoresponse of the composite photocatalyst was broadened due to the doped GQDs. Furthermore, density functional theory calculations revealed that the formation of a Z -scheme heterojunction between the two crystal planes of CdS generated an internal electric field in CdS, resulting in a novel carrier transfer channel. Through GQD doping, this work successfully addressed the occurrence of serious photocorrosion in CdS, providing a novel composite dedicated to the efficient removal of Hg 0 from flue gas under visible light.