Linear Sweep Voltammograms Research Articles

Effect of Annealing Time on Various PtNi/C Binary Alloy Catalysts for ORR in PEFCs

Polymer electrolyte fuel cells (PEFCs) are used in automotive power supplies due to their advantages of low environmental impact and high energy conversion efficiency. However, Pt used for electrocatalysts is expensive and its activity and durability are problematic. In this study, the PtNi/C catalysts were prepared with different annealing times and the oxygen reduction reaction activity was evaluated. The linear sweep voltammograms and current-voltage curves showed that the PtNi/C catalysts annealing time for 60 min performed better than the commercial catalyst. This would be attributed to the internal alloying of Ni and better electronic structure due to the longer annealing time.

Facile synthesis of spherical-shaped CeC2–TiO2 nanocomposite electrocatalyst with boosted alkaline OER

Developing noble metal-free multifunctional electrocatalysts to catalyze water oxidation is vital for future renewable energy systems. Herein, through several defect modifications, the CeC2–TiO2 nanocomposite on the strength of enriched oxygen vacancies was successfully fabricated by facile hydrothermal method on SS (stainless steel) substrate, attributed to the conductive ability for fast electron transportation. A well-defined phase growth, vibrational bonding of metal atoms, morphological determination, and elemental composition for synthesized heterostructured electrocatalysts were revealed by XRD, FTIR, TEM, and EDX, respectively. XPS has complied to understand the moderate binding energies of CeC2–TiO2 for OER intermediates, which signifies the strong interactions between electronic states of Ce, C, Ti, and O atoms. With the plentiful catalytic active sites, the resultant CeC2–TiO2 entails low overpotentials of only 169 mV and 108.8 mV/dec Tafel slope to afford 10 mA cm−2 for OER in 1.0 M KOH are tested through cyclic and linear sweep voltammogram measurements, thereby exhibit promising activity in alkaline water electrolysis. EIS measurements revealed a decreased polarization resistance for the composite dominated by the small semicircle diameter, corresponding to the adsorption of intermediates. Finally, observed results strongly recommended that the CeC2–TiO2 catalyst exhibited superior OER performance due to excellent electrical chemical coupling between CeC2 and TiO2.

Catalytic Activities of Ir-Based Pyrochlore-Type Oxides Doped with Divalent Cations for Oxygen Evolution Reaction

Alternative energy sources to fossil fuels are essential for a sustainable society, and hydrogen energy is expected to be a solution to environmental and energy problems. Currently, proton exchange membrane water electrolyzers are becoming widely used for the electrochemical production of hydrogen due to their advantages such as high efficiency. However, the highly acidic conditions and the large overpotentials of oxygen evolution reaction (OER) at the anode are problems, and the development of catalysts that are stable and highly active in acidic aqueous solutions is important for further popularization.Ir-based oxides with pyrochlore structure (A2B2O7) are known to exhibit high catalytic activities in acidic aqueous solutions. Recently, it has been reported that the improved catalytic activities of Pr2Ir2O7 by Zn doping, which controlled the composition of A-site elements in the pyrochlore structure [1]. In this study, we synthesized Pr2-x MgxIr2O7 (x = 0, 0.1, 0.2, 0.3, 0.4, and 0.5), in which a part of trivalent cation Pr3+ was replaced by divalent cation Mg2+ and improved the OER catalytic activity in acidic aqueous solutions.Pr2-x MgxIr2O7 was synthesized by the hydrothermal method. The catalyst was mixed with a conductivity aid carbon (Vulcan XC-72) and a cationic conductive ionomer (Nafion) at a weight ratio of 5:1:1 and dispersed in 2-propanol to form a catalyst ink. The catalytic activity was evaluated by cyclic voltammetry (CV) using a glassy carbon rotating disk electrode (RDE) as a working electrode, a reversible hydrogen electrode (RHE) as a reference electrode, and a platinum wire as a counter electrode. The electrolyte was a 0.1 mol dm-3 HClO4 solution saturated with oxygen, and the CV scanning range was 1.1 to 1.7 V with respect to the RHE, scanning speed was 20 mV s-1, and the RDE rotation speed was 1200 rpm. The stability of the catalyst in acidic aqueous solutions was evaluated by chronopotentiometry (CP) using the same cell.X-ray diffraction and energy-dispersive X-ray analysis measurements of the synthesized materials confirmed that the desired compounds were obtained, and CV measurements showed that the OER activity of Pr2-x MgxIr2O7 increased in the first 20 cycles for all compositions, and then stabilized over several tens of cycles. The cycle change was similar to that of Pr2Ir2O7, suggesting that the surface rearrangement proceeds in acidic aqueous solutions [2]. Linear sweep voltammogram (LSV) and OER activity normalized by Brunauer-Emmett-Teller (BET) specific surface area were measured at the 20th cycle, and the catalytic activity stabilized at a high value. The OER activity was enhanced by Mg substitution in the catalysts of Pr2-x Mg x Ir2O7.References L. Zhu, C. Ma, Z. Wang, X. Gong, L. Cao, and J. Yang, Appl. Surf. Sci., 31, 151840 (2022).C. Shang, C. Cao, D. Yu, Y. Yan, Y. Lin, H. Li, T. Zheng, X. Yan, W. Yu, S. Zhou, and J. Zeng, Adv. Mater., 31, 1805104 (2018).

Genuine differential voltammetry

A novel form of differential voltammetry is proposed, developed through the implicit anodic and cathodic current components of the experimentally accessible conventional net current measured in a voltammetric experiment. By employing basic mathematical modelling of an electrode reaction of a dissolved redox couple at a conventional, macroscopic electrode within the framework of the Butler-Volmer electrode kinetic model, the implicit anodic and cathodic current components of the net conventional current are clearly defined and can be estimated. Consequently, a novel form of differential current, calculated as the difference between anodic and cathodic implicit current components associated with a single potential of the voltammetric experiment, can be established. This differential current demonstrates remarkable characteristics in terms of electrode kinetics and analytical performance, particularly in cases involving fast, seemingly electrochemically reversible electrode processes. It holds promise to be analytically superior to the best-known differential voltammetric techniques so far (e.g., square-wave voltammetry), as well as provides a means for estimating the rate constants of very fast, apparently reversible electrode processes at macroscopic electrodes under mild experimental conditions (i.e., studied at slow potential scan rates). The practical implication of the novel methodology is significant: a simple linear sweep voltammogram of a quasi-reversible electrode reaction with unknown electrode kinetic parameters can be readily transformed into the novel type of differential voltammogram through a convolution procedure of the conventional net current, paving a new way for studying electrode processes by voltammetry.

Direct Electrooxidation of Ammonia-Enriched Wastewater Using a Bipolar Membrane-Integrated Electrolytic Cell

The treatment of reject water containing concentrated ammonia and non-biodegradable organics is a challenging task in wastewater treatment plants. To address this problem, we propose a novel process consisting of a selective ammonium-exchange resin and an ammonia electrooxidation reaction (AmER-AOR). Because an alkaline condition is essential for direct ammonia oxidation, the use of a bipolar membrane (BPM) was helpful. Nonetheless, an initial pH of 13 and KOH addition were required to maintain a high alkalinity for the complete elimination of ammonia. The linear sweep voltammogram elucidated the high pH requirement and ammonia oxidation promotion. When the current density varied from 30 to 80 mA cm−2, 60 mA cm−2 showed the highest current efficiency (30.39%) and the lowest specific energy demand (95.3 kWh/kg-N), indicating the most energy-effective condition. Increasing the initial concentration of ammonia from 0.1 M to 0.5 M improved the current efficiency (51.57%), demonstrating an additional energy-effective strategy for the AmER-AOR. The energy efficiency of pure H2 production in the cathodic chamber was 30%. To estimate the viability for practical applications, reject water collected from a local wastewater treatment plant was applied in the AmER-AOR. Notably, no significant difference in the ammonia removal rate was observed with synthetic wastewater. To the best of our knowledge, this is the first study that employs a BPM as a separator and OH− supplier for direct ammonia oxidation. Our findings reveal that the AmER-AOR with a BPM has promising practical applicability in the treatment of reject water and energy production.

Fabrication of mesoporous titania films and kinetics of photoelectrocatalytic degradation of organic dye

Mesoporous titania films with worm-like patterns were fabricated on indium-tin oxide (ITO) glass by dip-coating skill, and were characterized systematically. Impacts of the process and technical parameters on the formation of the films were investigated. The mesoporous films were characterized by low-angle X-ray diffraction (XRD) and wide-angle XRD, transmission electron microscopy (TEM), scanning electron microscope (SEM), linear sweep voltammograms and nitrogen adsorption/desorption isotherms. Subsequently, the films were used in a photoelectrocatalytic system for the degradation of methyl orange. The influence of operation variables, including pH values, bias potential, light intensity, organics concentration and the mass of the films, on the degradation of the dye was investigated in details. More than 96 % degradation of the organics was achieved in 2 h. The kinetic results for the photoelectrocatalytic oxidation of the organic were also presented in this paper.

Enhanced electro-catalytic activity of TNTs/SnO2-Sb electrode through the effect mechanism of TNTs architecture

The TiO2 nanotubes arrays/SnO2-Sb (TNTs/SnO2-Sb) electrode is successfully fabricated using the solvothermal synthesis technique. Various architectures of TNTs are constructed by varying the anodization voltage and time, aiming to investigate their impact on the structural and electrochemical properties of the SnO2-Sb electrode. The anodization voltage is identified as the primary influencing factor on the morphology and surface hydrophilia of TNTs arrays, which is evidenced by scanning electron microscopy (SEM) and contact angle testing. In contrast, the effect of anodization time is relatively small. SEM, X-ray diffraction (XRD), linear sweep voltammograms (LSV), and electrochemical impedance spectroscopy (EIS) results indicate that the morphology and crystal size of the catalytic coating, as well as the oxygen evolution potential of the electrode, are influenced by the pore size of TNTs arrays. The influencing mechanism of enhanced electrochemical activity by adjusting the architecture of TNTs arrays is investigated using X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR), and hydroxyl radicals (·OH) generation test. The results reveal a higher concentration of oxygen vacancies on the sample with a compact and smaller particle coating, indicating the presence of more adsorbed oxygen species. Consequently, this enhances the generation capacity of active radicals for organic matter degradation. The electrode featuring TNTs arrays with a length of 950 nm and a pore diameter of 100 nm exhibits the most effective remediation of phenol-containing wastewater, achieving approximately 92% ± 4.6% removal after a duration of 2 h.

Selective additions of dopants, Co-catalyst and surfactant on the hydrothermally synthesized BiVO4 semiconductors for outstanding photoelectrochemical water oxidation behavior

The present study describes the significant improvement of the PEC performance through modifications via co-doping of Mo/W and optimizing the level of surfactant (Triton-X 100; TX-100) addition to the hydrothermally synthesized BiVO4 photoanode. The photoelectrochemical performance is improved when the precursor solution contains an optimized 5 % TX-100 surfactant level. The visible light responsiveness of the semiconductor photocatalyst has been confirmed using linear sweep voltammograms under periodic chopped illumination of UV–vis and visible irradiation for H2O → O2 oxidation. Adding an optimized level of Mo and W to the precursor solution leads to modifications of the crystallites, which facilitates the water oxidation reaction and exhibits the highest photo-current of ∼0.61 mA cm−2. Selective loading of oxygen evolution catalyst (OEC) in the surface boosts the PEC performance to 1.05 mA cm−2 and significantly increases photon current conversion efficiency.

Analysis of Anodic Linear Sweep Voltammograms Considering Insufficient Lability of Cu|Cu(II), Glycine System

Anodic LS voltammograms of the alkaline Cu|Cu(II), glycine system were converted into mass-transport corrected Tafel plots considering that the glycinate anion L− takes part in the first stage of copper ionization. The anodic current density was normalized relative to the surface concentration of L− species, which was determined using the mass transfer model of chemically interacting species. The lability of the system was assessed based on available kinetic characteristics and specific experimental data. To linearize the Tafel plots, corrections were made to account for the insufficient mobility of the proton attached to glycine amino group. Obtained Tafel constants indicate that the second step of copper ionization, involving the oxidation of the intermediate copper(I)-glycine complex, is the rate-determining step.

Fabrication of some Quaternary Spinel Structure Electrodes for Photoelectrochemical Applications.

In this study, nanostructured ZnNiCo2O4 and MnNiCo2O4 electrodes were fabricated by spray pyrolysis method and annealed at 550oC for 2 h. The structural, optical, and Photoelectrochemical properties were studied. The structural properties were examined using X-ray diffraction (XRD). The results show that the samples have cubic spinel structure. The atomic percentage determined by (EDX) and the thickness (cross section) of films measured by (FE-SEM), as well as the surface roughness measured through (AFM) are all used for analysis. The optical properties were investigated by UV-visible spectrophotometer, the energy band gaps of ZnNiCo2O4 and MnNiCo2O4 were estimated to be approximately 2.2 and 2.4 eV respectively. The photoelectrochemical, comprising of photocurrent density, linear sweep voltammograms (LSV) and Mott-Schottky (MS), displayed flat band values of (1.5 eV and -0.55 eV) Vs NHE for ZnNiCo2O4 and MnNiCo2O4 respectively, where the conduction band and valance band values of ZnNiCo2O4 were (C. B= -0.6 eV and V.B= 1.6 eV ), while those of MnNiCo2O4 were (C.B= -0.65 eV and V.B= 1.75 eV ). The corresponding photocurrent densities for ZnNiCo2O4 and MnNiCo2O4 were 35 µA/cm2 and 50 µA/cm2, respectively. The electrodes were comprehensively studied for ZnNiCo2O4 and MnNiCo2O4 under a neutral water condition.

High Power Density of a Hydrogen Peroxide Fuel Cell Using Cobalt Chlorin Complex Supported on Carbon Nanotubes as a Noncorrosive Anode.

Hydrogen peroxide fuel cells (HPFCs) have attracted much attention due to their simple one-compartment structures and high availability under harsh conditions such as an anaerobic environment; however, catalysis improvement is strongly demanded for both anodes and cathodes in terms of activity and durability. Herein, we report the high catalytic activity of CoII chlorin [CoII(Ch)] for hydrogen peroxide (H2O2) oxidation with a low overpotential (0.21 V) compared to that of the CoII phthalocyanine and CoII porphyrin complexes, which have previously been reported as active anode catalysts. Linear sweep voltammograms and differential pulse voltammograms of the CoII complexes (CoIIL) and the corresponding ligands clearly showed that the CoIIIL species are the active species for H2O2 oxidation. Then, one-compartment HPFCs were constructed with CoII(Ch) supported on multiwalled carbon nanotubes (CNTs) as the anode together with FeII3[CoIII(CN)6]2 supported on CNTs as the cathode. The maximum power density of the HPFCs reached 151 μW cm-2 with an open circuit potential of 0.33 V when the coverage of CNT surfaces with CoII(Ch) exceeded ∼60% at the anode.

OER Activity of Iridium Nanoparticle Catalysts By RDE and Comparison with MEAs

To accelerate the deployment of green hydrogen, lowering the cost of water electrolyzer is one of the important issues. Iridium anode catalyst is a key material for highly efficient and stable operation of proton exchange membrane (PEM) water electrolyzer, however, limited resources of iridium lead to higher cost and the limited availability. Therefore, there is a strong need to develop novel catalysts that can reduce iridium usage without compromising on activity. Rotating electrode half-cell is a useful technique for OER activity measurement of anode catalysts [1], however broader consensus about the activity measurement protocol is still missing. In addition, it is also unclear whether the measured activity values from the RDE are consistent with those of the MEA. The RDE activity is influenced by various measurement parameters; catalyst loading on the disk electrode, ionomer content, electrolyte conductivity, potential range etc. Here, we demonstrate the impact of these RDE parameters on the measured OER activity using various iridium catalysts [2]. The OER activity was evaluated by linear sweep voltammogram at a scan rate of 1 mV sec-1 and a disk rotation rate of 3,600 rpm to minimize the contribution of capacitive current and mass transfer loss due to O2 bubbles. Too much catalyst loading on the disk electrode leads to a decrease in apparent OER activity, so that catalyst loading should be in the range where the catalyst activity is independent of the loading amount. Electrolyte solution was also found to have a significant effect on OER activity; comparing to the activity in perchloric acid solution (0.1 M HClO4), sulfuric acid solution (0.05 M H2SO4) and phosphoric acid (0.1 M H3PO4) showed 60% and 40% activity, respectively. To verify the obtained values of OER activity by RDE at the optimized condition, the OER activities were also determined by MEAs at corresponding conditions. The OER activities of MEA and RDE were found to be approximately the same regardless of catalyst species. Detailed measurement conditions and results will be discussed at the Meeting. References S. M. Alia, G. C. Anderson, J. Electrochem. Soc., 166 (2019) F282. T. Ioroi, T. Nagai, Z. Siroma, K. Yasuda, Int. J. Hydrogen Energy, 47 (2022) 38506.

(Invited) Probing the Oxygen Reduction and Hydrazine Oxidation Reactions Using Transient Amperometric Techniques

The kinetics of electrochemical reactions affected by mass transfer is often investigated by rotating disc electrode (RDE) and rotating ring disc electrodes. However, these hydrodynamic techniques require electrodes that can be shaped into a disk or catalysts that can be drop casted on the surface of a disk electrode. Instead, transient amperometric techniques such as chronoamperometry and sampled current voltammetry (SCV) hold potential to investigate the kinetics of reactions without such requirements.In SCV, a series of chronoamperograms are recorded for a range of target potentials, and the current sampled at a fixed time or over a range of time scales. Sampled current voltammograms are obtained by plotting the selected currents vs the target potentials. 1-3 As we demonstrated recently with ferri/ferrocyanide ions and with oxygen reduction reaction (ORR) on Pt polycrystalline disk electrode, proper selection of the sampling times leads to the same mass transfer coefficients as in the RDE, and so the obtained SCV are equivalent to the linear sweep voltammograms recorded with a RDE. 4 Moreover, the kinetically controlled current can be extracted from the current transients, by plotting the inverse of the current vs the square root of time and by extrapolating to infinitely short times (large mass transfer coefficients). Tafel analysis can then be conducted. 4 In this talk, we will first present how these transient amperometric techniques were used to investigate the oxygen reduction on Au (001) thin films with different thicknesses grown on insulating MgO (001) substrates. 5 It will be shown that SCV is sensitive to the structure and to themosaicity of the thin films, and thus suitable to establish reactivity structure relationships. Then, we will show some of our recent work on the hydrazine oxidation on Au and Pt polycrystalline surfaces. 6 References [1] A. J. V and L. R. Faulkner, Electrochemical methods: Fundamentals and Applications; Wiley, 2001.[2] S.C. Perry and G. Denuault, Phys. Chem. Chem. Phys. 17, 30005 (2015).[3] L. Mignard, M. Denoual, O. Lavastre, D. Floner and F. Geneste, J. Electroanal. Chem., 689, 83 (2013).[4] C. O. Soares, O. Rodríguez, G. Buvat, G., M. Duca, S. Garbarino, D. Guay, G. Denuault and A. C. Tavares, Electrochim. Acta, 362, 136946 (2020).[5] C. O. Soares, G. Buvat, Y. G. Hernández, S. Garbarino, M. Duca, A. Ruediger, G. Denuault, A. C. Tavares and D. Guay, ACS Catal 12, 1664 (2022).[6] D. Kashyap, C. O. Soares, A. C. Tavares, G. Denuault, D. Guay, in preparation. Acknowledgements This work was supported by the Natural Sciences and Engineering Research Council of Canada (NSERC, Strategic Partnership program). Cybelle Oliveira Soares acknowledges the FRQNT funding by means of the PBEEE merit scholarship and an internship received from the Engineered Nickel Catalysts for Electrochemical Clean Energy project administered from Queen’s University and supported by Grant No RGPNM 477963-2015 under the NSERC Discovery Frontiers Program.

Impact of the Electrochemically Inert Furan Ring on the Oxidation of the Alcohol and Aldehyde Functional Group of 5‐Hydroxymethylfurfural (HMF)

AbstractThe electrochemical oxidation of bio‐based 5‐hydroxymethylfurfural (HMF) results in 2,5‐furandicarboxylic acid (FDCA), which is a renewable and environmentally friendly alternative to terephthalic acid. Using a gold electrode, we compare the electrochemical oxidation of the aldehyde and alcohol functionality in HMF to the isolated functionalities represented by ethanol and acetaldehyde. Thereby, we investigate the effect of the inert furan ring on the electrochemical reaction. The linear sweep voltammogram (LSV) of HMF in a weakly adsorbing electrolyte differs only marginally from the superposition of LSVs obtained in ethanol and acetaldehyde containing electrolytes. However, in the presence of strong adsorbates, only the kinetics of ethanol and acetaldehyde oxidation but not of HMF oxidation are hampered. We assign this to a stronger adsorption of HMF through the furan ring than through the alcohol and carbonyl functionality of ethanol and acetaldehyde. Hence, HMF is better equipped to compete for adsorption sites than aliphatic compounds.

Durability Estimation for Pt/Carbon-Sphere with the Reduced Graphene Oxide Wall Using the Start/Stop and the Load Fluctuation Tests in Acidic Electrolyte

Polymer electrolyte fuel cells (PEFCs) are attracting attention as a next-generation power source with low environmental impact. However, PEFCs have significant issues for widespread commercialization, which are high cost and short service life. Increasing Pt utilization in the catalyst layer will reduce the PEFCs cost. We reported new catalyst support with increasing Pt utilization compared to traditional carbon support [1]. Our carbon sphere (CS) support is composed of a SiO2 bead core and a reduced graphene-oxide wall. And it was successful that Pt nanoparticles supported on a CS. The Pt utilization of Pt/CS was ~20% higher than that of commercial Pt/KB. Pt/CS is expected to decrease the cost of electrocatalyst of PEFCs. However, the durability of Pt/CS was not estimated, although the reduced graphene oxide was reported to have a high tolerance for carbon corrosion [2]. In this study, the durability of Pt/CS was estimated by two methods which were start/stop and load fluctuation tests proposed by the Fuel Cell Commercialization Conference of Japan. The preparation method of Pt/CS was followed by our previous study [1]. Durability tests were conducted using a three-electrode cell which was composed of a working electrode, Pt counter electrode, Ag/AgCl reference electrode, and 0.1 M HClO4 electrolyte. This study converted the potentials from Ag/AgCl reference to RHE reference.Conditions of the start/stop test were 10,000 cycling between 1.0 V to 1.5 V with 2 s/cycle of the triangular potential waveform. The load fluctuation test was conducted by the potential step at 3 seconds at 0.6 V and 1.0 V with 10,000 cycles. Both test temperatures were 60°C. The Oxygen reduction-reaction (ORR) activity and the electrochemical active surface area (ECSA) were evaluated before and after durability tests.The initial state of Pt/CS showed high ORR activity and almost the same ECSA in comparison with commercial Pt/KB (TEC10E50E). These results agreed with our previous study [1]. After the start/stop test, commercial Pt/KB drastically degraded that ECSA dropped ~80% of the initial state, and the potential at half the value of a linear sweep voltammogram (E 1/2) negative shifted to 0.35 V. In contrast, Pt/CS demonstrated high durability for the start/stop test. Its ECSA was kept at ~84% of the initial state, and the difference of E 1/2 between before and after the start/stop test was 0.06 V. Compared with SEM images after the start/stop test, the shape of carbon support in commercial Pt/KB was collapsed by the carbon corrosion reaction, although that of CS support in Pt/CS was maintained. The difference in durability between Pt/CS and Pt/KB was probably attributed to the number of functional groups at the support surface. Especially number of hydroxyl groups on the surface may affect the stability of the carbon corrosion.In the load fluctuation test, Pt/CS also demonstrated higher stability than commercial Pt/KB. ECSA retention of Pt/CS was ~67%, and it was about five times higher than that of commercial Pt/KB. Pt/CS was kept ~85% of the initial E 1/2 when commercial Pt/KB decreased to 55% of the initial E 1/2. After the load fluctuation test, the Pt particle size immensely differed between Pt/CS and Pt/KB. In Pt/CS, the increase of Pt particle size was limited from 6.7 nm to 8.6 nm. In contrast, the Pt particle size of commercial Pt/KB increased from ~5 nm to 10.4 nm. The results of the XPS analysis indicated the chemical state of Pt in Pt/CS was the difference in Pt/KB, and it probably was affected by a CS as the catalyst support. The difference in catalyst stability of Pt/CS and commercial Pt/KB may be attributed to the strength of the interaction of Pt and the catalyst support.This study estimated the durability of Pt/CS, which had spherical catalyst support with the reduced graphene oxide wall, compared with that of commercial Pt/KB. Pt/CS demonstrated better initial ORR activity, and higher durability about the start/stop and the load fluctuation test than Pt/KB. The above results indicated that the carbon sphere was most likely one of the useful catalyst supports for PEFCs cathode catalysts.[1] T. Saida, et al., Energy & Fuels, 36, 1027-1033 (2022).[2] P. Zhang, et al. Int. J. Electrochem. Sci., 11, 10763-10778 (2016).

Environmental and Chemical Changes in Palm Oil Biodiesel using Homogeneous Catalysts

<p>The production of biofuels in several nations has increased dramatically in recent decades. Their characterization necessitates the use of distinct assessment methods. A commercial diesel specimen is compared to the properties of the biodiesel using electrochemical impedance spectroscopy, linear scanning voltammetry, and open circuit potential. During the biodiesel production process using homogeneous catalysts, emissions of volatile organic compounds (VOCs) and particulate matter can occur. VOCs and particulate matter are harmful air pollutants that can have negative health impacts on humans and the environment. Here, ultrasound was employed to propel a transesterification process among palm oil and methanol. High performance liquid chromatography (HPLC) measures triglyceride conversion into biodiesel; a molar ratio of 7:1 of methanol to oil (M:O) and a reaction period of 80 minutes at 60◦C yields a 94.16% yield. There was 1g of potassium hydroxide catalyst for every 100g of oil. The open circuit potential (OCP) values for biodiesel samples were frequently below 810 mV, and the stabilization periods were less than 2 minutes, as shown by linear sweep voltammograms (LSV). In order to better understand the properties of biofuels and related materials, electrochemical impedance spectroscopy (EIS) was created and it discovered a capacitive system with a typical impedance of MΩ cm2 at low frequencies. ctrochemical impedance spectroscopy (EIS) was created and it discovered a capacitive system with a typical impedance of MΩ cm2 at low frequencies.</p>

Hybrid cobalt phthalocyanine polymer as a potential electrocatalyst for hydrogen evolution reaction

In this work, simple, novel, eco-friendly, low-cost and highly-active cobalt oxytyramine phthalocyanine polymer, poly[CoOTPc] is synthesized and characterized with various spectro-analytical techniques to demonstrate the successful construction of poly[CoOTPc]. In order to enhance the conductivity and electrocatalytic performance of poly[CoOTPc], an organic-hybrid composite with Ketjen-Black (KB) is prepared in different ratios and their activity was assessed towards hydrogen evolution reaction (HER). The linear sweep voltammogram of organic-hybrid composite (3.5:1.5 ratio of polymer to KB) exhibited least overpotential of −79 mV at −10 mA cm−2 current density towards HER in 0.5 M H2SO4 with a Tafel slope closer to the standard catalyst (Pt/C) both in lower and higher overpotentials. In addition, lower charge-transfer resistance is noticed at the hybrid catalyst and is comparable with the standard catalyst suggesting that the designed poly[CoOTPc]+KB organic-hybrid composite is one of the superior, low-cost electrocatalyst towards HER with excellent stability and efficiency for the large-scale integrated green energy systems.

Electrochemical detection of dopamine through hydrothermally prepared lanthanum metal–organic framework (La-BTC) /carbon nanotube nanohybrid

Non-enzymatic dopamine detection utilizing electrochemical techniques is critical for a variety of reasons. For example, electrochemical sensing eliminates the need for costly and difficult enzymatic tests, which are frequently time-consuming and demand specialist equipment. It also detects dopamine in real time, making it perfect for in-vivo monitoring. Electrochemical detection might be extremely useful in diagnosing and treating illnesses like Parkinson’s and other dopamine-related disorders. Overall, this approach is a robust tool for identifying and evaluating dopamine levels, with various potential therapeutic and research applications. The direct integration of lanthanum metal–organic framework (La-BTC) and carbon nanotube (CNT) hybrid onto an electrode for electrochemical sensing is demonstrated. La-BTC/CNT composite is batch fabricated using a hydrothermal technique. For structural analysis, the prepared La-BTC is examined using X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy in combination with energy dispersive X-ray spectroscopy (SEM/EDS), and X-ray photoelectron spectroscopy (XPS) to determine its crystalline nature, surface functionalities, graphitic nature, thermal stability, and surface composition. Electrochemical sensing of dopamine is investigated using the cyclic voltammogram (CV) and linear sweep voltammogram (LSV) responses. Compared to La-BTC, the La-BTC/CNT sample demonstrated good electrocatalytic activity towards dopamine. The LOD and LOQ are measured to be 0.073 µM and 0.24 µM, respectively. The calibrated sensitivity of the modified electrode is 2.953 μAμM−1cm−2. Several potential interferences, including glucose, potassium chloride, sodium hydroxide, and sulfuric acid, show a negligible impact. The modified La-BTC/CNT electrode exhibits good stability. The results indicate that La-BTC/CNT nanohybrids can be promising for non-enzymatic dopamine sensing.

Chitin-derived biochar with nitrogen doping to activate persulfate for phenol degradation: Application potential and electron transfer pathway in system

The fast and efficient removal of organic pollutants (e.g., phenolics) remains one of the focus problems in environment pollution. Thus, a chitin-derived biochar with nitrogen doping (N-BC) was successfully prepared at a lower calcination temperature of 600 °C, which is environmentally friendly and energy saving. The N-BC was analyzed by SEM, FTIR, BET, XRD, XPS and Raman spectroscopy to confirm that the doping of nitrogen element provided sufficient defect sites to promote the activation of persulfate (PDS). Quenching experiments and EPR results revealed the presence of •OH and •O2− contributed to phenol degradation in N-BC 600/PDS system. In addition, the linear sweep voltammogram experiments also demonstrated the existence of electron transfer pathway. The electrons were donated from phenol and shifted to PDS through N-BC. The graphitic N and carbon defects in N-BC served as the active sites of the reaction and involved absorption and transfer of electrons as the key character. Moreover, the removal rates of phenol and TOC reached 98.8% and 58.2% within 2 h, indicating that N-BC effectively activated the persulfate to degrade phenol. This study provides the theoretical support and potential applications for the activation of persulfate by nitrogen-doped biochar to degrade other phenolic compounds.

Synthesis of tin oxide (SnO2) for the fabrication of voltammetric hydrazine sensor

This work demonstrates the synthesis of tin oxide (SnO2) using simple approaches. The structural, composition, morphology and surface area properties of the SnO2 were studied by using PXRD, EDS, FESEM and BET methods. The FESEM reveal that the synthesized SnO2 possesses a hexagonal like shape structure. Moreover, SnO2 has good surface area of 43.5 m2/g confirmed by BET analysis. Further, we have used gold electrode (GE) as working substrate to fabricate the hydrazine sensor. In this regard, ink of SnO2 was prepared and drop-casted on the active surface of GE. The modified electrode (SnO2-GE) was utilized as hydrazine sensor using three electrode assembly system. The cyclic voltammogram (CV) and linear sweep voltammogram (LSV) responses of the SnO2-GE were obtained in presence of hydrazine to determine the performance of the fabricated SnO2-GE. The fabricated electrode (SnO2-GE) showed a rapid electronic communication towards hydrazine with a low detection limit (LOD) of 2.47 μM and a sensitivity of 0.43 μAμM−1cm−2 using CV, whereas an improved LOD of 0.17 μM with sensitivity of 0.39 μAμM−1cm−2 was obtained by using LSV. The modified SnO2-GE shows excellent performance in terms of low detection limit, cyclic repeatability and cyclic stability.