Comparative EIS study of the adsorption and electro-oxidation of thiourea and tetramethylthiourea on gold electrodes

Electrochemical Performance and Hydrogen Storage of Ni-Pd-P-B Glassy Alloy

The search for hydrogen storage materials is a challenging task. In this work, we tried to test metallic glass-based pseudocapacitive material for electrochemical hydrogen storage potential. An alloy ingot with an atomic composition of Ni₆₀Pd₂₀P₁₆B₄ was prepared via arc melting of extremely pure elements in an Ar environment. A ribbon sample with a width of 2 mm and a thickness of 20 mm was produced via melt spinning of the prepared ingot. Electrochemical dealloying of the ribbon sample was conducted in 1 M H₂SO₄ to prepare a nanoporous glassy alloy. The Brunauer-Emmett-Teller (BET) and Langmuir methods were implemented to obtain the total surface area of the nanoporous glassy alloy ribbon. The obtained values were 6.486 m²/g and 15.082 m²/g, respectively. The Dubinin-Astakhov (DA) method was used to calculate pore radius and pore volume; those values were 1.07 nm and 0.09 cm³/g, respectively. Cyclic voltammetry of the dealloyed samples revealed the pseudocapacitive nature of this alloy. Impedance of the dealloying sample was measured at different frequencies through use of electrochemical impedance spectroscopy (EIS). A Cole-Cole plot established a semicircle with a radius of ~6 Ω at higher frequency, indicating low interfacial charge-transfer resistance, and an almost vertical Warburg slope at lower frequency, indicating fast diffusion of ions to the electrode surface. Charge-discharge experiments were performed at different constant currents (75, 100, 125, 150, and 200 mA/g) under a cutoff potential of 2.25 V vs. Ag/AgCl electrode in a 1 M KOH solution. The calculated maximum storage capacity was 950 mAh/g. High-rate dischargeability (HRD) and capacity retention (Sn) for the dealloyed glassy alloy ribbon sample were evaluated. The calculated capacity retention rate at the 40th cycle was 97%, which reveals high stability.

Modification of carbon foam with 4-mercaptobenzoic acid functionalised gold nanoparticles for an application in a yeast-based microbial fuel cell

Modification of carbon foam with gold nanoparticles (AuNPs) was successfully performed through a hydrothermal method. The modified AuNPs were functionalised with 4-mercaptobenzoic acid (MBA) to improve their affinity toward microorganisms. TEM and SEM characterization indicated that although polydisperse spherical nanoparticles of AuNPs with particle sizes around 17 nm were obtained, the attached nanoparticles were agglomerated to be around 0.4 to 1.5 μm in size on the carbon foam surface. The electrochemical studies using cyclic voltammetry technique affirmed that the modified carbon foam electrodes have electroactive properties against glucose. Evaluation of the electrode was performed for a microbial fuel cell using Candida fukuyamaensis yeast as the microorganisms. The polarization curves showed that functionalisation of AuNPs-modified carbon foam with MBA provides around three times higher current density (1226.93 mA m-2) and power density (330.61 mW m-2) compared to the unmodified one. This result indicated that the modification is suitable to improve yeast attachment on the electrode surface.

Reactivity of carbon black diamond electrode during the electro-oxidation of Remazol Brilliant Blue R

This article reports for the first time, the reactivity of Carbon Black Diamond (CBD) electrode using cyclic voltammetry and electrochemical impedance techniques in 0.25 M H₂SO₄ solution containing 0.5 mM K₄Fe(CN)₆.