Size dependent photogeneration charge carrier density of hollow ZnIn2S4 microspheres for enhanced photocatalytic activity

The effect of the morphology of semiconductors on the photocatalytic performance is commonly observed but ambiguous due to the other structural changes usually occur simultaneously along with morphology variation. In this work, we have successfully constructed a series of ZnIn2S4 hollow microspheres (named ZIS-x, x  = 0.6, 0.2, 0.15, 0.1, 0.06.) with systematically decreased size in both shell thickness and diameter of the sphere and comparable band structures, degree of crystallinity and density of defects as confirmed by extensive characterizations. Taking advantage of the above features, the decoupled effect of size on photocatalytic activity is investigated and established, which displays a volcano-type relationship. The best performed ZIS-0.1 displays a hydrogen evolution rate of 3.76 mmol g-1h−1, which is 2.66 times that of the worst performed ZIS-0.6. Further mechanistic studies disclose that the observed size dependent hydrogen evolution rate originates from the ability of charge carrier generation under light, which increases with the light harvesting ability of the hollow microspheres. This work explicitly reveals the effect of the morphology on the photocatalytic activity of semiconductors, which highlights the route to improve the photocatalytic performance morphologically.