Graphite Rod Research Articles

Simulation of a thermo-electrochemical cell with graphite rod electrodes.

The rapid development of human society has resulted in the extensive release of waste heat. The thermo-electrochemical cell (TEC), a cutting-edge technology that converts low-grade waste heat into electricity, has garnered increasing attention. However, the complex interactions among various processes, such as fluid flow, electrochemical reactions and heat transfer, make it challenging to evaluate their effect on the overall performance of the TEC. Understanding the synergistic mechanisms and coupling effects of these processes is crucial for optimizing and implementing TECs in practical applications. In this paper, a mathematical model is developed by coupling electrochemical reactions and heat/mass transfer. The distributions of ion concentration, electrolyte velocity and temperature are analyzed under varying temperature differences and electrode distances. The results demonstrate a significant interaction between heat transfer and electrolyte flow. Higher temperatures not only improve the open circuit voltage, but also promote ion transport convection and hence enhance the current density. In addition, a higher concentration of ions or smaller electrode spacing exhibits an apparently improved performance of the TEC, due to the facilitated ion transport and reduced concentration overpotential. Notably, electrode spacing has a negligible effect on the maximum power density of the TEC under a constant heat flux, but it does enhance the current density due to the combined effect of heat and ion transfer. Overall, the proposed mathematical model provides deeper insight into the physical-chemical processes involved in TECs and offers valuable guidance for TEC design and practical applications.

Promoted glucose electrooxidation at Ni(OH)2/graphene layers exfoliated facilely from carbon waste material.

Nowadays, the glucose electro-oxidation reaction (GOR) is considered one of the most important solutions for environmental pollution. The GOR is the anodic reaction in direct glucose fuel cells and hybrid water electrolysis. In this study, the GOR is boosted using a carbon support modified with Ni(OH)2 as a non-precious catalyst. The carbon support, with in situ generated graphene nanosheets having a large surface area, grooves, and surface functional groups, is prepared via a simple electrochemical treatment of the carbon rods of an exhausted zinc-carbon battery. Ni(OH)2 is electrodeposited on the surface of the functionalized exfoliated graphite rod (FEGR) via the dynamic hydrogen bubbling technique (DHBT) and tested for GOR. The thus-prepared Ni(OH)2/FEGR electrode is characterized by SEM, mapping EDX, HR-TEM, XRD, and XPS characterization tools. Ni(OH)2/FEGR displays an onset potential of 1.23 V vs. the reversible hydrogen electrode (RHE) and attains high current densities at lower potentials. Additionally, Ni(OH)2/FEGR showed prolonged stability toward GOR by supporting a constant current over a long electrolysis time. The enhanced catalytic performance is attributed to the superb ionic and electronic conductivity of the catalyst. Importantly, ionic conductivity increased, due to (i) a large surface area of in situ generated graphene layers, (ii) enhanced distribution of active material during deposition using DHBT, and (iii) increased hydrophilicity of the underlying substrate. Therefore, the Ni(OH)2/FEGR electrode can be used efficiently for GOR as a low-cost catalyst, achieving low onset potential and high current densities at low potentials.

Influence of Graphene Sheets Accumulation on Optical Band Gap Enhanced Graphite Exfoliation

Recently, graphene has been adopted to replace other expansive materials in various devices that perform numerous functionalities in many industrial fields. Meanwhile, researchers are still investigating the amazing properties of graphene. Herein, reduced graphene oxide (rGO) has been successfully exfoliated directly using a graphite rod in a modified electrolyte including a table salt as a co-electrolyte. The structure of graphene obtained by using exfoliation methods shows a low ratio of O/C and confirms the high crystallinity of rGO. The thickness of rGO was adjusted during the drying of the drops of rGO solution and obtained about an 8-80 nm rGO thick. The increased O/C ratio and crystallinity enhancement could be attributed to the quantum confinement effect. Further investigations to estimate the decay constant of the optical band gap during the thinning of the rGO layers show that the optical band gap was associated with thicknesses of the rGO at a decay constant of 0.3367±0.00205. These results would be crucial in several optical applications that depend on the thicknesses and the band gap.

Electrodeposition of Ni - Fe on graphite rod as an efficient and binder-free electrocatalyst for oxygen and hydrogen evolution reactions

In this paper, nickel-iron (Ni-Fe) on a graphite substrate was electrodeposited as an effective electrocatalyst for hydrogen and oxygen evolution reactions using the cyclic voltammetry method for the first time. Some important factors such as the range of applied potential, scan rate, and the number of cycles were optimized. In addition, the used substrate is a graphite rod, which is cheap, stable, and has good electrical conductivity. The main results show that the improved Ni-Fe coating on graphite rod has promising hydrogen evolution reaction (HER) activity, which exhibits small over voltages of − 191.2, − 394.0, and − 687.3 mV at the current densities of − 10, − 100, and − 400 mA. cm−2, respectively. Furthermore, the synthesized Ni-Fe electrocatalyst only needs 284 mV overpotentials to operate at a current density of 10 mA. cm−2, indicating its great performance for the oxygen evolution reaction (OER). This paper offers a method for generating a bifunctional, binder-free, affordable, and fast water splitting electrocatalyst that has excellent performance.

Efficient expression of heterologous protein by engineered Komagataella phaffii by harnessing a bioelectrical CO2 reduction system

Methylotrophic yeast Komagataella phaffii (syn. Pichia pastoris) is an important host for heterologous protein expression although its traditional inducer methanol is toxic and flammable. Using green fluorescent protein (GFP) as a model of heterologous protein in this research, recombinant K. phaffii was constructed through wild-type formate dehydrogenase gene knockout, intracellular and extracellular expression of Candida boidinii formate dehydrogenase gene under sorbitol dehydrogenase promoter (PSDH) respectively to reduce carbon dioxide (CO2) to formate in a two-chamber H-shaped three-electrode bioelectrical reactor equipped with a solar panel stage by stage. Generated formate in the bioelectrical reactor was used as a safe inducer of engineered K. phaffii strains expressing GFP successfully. Further, the electrical potential was optimized and three cathodes, graphite disk electrode, graphite rod electrode, and glassy carbon electrode, were used and modified subsequently with poly(neutral red) to obtain the highest volumetric GFP intensity and specific GFP intensity as 4424.5 a.u. and 384.0 a.u./OD600, which was 1.7- and 3.2- fold of that of methanol induction respectively, 3.9-fold of that formate induction. Therefore, a safe recombinant K. phaffii system was developed successfully for heterologous protein expression, and demonstrated a new approach to utilize CO2.

Strategically improving electrical conductivity of reduced graphene oxide through a series of reduction processes

Current work aims at producing reduced graphene oxide(rGO) with highest possible conductivity, starting with graphene oxide(GO) produced by electrochemical exfoliation(ECE) of graphite rod salvaged from C-type primary batteries. Six single-step reduction process were used to reduce GO in the first stage. Following that, most effective three reduction methods, namely water-based reduction(W), hydrothermal reduction(H), and microwave reduction(MW), were used in two combinations (W-H-MW and W-MW-H). The conductivity of rGO(W-H-MW) and rGO(W-MW-H) is 43.78Sm−1 and 28.33Sm−1 respectively with rGO(W-H-MW) having highest conductivity of all selected reduction methods. It is also found that sequence of reduction processes has a big impact on the final product's conductivity, ID/IG ratio, and XRD peak intensity. Characterization by XRD, XPS, TEM, FEG-SEM, FTIR, Raman etc. is used to discuss the findings. Chemical structure, morphology and specific surface area of rGO(W-H-MW) are compared to those of GO and their influence on bulk conductivity of rGO’s are discussed.

Efficient Removal of Mercury from Polluted Aqueous Solutions Using the Wireless Bipolar Electrochemistry Technique.

Mercury represents one of the major toxic pollutants in water that affect human and ecosystem. Extensive efforts have been globally invested to remove mercury using various chemical and electrochemical approaches. In this study, I propose the use of bipolar electrochemistry for the first time for mercury depollution process. Mercury(II) is removed from aqueous solutions by direct electrodeposition on millimeter scale graphite rods held in a bipolar setup. By adjusting the strength of the applied electric field and the number of the graphite rods the efficiency of the system can be controlled. This wireless technique allows the use of multiple graphite rod arrays within the bulk cell which resulted in high removal efficiency (98 %) of Hg2+ ions from the polluted solution. The method is straightforward, green, and efficient. The concept can be adapted to remove other heavy metal ions or electrochemically active contaminants from polluted water as long as their reduction potentials are within the water stability window.

Electrochemical Reduction of Hexavalent Chromium in the Tannery Effluents in the Quindío Department, Colombia

Considering the essential participation of Colombia in leather production, it is necessary to consider new alternatives for wastewater degradation as a factor for its development. This industry is recognized worldwide as one of the most polluting water due to the chemical processes. The effluents of the leather industry constitute one of the most complex residues for their treatment due to the characteristics of their contaminant load. Thus, an adequate treatment of such wastewater is essential from an environmental and health viewpoint. This study aims to reduce hexavalent chromium in the tannery effluents of the Quindío Department. This study applied different electrochemical methods to simulated wastewater with hexavalent chromium concentrations similar to those of tannery effluents in the Quindío Department, such as cyclic voltammetry, linear sweep voltammetry, and chronoamperometry, using graphite rod and carbon cloth as working electrodes. Obtaining a chromium reduction of around 99.45% is a very satisfactory result considering that the tanning industries in Colombia do not comply with the legislation for eliminating chromium in their effluents. Finally, the electrochemical techniques employed proved to be very efficient and reliable for remediating industrial wastewater, specifically with the effluents treated in this study, since they have economically sustainable characteristics in terms of operating costs, in addition to being environmentally friendly.

Enhanced Acetaminophen Electrochemical Sensing Based on Nitrogen-Doped Graphene.

Because of the widespread acetaminophen usage and the danger of harmful overdosing effects, developing appropriate procedures for its quantitative and qualitative assay has always been an intriguing and fascinating problem. A quick, inexpensive, and environmentally friendly approach based on direct voltage anodic graphite rod exfoliation in the presence of inorganic salt aqueous solution ((NH4)2SO4-0.3 M) has been established for the preparation of nitrogen-doped graphene (exf-NGr). The XRD analysis shows that the working material appears as a mixture of few (76.43%) and multi-layers (23.57%) of N-doped graphenes. From XPS, the C/O ratio was calculated to be 0.39, indicating a significant number of structural defects and the existence of multiple oxygen-containing groups at the surface of graphene sheets caused by heteroatom doping. Furthermore, the electrochemical performances of glassy carbon electrodes (GCEs) modified with exf-NGr for acetaminophen (AMP) detection and quantification have been assessed. The exf-NGr/GCE-modified electrode shows excellent reproducibility, stability, and anti-interfering characteristics with improved electrocatalytic activity over a wide detection range (0.1-100 µM), with a low limit for AMP detection (LOD = 3.03 nM). In addition, the developed sensor has been successfully applied in real sample analysis for the AMP quantification from different commercially available pharmaceutical formulations.

Carbon Nanofibers-Sheathed Graphite Rod Anode and Hydrophobic Cathode for Improved Performance Industrial Wastewater-Driven Microbial Fuel Cells.

Carbon nanofiber-decorated graphite rods are introduced as effective and low-cost anodes for industrial wastewater-driven microbial fuel cells. Carbon nanofiber deposition on the surface of the graphite rods could be performed by the electrospinning of polyacrylonitrile/N,N-Dimethylformamide solution using the rod as nanofiber collector, which was calcined under inert atmosphere. The experimental results indicated that at 10 min electrospinning time, the proposed graphite anode demonstrates very good performance compared to the commercial anodes. Typically, the generated power density from sugarcane industry wastewater-driven air cathode microbial fuel cells were 13 ± 0.3, 23 ± 0.7, 43 ± 1.3, and 185 ± 7.4 mW/m2 using carbon paper, carbon felt, carbon cloth, and graphite rod coated by 10-min electrospinning time carbon nanofibers anodes, respectively. The distinct performance of the proposed anode came from creating 3D carbon nanofiber layer filled with the biocatalyst. Moreover, to annihilate the internal cell resistance, a membrane-less cell was assembled by utilizing a poly(vinylidene fluoride) electrospun nanofiber layer-coated cathode. This novel strategy inspired a highly hydrophobic layer on the cathode surface, preventing water leakage to avoid utilizing the membrane. However, in both anode and cathode modifications, the electrospinning time should be optimized. The best results were obtained at 5 and 10 min for the cathode and anode, respectively.

Electrochemical oxidation of meglumine in a pharmaceutical formulation using a nanocomposite anode

The electrocatalytic oxidation of meglumine and gadoterate meglumine (Gd-DOTA) on a TiO2-Ni(SO4)0.3(OH)1.4 composite anode was investigated in alkaline medium (5 M KOH) using cyclic voltammetry and chronoamperometry. The composite was prepared by hydrothermal method and the morphology and structure of the produced nanoparticles were studied by scanning electron microscopy with energy-dispersive X-ray spectroscopy, X-ray diffraction, atomic force microscopy, BET surface area analysis and Fourier transform infrared spectroscopy. The characterization revealed the formation of Ni(SO4)0.3(OH)1.4 nanobelts dispersed on TiO2 nanoaggregates. The composite was coated onto a porous graphite rod, showing good adherence without requiring any binder (according to their anodic and cathodic charges). The supported composite was electrocatalytic, allowing the oxidation of meglumine, either as pure reagent or contained in gadoterate meglumine solutions. Electrochemical methods allowed determining the kinetic parameters, such as the electron transfer coefficient α, the total number of electrons n and the standard heterogeneous rate constant k0 for the reaction of meglumine. The chronoamperometric tests informed about the good stability of the composite anode upon meglumine oxidation at +0.6 V for 10 h. The electrochemical oxidation of meglumine in a commercial pharmaceutical formulation (Dotarem®) was corroborated via ultra-high performance liquid chromatography coupled to electrospray ionization and quadrupole time-of-flight mass spectrometry.

Effect of steel rod embedded in electrode on continuous consumption of graphite by using numerical simulation

ABSTRACT Under the dual requirements of cost reduction and double carbon goal, it is more meaningful to reduce the continuous consumption of graphite electrode in ladle furnace. In this paper, the three-dimensional coupling model of electromagnetic field, heat transfer, flow field is established, and the influence of embedded steel rod on the current, temperature and continuous consumption of graphite in the electrode was studied. The current in graphite and steel rod is mainly distributed in the edge area near the left electrode, respectively. With the increase of the radius of the steel rod, the proportion of the current passing through the steel rod to the total current increases, the area of each temperature range above 500 K and the total continuous consumption rate of the electrode decrease.

A robust electrochemical sensing platform for the detection of erlotinib based on nitrogen-doped graphene quantum dots/copper nanoparticles-polyaniline-graphene oxide nanohybrid

Erlotinib is a potent and highly specific tyrosine kinase inhibitor with the hindering effects on the growth of cancer cells. An electrochemical sensor with the great sensitivity and selectivity was fabricated for determining erlotinib by using a graphite rod electrode modified by the nitrogen-doped graphene quantum dots (N-GQDs) and a ternary nanohybrid comprising copper nanoparticles, polyaniline, along with graphene oxide (N-GQDs/CuNPs-PANI@GO) for the first time. The establishment of PANI and CuNPs was done simultaneously on the GO surface by the in situ oxidative polymerization method. The morphological characteristics and elemental structure of the synthesized nanoparticles were examined by some microscopy techniques and x-ray energy/diffraction methods. The fabricated sensor represented the electrocatalytic activity towards erlotinib with a linear detection range from 1.0 nM to 35.0 μM, a detection limit of 0.712 nM, and a sensitivity of 1.3604 μA μM−1. Moreover, the N-GQDs/CuNPs-PANI@GO sensor showed acceptable stability up to 30 d (94.82%), reproducibility (RSD values of 3.19% intraday and 3.52% interday), and repeatability (RSD value of 3.65%) as a novel and powerful electrochemical sensor. It was successfully applied to monitor erlotinib in the drug-injected aqueous solution, serum, and urine samples that proved the capability of the sensor for the erlotinib monitoring in the biological samples.

A new ultrasensitive platform based on f-GCNFs@nano-CeO2 core-shell nanocomposite for electrochemical sensing of oxidative stress biomarker 3-nitrotyrosine in presence of uric acid and tyrosine

Electrode materials with high sensitivity and selectivity play a central role in the fabrication of electrochemical sensing platforms. In this work, functionalized graphitized carbon nanofibers (f-GCNFs)core and nano-sized CeO2 (nano-CeO2)shell was synthesized. The XRD, SEM, HRTEM and the EDX results confirmed the formation of the f-GCNFs@nano-CeO2 core–shell nanocomposite. To construct the sensor, the graphite rod electrode (GRE) has been modified with f-GCNFs@nano-CeO2. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) results revealed that the charge transfer on the f-GCNFs@nano-CeO2/GRE was dramatically enhanced compared to the other electrodes. The prepared platform (f-GCNFs@nano-CeO2) exhibited high electro-catalytic activity and the strong synergistic activity between f-GCNFs and nano-CeO2 increased the electroactive surface area. The fabricated f-GCNFs@nano-CeO2/GRE sensor has been utilized for the detection of the oxidative stress biomarker nitrotyrosine (NTyr) using SW-AdASV. The LOD and the LOQ are found to be 0.86 and 2.9 nM, respectively, with the dynamic range 2.0–1720 nM and sensitivity of 145 μAμM−1 cm−2. The developed sensor is highly selective for NTyr detection in the presence of uric acid (UA) and tyrosine (Tyr). Moreover, the fabricated sensor also shows good selectivity, favorable reproducibility, and long-term stability. The applicability of the fabricated sensor demonstrated excellent recovery of NTyr in spiked human serum, urine, and saliva samples. In the end, f-GCNFs@nano-CeO2/GRE was applied to the determination of UA, NTyr, and Tyr simultaneously.

(Digital Presentation) Electrodeposition of Si Metal in Molten CaCl2 with the Molar Ratio of CaO to SiO2=1.8, 2.2 Compounds

An innovative production process of metallic Si is desired to reduce energy consumption and CO2 exhaustion. The authors carried out electrolysis in molten CaCl2 with CaSiO3 above 1300 K, and showed that Si metal could be electrodeposited. The influence of the molar ratio of CaO to SiO2 (R CaO/SiO2 , the same hereinafter) on Si metal deposition was also examined using various calcium silicates, and it was shown that R CaO/SiO2 seemed not to affect the deposition strongly. The suitable condition seemed R CaO/SiO2 =2.0, but it was suggested that the detailed study around R CaO/SiO2 =2.0 was necessary. In this study, the effect of Si electrodeposition in molten CaCl2 containing calcium silicates of R CaO/SiO2 =1.8, 2.2 was investigated, and the appropriate condition for Si metal deposition was investigated. The calcium silicates of R CaO/SiO2 =1.8 and 2.2 were prepared by sintering a molded mixture of CaO and SiO2. Molten CaCl2 containing the prepared calcium silicate was used in the baths at 1673 K. The concentration of solute in the bath was represented by the value calculated from SiO2 amount. A MoSi2 rod with a BN receiver to collect the electrodeposit efficiently was used as the working electrode. A graphite rod and a Mo wire were used as counter and quasi-reference electrodes, respectively. The potential of the quasi-reference electrode was calibrated against the Mo dissolution potential measured by cyclic voltammetry. The cathodic reaction was investigated by cyclic voltammetry, and potentio-static electrolysis was carried out at -1.85 ~ -2.1 V[vs. Mo diss., (the same hereinafter)]. The obtained electrodeposit was analyzed by XRD and SEM-EDX. Current peaks in cyclic voltammogram were not observed in all baths, which is thought due to high temperature. However, the cathode current got larger with increasing R CaO/SiO2 even in the bath of the same SiO2 concentration. This result showed that the reduction of Si ion in the bath occurred, and that the reduction depended on R CaO/SiO2 . In the baths of R CaO/SiO2 =1.8, metallic Si was deposited by the potentio-static electrolysis at -1.85 ~ -2.1 V. The current efficiency was about 28 % at -1.95 V, and slightly decreased at 2.1 V as shown in Fig.1. In the bath of R CaO/SiO2 =2.2, metallic Si was also obtained in the same potential region, but the current efficiency sharply decreased below -2.0 V. It was shown in our previous study that Ca co-deposited with metallic Si by electrolysis at -2.0 V in the bath of R CaO/SiO2 =2.0, and that the current efficiency became low in this condition. These results suggest that co-deposition of Ca with Si occurs more easily in the bath of R CaO/SiO2 2.0 and obstructs the efficient electrodeposition of metallic Si. It was indicated that the bath of R CaO/SiO2 < 2.0 was preferable for the electrodeposition of metallic Si. However, the current efficiency was still limited to around 30 %, so the detailed study to clarify the suitable condition for better electrolysis should be necessary. Figure 1

Sulphur-doped graphene based sensor for rapid and efficient gallic acid detection from food related samples

BackgroundNowadays, the food safety issue represents a hot topic. The emerging evidence over the past decade confirms that gallic acid (GA) plays a crucial role, with multiple pharmacological and therapeutic interventions in numerous health complications. MethodsSulphur-doped graphene material (exf-SGR) was obtained from graphite rod electrochemical exfoliation in the presence of inorganic salts mixture such as sodium thiosulfate and ammonium sulphate, Na2S2O3 / (NH4)2SO4 (0.2 M each), at low applied bias (6 V). The complete physico-chemical characterization of the as-prepared material was performed by means of TEM, SEM, STEM-EDS, XRD and XPS analysis. Furthermore, the electrochemical performances of bare glassy carbon (GCE) and modified (exf-SGR/GCE) electrodes for GA assay were evaluated. Significant findingsTEM/SEM images reveal the formation of large dimension graphene sheets having uniformly distributed spherical sulphur crystallites on the surface. XRD demonstrates that the material consists of few-layer S-doped graphenes. From XPS analysis the C/O ratio was determined to be 0.473 while C/S ratio equals 2.741, indicating a high heteroatom doping degree. The exf-SGR/GCE modified electrode shows a superior electrochemical behaviour over a broad GA detection range (0.1–100.0 µM), with a low detection limit (3.03 × 10−8 M). The electrode retains 96.83% of its initial response after 50 consecutive CV measurements indicating an excellent long-term stability and repeatability. The sensor possesses very good anti-interfering capabilities in complex matrix. The developed electrochemical sensor can provide a fast model for GA detection in food related and biological real sample analysis.

Dechlorination of dichloromethane by a biofilter enriched with electroactive bacteria: Performance, kinetics, and microbial community

Dichloromethane (DCM) is a recalcitrant volatile organic compound that exhibits biological toxicity and bioaccumulation. In this study, gaseous DCM was removed using an electroactive bacterial biofilter (EBB) with graphite rod as the anode and carbon felt as the cathode. The highest removal efficiency (97.09%) was achieved at a cathodic potential of −600 mV (vs. Ag/AgCl). The EBB had a maximum elimination capacity of 79.29 g m−3 h−1 when the inlet load was 96.48 g m−3 h−1. There was no substrate inhibition phenomenon observed in the EBB, and the Michaelis–Menten model was used to describe the kinetics of the EBB. High-throughput sequencing indicated that electroactive genera such as Rhodanobacter sp., Sphingomonas sp., Pseudomonas sp., Chryseobacterium sp., Pseudochrobactrum sp., and Mycobacterium sp. dominated the EBB. The microbial communities were stable and were slightly affected by the DCM inlet concentration. The results can be applied for the effective treatment of recalcitrant volatile organic compounds (VOCs).

Development of a membraneless single-enzyme biofuel cell powered by glucose

This work presents the development of a membraneless single-enzyme biofuel cell powered by glucose (GBFC). The GBFC biocathode is based on a graphite rod electrode (GRE) coated with a layer of Prussian blue (PB) nanoparticles entrapped into poly(pyrrole-2-carboxylic acid) (PPCA) shell, an additional layer of PPCA, and covalently to polymer linked glucose oxidase (GOx). The bioanode is based on GRE modified with a nanobiocomposite composed of poly(1,10-phenanthroline-5,6-dione), gold nanoparticles entrapped in a PPCA shell, and GOx linked by an amide bond to polymer. The operation of the developed single-enzyme GBFC is based on GOx-catalysed oxidation of glucose on both the bioanode and biocathode and reduction of H2O2 electrocatalysed by PB on the biocathode. The GBFC operated in O2-saturated buffer medium pH 6.0 containing glucose. An open-circuit voltage (OCV) of 646 mV, a maximum power density of 10.94 μW/cm2 and a current density of 60.52 μA/cm2 at 40 mM glucose were determined. OCV and current density were directly proportional to glucose concentration in 0.01–10.00 mM and 0.05–124.00 mM concentration ranges, respectively. In addition, GBFC had good operational stability and retained more than 90% of the initial OCV after 36 days.

Metal-supported cathodically activated graphite via self-reduction as electrocatalysts for efficient hydrogen evolution reaction

Surface modification is a promising approach to modulate the electrocatalyst properties for their further use in energy storage and conversion. In this work, electrochemical-based approach was proposed to generate metallic particles-supported graphite rod (GR). The approach is based on the cathodic activation of GR in the presence of alkali metal salts in dry organic solvent. The activated GR possess a high reducing power that was successfully employed to spontaneously reduce metallic salts in aqueous media. The surface analyses confirm the formation of metallic nanoparticles supported GR. Interestingly, the metallic nanoparticles were found to be generated onto and intercalated into the GR. Next, the generated materials were used as electrocatalyst to drive the hydrogen evolution reaction. Our results demonstrate that the electrocatalytic performances depend on various parameters including the radius of the alkali metal cation and the injected charge during the electrochemical activation. The as-prepared Pt/Li-GR exhibits the best electrochemical activity and stability toward the hydrogen evolution reaction. The necessary overpotential value to reach a current density of 10 mA cm−2 is 40 mV for the Pt/Li-GR, and almost negligible overpotential change is observed during the stability tests. In addition, the proposed approach was successfully used to generate Pd/Li-GR catalyst. More impressively, the latter displays higher HER performances when compared to other reported Pd-based catalysts and comparable performance with commercial Pt/C catalyst.

Highly Sensitive Electrochemical Detection of Azithromycin with Graphene-Modified Electrode

An electrochemical cell containing two graphite rods was filled with the appropriate electrolyte (0.2 M ammonia + 0.2 M ammonium sulphate) and connected to the exfoliation system to synthesize graphene (EGr). A bias of 7 V was applied between the anode and cathode for 3 h. After synthesis, the morphology and structure of the sample was characterized by SEM, XRD, and FTIR techniques. The material was deposited onto the surface of a glassy carbon (GC) electrode (EGr/GC) and employed for the electrochemical detection of azithromycin (AZT). The DPV signals recorded in pH 5 acetate containing 6 × 10−5 M AZT revealed significant differences between the GC and EGr/GC electrodes. For EGr/GC, the oxidation peak was higher and appeared at lower potential (+1.12 V) compared with that of bare GC (+1.35 V). The linear range for AZT obtained with the EGr/GC electrode was very wide, 10−8–10−5 M, the sensitivity was 0.68 A/M, and the detection limit was 3.03 × 10−9 M. It is important to mention that the sensitivity of EGr/GC was three times higher than that of bare GC (0.23 A/M), proving the advantages of using graphene-modified electrodes in the electrochemical detection of AZT.