Characterization of Bacterially Precipitated Cadmium Sulfide Nanoparticles for Photoelectrochemical Applications

Abstract

Cadmium sulfide (CdS) is one of the most commonly used II/VI semiconductor materials because of its electron energy band edge positions. CdS nanoparticles (NPs) are widely used in applications such as photodegradation of organic molecules, photocatalysis of water splitting, and as building blocks of photovoltaic devices. Bacterial precipitation of CdS NPs provides an innovative, environmentally friendly route for the synthesis of NPs with controllable electronic properties. Our previous research shows that CdS NPs can be extracellularly precipitated with tunable CdS crystallite sizes ranging from 5 nm to over 15 nm in diameter. In this thesis, I investigated the potential application of these bacterially precipitated CdS NPs for photodegradation of organic molecules, photocurrent generation, and for photoelectrochemical (PEC) hydrogen evolution. The results show that the bacterially precipitated CdS NPs and their devices performed competitively when compared with their counterparts that were synthesized via chemical bath deposition (CBD). In photodegradation experiments, the bacterially precipitated CdS NPs showed a slower rate of degradation than CBD CdS. In transient photocurrent response experiments, the devices incorporating bacterially precipitated CdS NPs showed a higher current response to visible light. Furthermore, in electrochemical hydrogen generation experiments, the bacterially precipitated CdS NP device showed a lower onset potential to trigger the reaction when irradiated with light. Collectively, the preliminary results show that biosynthesized CdS NPs have potentially promising applications for the photodegradation of organic molecules and for the photoelectrochemical hydrogen generation.