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.
Highlights
Accepted: 18 May 2021The growing demand for energy and concerns about environmental pollution are driving the replacement of materials and equipment for sustainable and renewable energy sources [1]
This work represents a significant advancement in the green synthesis of metal chalcogenides, which can be used directly in the natural environment of heavy metal waste water for highly efficient solar H2 production. This is the first report on the biosynthesis of visible-light-responsive ZnCdS photocatalysts by extracellular biosynthesis
The sulfate-reducing bacteria (SRB)-derived active supernatant, which contains a massive quantity of biogenic S2− and a high content of specific extracellular proteins (EPs), enables the rapid and extracellular biosynthesis, which lays the foundation for large-scale production
Summary
Accepted: 18 May 2021The growing demand for energy and concerns about environmental pollution are driving the replacement of materials and equipment for sustainable and renewable energy sources [1]. Most photocatalysts have poor catalytic performance in visiblelight-driven reactions, even if precious metals are used as co-catalysts, which greatly limits their practical application [6,7,8]. To solve this problem it is necessary to develop new photocatalysts based on the abundant elements on Earth which can be as efficient as precious-metal-based catalysts. CdS QDs have been widely studied in water hydrogen production under visible light, considering their high activity and sufficient negative conduction band position [15]; they have high toxicity and poor photocorrosion resistance [16,17].
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