Non‐Conventional Electrochemical Techniques for Assembly of Electrodes on Glassy Carbon‐Like PPF Materials and Their Use in a Glucose Microfluidic Fuel‐Cell

This paper addresses the electrochemical growth of PtAg and Au nanoparticles on pyrolyzed photoresist films (PPFs). The PtAg/PPF electrode was evaluated toward oxygen reduction reaction (ORR) in the absence and presence of glucose; meanwhile the electrocatalytic activity of Au/PPF was investigated for the glucose electrooxidation reaction (GOR) in 0.3 M KOH in the absence and presence of air as an oxygen source. The results obtained using the electrochemical studies showed that the PtAg/PPF electrode exhibited tolerance toward the ORR in the presence of low glucose concentrations. Moreover, Au/PPF showed good affinity toward glucose oxidation at high concentrations (50 and 100 mM) in the presence of oxygen instead further oxidations of glucose by‐products. Both electrocatalysts were evaluated as the cathode (PtAg/PPF) and the anode (Au/PPF) in a glucose microfluidic fuel cell (G‐μFC) constructed using a UV‐lithography technique and several sheets of different polymeric materials. The G‐μFC was tested using 100 mM glucose with 0.3 M KOH as electrolyte in the absence of an external source of nitrogen or oxygen as the fuel at zero flow rate; this cell reached a maximum power density of 0.085 mW cm⁻² using a low Pt loading (approximately 20% of weight percentage) mixed with non‐noble materials, such as Ag.     

Fabrication and evaluation of a passive SU8-based micro direct glucose fuel cell

Microsystem Technologies - A passive micro direct glucose fuel cell (μDGFC) using SU8-current collector structures of 8 × 14 mm with a grid that allows the delivery...     

A semi-conducting polypyrrole/coffee grounds waste composite for rhodamine B dye adsorption

A composite based on coffee grounds waste (CGW) coated with the semi-conducting polypyrrole (PPy) was prepared by pyrrole polymerization using potassium persulfate as oxidant. The composite was characterized by FTIR spectroscopy, cyclic voltammetry, UV/vis spectroscopy, scanning electron microscopy (SEM) and TGA analysis. SEM analysis showed homogeneous coating of coffee fibers with spherical nanoparticles of PPy with diameters in the range of 200–300 nm. Aqueous adsorption experiments of rhodamine B dye (RhB) onto the as-prepared composite were performed. The effect of pH and initial dye concentration (C₀) on the adsorption behavior was studied. The results showed that this material was an efficient adsorbent of RhB dye at alkaline pH. The adsorption experiments were set at C₀ = 200 mg/L and initial pH values of 2.0, 3.25 and 9.0, the adsorption capacities were 7.22, 13.8, and 19.0 mg of dye/g of the composite, respectively. Nonetheless, when pH was maintained at 9.0 throughout adsorption time, the adsorption capacity increased to 32 mg of dye/g of the composite. When performing adsorption tests using pure CGW, dye adsorption was insignificant at any pH level. Adsorption isotherm for RhB at controlled pH of 9.0 was well described by the Redlich–Peterson model and by the typical Langmuir adsorption model with a theoretical maximum adsorption capacity (q_max) of 50.59 mg of dye/g of composite.     

Glycerol oxidation in a microfluidic fuel cell using Pd/C and Pd/MWCNT anodes electrodes

Pd/C and Pd/MWCNT based electro-catalysts were prepared by impregnation and used as anodes for glycerol electro-oxidation in a microfluidic fuel cell. Average particle size and lattice parameters of the catalysts were determined by X-ray diffraction, resulting in 7.5 and 3.5 nm for Pd/C and Pd/MWCNT respectively. The electro-catalytic activity of Pd/C and Pd/MWCNT was investigated in 0.1 M glycerol. The results obtained by electrochemical studies in half cell configuration showed that the onset potential for glycerol oxidation on Pd/MWCNT was characterized by a negative shift ca. 40 mV compared to Pd/C. The maximum power density obtained was 0.51 and 0.7 mW cm⁻² for Pd/C and Pd/MWCNT respectively. These results are comparable with those obtained for a microfluidic fuel cell that uses glucose as fuel. The results of this work not only show that glycerol can be used as fuel in a microfluidic fuel cell but also its performance is similar to that obtained with others fuels.     

Harvesting energy from real human urine in a photo-microfluidic fuel cell using TiO2–Ni anode electrode

The use of a liquid sample employed for analysis in microfluidic fuel cells has been increased because it can be used in order to obtain medical diagnostic and at the same time as fuel. This document presents the construction and evaluation of a photo-assisted microfluidic fuel cell (photo-μFC) that uses human urine as a fuel. For the construction of this photo-μFC, TiO₂ nanoparticles modified with Ni(OH)₂ were synthesized for use as a photoanode in the oxidation of the urea content in urine, finding an increase in the absorption of light in the visible spectrum with respect to TiO₂. Nanoparticles of TiO₂–Ni in a mixture of anatase (60%) and brookite (40%) phases were found with crystallite sizes of 9 and 15 nm, respectively. The photo-μFC proved with urine, showed an open-circuit potential of 0.70 V, a maximum current density of 1.7 mA cm^?2 and a maximum power density of 0.09 mW cm^?2. The photo-μFC developed was evaluated for 15 consecutive hours at room temperature to observe the lifetime and stability of the photoanode with respect to the generated current. In addition, the oxidation of the urea by the photogenerated holes (h⁺) in the TiO₂ was verified. This research shows the novelty of a promising advance in the use of a microfluidic fuel cell operated with a single-stream from human urine and using photoanodes (TiO₂–Ni) to obtain electrical power with a feasible application in low power portable medical devices.     

Monitoring External Corrosion of a Pipeline Covered with a Polyolefin Tape Using Electrochemical Impedance Spectroscopy

Protection of Metals and Physical Chemistry of Surfaces - The external corrosion of a pipeline buried or submerged under specific conditions was studied. The pipelines were made of API 5L X52 steel...