Two-electrode Configuration Research Articles

Fast-track microwave-assisted synthesis of CdMoO4 and CdWO4 nanoparticles for hybrid rGO/NPs electrodes in high-performance supercapacitors

Fast and facile synthesis of nanomaterials is always a challenge for industrial applications in various sectors. In this work, CdMoO₄ and CdWO₄ nanoparticles are synthesized by using a fast and cost-effective microwave-assisted method. The synthesized nanoparticles are mixed with reduced graphene oxide (rGO), to form active electrode materials for supercapacitor and their electrochemical performances were studied in detail. The electrodes were prepared by simple mixtures of rGO/CdMoO₄ and rGO/CdWO₄, and electrochemical performance were measured in both, two- and three-electrode configurations. In general, both rGO/CdMoO₄ and rGO/CdWO₄ mixtures exhibit an increased specific capacitance (Cp) compared to pure rGO. Notably, the rGO/CdMoO₄ mixture shows a Cp exceeding 543 Fg⁻1 at a scan rate of 5 mVs⁻1, which represents a significant improvement over rGO alone (Cp = 225 Fg⁻1). This increase in Cp can be attributed to the higher surface area of the rGO/CdMoO₄ electrode material due to smaller size of CdMoO₄ nanoparticles and their intercalation between the rGO layers in comparison to the rGO/CdWO₄ electrode material. Furthermore, the rGO/CdMoO₄ mixture demonstrated 77% capacitance retention over 5,000 charge/discharge cycles in the two-electrode configuration. The promising electrochemical performance and rapid, low-cost synthesis suggest that these materials have great potential for further use in high efficiency energy-storage devices.

Enhanced supercapacitor performance and hydrogen evolution reaction using Nb2CTx MXene-integrated HKUST-1 MOF

Abstract This work aims to investigate how HKUST-1 metal-organic framework (MOF) and Nb2CTx MXene operate in concert to improve the catalytic activity in the hydrogen evolution reaction (HER) and the effectiveness of supercapacitors. While HKUST-1 offers a very porous structure that is favorable for charge storage, Nb2CTx serves as both a conductive substrate and a catalytic site for HER. This combination leads to better charge transfer channels and increased electroactive sites, which ultimately results in higher HER efficiency (shown by a notably lower Tafel slope of 52.42 mV/dec). In configurations of two and three electrodes, a specific capacity of 2168 C/g at a current density of 1.0 A/g is demonstrated by HKUST-1/Nb2CTx Moreover, the theHKUST-1/Nb2CTx combination, in particular the HKUST-1/Nb2CTx//AC composite, shows remarkable stability; after 1000 cycles, they still retain 95 % of their capacity and achieve 97% coulombic efficiency. The HKUST-1/Nb2CTx decorated electrode exhibited energy and power density, reaching approximately 89 Wh/kg and 938 W/kg in two-electrode (real device) configurations. These results highlight the HKUST-1/Nb2CTx composite excellent potential in energy conversion and storage applications.

Novelle approach to simulating spinal cord stimulation during tSCS using CT images and FEM

Abstract Transcutaneous spinal cord stimulation (tSCS) offers non-invasive relief for chronic pain and improves motor function in spinal cord injured (SCI) patients. However, its mechanisms are not currently fully understood, and patientspecific factors, such as Body mass index (BMI) and age, complicate treatments. This paper aims to understand tSCS better by developing a novel Finite Element Model (FEM) of the human body using CT scans. Three subjects (sex, male, female, male. Age: 26, 27, 64. BMI: 38.9, 24.1, 28.4) underwent a CT scan, performed on a Cannon Aquilion Prime (Slice thickness [mm]: 0.8, Voxel size [mm3]: 0.564, 0.328, 0.527), which imaged the trunk of the body, from top of the abdomen to the bottom of the pelvis. The images were then used in Materialize Mimics Research 21.0 to create 3D images of individual organs, skin, fat, muscles, skeleton, and spinal cord. After pre-processing in Autodesk Meshmixer, the models were converted into solid CAD objects in Ansys SpaceClaim R2021 and combined into a single abdominal model. Ansys Maxwell R2021 was then used for simulations. Five different two-electrode configurations were tested in the prototype phase with a simplified model setup. The positive electrodes were placed over the (Thoracic) T10, T12, (Lumbar) L2 and L4 vertebrae sequentially, with the negative electrode over (Sacral) S2. The simulations took on average 47.4 hours. A marked decline in electrical current penetration depth was observed as the electrodes were placed closer together which was consistent with known current distribution patterns. A preliminary validation test was also performed using a lamb’s thigh. Two electrodes were placed a known distance apart and a stimulation was given, needle electrodes were then inserted in a grid-like pattern to obtain voltage values. The setup was recreated and simulated in Ansys Maxwell. The resulting average percent difference was 44.93 ± 33.3 % (5Vpp Square wave) and 35.02 ± 23.38 % (5V DC). In both instances, the highest difference was at the edges of the electrodes and the lowest difference in the midpoint between electrodes. Later versions of FEM models incorporated more organs and had improved on previous mesh generation flaws, but encountered new mesh generation errors which could not be rectified before the conclusion of the master’s project. Despite complications, this project has provided a pipeline for creating similar models and shown their usability. Future work will involve overcoming the current mesh generation errors, reducing calculation time, and performing a thorough validation test.

Tailored Ni(OH)2/CuCo/Ni(OH)2 Composite Interfaces for Efficient and Durable Urea Oxidation Reaction.

Electrocatalytic urea oxidation reaction is a promising alternative to water oxidation for more efficient hydrogen production due to its significantly lower thermodynamic potential. However, achieving efficient electrochemical urea oxidation remains a formidable challenge, and development of an improved electrocatalyst with an optimal physicochemical and electronic structure toward urea oxidation is desired. This can be accomplished by designing a tailored two-dimensional composite with an abundance of active sites in a favorable electronic environment. In this study, we demonstrate the fabrication of a self-supported, electrochemically grown metal/mixed metal hydroxide composite interface via a two-step electrodeposition method. Specifically, Ni(OH)2 was electrodeposited on the top of the CuCo layer (Ni(OH)2/CuCo/Ni(OH)2), and the resultant 2D composite structure required 1.333 ± 0.006 V to oxidize urea electrochemically to achieve a current density of 10 mA cm-2, which outperformed the potential required for individual components, Ni(OH)2 and CuCo. The high density of Ni3+ active sites in the composite structure facilitated high electrocatalyst activity and stability. Ni(OH)2/CuCo/Ni(OH)2 was stable for at least 50 h without any noticeable degradation in the activity or alteration of the morphology. As a bifunctional electrocatalyst, the material also exhibited excellent performance for water oxidation with 260 mV overpotential and 50 h stability. In a two-electrode configuration coupled with a NiMo cathode catalyst, the electrolyzer required 1.42 V cell voltage for overall urea splitting. Overall, the engineered Ni(OH)2/CuCo/Ni(OH)2 composite demonstrated exceptional potential as an efficient and stable electrocatalyst for both urea and water oxidation reactions, paving the way for more effective hydrogen production technologies.

Electrochemical Production of Nitrite and Nitrate via Cathodic Oxygen Activation in Liquefied Ammonia

Nitrite and nitrate play pivotal roles in industrial applications, being utilized in the synthesis of pharmaceuticals, nylon precursors, explosives, and especially as fertilizer compounds. However, their synthesis primarily relies on the energy-intensive Ostwald process, which operates at high temperatures. Recently, there has been growing interest in producing nitrite and nitrate through the electrooxidation of ammonia. This method shows promise for enabling decentralized small-scale production under mild conditions while directly utilizing renewable energy sources.[1] However, production is currently restricted to low ammonia concentrations (typically 0.1 M) in aqueous systems while requiring high cell voltages.[2,3] An alternative yet unexplored concept is the electrooxidation of liquefied ammonia gas with molecular oxygen. This concept would enable nitrite and nitrate production at lower cell voltages without being restricted to low ammonia concentrations. In fact, the pioneering studies of Allen Bard have demonstrated that cathodic activation of gaseous oxygen in liquefied ammonia is possible.[4] Nonetheless, the possibility of producing nitrite and nitrate in liquefied ammonia has yet to be investigated.By using an autoclave for electrochemistry experiments, we are able to investigate the possibility of nitrite and nitrate synthesis at ammonia equilibrium pressures, elevated temperatures, and different oxygen partial pressures.[5] In a two-electrode configuration, a Pt coil and a Pt sheet (1cm x 1cm) are used as the cathode and anode, respectively. In this work, we utilize the high overpotential of Pt electrodes in the hydrogen evolution reaction (HER) in liquefied ammonia to selectively form active oxygen species via the competitive oxygen reduction reaction (ORR). The so-formed oxygen species then react with the ammonium-containing electrolyte to form nitrogen oxides.By introducing 30 bars of pressure of O2 (4%) in Ar, we observed a reduction in the overall cell voltage by approximately 800 mV at current densities of 20 mA cm-2. After transferring 100 C of charge, ion chromatography (IC) confirms the formation of both nitrite and nitrate with formal faradaic efficiencies of 15% and 41%, respectively. Additional headspace analysis via diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) disproved the formation of significant amounts of gaseous NOx species. Via GC analysis, we confirmed that the ORR successfully suppresses the HER. At the same time, the Faraday efficiency towards the anodic nitrogen evolution (NER) is unchanged, indicating a solely cathodically driven reaction mechanism. To determine the role of in-situ formed water in the reaction mechanism, we conducted experiments examining the impact of water addition. These investigations revealed that adding water is advantageous in the presence of oxygen. However, when water was the exclusive source of oxygen, only trace amounts of nitrite were observed, and no nitrate was formed. This indicates that in-situ-formed water molecules are not the primary active species responsible for the production of nitrite and nitrate. Currently, we further study the reaction mechanism and the influence of different electrolyte salts and ammonium-ion concentrations on the nitrite and nitrate yield. In addition, experiments at various reaction temperatures have been conducted, further improving nitrite and nitrate efficiency.In summary, we present a novel method for the electrochemical formation of nitrite and nitrate in liquefied ammonia under equilibrium pressures, which, to the best of our knowledge, is the first study of this kind. By exploring various reaction parameters, we additionally probe the impact of water content, reaction temperature, and different electrolyte salts on the yields of the nitrogen oxides, thereby advancing our understanding of the underlying reaction mechanism.[1] Chen, J. G.; Crooks, R. M.; Seefeldt, L. C.; Bren, K. L.; Bullock, R. M.; Darensbourg, M. Y.; Holland, P. L.; Hoffman, B.; Janik, M. J.; Jones, A. K.; Kanatzidis, M. G.; King, P.; Lancaster, K. M.; Lymar, S. V.; Pfromm, P.; Schneider, W. F.; Schrock, R. R. Beyond fossil fuel-driven nitrogen transformations. Science 2018, 360 (6391). DOI: 10.1126/science.aar6611.[2] Bunce, N. J.; Bejan, D. Mechanism of electrochemical oxidation of ammonia. Electrochim. Acta 2011, 56 (24), 8085–8093. DOI: 10.1016/j.electacta.2011.07.078.[3] Tian, Y.; Mao, Z.; Wang, L.; Liang, J. Green Chemistry: Advanced Electrocatalysts and System Design for Ammonia Oxidation. Small Structures 2023, 4 (6), B83. DOI: 10.1002/sstr.202200266.[4] Uribe, F. A.; Bard, A. J. Electrochemistry in liquid ammonia. 5. Electroreduction of oxygen. Inorg. Chem. 1982, 21 (8), 3160–3163. DOI: 10.1021/ic00138a048.[5] Britschgi, J.; Kersten, W.; Waldvogel, S. R.; Schüth, F. Electrochemically Initiated Synthesis of Methanesulfonic Acid. Angew. Chem. In. Ed. 2022, 61 (41), e202209591. DOI: 10.1002/anie.202209591. Figure 1

Asymmetrical Supercapacitor Based on Iodide Ion Containing Ionic Liquid Mixture

The increased global energy demand and environmental pollution require energy generated from renewable energy sources such as wind, solar, etc. As the adoption of these energy resources increases, developing different energy storage systems becomes important. The applicability of room-temperature ionic liquids (RTILs) as electrolytes for supercapacitors (SCs) and batteries has been discussed in many papers. RTILs have lower conductivity and higher viscosity; thus, they have narrower low-temperature operation limits compared to aqueous and non-aqueous electrolytes. However, compared with volatile aqueous and organic electrolytes, RTILs are much safer in SCs applications. To improve the power and energy densities of SCs, various mixtures of ionic liquids have been investigated, including systems of 1-ethyl-3-methylimidazolium tetrafluoroborate (EMImBF4) with bromide ion addition on carbon cloth1, EMImBF4 with iodide ion addition on Bi(111) electrode2 and D-glucose derived activated carbon (GDAC)3. However, in studies1,3 the capacitance and ideal polarizability of positively and negatively charged carbon cloth and GDAC electrodes were not taken into account, limiting the overall energy storage capability, efficiency, and cycle life of these systems. Therefore, characterization of these materials-based SCs in three- and two-electrode configurations are inevitable to overcome these mentioned shortcomings4. In the present research EMImBF4 with addition of 5 wt% 1-ethyl-3-methylimidazolium iodide (EMImI) was selected to study the influence of iodide anions addition on the electrochemical performance of micro- and mesoporous carbon material-based SC system4. Based on electrochemical data established by cyclic voltammetry, electrochemical impedance spectroscopy, constant current charge/discharge, and constant power discharge methods, the asymmetrical SC with ionic liquid mixture compared to the symmetrical SC with neat EMImBF4 demonstrated increase in cell capacitance about 5 F g-1 (33 F g-1 vs 27 F g-1 in cell potential range of 2.4 V) and specific energy about 3.5 W h kg-1 (28.1 W h kg-1 vs 24.4 W h kg-1 in cell potential range of 2.4 V). However, the ideal polarizability region, i.e., electrochemical stability of the iodide ion containing ionic liquid mixture-based SC is somewhat lower as well as specific adsorption and partial charge transfer is not fully reversible leading to the lower coulombic and energy efficiency values4. Acknowledgments: This research was supported by the EU through the European Regional Development Fund under project TK141, "Advanced materials and high-technology devices for energy recuperation systems" (2014–2020.4.01.15–0011) and TK210, “Estonian Centre of Excellence in Green Hydrogen and Sustainable Energetics”, Institutional Research grant IUT20–13, European Spallation Source: Estonian Partition in ESS Instrument design, development and building and application for science research project SLOKT12026T and by Estonian Research Council grants PUT1033, PUT55, and PRG676.

Synthesis and Characterization of Novel Polymerizable Boronium Ionic Liquids

Boronium ionic liquids (BILs) are an emergent class of zwitterionic materials that have great potential as electrolytes for electrochemical energy storage. Their high electrochemical stability, afforded by charge delocalization across the cation, and thermal stability make them attractive electrolytes for supercapacitors. In this work, a series of novel polymerizable BIL (polyBIL) cations were paired with bis(trifluoromethane)sulfonimide, [TFSI]-, creating stable ILs with low melting points. These BILs were applied as electrolytes to symmetric double layer capacitors comprised of carbon nanofoam paper (CNP) electrodes. Monomeric polyBILs were characterized using cyclic voltammetry, differential scanning calorimetry, thermal gravimetric analysis, broadband dielectric spectroscopy and compared to previously reported non-polymerizable analogs. Their operational voltage windows were studied in a two-electrode configuration using cyclic voltammetry. Then, galvanostatic charge/discharge cycling was performed to assess the performance and long-term stability of the cells.

Experimental and Numerical Analysis of Alkaline Exchange Membrane Water Electrolyzers

The operation of fuel cells and electrolyzers in alkaline conditions allows for the use of: i) less expensive electrocatalyst, such as nickel alloys and silver, ii) cheaper metals for porous layers and bipolar plates due to the less corrosive environment at high pH, e.g., nickel and stainless steel compared to titanium in PEMWE; and, iii) seawater for electrolysis [1]. However, it is only in the past decade that remarkable strides in polymer synthesis and stabilization techniques have enabled the fabrication of AEMs and ionomers that are stable at high pH and above 80oC, and have ionic conductivities as high as the standard PEM materials. Currently, several commercial AEMs and ionomers are available, e.g., Ionomr Aemion (hexamethyl-p-terphenyl poly(benzimidazolium)), Versogen and Sustanion. AEMWEs have demonstrated remarkable power and current densities, e.g., 2 A/cm2 at 1.8 V using 1 M KOH [2] and and 1 A/cm2 at 1.8 V using pure water and PGM-free catalysts [3]. Molero-Gonzalez et al. [4] also demonstrated AEMWE degradation rates of 13 μV/h over 8,900 h at a current density of 600 mA cm−2. Research however is still needed for the development of AEMWE with low-PGM and PGM-free electrodes that are able to operate over a wide range of operating conditions, e.g., alkalinity, temperature, pressure and low flow rate and with high durability. The development of these systems necessitates research and development in the areas of electrode fabrication, characterization, testing and numerical simulation to highlight the most critical limiting kinetic and transport processes in a wide range of available AEMs and catalysts.In this presentation, catalyst coated membranes (CCMs) fabricated in-house by inkjet printing using platinum and iridium as the cathode and anode catalysts onto reinforced Aemion+ membranes are assessed for their performance under a variety of feed methods. Three possible feed configurations are investigated: two-electrode feed, anode-only feed, and cathode-only feed, using a 1 M KOH solution as feedstock. These CCMs resulted in a performance of 0.9 A/cm2 at 2 V in two-electrode and anode-only feed configurations, but under cathode-only feed, the performance decreased to 0.55 A/cm2 at 2 V, as shown in the figure. Therefore, supplying electrolyte only to the anode does not lead to any performance penalties and eliminates the need for a gas separation unit. Short-term stability was also acceptable for anode-only and two-electrode feed but suffered under cathode-only feed. This performance disparity was not caused by an increase in membrane resistance, as the measured high frequency resistance did not change significantly. A reference electrode was integrated into the cell hardware to investigate the reasons for the difference in performance, finding that the poor cathode-only feed performance was largely caused by an increase in the anode overpotential. A two-dimensional AEMWE model was also developed to further analyze experimental results, and study ion and reaction distribution in each electrode, as well as the sensitivity of AEMWE performance on KOH concentration.Reference[1] Du et al. Chemical Reviews, 122 (13):11169-11896, 2022.[2] Fortin et al. Journal of Power Sources, 451:227814, 2020.[3] Li et al., Nature Energy, 5:378-385, 2020.[4] Molero-Gonzalez et al. Journal of Power Sources Advances 19:100109, 2023. Figure 1

Enhancing the Output Performance of Triboelectric Nanogenerators By Inserting CdS into Dielectric Layer

Triboelectric nanogenerators (TENGs) have emerged as promising devices for harvesting mechanical energy from various environmental sources. In this study, we focus on enhancing the performance of TENGs by inserting nano-sized cadmium sulfide (CdS) into a polydimethylsiloxane (PDMS) material. The synthesis of CdS nanomaterials was achieved through an ultrasonication method, resulting in a significant reduction in particle size compared to commercial CdS. The fabrication process of the TENG involved dispersing CdS nanoparticles into PDMS and depositing the composite thin film onto a polyethylene terephthalate (PET) substrate. Characterization studies using field emission scanning electron microscopy (FE-SEM) and UV-visible spectroscopy confirmed the successful transformation of micron-level CdS into nano-level CdS with improved optical and morphological properties.The TENG device was assembled employing a two-electrode configuration, comprising copper foils as electrodes and the CdS/PDMS composite thin film as the friction layer. Subsequent electrical measurements were conducted to assess the TENG's performance, encompassing evaluations of open circuit voltage, short circuit current, and charge transfer density. The findings revealed that the integration of CdS nanoparticles into PDMS significantly augmented the TENG's output, manifesting in notable increases in both voltage and current in comparison to PDMS-based TENGs. Moreover, a comparison between TENGs incorporating nano-scale CdS and those utilizing micro-scale CdS exhibited superior performance of the former, attributed to the enhanced charge transfer properties facilitated by the nanoparticles. Specifically, these findings indicate a threefold enhancement in output voltage and a 2.5-fold enhancement in current compared to the initial PDMS-based TENG.Additionally, a comprehensive study on the impact of external load resistance on the TENG's output energy density demonstrated its potential for practical applications, with the device capable of powering LEDs continuously. Rectification of the TENG's output voltage using a full bridge rectifier showcased efficient conversion of mechanical energy into electrical energy without a significant performance decline. Stability tests conducted over multiple days confirmed the reliability of the TENG based on CdS/PDMS, suggesting its suitability for long-term applications.In conclusion, the integration of nano-level CdS into PDMS material presents a promising approach to enhance the TENG performance for mechanical energy harvesting. Despite challenges such as CdS agglomeration in the polymer matrix, our findings highlight the potential of CdS-based TENGs for various energy harvesting applications and pave the way for future research in optimizing their performance and stability.

Crystalline/Amorphous Interface Engineering and d-sp Orbital Hybridization Synergistically Boosting the Electrocatalytic Performance of PdCu Bimetallene toward Formic Acid-Assisted Overall Water Splitting.

Advanced electrocatalysts capable of bifunctional catalysis for formic acid oxidation (FAOR) and hydrogen evolution reaction (HER) have garnered significant attention due to their exceptional energy efficiency. In this research, we have meticulously designed a PdCu bimetallene characterized by numerous crystalline/amorphous (c/a) interfaces and robust d-sp orbital hybridization, achieved by integrating the p-block metalloid boron within the PdCu matrix (B-PdCu-c/a). The B-PdCu-c/a bimetallene revealed a multitude of surface atoms and unsaturated defect sites, offering abundant catalytic active sites and an optimized electronic structure. The B2-PdCu-c/a exhibited the best performance in FAOR and HER, achieving a mass activity of 1106 mA mgcat-1 and an overpotential of 52 mV, respectively. Significantly, the two-electrode configuration of B2-PdCu-c/a∥B2-PdCu-c/a attained a low cell voltage of 0.19 V at 10 mA cm-2 during formic acid-assisted overall water splitting. Density functional theory (DFT) calculations indicated that c/a interface engineering and d-sp orbital hybridization synergistically optimized the electronic configuration of pristine PdCu bimetallene. This led to an elevation of the d-band center and an accumulation of charge at the c/a interface, which enhanced the adsorption of intermediates, facilitated C-H bond cleavage, and balanced the adsorption-desorption of hydrogen, thereby improving electrocatalytic activities for FAOR and HER, respectively. This study not only presents a viable strategy for effectively tuning the electronic configuration of bimetallene but also offers valuable insights into the development of electrocatalysts.

Sustained hydrogen production through alkaline water electrolysis using Bridgman–Stockbarger derived indium-impregnated copper chromium selenospinel

The depletion of conventional fossil fuels necessitates the development of sustainable energy alternatives, with electrochemical water splitting for hydrogen (H2) production being a promising solution. However, large-scale hydrogen generation is hindered by the scarcity of cost-effective electrocatalysts to replace noble metals such as Pt and RuO2 in the Oxygen Evolution Reaction (OER) and Hydrogen Evolution Reaction (HER). In this study, we report the synthesis of CuCr2-xInxSe4 (x = 0, 0.2, 0.4) using a dual approach combining the Bridgman-Stockbarger method and ball milling. Among the synthesized materials, CuCr1.8In0.2Se4 demonstrates outstanding HER activity in 1.0 M KOH, achieving a potential of −0.16 V vs. RHE at a current density of 10 mA cm−2. Moreover, the material shows remarkable durability during a three-electrode accelerated degradation test in an alkaline medium, maintaining its performance over 24 h at a constant current density of −200 mA cm−2, with a stable potential of −0.57 V vs. RHE. Additionally, CuCr1.8In0.2Se4 was tested in a two-electrode configuration alongside CoFe LDH, achieving a benchmark of 1.7 V for overall water splitting. It sustained a current density of 400 mA cm−2 for 24 h in an accelerated degradation test, exhibiting a minimal loss of 0.1 V after the testing period. These results highlight CuCr1.8In0.2Se4 as a promising non-noble metal catalyst for HER, demonstrating its potential to reduce reliance on noble materials for large-scale hydrogen production.

Rectification of high-frequency artifacts in EIS data of three-electrode Li-ion cells

The use of a reference electrode and the analysis of Electrochemical Impedance Spectroscopy (EIS) data recorded in three-electrode configuration are beneficial for understanding the underlying electrochemical reaction mechanisms in Li-ion batteries. However, analysis of EIS data recorded both in two-electrode and especially three-electrode configurations is prone to misinterpretation due to presence of unidentified artifacts. Using the commercially available instrument (Biologic VMP3), EIS data is recorded simultaneously for both working and counter electrodes in three-electrode five-wire configuration and are algebraically summed to obtain the data for two-electrode configuration. This data is then compared to that recorded in two-electrode configuration. This arrangement of instrument helps in identifying the otherwise hidden and anomalous features, such as a high-frequency arc and extended solid electrolyte interphase (SEI) region, in the three-electrode configuration and the reason for their absence in the two-electrode configuration. Moreover, these additional features are found State-of-Charge (SoC) i.e., cell-electrochemistry dependent and can be highly influenced by the resistance of current/potential measuring leads. Additionally, a new methodology is established to rectify the EIS data and obtain ‘artifact-free’ electrochemical data.

Benchmarking overall water splitting performance of heterostructured Fe-doped NiMo/NiCo@NF bifunctional electrocatalyst

The design of high-efficiency and cost-effective electrocatalysts for water splitting has recently received much attention. Herein, a self-supported Fe-doped NiMo/NiCo bifunctional electrocatalyst was synthesized using hydrothermal method on nickel foam (NF) to enhance both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). SEM observations revealed NiCo microspheres arranged in a flower-like structure, with Fe-doped NiMo rods decorating the surface. This electrocatalyst demonstrated impressive HER performance, requiring a low overpotential of 63 mV, versus reversible hydrogen electrode (RHE), at a cathodic current density of −10 mA/cm2, and a small charge transfer resistance (Rct) of 2.43 Ω at −200 mV (RHE). For OER, the synthesized electrocatalyst revealed excellent activity, with a low overpotential of 151 mV (RHE) to afford an anodic current density of 10 mA/cm2 and a small Rct of 0.43 Ω at 300 mV (RHE). Meanwhile, the Fe-doped NiMo/NiCo@NF electrocatalyst in a two-electrode configuration needed only a cell voltage of 1.53 V to deliver a current density of 10 mA/cm2. Overall, this work disclosed that the combination of NiCo and NiMoFe results in the synthesis of a heterogeneous electrocatalyst that offers high efficiency for water splitting and maintains good stability over 10 h.

Dahlia ball shape bimetallic phosphide-tungsten phosphide composite for anion-exchange membrane water electrolysis

Revolutionizing Water Splitting: Introducing a Breakthrough Single Heterostructure Catalyst for Highly Efficient Hydrogen and Oxygen Evolution Reactions. In this study, we present an innovative method for water splitting that introduces a remarkable single heterostructure catalyst capable of efficiently catalyzing both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Our research utilizes a highly effective hydrothermal synthesis technique to create a unique nanosphere composed of iron cobalt phosphide and tungsten phosphide (FCPWP). This FCPWP nanosphere exhibits finely tuned electronic structures and incorporates multiple active sites, resulting in significantly reduced overpotentials. When operating at current densities of 50 and 100 mA cm−2, the HER overpotentials are as low as 220 mV and 280 mV, respectively, while the OER overpotentials are only 270 mV and 350 mV. By employing the FCPWP nanosphere in a two-electrode electrolyzer configuration, we achieve exceptional results with minimal power requirements. At an operating current density of 10 mA cm−2, the electrolyzer functions at an impressively low voltage of 1.44 V, and at 1.85 V, it attains a high current density of 425 mA cm−2, showcasing an outstanding cell efficiency of 71.63% in an anion exchange membrane electrolyzer. These experimental findings are further supported by computational study. The FCPWP nanosphere emerges as an extraordinary electrocatalyst with dual-functionality for water splitting, offering great promise in the efficient production of hydrogen through electrochemical means. Our research not only introduces a fresh perspective but also paves the way for significant advancements in renewable energy technologies.

Synthesis of Carbon Nanofibers from Lignin Using Nickel for Supercapacitor Applications

Carbon fiber is known for being lightweight and adaptable, making it useful for various current and future applications. However, to broaden the use of carbon fibers beyond niche applications, production costs must be lowered. A potential approach to achieving this is by using more affordable raw materials, such as lignin, which is renewable, cost-effective, and widely available compared with the materials commonly used in industry today. This study explores the impact of metal ions on the quality of carbon fiber derived from lignin, focusing on its mechanical and electrochemical properties and morphology. The effect of a specific metal ion (Ni(NO3)2·6H2O) was examined by incorporating it into the spinning solution. The carbonization stage of the fiber was conducted at temperatures of 800, 900, and 1000 °C in an inert atmosphere. Scanning electron microscopy (SEM) analysis showed no defects or damage in any of the fibers. Therefore, it was concluded that moderate concentrations of Ni2+ ions in the fibers do not influence the stabilization or carbonization processes, thus leaving the mechanical properties of the final carbon fiber unchanged. These carbon nanofibers were also tested as a sustainable alternative to the non-renewable materials used in electrodes for energy storage and conversion devices, such as supercapacitors. Electrochemical performance was assessed in a 6 M KOH solution using a two-electrode cell configuration. Galvanostatic charge–discharge tests were performed at different current densities (0.1, 0.25, 0.5, 1.0, and 2.0 A g−1). The specific capacitance of the carbon nanofibers was determined from CVA data at various scan rates: 5, 10, 20, 40, 80, and 160 mV s−1. The results indicated that at 0.1 A g−1, the capacitance reached 108 F g−1, and at a scan rate of 5 mV s−1, it was 91 F g−1. The innovation of this work lies in its use of lignin, a renewable and widely available material, to produce carbon fibers, reducing costs compared with traditional methods. Additionally, the incorporation of nickel ions enhances the electrochemical properties of the fibers for supercapacitor applications without compromising their mechanical performance.

High-voltage aqueous supercapacitors enabled by polysiloxane passivation coating-modified carbon cloth electrode

The voltage window plays a crucial role in determining the energy density of supercapacitors. The limited energy density of carbon-based supercapacitors poses a significant challenge to their widespread adoption. Here, we propose a novel approach to modify carbon cloth by implementing a polysiloxane (PSiO) passivation coating. This forms an ion-conductive and electron-insulating thin film on the surface, effectively impeding electron conduction from electrode surface to electrode/electrolyte interface and suppressing electrolyte electrolysis. Consequently, an expanded voltage window is realized, thereby enhancing the energy density of aqueous carbon-based supercapacitors. The carbon cloth electrode modified with the PSiO passivation coating (CC-A-KH560) exhibits exceptional electrochemical performance, with a significantly increased 78.6 % widened applicable potential range compared to the activated carbon cloth electrode (CC-A). In a two-electrode configuration, the voltage window is broadened from 0.8 V for CC-A to 1.4 V for CC-A-KH560, and the energy density based on CC-A-KH560 is 8 times that based on CC-A. The good stability and durability are also obtained for the firm C–O–Si bonds during PSiO modification. More importantly, this design provides a generic solution of PSiO passivation coating-modified carbon electrode, applicable for diversified silicane couple agents, to realize a high-voltage energy storage performance for aqueous supercapacitors.

Doping-mediated interface engineered Ni3S2: Economically viable electrochemical methanol-mediated water splitting

Electrochemical water splitting is the front runner to meet the global green hydrogen demand. The development of a noble metal-free earth-abundant electrocatalyst is desired to rationalize an economically viable electrochemical water-splitting system. The sluggish anodic oxygen evolution reaction (OER) is the bottleneck of the electrochemical water-splitting system. Herein, to improve OER kinetics, group VIB elements such as chromium (Cr), molybdenum (Mo), and tungsten (W) doped nickel sulfides (Ni3S2) nanosheets (NSs) are synthesized by two-step hydrothermal method to modulate the intrinsic electrocatalytic activity of the pure Ni3S2. Among all the doped samples, the Cr-doped Ni3S2 catalyst exhibited excellent OER with an ultra-low overpotential of 248 mV and MOR with a potential of 1.36 V @ 10 mA cm−2 vs RHE achieving a lower Tafel slope of 95.5 mV/dec and 46.4 mV/dec and outstanding durability with negligible degradation respectively. Furthermore, the Pt/C||Cr-Ni3S2 (1.48 V) system outperforms commercial Pt/C||RuO2 (1.53 V @ 10 mA cm−2) in a two-electrode configuration. The methanol-mediated hybrid water splitting system only warranted a cell voltage of 1.38 V to attain 10 mA cm−2 for the Pt/C||Cr-Ni3S2 system in the presence of 0.1 M methanol (MeOH). The methanol oxidation reaction (MOR) mediated the hybrid water electrolyzer system demonstrates reduced operation cell voltage while additionally electro-synthesizing formate as a value-added chemical. The overall work is motivated to rationalize the importance of doping-mediated interface-engineered catalyst synthesis to improve the electrocatalytic efficiency of the hybrid water electrolyzer.

Harnessing dysprosium telluride/GPE as an effective electrode for energy storage and conversion

Hydrogen stands out as a clean alternative to fossil fuels, and its production via water electrolysis is promising, although the slow kinetics of the oxygen evolution reaction (OER) pose a significant challenge. Alongside energy conversion, the quest for effective energy storage remains critical. This study explores the potential of dysprosium telluride (Dy2Te3) as a highly efficient catalyst for OER and a supercapacitor electrode. The hydrothermally synthesized Dy2Te3 exhibits exceptional OER activity, characterized by an overpotential of 294 mV at 1.48 V vs. RHE, a low Tafel slope of 48 mV dec−1, and minimal interfacial resistance of 13 Ω. In a 1.0 M KOH solution, Dy2Te3 nanoparticles demonstrate outstanding supercapacitor performance, achieving a power density of 283.5 W kg−1, specific capacitance of 645.33 F g−1, and energy density of 22.8 Wh kg−1 at 1 A g−1. The high performance is attributed to enhanced electrical conductivity and a low impedance of 0.352 Ω in a three-electrode system. In a practical two-electrode configuration, Dy2Te3 nanoparticles deliver a specific capacitance of 479 F g−1, energy density of 94 Wh kg−1, and power density of 0.32 kW kg−1, with a reduced interfacial resistance of 1.03 Ω. These results underscore the potential of Dy2Te3 as a viable electrode material for both supercapacitors and water splitting, offering valuable insights into the application of lanthanide-based metal chalcogenides in energy technologies.

Moisture-Stable CsSnBr2Cl Halide Perovskite: Electrochemical Insights in Aqueous Environments.

In this investigation, moisture-stable CsSnBr2Cl nanoparticles were synthesized by incorporating Cl into CsSnBr3 halide perovskite using the hot injection method. Various analyses including XRD, XPS, UV-vis absorbance, photoluminescence, and Mott-Schottky have confirmed that the structural properties, chemical states, optical properties, and electronic band structure of CsSnBr2Cl nanoparticles remain intact even after 75 days of water immersion, thereby conclusively demonstrating their moisture stability. In a three-electrode system, the comparative electrochemical performance of pristine CsSnBr3 nanoparticles and moisture-stable Cl-incorporated CsSnBr2Cl nanoparticles was evaluated in various aqueous electrolytes, including HCl, Na2SO4, and KOH. The results indicate that the CsSnBr2Cl electrode material exhibits superior electrochemical properties, such as a larger integrated cyclic voltammetry (CV) area, a wider potential window, longer charge-discharge times, and lower impedance parameters compared to the pristine CsSnBr3 nanoparticles. The electrochemical performance of CsSnBr2Cl nanoparticles was evaluated for potential applications in batteries, supercapacitors, fuel cells, and water splitting, with a focus on reaction kinetics, charge storage mechanisms, and impedance parameters. The electrochemical properties of the nanoparticles were assessed using a three-electrode configuration across various 0.5 M aqueous electrolytes (HCl, Na2SO4, and KOH). In HCl, the nanoparticles demonstrated impressive charge storage capability, achieving a capacitance of 474 F g-1 at 1 A g-1, affirming their suitability for energy storage devices. In Na2SO4(aq.), the nanoparticles exhibited excellent stability for supercapacitors, operating up to 1.6 V without significant oxygen evolution. Notably, in KOH, they demonstrated potential as effective water-splitting electrodes. The practical applicability of the nanoparticles was evaluated using a symmetric two-electrode configuration with HCl and Na2SO4 electrolytes. The capacitance values were 117 F g-1 in HCl and 70 F g-1 in Na2SO4 at 1 A g-1. Notably, after 5000 GCD cycles in HCl(aq.), the nanoparticles retained 93% of their capacitance and maintained 91% Coulombic efficiency. They also demonstrated stable operation across a temperature range of 3 to 60 °C, achieving an energy density of 5.83 W h kg-1 at a power density of 600 W kg-1. This study emphasizes the considerable potential of CsSnBr2Cl nanoparticles in advancing electrochemical energy storage technologies and sets a solid foundation for future research and development in metal halide perovskites.

Symmetric two-electodes pseudosupercapacitor from trichalcogenide MoS3-MoO3-poly-O-amino-benzenethiol nanocomposite

A novel nanocomposite, MoS3-MoO3/poly-O-amino-benzenethiol (MoS3-MoO3/POABT), has been synthesized in a one-pot process and demonstrates promising applications as a material for a two-electrode configuration supercapacitor. This nanocomposite exhibits remarkable morphological characteristics, featuring uniform particles with an average diameter of 80 nm and a porous structure. The advantageous morphology contributes to the enhanced performance of the fabricated pseudo supercapacitor. The evaluation of the charge/discharge behavior and cyclic voltammetry curves of the redox reaction of the MoS3-MoO3/POABT nanocomposite reveals its efficacy as a supercapacitor material. The specific capacitance (CS) achieved for this fabricated supercapacitor is noteworthy at 152 F/g. Furthermore, the energy density (E) peaks at 12.6 W h kg−1 when operating at a current density of 0.2 A/g. This high energy density demonstrates the supercapacitor’s ability to store significant energy for practical use efficiently. Importantly, its stability remains strong, with an impressive 98% retention after 250 cycles, and even after 1000 cycles, it only slightly decreases to 95%. This remarkable stability over extended cycling periods underscores the durability of the materials in the supercapacitor. Such reliable performance establishes the MoS3-MoO3/POABT nanocomposite as a dependable choice for supercapacitor applications, ensuring longevity and consistent performance in diverse energy storage needs.