Abstract
Palladium (Pd) is a cheap and effective electrocatalyst that is capable of replacing platinum (Pt) in various applications. However, the problem in using chemically synthesized Pd nanoparticles (PdNPs) is that they are mostly fabricated using toxic chemicals under severe conditions. In this study, we present a more environmentally-friendly process in fabricating biogenic Pd nanoparticles (Bio-PdNPs) using Citrobacter sp. isolated from wastewater sludge. Successful fabrication of Bio-PdNPs was achieved under anaerobic conditions at pH six and a temperature of 30 °C using sodium formate (HCOONa) as an electron donor. Citrobacter sp. showed biosorption capabilities with no enzymatic contribution to Pd(II) uptake during absence of HCOONa in both live and dead cells. Citrobacter sp. live cells also displayed high enzymatic contribution to the removal of Pd(II) by biological reduction. This was confirmed by Scanning Electron Microscope (SEM), Electron Dispersive Spectroscopy (EDS), and X-ray Diffraction (XRD) characterization, which revealed the presence Bio-PdNPs deposited on the bacterial cells. The bio-PdNPs successfully enhanced the anode performance of the Microbial Fuel Cell (MFC). The MFC with the highest Bio-PdNPs loading (4 mg Bio-PdNP/cm2) achieved a maximum power density of 539.3 mW/m3 (4.01 mW/m2) and peak voltage of 328.4 mV.
Highlights
Abio-electrochemical system such as Microbial Fuel Cell (MFC) has drawn interest as a promising technology for renewable energy generation using widely available fuel sources and moderate operational conditions [1,2,3].MFCs have a distinctive characteristic in which electrogenic microbes help to transform chemical energy to electrical energy using organic compounds such as glucose, formate, and acetate as a fuel source [4]
This distinctive characteristic depends on the attachment of electrogens, which greatly affect the performance of MFCs provided that the transfer of electrons is through direct mechanism [5], and since the primary location of the attachment is on the anode electrodes
The microbial growth was measured in optical density (OD) at wavelength of 600 nm using a UV/Vis spectrophotometer
Summary
MFCs have a distinctive characteristic in which electrogenic microbes help to transform chemical energy to electrical energy using organic compounds such as glucose, formate, and acetate as a fuel source [4]. This distinctive characteristic depends on the attachment of electrogens, which greatly affect the performance of MFCs provided that the transfer of electrons is through direct mechanism [5], and since the primary location of the attachment is on the anode electrodes. The properties of the anode material can greatly affect attachment and transfer of electrons between the microbes and anode electrodes [6]. Numerous chemical and physical modifications have been made to these materials in order to enhance bacterial attachment and electron transfer [6]
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