Controlling the Carbon-Bio Interface via Glycan Functional Adlayers for Applications in Microbial Fuel Cell Bioanodes

Surface modification of electrodes with glycans was investigated as a strategy for modulating the development of electrocatalytic biofilms for microbial fuel cell applications. Covalent attachment of phenyl-mannoside and phenyl-lactoside adlayers on graphite rod electrodes was achieved via electrochemically assisted grafting of aryldiazonium cations from solution. To test the effects of the specific bio-functionalities, modified and unmodified graphite rods were used as anodes in two-chamber microbial fuel cell devices. Devices were set up with wastewater as inoculum and acetate as nutrient and their performance, in terms of output potential (open circuit and 1 kΩ load) and peak power output, was monitored over two months. The presence of glycans was found to lead to significant differences in startup times and peak power outputs. Lactosides were found to inhibit the development of biofilms when compared to bare graphite. Mannosides were found, instead, to promote exoelectrogenic biofilm adhesion and anode colonization, a finding that is supported by quartz crystal microbalance experiments in inoculum media. These differences were observed despite both adlayers possessing thickness in the nm range and similar hydrophilic character. This suggests that specific glycan-mediated bioaffinity interactions can be leveraged to direct the development of biotic electrocatalysts in bioelectrochemical systems and microbial fuel cell devices.

Bias-induced impedance effect of the current-carrying conductors

<p class="Abstract">The paper presents the previously unstudied properties of current-carrying conductors utilising impedance spectroscopy. The purpose of the article is to present discovered properties that are the significant context of impedance research. The methodology is based on the superposition of test signals and bias affecting the objects under study. These are the main results obtained in this work: the studied objects have an additional low-frequency impedance during the passage of an electric current; the bias-induced impedance effect (Z_BI-effect) is noticeably manifested in the range of 0.01 Hz … 100 Hz and it has either capacitive or inductive nature or both types, depending on the bias level (current density) and material types. The experiments in this work were done using open and covered wires made of pure metals, alloys, and non-metal conductors, such as graphite rods. These objects showed the Z_BI-effect that distinguishes them from other objects, such as standard resistors of the same rating, in which this phenomenon does not occur. The Z_BI-effect was modeled by equivalent circuits. Particular attention is paid to assessing the consistency of experimental data. Understanding the nature of this effect can give impetus to the development of a new type of instrument in various fields.</p>

One-step Synthesis of Molybdenum Oxide/graphene Composites

We herein introduce a new approach to synthesize MoO2/graphene composites via plasma-enhanced electrochemical exfoliation process. Our samples were prepared by electrifying graphite rods in (NH4)2Mo7O24 solution under a DC voltage of 70V. By controlling the experimental parameters such as the initial ratio of [Mo7O24]2– precursor, the current and time, we can modify the size and the size distribution of MoO2 nanoparticles on graphene sheets. The composites were characterized with Scanning Electron Microscopy, Transmission Electron Microscopy, X-ray Diffraction and Raman Spectroscopy.

Investigation of L-Tryptophan Electrochemical Oxidation with a Graphene-Modified Electrode

A graphene sample (EGr) was prepared by electrochemical exfoliation of graphite rods in solution containing 0.05 M (NH4)2SO4 + 0.1 M H3BO3 + 0.05 M NaCl. The exfoliation was performed by applying a constant voltage (12 V) between the graphite rods, while the temperature was kept constant (18 °C) with a temperature-controlled cryostat. The structural investigation of the graphene sample, performed by X-ray powder diffraction (XRD), revealed that the sample consists of a mixture of few-layer (69%), multi-layer graphene (14%) and graphene oxide (17%). In addition, XPS analysis proved that the sample was triple-doped with heteroatoms such as nitrogen (1.7 at%), sulfur (2.5 at%), and boron (3 at%). The sample was deposited onto the surface of a clean, glassy carbon electrode (GC) and investigated for the non-enzymatic electrochemical detection of L-tryptophan (TRP). The electrocatalytic properties of the EGr/GC electrode led to a considerable decrease in the oxidation potential from +0.9 V (bare GC) to +0.72 V. In addition, the EGr/GC electrode has higher sensitivity (two times) and a lower detection limit (ten times) in comparison with the bare GC electrode.

Pencil Graphite Rods Decorated with Nickel and Nickel-Iron as Low-Cost Oxygen Evolution Reaction Electrodes

Society is demanding clean energy to substitute the greatly pollutant carbon-based fuels. As an alternative, the green hydrogen produced by electrocatalysis constitutes a nice strategy as its products and reactants...

In situ generation of exfoliated graphene layers on recycled graphite rods for enhanced capacitive performance of Ni–Co binary hydroxide

A functionalized exfoliated graphite rod (FEGR), with a high surface area, is produced for use as a promising substrate for supercapacitors, via controlled oxidative treatment of a recycled graphite rod of exhausted zinc–carbon batteries.