Three-electrode Measurements Research Articles

Evaluation of Enzyme Cascade Electrode Reactions at Nanoscale Area

Introduction Enzymes are promising catalysts with high selectivity and low environmental load. Especially, redox enzymes are attracting attentions because of their applicability to electrodes for biosensors and biofuel cells. For example, wearable lactate biosensors which can detect lactate in sweat and use the reaction to drive itself have been developed recently[1]. Various biosensors are already available today. However, most of them use single-enzyme electrodes. Compared to single-enzyme electrodes, multi-enzyme electrodes are expected to improve the performance of conventional biosensors and biofuel cells by realizing detection of multiple biomarkers and increased energy density. This study uses the multi-enzyme system involving lactate oxidase (LOx), pyruvate decarboxylase (PDC), and aldehyde dehydrogenase (ALDH) as the reaction model. In this system, four electrons are produced during one lactate molecule is converted into acetate via pyruvate, which is double the number of what are produced by an LOx single-enzyme electrode used in conventional lactate biosensors. This study aims to improve the current response of bioelectrodes by causing enzyme cascade reactions within nanoscale pores of MgO-templated carbon (MgOC). MgOC is a porous carbon material, which is believed to enhance the efficiency of cascade reactions by providing high surface area and control the enzyme activity by changing the solution environment within the nanoscale pores[2]. The prepared electrodes were evaluated electrochemically to investigate how enzyme cascade and the use of MgOC affect the electrode performance. Experimental The ink containing MgOC was dropped to glassy carbon (GC) electrodes to make MgOC electrodes. Subsequently, solution of 1,2-naphtoquinone, the mediator, was added to the MgOC surface. Finally, the mixture of certain ratios of enzymes, crosslinker, Mg-salt, and thiamine pyrophosphate (TPP) was dropped. The latter two were added to promote enzyme reactions. Using the MgOC electrode as a working electrode, three-electrode measurement system was constructed. The measurement solution was 0.1 M phosphate buffer solution (pH 7.0) containing about 15 mM of L-lactate as the substrate. Chronoamperometry (CA) was carried out with an MgOC electrode and a flat GC electrode immobilized with the same amount and ratio of enzymes to see how the use of MgOC affect the current response. Then, the enzyme cascade effect was evaluated by measuring CA of single-enzyme (LOx) electrodes and multi-enzyme (LOx+PDC+ALDH) electrodes. Furthermore, solution environment dependence of the cascade effect was measured by changing the concentration of enzymes and ammonium sulfate ((NH4)2SO4), a kosmotropic salt which is known to salt out enzymes. Results and Discussion The current density observed with the MgOC electrode immobilized with LOx, PDC, and ALDH was about 6.8 times higher than that obtained from the GC electrode also dropped with the three kinds of enzymes. This result indicates the use of MgOC as the electrode surface material is beneficial for enzyme cascade systems because of its higher surface area. We also consider that MgOC has the effect to promote product transfer in cascade systems by containing enzymes in nanoscale pores. The relationship between the pore size of MgOC and the performance of enzyme cascade electrodes will be explored in future experiments.Enzyme cascade effect was evaluated by comparing the current density of single-enzyme MgOC electrodes dropped with only LOx and multi-enzyme MgOC electrodes with LOx, PDC, and ALDH. The figure shows the results. The multi-enzyme electrodes exhibited about 1.98 times higher current density than the single-enzyme electrodes. It implies that the enzyme cascade reactions caused by LOx, PDC, and ALDH increased the number of electrons produced in the system. In this experiment, enzyme solution contained 10 mg/mL of each enzyme and 1.5 mol/L of (NH4)2SO4. When the (NH4)2SO4 concentration was raised to 3.0 mol/L, the current density increased by 2.40 times from single-enzyme to multi-enzyme. On the other hand, it rose by 2.51 times with 5 mg/mL of enzymes and 3.0 mol/L of (NH4)2SO4. Judging from the reaction scheme, the current increase should not be more than double. The increase reached around 2.5 times probably because the forward enzyme reactions were promoted to balance the equilibrium which was displaced by the addition of PDC and ALDH. The enzyme cascade effect was enhanced with increased (NH4)2SO4 concentration, but was slightly affected by the enzyme concentration. These results indicate kosmotropic salts like (NH4)2SO4 shorten the distance between enzymes by salting them out, which can positively impact the cascade reactions. The relationship between enzyme cascade effect and (NH4)2SO4 concentration will be further investigated in future studies.[1] I. Shitanda, et al., ACS Sens. 8(2023), 6, 2368-2374.[2] S. Tsujimura, K. Murata, and W. Akatsuka, J. Am. Chem. Soc. 136 (2014) 14432-14437. Figure 1

Self-Exfoliating Benzotristriazine Macrocyclic Network: A New 2D Material for High-Performance Electrochemical Energy Storage.

Aza-fused aromatic π-conjugated networks are an important class of 2D graphitic analogs, which are generally constructed using aromatic precursors. Herein, the study describes a new synthetic approach and electrochemical properties of a self-exfoliating benzotristriazine 2D network (BTTN) constructed using aliphatic precursors, under relatively mild conditions. The obtained BTTN exhibits a nanodisc-like morphology, the self-exfoliation tendency of which is ascribed to the presence of structurally different macrocycles with high electronic repulsion between the layers. The benzotristriazine repeat units of BTTN is electroactive and holds higher carbon/nitrogen ratio when compared with the conventional graphitic aza-fused π-conjugated networks. The self-exfoliated BTTN nanodiscs show excellent electrochemical energy storage of 485 and 333 F g-1 at 1 A g-1 in three-electrode and two-electrode measurements, respectively. BTTN in a symmetric coin-cell architecture exhibits a high specific energy value of 46Wh kg-1 at a power density of 1kW kg-1 and shows excellent cyclic stability of 96% for 10000 and 90% for 30000 charge-discharge cycles at a higher current density of 5 A g-1, surpassing the device performance of most of the reported all-organic pseudocapacitive 2D networks.

Impressive electrochemical characteristics of freeze-dried nanosheet structured Mn2P2O7 for affordable electrochemical capacitor

The electrochemical capacitive performance of supercapacitors (SCs) is mainly evaluated by active electrode material, which plays a critical participation. At present, transitional metallic pyrophosphates (TMPs) have grabbed more interest as active electrodes in SC configuration. In this work scenario, we informed a novel strategic synthesis route for constructing Mn2P2O7 (MP) through an ultrasonic probe-assisted chemical reaction approach. The electrode in the form of a monoclinic, freeze-dried nanosheet structure characterized by XRD, FESEM- TEM, and its signature chemical bonds and chemical composition were confirmed via FTIR and EDS analysis, respectively. As prepared active sample was successfully sent into electrochemical investigation tools such as Cyclic Voltagrams (CV), Galvanostatic charge/discharge (GCD), electrochemical impedance analysis (EIS), and Cycling life span (stability) using three and two-electrode set-up. These tests indicate that the active sample holds an impressive capacitive value of 558 F/g at scanning range of 2 mV/s, a specific capacity of 420 C/g at 1 A g-1, magnificent rate capability, 90 % retention over 10,000 successive voltammograms in three-electrode measurements. Additionally, the fabricated symmetric supercapacitor device shows superior energy density, power density, and good rate capability in two electrode investigations. The mentioned prominent results reflect that engineered MP and its characteristics are the efficient fruits in manufacturing affordable electrochemical capacitors.

Areal capacity balance to maximize the lifetime of layered oxide/hard carbon sodium-ion batteries

Optimizing the areal capacity balance between the negative and positive electrodes is crucial for enhancing the performance of sodium-ion batteries (SIBs). This study investigates NaNi1/3Fe1/3Mn1/3O₂ || hard carbon full cells with varying N/P ratios, employing three-electrode measurements to evaluate cycling performance and identify failure mechanisms in situ. A novel full cell design principle is proposed to determine the threshold N/P ratio for sodium plating. Electrochemical tests demonstrate that an N/P ratio slightly above the threshold value, particularly around 0.9, provides the best cycling performance within 1.5–4.1 V. The cycling degradation mechanism with different N/P ratios was also elucidated. It is due to either the PE or NE exceeding its critical window, leading to active material loss on the positive side and loss of sodium inventory on the negative side. The research further emphasizes that reasonably adjusting the working voltage window can significantly extend the battery's lifetime by suppressing degradation processes. The optimized cell, with an N/P ratio of 0.9 and operating within a 1.0–4.0 V window, demonstrates an 81 % capacity retention over 500 cycles. These findings provide a practical framework for designing high-performance SIBs that balance energy density and longevity.

Fractal supported electrochemical analysis of MoO3 decorated AlOOH binary composite for supercapacitor application

The AlOOH/MoO3 binary composite electrodes are synthesized by layer-by-layer method to enhance the supercapacitive property of AlOOH by taking advantage of multiple oxidation states of molybdenum. The X-ray diffraction characterization reveals the polycrystalline nature of nanocomposite. The elements and their chemical states are analysed using X-ray photoelectron spectroscopy. The binary composite exhibits interconnected network-like morphology resembling a fractal nature. The three-electrode measurement in 1 M KOH electrolyte shows the highest specific capacity (Cs) of 1638.15 C g-1@ 5 mV s-1 for binary composite, which is greater than the capacity of individual components. Also, we get Cs of 1124.41 C g-1 for 10 cycle MoO3 while its theoretical capacity is 1005 C g-1. The excellent electrochemical performance is a consequence of multiple redox active sites present in the nanocomposite, lower resistance, porous interconnected network-like structure, and shorter relaxation time. The synergy of AlOOH with MoO3 enhances its charge storage capacity. The obtained electrochemical results are also theoretically supported by fractal analysis. Among all the electrodes, the 10 cycle AlOOH/MoO3 nanocomposite displays high value of fractal dimension, which is advantageous for supercapacitor application. Furthermore, we have fabricated a symmetric supercapacitor device to understand the practicality of current work. The fabricated device displays Cs of 68.41 F g-1 within 1.6 V potential window with ∼71 % capacity retention and 100 % coulombic efficiency after 7000 charge-discharge cycles. The highest energy density of 24.32 Wh kg-1 is achieved for the power density of 3907 W kg-1.

A High-Performance, Low Defected, and Binder-Free Graphene-Based Supercapacitor Obtained via Synergistic Electrochemical Exfoliation and Electrophoretic Deposition Process.

An integrated electrochemical exfoliation and electrophoretic deposition (EPD) method is developed to achieve a high-performance graphene supercapacitor. The electrochemical delamination of graphite sheet has obtained a low-defected few-layer graphene adorned with oxygen-containing functional groups. Then, the EPD process produced a binder-free electrode to alleviate the graphene restacking problem. The electrode prepared using a deposition voltage of 5 V exhibits the highest specific capacitance of 145.95 F/g at 0.5 A/g from three-electrode measurement. Moreover, this EPD-prepared electrode also demonstrates superior electrochemical properties compared to electrodes fabricated using PVDF binder. In the real symmetrical cell, the EPD-prepared electrode also shows excellent performance with a high rate capability of 82.31 % (from 0.5 A/g to 10 A/g), high cycling stability of 95.00 % (at 5 A/g) after 10,000 cycles, and rapid frequency response with short relaxation time ( ) of 9.73 ms. These results indicate that this integration method is beneficial to construct a high performance binder-free supercapacitor electrode consisting of low-defected graphene materials, low electrode resistance, and less agglomeration of graphene sheets by utilizing an environmentally friendly process.

A Case of Inverted Crosstalk in High-Voltage Lithium-Ion Batteries with Carbonate-Based Electrolytes and LiNi0.5Mn1.5O4 Cathodes

The deployment of spinel LiNi0.5Mn1.5O4 (LNMO) cathodes can be key to develop lithium-ion batteries (LIBs) with higher energy density and lower costs. However, the most common carbonate-based electrolytes for LIBs suffer from severe degradation at high potentials, potentially causing cell failure and safety hazards.[1,2] Therefore, investigating the degradation mechanisms in battery cells employing high-voltage battery cathodes such as LNMO is paramount. In this work [3], we studied the influence of linear carbonates on cycling and interfacial stability. Electrolytes consisting of LiPF6 dissolved in a mixture of cyclic (ethylene carbonate, EC), and linear carbonates (diethyl carbonate, DEC, or dimethyl carbonate, DMC), in a 3:7 EC:DEC/DMC weight ratio, were compared. Galvanostatic cycling and electrochemical impedance spectroscopy data of LNMO||Li cells indicate that the linear carbonate plays a fundamental role in cell failure. Specifically, cells with DEC-based electrolyte show early rollover failure, reaching 80% and 20% state of health at cycle 31 and 55, respectively. In contrast, cells with DMC-containing electrolyte have better stability, keeping 80% state of health until cycle 92, as shown in Figure 1. Three-electrode measurements and further characterizations, such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS), unveil that cell failure occurs due to instability of the cathode-electrolyte interface; when DEC-based electrolytes are used, a huge impedance build-up is correlated with the formation of a spotty deposit on LNMO particles. In contrast, these deposits are absent in cathodes cycled in the DMC-based electrolyte. These deposits can be explained as originating from electrolyte reduction products forming on the anode side as shown previously for layered oxide||Li cells.[4] Overall, this study provides an insightful discussion on an "inverted crosstalk", i.e., from anode to cathode, degradation mechanism. Importantly, improved cycling stability with DMC compared to DEC is also found for LNMO||graphite cells.[1] V. Nilsson, S. Liu, C. Battaglia, R.-S. Kühnel, Electrochim. Acta 427, 2022, 140867.[2] S. Liu, M. Becker, Y. Huang-Joos, H. Lai, G. Homann, R. Grissa, K. Egorov, F. Fu, C. Battaglia, R.-S. Kühnel, Batteries Supercaps 6, 2023, e202300220.[3] A. Curcio, W. Dachraoui, Ø. Dahl, N. P. Wagner, C. Battaglia, R.-S. Kühnel, submitted.[4] H.-J. Peng, C. Villevieille, S. Trabesinger, H. Wolf, K. Leitner, P. Novák, J. Power Sources 335, 2016, 91-97. Figure 1

An Aging-Optimized State-of-Charge-Controlled Multi-Stage Constant Current (MCC) Fast Charging Algorithm for Commercial Li-Ion Battery Based on Three-Electrode Measurements

This paper proposes a method that leads to a highly accurate state-of-charge dependent multi-stage constant current (MCC) charging algorithm for electric bicycle batteries to reduce the charging time without accelerating aging by avoiding Li-plating. First, the relation between the current rate, state-of-charge, and Li-plating is experimentally analyzed with the help of three-electrode measurements. Therefore, a SOC-dependent charging algorithm is proposed. Secondly, a SOC estimation algorithm based on an Extended Kalman Filter is developed in MATLAB/Simulink to conduct high accuracy SOC estimations and control precisely the charging algorithm. The results of the experiments showed that the Root Mean Square Error (RMSE) of SOC estimation is 1.08%, and the charging time from 0% to 80% SOC is reduced by 30%.

Improving electrochemical performance in three-electrode measurements with ferroelectric bimetallic Co-Fe-MgO/CNT composite

Supercapacitors have gained significant research interest within the research community due to their notable improvements in properties, including substantial capacity, high-rate capability, extended cycling durability, and safety. In this study, we have effectively prepared electrodes composed of Co-MgO/CNT, Fe-MgO/CNT, and Co-Fe-MgO/CNT using a combination of co-precipitation and chemical vapour deposition (CVD) processes. Electrode materials subjected to catalytic reduction were extensively studied by X-ray diffraction (XRD), Raman, morphological analysis by scanning electron microscopy (SEM). Our findings showed an increasing specific capacitive value: Co-MgO/CNT < Fe-MgO/CNT < Co-Fe-MgO/CNT, with specific capacity of 7.41 mAh/g, 7.73 mAh/g, and notably 15.1 mAh/g at 1 A/g, respectively. Furthermore, cyclic stability analysis revealed 77.51% capacitive retention over 10,000 cycles at 5 A/g. Significant enhance in specific capacity observed for the Co-Fe-MgO/CNT electrode explored the synergistic gap between the higher electrical conductivity of carbon nanotubes, which resulted in improved charge transport, and faradaic redox reactions occurring in bi-catalytically reduced Co-Fe-MgO surface. This unique combination creates active sites and reduces ion diffusion path, resulting an improved electrode electrochemical performance. This study explains the preparation of bi-catalytically reduced electrodes and provides insight into their potential application in energy storage systems.

Utilizing Activated Carbon Nanopores for Electrochemical Oxidation of Perylene to Redox-Active 3,10-Perylenedione: Application in Electrochemical Capacitor Electrodes.

We demonstrate that nanopores of activated carbon (AC) function as nanoreactors that oxidize perylene (PER) to a redox-active organic compound, 3,10-perylenedione (PERD), without any metal catalysts or organic solvents. PER is first adsorbed on AC in the gas phase, and the PER-adsorbed AC is subjected to electrochemical oxidation in aqueous H2SO4 as the electrolyte. Because gas-phase adsorption is solvent-free, PER is completely adsorbed on AC as long as the amount of PER does not exceed the saturated adsorption capacity of the AC, which enables accurate control of the amount adsorbed. PER is electrochemically oxidized to PERD in the nanopores of AC at above 0.7 V vs Ag/AgCl. The hybridized PERD undergoes a rapid reversible two-electron redox reaction in the nanopores owing to the large contact interface between the conductive carbon pore surfaces and PERD. The resulting AC/PERD hybrids serve as electrodes for electrochemical capacitors, utilizing the rapid redox reaction of PERD. The hybridization method is advantageous for quantitatively optimizing electrochemical capacitor performance by adjusting the amount of adsorbed PER. Moreover, because PERD hybridization in the AC nanopores does not expand the electrode volume, the volumetric capacitance increases with increasing hybridized PERD content. In three-electrode cell measurements, the volumetric capacitance at 0.05 A g-1 reaches 299 F cm-3, and 61% of this capacitance is retained at 10 A g-1 when 5 mmol of PER is used per gram of AC. Meanwhile, pristine AC delivers 117 F cm-3 at 0.05 A g-1 with a capacitance retention of 46% at 10 A g-1. Two-electrode cell measurements reveal that self-discharge is significantly suppressed by the hybridized PERD when AC/PERD hybrids and AC are used as cathodes and anodes, respectively, compared to that of a symmetrical AC cell. Moreover, PERD does not undergo cross-diffusion in the asymmetrical cells during self-discharge tests for 24 h.

Three-Dimensional Ni-MOF as a High-Performance Supercapacitor Anode Material; Experimental and Theoretical Insight.

A three-dimensional (3D) Ni-MOF of the formula [Ni(C4H4N2)(CHO2)2]n, has been reported, which shows a capacitance of 2150 F/g at a current density of 1A/g in a three-electrode setup (5.0 M KOH). Post-mortem analysis of the sample after three-electrode measurements revealed the bias-induced transformation of Ni-MOF to Ni(OH)2, which has organic constituents intercalated within the sample exhibiting better storage performance than bulk Ni(OH)2. Afterward, the synthesized MOF and reduced graphene (rGO) were used as the anode and cathode electrode material, respectively, and a two-electrode asymmetric supercapacitor device (ASC) setup was designed that exhibited a capacitance of 125 F/g (at 0.2 A/g) with a high energy density of 50.17 Wh/kg at a power density of 335.1 W/kg. The ASC further has a very high reversibility (97.9% Coulombic efficiency) and cyclic stability (94%) after 5000 constant charge-discharge cycles. Its applicability was also demonstrated by running a digital watch. Using sophisticated density functional theory simulations, the electronic properties, diffusion energy barrier for the electrolytic ions (K+), and quantum capacitance for the Ni(OH)2 electrode have been reported. The lower diffusion energy barrier (0.275 eV) and higher quantum capacitance (1150 μF/cm2) are attributed to the higher charge storage performance of the Ni-MOF-transformed Ni(OH)2 electrode as observed in the experiment.

Assessing the Feasibility of Implementing Porous Carbon Foam Electrodes Derived from Coal in Redox Flow Batteries

The feasibility of carbon foam electrodes derived from coal for the vanadium redox flow battery (VFB) is assessed as a pathway to repurpose mining waste for use in renewable energy storage technologies. Three-electrode, half-cell, and full-cell measurements provide proof-of-concept for coal foam as an electrode material for VFBs. Similarities in physical and chemical properties between the coal foam used here and other VFB electrode materials is characterised via SEM, micro-CT, XPS, MRI, and Raman spectroscopy. We show that significant improvement in electrochemical performance of the coal foam electrodes can be achieved via simple techniques to improve material wetting and remove impurities. The overall characteristics and electrochemical behaviour indicate that coal-derived foam can be feasibly utilised as an electrode material, and with further electrode activation, may provide a competitive solution to both cost-efficient VFBs and waste reduction.

A nanoengineered vanadium oxide composite as a high-performance anode for aqueous Li-ion hybrid batteries.

Aqueous lithium-ion batteries (LIBs) have received increasing attention as a promising solution for stationary energy storage systems due to their low environmental impact, non-flammability and low cost. Despite recent progress in electrolyte development and cathode manufacturing, the lack of anode materials with high specific capacity presents difficult challenges for a wide range of applications. In this study, we propose a novel synthetic strategy to fabricate a pseudocapacitive V2O5/graphene composite as a highly functional anode material for aqueous LIBs. The designed synthesis combines a fast laser-scribing step with controlled calcination to tune the morphology and oxidation state of the electrochemically active vanadium oxide species while obtaining a highly conductive graphene scaffold. The optimized V2O5/graphene anode shows an outstanding specific capacity of 158 mA h g-1 in three-electrode measurements. When the V2O5/graphene anode is paired with an LiMn2O4 cathode, the charge storage mechanism of the full cell is revealed to be dominantly surface-controlled, resulting in remarkable rate performance. Specifically, the full cell can reach a specific capacity of 151 and 107 mA h (g anode)-1 at C/6 and 3C, respectively. Moreover, this hybrid battery can achieve a high power density and an energy density of 650 W kg-1 at 15.6 W h kg-1 and 81.5 W h kg-1 at 13.6 W kg-1, respectively, outperforming most aqueous LIBs reported in the literature. This innovative strategy provides a pathway to incorporate pseudocapacitive electrodes for improving aqueous lithium-ion storage systems, enabling safe operation of large-scale energy storage without compromising their electrochemical performance.

Nanostructured viologen-phosphate bridged titanium dioxide frameworks: Tuning thermal growth for improving supercapacitance

Titanium dioxide (TiO2) has much potential for usage in supercapacitors because of its unique structural characteristics, outstanding chemical stability, low cost and availability, and lack of environmental impact. However, TiO2 presents a low specific capacitance due to its limited electrical conductivity. Incorporating a conductive matrix (e.g. carbon) is a logical way to exploit TiO2's electrochemical potential, but the efficiency of electron transport from the carbon matrix to TiO2 nanoparticles has been challenged by the weak interfacial stability between the two phases. To further address this issue, we leveraged on the highest stability of phosphate conjugated titanium dioxide (P-O-Ti) and have crafted an ionically-tunable viologen phosphate from which open porous viologen-bridged titanium (oxide) phosphate frameworks could be obtained. Thermal annealing was performed between 180 and 900 °C to investigate the effect of the conductive carbon matrix on supercapacitor performance. During carbonization, viologen serves as a nitrogen-containing carbon precursor while phosphates behave as a stabilizer by end-capping the surface of crystalline anatase titanium dioxide, limiting its thermally-induced sintering to <7 nm at 700 °C and delaying its transition to rutile phase until 900 °C. Based on three-electrode measurement, the material pyrolyzed at 700 °C displayed the best electrochemical performance among samples, with an areal specific capacitance of 283 mF/cm2 at 0.25 mA/mg (3.43 mA/cm2) in the potential range of −1 to +1 V vs. Ag/AgCl. Due to homogeneous dispersion of phosphate stabilized TiO2 nanoparticles within an N-doped conductive carbon matrix, VioP@TiO2–700 displays excellent rate capability. When the discharge current density increased by 16 times, the specific capacitance decrease was only of 14.3 %. The charge storage mechanism of TiO2-based electrodes showed that the surface-controlled process was dominant at the negative potential, while the diffusion-controlled process was dominant at the positive potential. Moreover, the symmetric cell exhibited a high energy density of 21.46 μWh/cm2 at a power density of 272.02 μW/cm2 and good capacitance retention of 95.3 % over 4000 cycles. The outlined supercapacitor performance suggested that the resulting nitrogen-containing carbon/phosphate-stabilized TiO2 nanocomposite is promising for energy storage applications.

Benchmarking Activity and Stability of Layered Double Hydroxides (LDHs) Electrocatalysts for Alkaline Water Electrolysis

In order to reduce the cost of producing hydrogen through water electrolysis, novel technologies must be improved. Recently, the merging of conventional alkaline electrolysis (AEL) and proton exchange membrane electrolysis (PEM) has led to the development of anion exchange membrane electrolysis (AEMWE), which offers several advantages over AEL and PEM. In a nutshell, this technique employs cheap, abundant, and easily available (non-geostrategic) transition metals with anionic exchange membranes, overcoming the drawbacks of AEL and PEM.[1]To reach the readiness level of this technology, new and scalable synthetic routes for catalysts that lower the overpotential of the sluggish oxygen evolution reaction (OER) are required. Amongst all the OER catalysts reported in the literature, Layered Double Hydroxides (LDHs) have gained increasing attention due to their low overpotentials and stabilities.[2] Besides, electrochemical protocols to determine the activity and stability of these catalysts in different electrochemical cells must be established to understand their properties. Thus, this work focuses on the advantages and limitations of different electrochemical techniques, such as rotating disk electrode (RDE), three-electrode cells, and single-cell tests, to determine the activity and stability of two different LDHs. Unlike laboratory scale LDHs ‒prepared by hydrothermal treatment (HT-LDH)‒ room temperature synthesized LDHs (RT-LDH) can be prepared in kilogram quantities and present chemical structure and morphology differences. In this work, the LDHs have been characterized with spectroscopic techniques to correlate the chemical structure and morphology of the materials to their electrochemical response by RDE, three-electrode cells, and single-cell measurements.All in all, the scalable RT-LDH presents higher activity compared to HT-LDH in all three techniques. On the one hand, small current densities can only be reached by RDE, and the short-term stability of the materials is affected by the catalyst layer interface. On the other side, single-cell test measurements require long operational times, and the contribution of the membrane degradation to the overall cell voltage is still unclear. Thus, three-electrode cell measurements offer the possibility of characterizing LDHs at relevant current densities in a fast and straightforward manner, without membrane contributions, and are further employed in this work to study the stability of these systems.

Surface chemistry induced robust SEI on graphite surface via soft carbon coating enables fast lithium storage

The realization of fast-charging lithium-ion batteries with long cycle life using graphite anode is typically hindered by the uncontrollable lithium plating on graphite surface. Herein we have systematically investigated the effects of soft carbon coating on SEI properties and Li+ storage capability. A variety of analytical studies combined with three-electrode impedance measurement and interface analysis demonstrate that the carbon coating effectively mitigates the formation of resistive films on the graphite surface, leading to facilitated charge transfer and low energy barrier. The depth-profiling XPS analysis clearly shows that the formation of a uniform, robust and LiF-rich SEI plays a dominant role in enhancing the interfacial kinetics, whereas the Li+ diffusion in bulk electrode is merely affected. As a result, the graphite anode with carbon coating exhibits enhanced fast-charging performance and cycle life, including a capacity retention ratio of 98.3 % after 100 cycles at 2C-CV. In general, this work reveals the critical role of coating layer chemistry in regulating the SEI properties and Li+ storage performance, which provides a valuable guidance for the rational design of practical graphite anode for fast-charging.

Mechanism of hydrogen plasma chemo-mechanical effect on properties of a MXene-based energy storage system

Direct-current hydrogen plasma (DCHP) parameters such as time of exposure, power, and temperature of treatment were examined in this study to find the optimum conditions regarding highest specific capacitance (sCap) enhancement of supercapacitor (SCs) electrodes fabricated by multi-layer nanostructure of Ti3C2Tx MXene. High sCap of 642 mF cm−2 was achieved in the three-electrode CV measurements (more than doubled from the primary value of untreated MXene electrode). The underlying mechanism of the observed enhancement in plasma-treated SCs is discussed as well and DCHP was found to have three important effects on the MXene-based SCs: i) MXenes are mechanically delaminated and disturbed, ii) dangling bonds of MXene were increased leading to generation of Ti4+ ions, and iii) higher proportion of H+ functional groups were generated on the surface of the SC. All of these have important role in increment of capacitance and also the decrease in impedance and stability enhancement of the fabricated MXene-based SC are attributed to the proposed optimum recipe of plasma treatment. Therefore, this experimental feasibility study confirms successfulness of DCHP method in dramatic life-time enhancement of devices and development of new internet-of-things systems as well as durable wearable devices.

Analysis of the potential of nickel selenide micro-supercapacitors as energy storage device

Microsupercapacitors (MSCs) are emerging as compelling electrochemical energy storage solutions, particularly for miniaturized portable electronics. Their appeal lies in their high-power density and exceptional cycling stability, making them promising alternatives to traditional batteries. However, current microfabrication techniques often involve costly steps that result in materials with structural defects, ultimately limiting their energy density. This research introduces an innovative approach by harnessing screen-printing technology, which offers an additive and cost-effective production process while reducing waste generation. The study centers on the assessment of three distinct electrode materials—NiSe2, Ni3Se4, and NiSe—synthesized via a hydrothermal process for their suitability in supercapacitor applications. Among these materials, NiSe emerges as a standout candidate, showcasing remarkable energy storage capabilities. It achieves an impressive specific capacity of 93.3 mAh g−1 at a current density of 12 A g−1 in three-electrode measurements and demonstrates outstanding cycling stability, retaining 98 % of its capacity over an impressive 30,000 charge-discharge cycles. The resulting flexible symmetric micro-supercapacitor (NiSe-MSC) exhibits a remarkable volumetric capacitance of 81.44 F cm−3 at a current density of 6 A g−1, accompanied by impressive power density (822.86 W cm−3) and energy density (5.28 mWh cm−3).

Fabrication of CH3NH3SnCl3 perovskite nanocrystal-based electrode for supercapacitor devices application

Lead-free halide perovskites nanocrystals (NCs) have been widely used not only in the field of optoelectronics but also in energy storage applications like electrochemical supercapacitors, which could replace electrochemical batteries due to their high power density and long cycle life. The low energy density of supercapacitors is one of the main reasons why they have limited commercial applications. Herein, we have reported synthesis of 3D methylammonium tin chloride perovskite (MASnCl3) nanocrystals (NCs) via a ligand-assisted re-precipitation process (LARP) and determined its performance as an electrochemical supercapacitor. The formation of MASnCl3 NCs is confirmed by different characterization tools. The supercapacitor performances of the synthesized NCs are studied by using three-electrode electrochemical measurements. The maximum specific capacitance, energy density, and power density are found to be 2050 Fg−1, 12 kWKg−1, and 102 WhKg−1, respectively. The charge storage mechanism is estimated from the power law equation by studying the diffusion-limited and capacitive processes and it has been found that the capacitance is 94.16 % capacitive to 5.84 % diffusive in nature. The supercapacitor performance of the synthesized MASnCl3 NCs are studied by fabricating a metal coin-based two-electrode system in which PVA-H2SO4 as solid state electrolyte and NCs act as an active material. The device has retained 80.7 % of its initial specific capacitance value even after 1000 GCD cycles. Interestingly, the developed device showed almost similar gravimetric capacitance value and is enabled to glow a light emitting diode (LED) smoothly.

Hierarchical nanosheets-assembled hollow NiCo2O4 nanoboxes for high-performance asymmetric supercapacitors

The conductivity of NiCo2O4 is at least 2 orders of magnitude higher than that of NiO or Co3O4, which makes it exhibit better electrochemical performance when it is used for supercapacitor applications. Morphology engineering is a crucial way to provide easy access for the electrolyte ions to the surface of the electrode to generate more surface redox reactions. Here, we use a sacrificial template method to prepare hollow NiCo2O4 nanoboxes and investigate their potential application for supercapacitors. SEM and TEM reveal that the unique hierarchical hollow NiCo2O4 nanoboxes were constructed by nanosheets with a large specific surface area and favorable pore structure, which provide fast electron and ion transport between the electrode and electrolyte and bring about abundant electrochemically active sites for redox reactions. Three-electrode electrochemical measurements show that it can deliver a high specific capacitance of 930 F g−1 and excellent cycling stability with 88 % retention after 2000 cycles. Moreover, an asymmetric supercapacitor (ASC) was constructed using hollow NiCo2O4 nanoboxes as the positive electrode and activated carbon (AC) as negative electrode. The device displays a maximum energy density of 51.7 Wh kg−1 at a power density of 800 W kg−1, and excellent performance stability with a capacity retention of 85.9 % after 10,000 cycles. These results demonstrate that the as-prepared hollow NiCo2O4 nanoboxes hold great potential as electrode materials for high performance supercapacitors.