Study on electrodeposited CuFe film on Cu electrode as an efficient catalyst for electrochemical reduction of nitrate

In this research, a novel CuFe catalyst was fabricated using a simple, single-step electrodeposition method on a traditional Cu electrode. CuFe films from various electrodeposition baths with different Cu and Fe ratios were prepared by chronopotentiometry and characterised by X-ray diffraction (XRD), Scanning electron microscope (SEM), Energy dispersive X-ray analysis (EDX), and Pb underpotential deposition (Pb-UPD). The Cu electrode coated with CuFe8020 (from electrodeposition bath containing 80% Cu and 20% Fe) showed the highest reduction current among the film produced. The Cu electrode coated with CuFe8020 exhibited three times higher nitrate reduction efficiency and less undesired products like NO2− và NH4+ than the traditional Cu.

Fe, N-Doped Metal Organic Framework Prepared by the Calcination of Iron Chelated Polyimines as the Cathode-Catalyst of Proton Exchange Membrane Fuel Cells

Aromatic polyimine (PIM) was prepared through condensation polymerization between p-phenylene diamine and terephthalaldehyde via Schiff reactions. PIM can be physically crosslinked with ferrous ions into gel. The gel-composites, calcined at two consecutive stages, with temperatures ranging from 600 to 1000 °C, became Fe- and N-doped carbonaceous organic frameworks (FeNC), which demonstrated both graphene- and carbon nanotube-like morphologies and behaved as an electron-conducting medium. After the two-stage calcination, one at 1000 °C in N2 and the other at 900 °C in a mixture of N2 and NH3, an FeNC composite (FeNC-1000A900) was obtained, which demonstrated a significant O2 reduction peak in its current–voltage curve in the O2 atmosphere, and thus, qualified as a catalyst for the oxygen reduction reaction. It also produced a higher reduction current than that of commercial Pt/C in a linear scanning voltage test, and the calculated e-transferred number reached 3.85. The max. power density reached 400 mW·cm−2 for the single cell using FeNC-1000A900 as the cathode catalyst, which was superior to other FeNC catalysts that were calcined at lower temperatures. The FeNC demonstrated only 10% loss of the reduction current at 1600 rpm after 1000 redox cycles, as compared to be 25% loss for the commercial Pt/C catalyst in the durability test.

Preparation of carbon anode sheet precursor using raw Air Laya–Bukit Asam coal and its application for battery

Research has been carried out on manufacturing carbon electrode thin sheets used as anode for solid battery cells. The material used is raw coal carbonized at 800 and 1000oC, polyvinylidene fluoride (PVDF), and N-Dimethylacetamide (DMAC) as a solvent. Observation of crystal structure by X-rays diffraction method shows a diffraction pattern where crystallites in all product samples have an intermediate structure between graphite and amorphous known as a turbostratic structure or a random layer lattice structure. The distance between the crystallite structure’s aromatic layers (d002) is in the range 3.52-3.62 Å. Aromaticity (fa) is in the range 0.42 - 0.48 for all samples. The high value of d002 indicated that the crystallinity or level of graphitization obtained by all samples was still low. Manufacturing technique using a Doctor Blade-based tape casting method. The discharge capacities of the samples reach about 60 and 18 mAh.g-1, while their charge capacities at the first cycle are 50 and 16 mAh.g1, respectively. Cyclic voltammetry (CV) was performed using anodes resulted at 0.1 to 2.3 volt. During the forward scan, CV curves of the sample reveal a reduction current starting from around 1.2 V and exhibiting two-reduction waves, between 1.2 and 0.6 V.

Degradation Kinetics and Mechanism of Polychloromethanes Reduction at Co-MoS2/Graphite Felt Electrode

In this study, the electrochemical dechlorination of different polychloromethanes (CCl4, CHCl3, and CH2Cl2) on a Co-MoS2 graphite felt cathode was investigated. The Co-MoS2 electrocatalyst was prepared hydrothermally on a graphite felt support. The prepared catalyst’s characterization revealed the formation of hybridized CoSx and MoS2 nanosheets deposited on the pore structures of graphite. The influencing factor for the electro-dechlorination parameters such as applied current density, pH, and sample concentration on the dechlorination rate was optimized. A significant capacitive reduction current density peak of approximately 1 mA/cm2 was noted for CCl4 at a potential of −0.3 V (vs. AgCl). The dechlorination mechanism was attributed to the stepwise hydrogenolysis mechanism that involves the organochlorides bond cleavage by H* insertion. It was noted that the Co-MoS2 graphite felt electrode exhibited excellent catalytic activity toward the reduction of each of the chlorinated compounds with high selectivity toward the higher-order organochloride. Moreover, the dechlorination rates for each of the compounds were suited to the first-order kinetic model, and the estimated apparent rate constants showed the dechlorination in the following sequence CH2Cl2 (k3 = 9.1 × 10−5 s−1) < CHCl3 (k2 = 1.5 × 10−3 s−1) < CCl4 (k1 = 2.8 × 10−3 s−1).

Synthesis of Fe(II)/Co(II)-Fused Triphenyl Porphyrin Dimer as Candidate for Oxygen Reduction Reaction Catalyst

This paper reports the synthesis of Fe(II)/Co(II) fused triphenyl porphyrin dimers as candidate of hybrid organic metal electrocatalyst. The synthesis was conducted in five-step reactions using the starting materials pyrrole and benzaldehyde. The fuse oxidative reaction was done via free-base form of triphenyl porphyrin to omit metal insertions/removals of intermediate products. This strategy is very beneficial for the synthesis of metal fused triphenyl porphyrin that needs less reactions where phenyliodine(III) bis(trifluoroacetate) (PIFA) was successfully deployed in the oxidative reaction of two free-base triphenyl porphyrins. Here, the comparisons of NMR spectra were presented to see the changes of the starting material to the product. Initial electrochemical tests showed that reduction current of planar structure of Fe/Co fused triphenyl porphyrin dimer was on the potential range at -1.10 V to 0.45 V vs Au. Fe-fused triphenyl porphyrin dimer with 7.58 × 10–4 A (-1.05 V) showed slightly better performance than Co-fused triphenyl porphyrin dimer with 5.67 × 10–4 A (-0.97 V).

Study the Gold Compound (AuCl4) in KCl using Cyclic Voltammetry by Nano Sensor

Gold compound AuCl4 used in different medical purpose especially in different diseases such as Arthritis, the study focused on the electrochemical properties of gold compound in an electrolyte (KCl solution) using modified glassy carbon electrode with carbon nanoparticles (CNT/GCE) as a good nanosensor to determine the chemical behavior of gold compound by the oxidation – reduction current peaks as appeared in the cyclic voltammogram at 115 and 500 mV respectively. It was studied in this study the different concentrations, scan rates, pH, and the reliability (stability), also the effect of ascorbic acid on the redox current peaks of the gold compound was studied. The results were discussed to promising the gold compound as a treatment in different disease in an alkaline medium because the Au(IV) compound acts as antioxidant by disappearing current peak of the oxidation and enhanced the reduction current peak.

Nanoscale Assembly of BiVO4/CdS/CoOx Core–Shell Heterojunction for Enhanced Photoelectrochemical Water Splitting

Porous BiVO4 electrodes were conformally decorated with CdS via a chemical bath deposition process. The highest photocurrent at 1.1 V vs. RHE was achieved for a BiVO4/CdS composite (4.54 mA cm−2), compared with CdS (1.19 mA cm−2) and bare BiVO4 (2.1 mA cm−2), under AM 1.5G illumination. This improvement in the photoefficiency can be ascribed to both the enhanced optical absorption properties and the charge separation due to the heterojunction formation between BiVO4 and CdS. Furthermore, the BiVO4/CdS photoanode was protected with a CoOx layer to substantially increase the photostability of the material. The new BiVO4/CdS/CoOx nanostructure exhibited a highly stable photocurrent density of ~5 mA cm−2. The capability to produce O2 was locally investigated by scanning photoelectrochemical microscope, which showed a good agreement between photocurrent and O2 reduction current maps. This work develops an efficient route to improve the photo-electrochemical performance of BiVO4 and its long-term stability.

Electric Stimulation of Astaxanthin Biosynthesis in Haematococcus pluvialis

The green microalga Haematococcus pluvialis accumulates astaxanthin, a potent antioxidant pigment, as a defense mechanism against environmental stresses. In this study, we investigated the technical feasibility of a stress-based method for inducing astaxanthin biosynthesis in H. pluvialis using electric stimulation in a two-chamber bioelectrochemical system. When a cathodic (reduction) current of 3 mA (voltage: 2 V) was applied to H. pluvialis cells for two days, considerable lysis and breakage of algal cells were observed, possibly owing to the formation of excess reactive oxygen species at the cathode. Conversely, in the absence of cell breakage, the application of anodic (oxidation) current effectively stimulated astaxanthin biosynthesis at a voltage range of 2–6 V, whereas the same could not be induced in the untreated control. At an optimal voltage of 4 V (anodic current: 30 mA), the astaxanthin content in the cells electro-treated for 2 h was 36.9% higher than that in untreated cells. Our findings suggest that electric treatment can be used to improve astaxanthin production in H. pluvialis culture if bioelectrochemical parameters, such as electric strength and duration, are regulated properly.

Electrochemical Trimethylamine N-Oxide Biosensor with Enzyme-Based Oxygen-Scavenging Membrane for Long-Term Operation under Ambient Air

An amperometric trimethylamine N-oxide (TMAO) biosensor is reported, where TMAO reductase (TorA) and glucose oxidase (GOD) and catalase (Cat) were immobilized on the electrode surface, enabling measurements of mediated enzymatic TMAO reduction at low potential under ambient air conditions. The oxygen anti-interference membrane composed of GOD, Cat and polyvinyl alcohol (PVA) hydrogel, together with glucose concentration, was optimized until the O2 reduction current of a Clark-type electrode was completely suppressed for at least 3 h. For the preparation of the TMAO biosensor, Escherichia coli TorA was purified under anaerobic conditions and immobilized on the surface of a carbon electrode and covered by the optimized O2 scavenging membrane. The TMAO sensor operates at a potential of −0.8 V vs. Ag/AgCl (1 M KCl), where the reduction of methylviologen (MV) is recorded. The sensor signal depends linearly on TMAO concentrations between 2 µM and 15 mM, with a sensitivity of 2.75 ± 1.7 µA/mM. The developed biosensor is characterized by a response time of about 33 s and an operational stability over 3 weeks. Furthermore, measurements of TMAO concentration were performed in 10% human serum, where the lowest detectable concentration is of 10 µM TMAO.