Three-electrode Configuration Research Articles

A Guide to Electrocatalyst Stability Using Lab-Scale Alkaline Water Electrolyzers

Green hydrogen from low-temperature water electrolysis has received significant attention with a projected thousand-fold global capacity expansion by 2030.1 Electrocatalyst research is crucial for water electrolysis technologies and has garnered substantial attention. However, despite a surge in publications centered on promising electrocatalytic materials, often claiming "outstanding" performance, few studies have scaled these materials to more realistic setups. This gap primarily stems from the inadequacy of testing environments and operating conditions in academic research. The prevalent use of three-electrode cell configurations fails to mimic practical electrolyzer conditions accurately.2,3 Electrocatalytic performance in these setups does not effectively represent real electrolysis devices operating in zero-gap configurations. Therefore, implementing stability tests in realistic device configurations is essential to assess compounded instability from all components, including the catalyst.2,4 Our group has developed and optimized a lab-scale electrochemical flow cell for alkaline water electrolysis (AWE), refined over four years of dedicated research (Figure 1a).4–7 This work outlines the operation of this device in a laboratory environment, focusing on accelerating the evaluation of electrocatalytic materials and their durability in alkaline conditions. We examined the performance of this lab-scale electrolyzer under industrially relevant conditions, including varying temperatures (Figure 1b). We examined the stability of three standard electrocatalytic materials to demonstrate the electrolyzer performance under fluctuating current conditions, including a benchmark NiFe anode for the oxygen evolution reaction (Figure 1c) and nickel nitride (Ni3N) precatalyst (Figure 1d). Furthermore, we propose a standardized protocol for assessing electrocatalysts under fluctuating and reverse currents, contributing to the understanding of catalyst deactivation. This initiative marks a significant advancement in AWE electrocatalysis research. Our goal is to establish an effective and straightforward protocol for evaluating and validating electrocatalysts in AWE, fostering accurate performance comparisons.

Monolithic Integration of Organic Solar Cell and Secondary Battery with Shared Electrode As a Photo-Rechargeable Energy Device

The solar cell-secondary battery energy system has been widely used as decentralized power generation and energy-storage system to reduce reliance on fossil fuel-based generation and mitigate fluctuations in solar cell energy supply. This typically involves power conversion by connecting two energy devices through charge controllers such as maximum power point tracker (MPPT) and pulse width modulator (PMW), which are technically mature and ensure reliable energy conversion and storage within the system. In the era of the fourth industrial revolution, characterized by the hyper-connectivity and hyper-mobility of the internet of things and wearable devices, solar-based integrated energy systems are emerging as a promising independent power source. To make devices more cost-effective, miniaturized, and energy efficient, many researchers are developing integrated energy devices that directly connect two energy devices without relying on a charge controller, a so-called "monolithic" form. However, most integrated devices reported to date still utilize a simple four-electrode structure. While this may visually resemble a monolithic device, it is functionally and structurally limited in its integration capabilities. To maximize the benefits expected from monolithic integrated devices, such as reduced process costs, miniaturization, and increased efficiency, it is essential to implement energy devices with three-electrode structures that share core components such as the electrode of the devices. In this regard, studies have been reported to realize a three-electrode energy device by utilizing the anode (or cathode) of a solar cell, which is a power generation device, as the electrode of an energy storage device, but there is a limitation that the energy density per unit area is low due to the use of a supercapacitor as the storage device, and the overall efficiency of the integrated device is low.In this study, we report on the design and implementation of a three-electrode integrated energy device sharing an electrode to improve the performance (e.g., areal capacity, energy efficiency). This integrated device uses an organic solar cell as the power generation device and a silver-zinc secondary battery as the energy storage device, and they share a silver electrode with each other. The shared silver electrode acts as a multifunctional layer that simultaneously serves as the positive electrode of the solar cell, the electrical connection between the solar cell and the secondary battery, and the cathode active material of the secondary battery. On the device perspective, by using a secondary cell instead of a capacitor, we have significantly increased the areal capacity. In order to further improve the efficiency of the integrated energy device, we applied the following three design strategies to the battery design. First, through the composition design of active ions in the electrolyte, the operating voltage of the secondary battery was matched to the same level as the maximum output voltage of the solar cell. This allows the solar cell to operate at its maximum power conversion efficiency when it charges the battery. Second, we improved the fast-charging characteristics of silver-zinc battery by ensuring that the area near the silver electrode surface is supersaturated with silver anion species during battery operation. This allows the secondary battery to accept the high-power density supplied by the solar cell at a low overvoltage, improving the efficiency of the integrated device. Finally, by applying a gel electrolyte with an optimized ratio of electrolyte components (gelling agent, hardener, salt, and plasticizer), we prevented the failure of the solar cell due to the penetration of electrolyte components and ensured the stable operation of the secondary battery. In conclusion, the aforementioned design improvements enabled the high-performance silver-zinc battery to be recharged near the maximum power point of the solar cell, achieving the highest photo conversion-storage efficiency (PSE) of any organic solar cell-based integrated energy system to date. In this presentation, the design and implementation of a solar cell-battery integrated energy device in a three-electrode configuration sharing a silver electrode will be presented in detail. In addition, secondary battery design strategies will be discussed to maximize the efficiency of the integrated device during high-power charging from solar cells.

Dynamic Activity and Stability of Transition Metal (oxy)Hydroxide Oxygen Evolution Electrocatalysts Under Steady and Intermittent Operation

The oxygen evolution reaction (OER) plays a critical role in several energy conversion technologies, requiring catalysts that combine high activity with stability for successful commercialization. Catalysts from first-row transition metal oxides have garnered considerable attention in this context. Their noteworthy OER activity and stability in alkaline environments position them as a more economical option than their counterparts in acidic media. However, recent studies have shown that these materials tend to experience significant dissolution issues and undergo changes in their chemical composition, a phenomenon observed even during steady-state operation.1–3 Addressing these challenges is essential for advancing commercial energy conversion technologies, which often face intermittent loads and reverse currents. A deeper understanding of the dynamic reconstruction under fluctuating conditions is crucial for developing more durable and efficient electrocatalytic materials.4 In this work, we investigate the dynamic performance of nickel cobalt (oxy)hydroxide electrocatalytic films containing iron active sites in alkaline media under steady and intermittent operation. First, we systematically examine the changes in OER catalytic activity in a typical three-electrode configuration, focusing on the incorporation and redissolution of iron and cerium during different electrochemical conditioning methods. As shown in Figure 1a, conditioning using chronopotentiometry decreases the OER overpotential without significantly shifting the redox peak. In contrast, conditioning using cyclic voltammetry significantly shifts the redox peak position (Figure 1b). These differences are attributed to the (oxy)hydroxide film thickness, which forms in situ during conditioning and affects the Fe dissolution and incorporation rates based on the conditioning method.5 We use different analytical techniques to probe chemical transformations during conditioning. Time-of-flight secondary ion mass spectrometry (TOF-SIMS) and X-ray photoelectron spectroscopy (XPS) are utilized to analyze compositional changes in the electrocatalytic films. Moreover, inductively coupled plasma mass spectrometry (ICP-MS) tracks metal dissolution.Next, we utilize an electrochemical flow electrolyzer with a zero-gap configuration, integrated with online ICP-MS and post-experimental TOF-SIMS and XPS, to study the reconstruction of these electrocatalysts under intermittent conditions. A NiFe anode operating in 6 M KOH with 1 ppm of Fe3+ shows a 40-mV change after 120 cycles of alternating low and high currents, including a simulated shutdown step (Figure 1c). This cell potential change, becoming more negative with continued cycling (Figure 1d), is attributed to the shutdown step. Our findings underscore how operating conditions affect the dynamic reconstruction of electrocatalytic materials, offering critical insights for developing more robust and resilient materials suitable for commercial applications.

A eutectic mixture catalyzed straight forward production of functional carbon from Sargassum tenerrimum for energy storage application

Here, we present a sustainable and scalable approach for synthesizing functionalized nanomaterials directly from an abundant natural seaweed resource coupled with a green eutectic mixture. The study utilized crushed seaweed granules obtained from fresh brown seaweed Sargassum tenerrimum (ST) and a eutectic mixture generated through the complexation of urea and a metal salt, which act as both solvent and catalyst to facilitate the straightforward production of metal oxide functionalized nanomaterials. Subjecting seaweed granules and the eutectic mixture to pyrolysis at temperatures between 700 °C and 900 °C in a nitrogen (N2) atmosphere resulted in the formation of ST-derived carbon (STC) functionalized with β-MnO2. The nanoneedles thus synthesized were examined for their electrochemical properties in both three-electrode and two-electrode configurations, employing 6 M KOH and 1 M Na2SO4 as electrolytes. Within the three-electrode framework, β-MnO2 functionalized STC at 800 °C (MSTC-8) displayed a remarkable specific capacitance, of 685.1 F g−1 in alkaline electrolyte and 308.3 F g−1 in neutral electrolyte at 0.1 A g−1, demonstrating a superior performance compared to MSTC-7 and MSTC-9. Additionally, two-electrode experiments and evaluations of cyclic stability were performed on MSTC-7, MSTC-8, and MSTC-9 symmetric supercapacitors. The fabricated symmetric supercapacitor in Na2SO4 with the operational voltage window up to 1.7 V, achieved a maximum energy density of 45.5 Wh/kg and a power density of 172.66 W kg−1. Moreover, the current investigation highlights the enduring performance of MSTC-8//MSTC-8 symmetric supercapacitor, with a capacitance retention of 95 % and 80 % over 20,000 cycles in KOH and Na2SO4 electrolytes respectively.

MXene-Derived TiO2/Starbon Nanocomposite as a Remarkable Electrode Material for Coin-Cell Symmetric Supercapacitor.

In this study, the synthesis of a MXene (Ti3C2Tx)-derivedTiO2/starbon (M-TiO2/Starbon-800°C) nanocompositeusingafacilecalcination method is explored. High-temperature exposure transforms layered Ti3C2Tx into rod-like TiO2 and starbon into amorphous carbon. The resulting M-TiO2/Starbon-800°C nanocomposite exhibits a significantly larger surface area and pore volume compared to its individual components, leading to superior electrochemical performance. In a three-electrode configuration, the nanocomposite achieved a specific capacitance (Csp) of 1352Fg⁻¹ at 1Ag⁻¹, while retaining more than 99% of its Csp after 50000 charge/discharge cycles. Furthermore, when incorporated into a two-electrode symmetric coin cell, it demonstrates a Csp of 115Fg⁻¹ along with exceptional long cycle life. Moreover, the device shows an energy density (ED) of 51Whkg-1 and a power density (PD) of 7912Wkg-1 at 5Ag-1. The enhanced charge storage is attributed to the formation of a porous structure with a high specific surface area resulting from the interaction between M-TiO2 nanorods and starbon, which facilitates efficient ion penetration.

Synergistic Advancements in Battery-Grade Energy Storage: AgCoS@MXene@AC Hybrid Electrode Material as an Enhanced Electrocatalyst for Oxygen Reduction Reaction

The extreme usage of fossil fuels and the rising conservation deterioration have made developing clean, renewable energy essential. Among the most promising methods for addressing the world’s energy dilemma are electrochemical energy storage devices (EES); batteries and supercapacitors (SCs) are two typical components in this class. Supercapacitors are incredibly impressive since they can store energy remarkably in seconds. In this work, we present a highly effective electrode material (AgCoS@MXene) for supercapattery device application that is produced hydrothermally. We examined the morphology and crystallinity of the synthesized materials using SEM and XRD studies. The synthesized compounds were subjected to a thorough electrochemical performance study employing a three-electrode configuration in a 1 M KOH electrolyte. AgCoS@MXene demonstrated an exceptional Qs of 943.22 C g−1 at a current density of 2.0 A g−1. We formed a supercapattery device (AgCoS@MXene//AC) with AgCoS@MXene as the positive electrode and activated carbon (AC) as the negative electrode. The supercapattery device was demonstrated to have a high specific capacity of 315.22 C g−1, a power density of 1275 W kg−1, and an energy density of 35.94 Wh kg−1. In addition, 5000 charging and discharging cycles were used to assess the device’s long-term longevity. The findings indicated that the device preserved nearly 82% of its initial capacity. Besides, the hybrid electrode is used for the electrocatalytic activity for the oxygen reduction reaction. These promising findings imply that AgCoS@MXene is a beneficial electrode material for upcoming energy storage devices to enhance the electrocatalytic activity for the oxygen reduction reaction.

Fe7S8 coupled with VS4 heterogeneous interface engineering driven by FeV bimetallic MOFs: An efficient all-pH and durable hydrogen evolution

Rational design and preparation of a multiphase electrocatalyst for hydrogen evolution reaction (HER) has become a hot research topic, while applicable and pH versatility of vanadium tetrasulfide (VS4) and heptairon octasulfide (Fe7S8) composites have rarely been reported. Here, the facile topological sulfide self-template sacrifice method using FeV bimetallic MOFs is designed to obtain Fe7S8 coupled with VS4 heterostructures, enhancing the electron precipitation in the catalysts and attracts electrons to migrate. According to DFT simulations, the electronic coupling at the atomic orbital level and the modulation of interfacial electrons among various interfaces play a crucial role in enhancing the intermediate state process of the hydrogen evolution reaction (HER) across the entire pH range, promoting the optimal d-band centroid value (εd). Reassuringly, the prepared 3D Fe7S8/VS4 electrodes possessed excellent performances of η10 = 53 mV, η10 = 135 mV and η10 = 38 mV in a conventional three-electrode configuration in a 1 M KOH, 1 M Na2SO4, and 0.5 M H2SO4, and the stabilized currents can all be maintained for 48 h. This innovative design of in situ heterostructured materials constructed from dual transition metal sulfides provides inspiring ideas for the preparation of all-pH catalysts.

Advanced supercapacitor electrodes: Synthesis and electrochemical characterization of graphene oxide-bismuth metal-organic framework composites for superior performance

The primary requirements for a viable supercapacitor electrode material are increased energy density, high specific capacitance, and excellent cycle stability. The desired outcome may be attained by combining diverse active materials. In this research, two Bi-MOFs with 1,4-benzenetdicarboxylic (H2BDC) and 1,3,5-benzenetricarboxylic (H3BTC) organic linkers were synthesized by facile solvothermal method and bonded on the surface of graphene oxide to produce FGO-Bi(BTC) and FGO-Bi(BDC) composites. The electrochemical characteristics of the two electroactive compounds were evaluated by GCD, CV, and EIS tests in a three-electrode setup. Comparative electrochemical analyses demonstrated that the composites exhibit remarkable performance with reduced charge transfer resistance. In the three-electrode configuration, FGO-Bi(BDC) and FGO-Bi(BTC) exhibited specific capacitances of 559 and 422 F g-1 at 1 A g-1, respectively. After conducting 10,000 cycles of charge and discharge at 8 A g-1, the FGO-Bi(BDC) and FGO-Bi(BTC) electrodes exhibited impressive retention rates of 97.6% and 95.64% for their initial specific capacitance (Cs). Notably, the three-electrode system's results indicated superior electrochemical performance of the FGO-Bi(BDC) electrode over the FGO-Bi(BTC) electrode. This superiority is attributed to the FGO-Bi(BDC)'s larger specific surface area (SSA) and reduced oxygen concentration. For a more practical assessment, the FGO-Bi(BDC) composite was selected for evaluation in the two-electrode system. The FGO-Bi(BDC)//FGO-Bi(BDC) two-electrode system demonstrated a cyclic stability of 94.2% over 10,000 cycles, attaining a substantial Cs of 295 F g-1 at 1 A g-1. Moreover, it accomplished a power density of 750 W kg-1 and an energy density of 34.61 Wh kg-1, emphasizing the exceptional electrochemical attributes that position the FGO-Bi(BDC) composite as a promising electrode material for supercapacitors.

Synthesis of tin oxide nanoparticles by chemical and biological methods and their applications in high performance supercapacitor electrode, antibacterial and antifungal activity

The advancement of supercapacitor technology is impeded by a dearth of advanced electrode materials that can augment energy storage capabilities. In this-work, we propose a novel, sustainable methodology for synthesizing tin oxide nanoparticles (SnO2-PJ NPs) utilizing Prosopis juliflora aqueous leaf extract as a stabilizing and reducing agent for the first time. These nanoparticles were evaluated in comparison to those synthesized via traditional chemical methods (SnO2-pure NPs). The samples were analyzed using an array of techniques including UV, FTIR, EDX, SEM, PL, XRD and XPS. The results indicated that the SnO2-PJ NPs exhibited superior performance as supercapacitor electrodes in both three-electrode and two-electrode system configurations. The symmetric supercapacitor device SnO2-PJ NPs displayed a high specific capacitance (98 F g−1 at 1 A g−1) and energy density (31 Wh kg−1 at 0.35 kW kg−1) in an acidic electrolyte of 1 M H2SO4. Additionally, the SnO2-PJ NPs demonstrated exceptional cycling stability, maintaining 100% of their specific capacitance after 10,000 cycles. In conclusion, the SnO2-PJ NPs exhibit tremendous potential as a next-generation energy storage material, owing to their high-power density, high-energy density, and outstanding capacity. Additionally, antibacterial and antifungal activity of synthesized SnO2 NPs is studied. The bio-synthesized SnO2 PJ NPs possesses highest antibacterial activity against two Gram-positive bacteria Staphylococcus aureus (17.0 ± 0.08 mm) and Bacillus subtilis (17.5 ± 0.74 mm) as well as one Gram-negative bacteria Escherichia coli (15.0 ± 0.06 mm) at 200 μl. Furthermore, the bio-synthesized SnO2 PJ NPs possesses highest antifungal activity against Aspergillus niger (10.0 ± 0.11 mm) and Aspergillus flavus (08.0 ± 0.12 mm) at 200 μl. The present work demonstrated an eco-friendly preparation of SnO2 NPs with high-performance supercapacitor electrode, good antibacterial and antifungal properties.

Synergistic performance of co-precipitated CoCuFe Prussian blue analogue and hydrothermally synthesized V₂C MXene in a solid-state asymmetric supercapacitor

Asymmetric supercapacitors (ASCs) have gained significant attention for their high energy density and extended potential window, ensuring optimal power density. This study presents a solid-state ASC using CoCuFe Prussian blue analogue (PBA) as the positive electrode and hydrothermally grown Vanadium MXene (V2C) as the negative electrode. SEM analysis reveals CoCuFe PBA's coagulated skeleton-like structure and V2C MXene's nanosheet-like morphology. In a three-electrode configuration, CoCuFe PBA shows a specific capacitance of 441 F/g at 0.8 A/g (0 to 0.5 V), while V2C MXene achieves 243 F/g at −1 to 0 V with a 2 M KOH electrolyte. The CoCuFe PBA//V2C ASC device achieves 185 F/g at 1 A/g with a PVA-KOH electrolyte at 1.5 V. This combination facilitates rapid ion diffusion, yielding an energy density of 57.8 Wh/kg and a power density of 1500 W/kg. The device also retains 82 % of its capacitance after 10,000 charge-discharge cycles at 6 A/g, demonstrating excellent stability and potential for high-performance supercapacitors.

Real direct urea fuel Fell operation using standalone Ni-based metal-organic framework prepared by ball mill at room temperature

Climate change and health issues are exacerbated by fossil fuel use. Efficient environmental energy conversion devices can reduce these effects. For the first time, we used a simple ball milling approach to manufacture a Nickel-based metal-organic framework (Ni-MOF) at ambient temperature directly onto a carbon cloth surface (Ni-MOF/CC) for a direct urea fuel cell (DUFC) anode. The prepared materials' crystaline structure, surface topography, and elemental content were studied using X-Ray diffraction and a scanning electron microscope with an EDS analyzer. Cyclic voltammetry, impedance electrochemical spectroscopy, and chronoamperometry were used in a three-electrode cell configuration to evaluate the material's electrochemical oxidation efficiency, particularly toward urea. In-Situ, under real fuel cell operation circumstances, we tested the electrodes in a two-electrode cell configuration. The Ni-MOF/CC exhibited a 0.35 V onset potential owed to Ni(OH)2 (Ni+2)/Ni+3 NiOOH active site. The electrode was stable for urea oxidation and operated well under real fuel cell conditions, producing 5 mW/cm2 using 1 M urea. The Ni-based MOF's fast charge and mass transfer capabilities, which was directly synthesized onto the carbon cloth surface, make the produced electrode operate well compared with bare carbon cloth. The results of the current work allow for more efficient environmental energy conversion devices that will reduce global warming.

Performance tweaking of Co3O4 UV radiation detector via zirconium dopant microstructural and photo-electronic engineering

Incorporation of dopant impurities in semiconducting metal oxide nanostructures has been presumed to increase the pace at which photo-induced holes and electrons separate due to possible bandgap engineering and oxygen vacancy modulations. In this study, we have adopted an electrodeposition technique using a three-electrode configuration for the preparation of Co3O4 thin film samples and investigated the effect of Zr as a dopant ion on the UV radiation sensing performance of nanostructured Co3O4 host material via energy band engineering and microstructural modulation. Consistency in optical energy band gap measurements of the deposited Zr-doped Co3O4 (Zr@Co3O4) was unveiled with the aid of two models: Tauc’s and absorption spectrum fitting (ASF) methods. Ag/Zr@Co3O4/ITO/glass UV radiation detector was fabricated and a sample with 3 % Zr-dopant content demonstrated high UV-365 nm detector performance: detectivity, 1.2 ×1011 Jones, and responsivity, 1818 mA W−1, with high cycling stability, attributable to the host's dopant microstructural tailoring, and the enhancement in its electronic charge carrier number and their scattering potentials within the host's band structure, thanks to the synergistic impacts of dopant ion incorporation and UV irradiation.

Mild modification of sponge-like carbon: Ammonia post-treatment for enhanced CO2 adsorption and suitability for supercapacitors

During the synthesis of carbon-based CO2 adsorbents and supercapacitors, the introduction of nitrogen atoms into the carbon matrix has been identified as a means to enhance their performance. Nevertheless, the intricate effects of nitrogen doping on material properties pose a significant challenge in developing efficient methodologies. In this investigation, porous carbons resembling sponges were fabricated utilizing macadamia nut shells as a precursor and a dual salt comprising K2C2O4-KCl as an activating agent. Subsequent modification of the materials through ammonia post-treatment facilitated the production of nitrogen-doped porous carbon. The alterations in surface characteristics and pore morphology after ammonia treatment were meticulously examined to unravel the underlying mechanism of this modification process. The samples under scrutiny showcased remarkable CO2 adsorption capacities, peaking at 6.97 mmol/g at 0 °C and 4.65 mmol/g at 25 °C. Employing mathematical models to probe the influence of pore structure and surface properties on CO2 adsorption efficacy proved to be fruitful. A linear correlation was established to depict CO2 adsorption behavior, underscoring the joint impact of ultramicropore volume and nitrogen content on the adsorption process. Notably, the material exhibited a specific capacitance of 290.4F/g at a current density of 0.5 A/g within a three-electrode configuration, demonstrating commendable rate capability and cyclic stability. The pivotal findings from this inquiry emphasize that ammonia post-treatment represents a gentle modification strategy exerting minimal influence on the pore architecture, thereby efficaciously enhancing both CO2 adsorption and electrochemical performance.

Facile synthesis of CuMn2O4 nanoparticle supported on MoS2 nanorods via hydrothermal route for supercapacitor application

In the field of material sciences, synergistic effects manifest that the collective qualities of a composite material surpass the physical and chemical capabilities of its constituent components. The present study deals with the production of MoS2 (MS), CuMn2O4 (CMO) and MoS2/CuMn2O4 (MS/CMO) nanocomposites using a hydrothermal approach. The study examined the influence of MoS2 incorporation on electrochemical features of the nanohybrids. The notable enhancement in the electrochemical behaviour of the nanohybrid may be related to the synergistic interaction between the CMO and MS. The observed enhancement in electrochemical characteristics in the MS/CMO nanocomposite might be related to its increased specific interfacial area and small crystallite size. In conventional three-electrode configuration using 2.0 M KOH, MS/CMO nanohybrid exhibits notable specific capacitances of 1244 F g−1 at 1.0 A g−1. The noteworthy aspects of improved electrochemical phenomenon include high-rate capabilities and superior cyclability. The experimental findings demonstrate that a symmetric supercapacitor system, including an MS/CMO nanocomposite, has specific energy of 25 Wh kg−1 and a retention capacitance of 93 %. The production technique, which is characterized by its simplicity and positive electrochemical outcomes, provides support to our hypothesis that the proposed MS/CMO nanohybrid has the capacity for utilization in the advancement of efficient and effective supercapacitor devices.

Nanoporous Carbon Materials Derived from Zanthoxylum Bungeanum Peel and Seed for Electrochemical Supercapacitors.

In order to prepare biomass-derived carbon materials with high specific capacitance at a low activation temperature (≤700 °C), nanoporous carbon materials were prepared from zanthoxylum bungeanum peels and seeds via the pyrolysis and KOH-activation processes. The results show that the optimal activation temperatures are 700 °C and 600 °C for peels and seeds. Benefiting from the hierarchical pore structure (micropores, mesopores, and macropores), the abundant heteroatoms (N, S, and O) containing functional groups, and plentiful electrochemical active sites, the PAC-700 and SAC-600 derive the large capacities of ~211.0 and ~219.7 F g-1 at 1.0 A g-1 in 6 M KOH within the three-electrode configuration. Furthermore, the symmetrical supercapacitors display a high energy density of 22.9 and 22.4 Wh kg-1 at 7500 W kg-1 assembled with PAC-700 and SAC-600, along with exceptional capacitance retention of 99.1% and 93.4% over 10,000 cycles at 1.0 A g-1. More significantly, the contribution here will stimulate the extensive development of low-temperature activation processes and nanoporous carbon materials for electrochemical energy storage and beyond.

MIL-101(Fe)-derivatized cathode as an efficient oxygen electrocatalyst for rechargeable Zn-air battery

The exploration of multifunctional electrocatalysts with cost-effective and high kinetic activity for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) is crucial for the development of advanced energy conversion and storage equipment. Herein, a novel hierarchical mesoporous/macropores MIL-101(Fe) derivative carbon catalyst material was prepared by a simple molten ZnCl2-assisted synthesis route. Specifically, 1H-benzotriazole (BTA) organic ligands were intentionally introduced as nitrogen sources in order to induce the formation of charge-rich regions through an electronegative nitrogen doping control strategy, and most importantly, the lone pair electron-rich nature of element N could facilitate the separation and anchoring of iron species enchanted the utilization rate of active sites. Because of these properties, the as-prepared catalyst (denoted as FeSACs/NxC) possesses unrivalled bifunction electrocatalytic activity and durability for the ORR and OER. The FeSACs/N1.25C as working electrode exhibits a quite satisfactory electrochemical performance for the ORR (half-wave potential of 0.82 V) and OER (a small overpotential of 302 mV at 10 mA cm−2) in the classic three-electrode configuration. Moreover, the FeSACs/N1.25C-based air cathode imparts encouraging performance in a rechargeable Zn–air battery prototype with an open-circuit voltage of 1.45 V, a specific capacity of 792.16 mAh g−1, an energy density of 871.38 Wh kg−1, and excellent stability for 120 h. This work has opened the way for the development of low-cost, fast kinetic and stable non-noble metal multifunctional catalysts.

Synthesis and electrochemical investigation of Cu@FeLn (Eu, Sm, and Gd)-N-C composites for energy conversion and storage applications

The slow reaction rates observed in the Oxygen Reduction Reaction (ORR) pose a significant obstacle in advancing fuel cell technology. Consequently, ORR plays a pivotal role in determining the operational efficiency of fuel cell and energy storage systems. Accordingly, the synthesis of a cathodic electrocatalyst with high efficiency has become an attractive topic for researchers. In this empirical study, three trimetallic electrocatalysts are synthesized and electrochemically appraised. By introducing three lanthanides, namely Gadolinium (Gd), Samarium (Sm), and Europium (Eu), into CuFeZIF-8, new composites successfully are synthesized as Cu@FeLn (Eu, Sm, and Gd)-N-C. These functional materials find application in the context of the ORR and supercapacitor technologies. In order to enhance stability, control surface area, and prevent agglomeration during high-temperature pyrolysis, the silicon cover protection technique is employed. The primary objective in this investigation is to assess the influence of mSiO2 coating on the electrochemical parameters of these electrocatalysts. To characterize the fabricated samples, seven characterization tests are utilized. Electrochemical measurements are conducted employing a three-electrode cell configuration within an alkaline environment. The results illustrated that the Cu@FeGd-N-C sample, with an onset potential of −0.043 V vs. Ag/AgCl, exhibited the best ORR performance. Also, the electron transfer number of Cu@FeSm-N-C was computed as 3.56. The half-wave potentials of Cu@FeSm-N-C, Cu@FeEu-N-C, and Cu@FeGd-N-C were found to be −0.34, −0.23, and −0.18 V vs. Ag/AgCl, respectively. A less negative half-wave potential typically suggests superior performance, signifying a lower overpotential requirement for the ORR process. The specific capacitance for Cu@FeGd-N-C electrode at 1 A/g was determined as 144.4 F g−1. The inclusion of lanthanides, Fe, and Cu into ZIF-8 is observed to notably improve both catalytic activity and electron transfer. Also, the outcomes showed that mesoporous silica-protected pyrolysis could be a useful strategy for improving the efficiency of energy conversion and energy storage equipment.

Isolation and Electrochemical Analysis of a Facultative Anaerobic Electrogenic Strain Klebsiella sp. SQ-1.

Electricigens decompose organic matter and convert stored chemical energy into electrical energy through extracellular electron transfer. They are significant biocatalysts for microbial fuel cells with practical applications in green energy generation, effluent treatment, and bioremediation. A facultative anaerobic electrogenic strain SQ-1 is isolated from sludge in a biotechnology factory. The strain SQ-1 is a close relative of Klebsiella variicola. Multilayered biofilms form on the surface of a carbon electrode after the isolated bacteria are inoculated into a microbial fuel cell device. This strain produces high current densities of 625 μA cm-2 by using acetate as the carbon source in a three-electrode configuration. The electricity generation performance is also analyzed in a dual-chamber microbial fuel cell. It reaches a maximum power density of 560 mW m-2 when the corresponding output voltage is 0.59 V. The facultative strain SQ-1 utilizes hydrous ferric oxide as an electron acceptor to perform extracellular electricigenic respiration in anaerobic conditions. Since facultative strains possess better properties than anaerobic strains, Klebsiella sp. SQ-1 may be a promising exoelectrogenic strain for applications in microbial electrochemistry.

Precious Metal Free Hydrogen Evolution Catalyst Design and Application.

The quest to identify precious metal free hydrogen evolution reaction catalysts has received unprecedented attention in the past decade. In this Review, we focus our attention to recent developments in precious metal free hydrogen evolution reactions in acidic and alkaline electrolyte owing to their relevance to commercial and near-commercial low-temperature electrolyzers. We provide a detailed review and critical analysis of catalyst activity and stability performance measurements and metrics commonly deployed in the literature, as well as review best practices for experimental measurements (both in half-cell three-electrode configurations and in two-electrode device testing). In particular, we discuss the transition from laboratory-scale hydrogen evolution reaction (HER) catalyst measurements to those in single cells, which is a critical aspect crucial for scaling up from laboratory to industrial settings but often overlooked. Furthermore, we review the numerous catalyst design strategies deployed across the precious metal free HER literature. Subsequently, we showcase some of the most commonly investigated families of precious metal free HER catalysts; molybdenum disulfide-based, transition metal phosphides, and transition metal carbides for acidic electrolyte; nickel molybdenum and transition metal phosphides for alkaline. This includes a comprehensive analysis comparing the HER activity between several families of materials highlighting the recent stagnation with regards to enhancing the intrinsic activity of precious metal free hydrogen evolution reaction catalysts. Finally, we summarize future directions and provide recommendations for the field in this area of electrocatalysis.

Tribo-electrochemical investigation of 60NiTi alloy in saline solution

This research explores the tribocorrosion behaviour of 60NiTi alloy, also known as NiTiNOL60, when exposed to a saline environment. Our investigation focuses on understanding the relationship between corrosion and wear rates and assessing surface damage and material degradation. To conduct our experiments, we employed a linear reciprocating ball-on-plate tribometer coupled with electrochemical polarisation using a three-electrode cell configuration to assess the combined effects of corrosion and sliding wear. Surface characterisation was carried out through scanning electron microscopy and energy dispersion spectroscopy, revealing the material to be a Ni-rich 60NiTi alloy, with surface oxidation evident in the electrolyte medium. Our electrochemical findings indicate the occurrence of localised corrosion in both cathodic and anodic regimes, with corrosion pit nucleation, cavities, and cracks being accelerated by reciprocating sliding and corrosion potential. These interactions exposed the material surface to various wear mechanisms, including abrasive, adhesive, oxidative, corrosive, and fatigue processes. This study underscores the significant influence of mechanical properties on the rate of material degradation due to corrosion, while also highlighting the substantial impact of prevailing electrochemical conditions on the rate of mechanical material removal. This paper offers valuable insights for designers working on load-bearing structures in saline environments.