Double Effects of Interfacial Ag Nanoparticles in a ZnO Multipod@Ag@Bi2S3 Z-Scheme Photocatalytic Redox System: Concurrent Tuning and Improving Charge-Transfer Efficiency

Distinct functional materials in their combined form in a well-designed hybrid architecture offer great possibilities for creating a highly active photocatalytic system. Herein, a uniform multipod-shaped ZnO is synthesized through a natural template assisted route and progressively integrated with Ag nanoparticles (NPs) and Bi2S3 to form a three-component (3C) ternary photocatalytic system by a facile, two -step wet chemical approach. Encapsulation of polycrystalline Bi2S3 and assimilation of Ag NPs in between the interface of ZnO and Bi2S3 in the ternary hybrid are confirmed from electron microscopy and X-ray photoelectron spectroscopy, which resulted in improved UV-vis absorption, charge separation efficiency, and photocurrent response evaluated from optical absorption spectroscopy, photoluminescence, and photoelectrochemical cell measurements. This ternary hybrid shows high photoredox activity toward the hydrogen evaluation reaction (HER) (218.7 mu mol h(-1) g(-1)) and methyl orange (MO) oxidation (k = 3.21 x 10(-2) min(-1)) compared to their binary and single counterparts. Moreover, on the basis of the estimation of the predominant active species (O-2(center dot-), center dot OH) in the photoredox catalysis and band edge positions from the Mott-Schottky plot, it was determined that both binary ZnO multipod@Bi2S3 and ternary ZnO multipod Ag@Bi2S3 hybrids undergo a Z-scheme electron transfer mechanism under irradiation of light. Here, the Ag ingredient in the ternary hybrids acts as an interfacial charge-transfer mediator to accelerate the Z-scheme electron transfer between Bi2S3 and ZnO along with plasmonic photosensitization to trigger the generation of plasmon-induced hot electrons. Such a cooperative concurrent dual role of Ag NPs in the Z-scheme ternary hybrid system considerably boosts the photoredox performance compared to direct Z-scheme binary hybrids. This work will enlighten and uncover the essential roles of metal NPs along with their cooperative synergy in Z-scheme photocatalytic systems as a prototypical example for substantial solar energy conversion.