Controlled Biosynthesis of ZnCdS Quantum Dots with Visible-Light-Driven Photocatalytic Hydrogen Production Activity

Abstract

The development of visible-light-responsive photocatalysts with high efficiency, stability, and eco-friendly nature is beneficial to the large-scale application of solar hydrogen production. In this work, the production of biosynthetic ternary ZnCdS photocatalysts (Eg = 2.35–2.72 eV) by sulfate-reducing bacteria (SRB) under mild conditions was carried out for the first time. The huge amount of biogenic S2− and inherent extracellular proteins (EPs) secreted by SRB are important components of rapid extracellular biosynthesis. The ternary ZnCdS QDs at different molar ratios of Zn2+and Cd2+ from 15:1 to 1:1 were monodisperse spheres with good crystallinity and average crystallite size of 6.12 nm, independent of the molar ratio of Cd2+ to Zn2+. All the ZnCdS QDs had remarkable photocatalytic activity and stability for hydrogen evolution under visible light, without noble metal cocatalysts. Especially, ZnCdS QDs at Zn/Cd = 3:1 showed the highest H2 production activity of 3.752 mmol·h−1·g−1. This excellent performance was due to the high absorption of visible light, the high specific surface area, and the lower recombination rate between photoexcited electrons and holes. The adhered inherent EPs on the ZnCdS QDs slowed down the photocorrosion and improved the stability in photocatalytic hydrogen evolution. This study provides a new direction for solar hydrogen production.

Construction of CoS/Cd0.5Zn0.5S ohmic heterojunctions for improving photocatalytic hydrogen production activity

“…6d and Table S2, ESI †). 2,[52][53][54][55][56][57][58][59][60][61][62] The stability of a photocatalyst is vital for a catalytic reaction. Therefore, the cycling stability of the 30%-CoS/Cd 0.5 Zn 0.5 S nanocomposite was measured every three hours as one cycle and the results are shown in Fig.…”

Recent Advances in the Hydrogen Evolution Reaction of ZnxCd1−xS‐Based Photocatalysts

“…[27] Therefore, researchers have devoted great efforts to synthesizing Zn x Cd 1Àx S photocatalysts with several morphologies and structures to increase the PHE rate. [28][29][30][31][32] To date, Zn x Cd 1Àx S photocatalysts with various morphologies and structures have been synthesized using several methods, including 0D quantum dots (QDs), 1D nanorods, 3D nanospheres, QDs, and hollow nanostructures, as shown in Figure 2.…”

“…Qi et al reported the synthesis of biosynthetic ZnCdS QDs using sulfate‐reducing bacteria (SRB). [ 30 ] For ZnCdS QD synthesis, SRB‐derived active supernatant containing large amounts of biogenic S 2− and specific extracellular proteins (EPs) allows rapid and extracellular biosynthesis, which facilitates large‐scale production. The optimized Zn:Cd molar ratio was 3:1, which achieved a PHE rate of 3.752 mmol g −1 h −1 , slightly higher than that of Zn 0.5 Cd 0.5 S QDs reported by Chen et al The relatively higher photoactivity of ZnCdS QDs fabricated by biosynthesis is due to the large specific area, strong visible light absorption, abundant active sites, and lower charge recombination.…”

Enhancing the FRET by tuning the bandgap of acceptor ternary ZnCdS quantum dots

“…31,32 Moreover, QDs are generally considered to be toxic but their toxicity depends on their shape, size, and surface functionalization. 33 Also, the introduction of Zn reduces the toxicity of CdS and renders it more biocompatible and safe to use in cosmetic products. The experiments have revealed that the human skin is not labile for the penetration of commercially available QDs.…”