Search Results (190)

The multifunctional bismuth-containing cuprate ceramic—Bi_1.7Pb_0.3Sr₂CaCu₂O_x (B(Pb)SCCO 2212)—has been employed as a functional additive at 5 wt.% for the zinc electrode in alkaline Ni-Zn batteries in order to improve electrochemical performance and cycling stability. Our study focuses on the electrochemical role of this additive in a 7 M KOH electrolyte, simulating the battery environment. Cyclic Voltammetry (CV) and Chronopotentiometry (CP) were used to investigate the electrochemical processes occurring during electrode operation. The obtained results reveal that an additional cathodic response associated with the B(Pb)SCCO 2212-containing electrode occurs at potentials preceding the main ZnO/Zn reduction process. The CV curves have shown broad cathodic a broad cathodic response consistent with the electrochemical reduction of Bi- and Cu-containing species originating from the ceramic additive. Since these processes occur before the main ZnO/Zn reduction, the formation of reduced Bi/Cu-containing phases may contribute to charge transport within the active mass and to the reduced polarization observed for the modified electrode. These findings provide a possible electrochemical explanation for the improved behavior of zinc electrodes containing 5 wt.% B(Pb)SCCO 2212. Full article

Carbon cloth is a lightweight and mechanically robust fibrous substrate with strong potential for value-added flexible electronic applications. In this study, carbon cloth/polypyrrole (CC/PPy) composites were fabricated via vapor-phase polymerization (VPP) and evaluated as radiating electrodes for flexible monopole patch RF antennas. By varying the polymerization time, the surface resistance and complex permittivity of the CC/PPy composites were systematically tuned, enabling simultaneous optimization of electrical conductivity and dielectric response. Among the prepared samples, the composite polymerized for 20 s exhibited the most balanced properties, with a sheet resistance of 1.86 Ω/sq, a real permittivity (ε′) of 5.78, and an imaginary permittivity (ε″) of 0.23. When applied as the antenna electrode, this material delivered a return loss of −34.81 dB, a radiation efficiency of 84.32%, a peak gain of 3.30 dBi, and a peak directivity of 3.91 dBi at 1.74 GHz. In addition, the antenna maintained stable performance after 5000 bending cycles, demonstrating excellent mechanical durability. These results show that simultaneous control of surface resistance and dielectric properties is critical for high-performance flexible RF electrodes and provide a practical surface-functionalization strategy for upgrading carbon-cloth-based fibrous materials into value-added electronic products. Full article

The growing demand for wearable and Internet of Medical Things (IoMT) devices is driving the development of compact, low-power platforms for continuous physiological monitoring. Bioimpedance analysis represents a versatile non-invasive technique for the assessment of tissue properties, body composition, and respiratory dynamics. This work presents a comprehensive experimental validation of a compact bioimpedance measurement platform based on the SENSIPLUS chip, a CMOS sensor interface integrating a frequency-programmable lock-in amplifier for Electrochemical Impedance Spectroscopy in the 10 kHz–1 MHz range. The platform was validated at three complementary levels: (i) electrical characterization on Debye tissue-equivalent circuits using a three-point bilinear calibration, with analysis of the electrode–skin contribution and repeatability assessment; (ii) in vivo multi-frequency bioimpedance spectroscopy (BIS) with Cole–Cole model fitting and hook-effect correction; and (iii) single-frequency thoracic impedance plethysmography for respiratory monitoring. Results were compared against an Agilent E4980A precision Inductance (L), Capacitance (C), and Resistance (R) meter and a calibrated spirometer. The presented device achieved a maximum resistance error below 5.7% and reactance deviation under 6 $\mathsf{\Omega }$ across the investigated frequency range, Cole–Cole parameters consistent with reference values, and strong linear correlation ($R^2=0.97$) between thoracic impedance variations and tidal volume, with respiratory rate estimation errors below 2% across the ten sessions, specifically 1.43% during normal breathing and 1.96% during deep breathing. These results demonstrate that the SENSIPLUS-based platform achieves metrological performance compatible with the requirements of wearable IoMT applications, here demonstrated in a single-subject proof-of-concept study, while relying for all critical analog functions on a compact ($1.5\times 1.5$) mm² system-on-chip with low power consumption (1.5 mW). Full article

The sluggish kinetics of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) at air cathodes severely restrict the practical application of rechargeable zinc–air batteries (ZABs). Herein, equimolar lanthanide-doped spinel Co₃O₄ bifunctional electrocatalysts were synthesized via a citric acid-assisted sol–gel method. Among Ce-, Pr-, La-, and Sm-doped catalysts, Sm-Co₃O₄ exhibits the optimal electrocatalytic performance with a high ORR half-wave potential of 0.72 V and superior OER activity with an overpotential of 1.65 V at 10 mA cm⁻², achieving a minimal potential gap ΔE of 0.93 V. Rotating ring-disk electrode (RRDE) measurements and Koutecky–Levich (K–L) analyses confirm the exclusive 4e⁻ ORR pathway. Characterizations reveal that Sm doping modulates the electronic structure and lattice distortion of Co₃O₄, raises the Co²⁺/Co³⁺ ratio (0.59) and creates abundant oxygen vacancies, thereby significantly lowering the overpotentials for both ORR and OER. This study provides new insights for designing high-performance spinel-based bifunctional electrocatalysts for ZABs. Full article

Chloride-induced corrosion is a major threat to excavated bronze artifacts, yet conventional alkaline desalination requires repeated solution replacement and generates secondary chemical waste. Herein, a series of BiOCl-loaded carbon nanofiber composites (CNFs@BiOCl-X) were prepared by KOH activation followed by hydrothermal growth of BiOCl, aiming to develop regenerable electrodes for chloride removal in capacitive deionization systems. Alkali activation regulated the surface roughness, oxygen-containing functional groups, hydrophilicity, and BiOCl loading of CNFs, while the three-dimensional conductive network helped immobilize BiOCl nanostructures and buffer the volume variation associated with reversible Bi/BiOCl conversion. Electrochemical analyses confirmed the pseudocapacitive chloride-storage behavior of the composites, with ion removal governed by the coupled effects of BiOCl redox activity, charge transfer, and interfacial ion transport. In a fixed-electrode membrane capacitive deionization system, CNFs@BiOCl-2 exhibited the best overall performance, delivering a salt adsorption capacity of 100.44 mg g⁻¹ at 1.4 V and retaining 93.17% of its desalination capacity after 35 cycles at 1.2 V. For flow-electrode capacitive deionization, the higher BiOCl-loading CNFs@BiOCl-5 showed superior utilization of active sites and achieved 94.75% NaCl removal from a 1000 mg L⁻¹ solution within 3 h, with an average desalination rate of 15.48 μg cm⁻² min⁻¹ and an energy consumption of 0.88 kWh kg⁻¹-NaCl. These findings demonstrate that rationally matching BiOCl loading with electrode configuration enables efficient and sustainable chloride management, offering a promising electrochemical strategy for conservation electrolytes and related desalination applications. Full article

For efficient alkaline water-splitting, it is crucial to have bifunctional electrocatalysts that exhibit low overpotentials, durability, and the possibility of being produced through scalable methods. This study involved the use of screen printing to apply a porous nickel microparticle/polymer interlayer onto commercial nickel foam, which then acted as a base for the solvothermal growth of cobalt-based oxide/hydroxide nanostructures. The optimized electrode showed excellent bifunctional capabilities in 1 M KOH, requiring only 61 mV for the hydrogen evolution reaction and 241 mV for the oxygen evolution reaction at a current density of 10 mA cm⁻². In comparison, the control electrodes, such as those with cobalt directly deposited on unmodified nickel foam and screen-printed nickel foam substrates without cobalt, exhibited poorer overall performance. Although the cobalt-modified nickel foam exhibited a higher C_dl-derived apparent electrochemical surface area, the cobalt-modified screen-printed electrode achieved the best ECSA-normalized HER and OER responses, indicating that the enhancement in activity was not solely due to the capacitive surface area of the electrode. The increased integrated redox charge suggests a greater contribution from electrochemically accessible Co/Ni redox-active species, while impedance analysis supports a more favorable apparent interfacial response under the tested HER- and OER-relevant conditions. Long-term chronopotentiometry and post-stability SEM confirmed stable bifunctional operation. Full article

Bismuth hexacyanoferrate (BiHCF), a Prussian blue analogue containing redox-active Fe–CN–Bi coordination motifs, was investigated as a model electrode for cathodic processes in chloride-rich saline and hypersaline electrolytes. Rather than evaluating BiHCF solely as a hydrogen evolution catalyst, this work focuses on the coupled electrochemical and interfacial processes that govern its response in NaCl solutions and natural brines from seawater, reverse osmosis (RO) reject, and high-altitude brine environments. Structural characterization by SEM–EDS, XRD and FTIR confirmed the formation of crystalline BiHCF with rod-like micrometric morphology and preserved cyanide coordination. Linear sweep voltammetry under controlled hydrodynamic conditions revealed a progressive cathodic displacement of the mixed potential with increasing NaCl concentration, together with a marked suppression of oxygen reduction kinetics at high chloride activity. Mixed-potential analysis showed that HER kinetics remain comparatively less sensitive to salinity than ORR, whereas the anodic contribution associated with BiHCF oxidation becomes strongly affected by chloride-induced surface transformation. Post-electrochemical characterization indicates the formation of a BiOCl-rich surface layer when the BiHCF is in contact with a hypersaline electrolyte during the cathodic subprocess (close to 0 mV_SHE), which accounts for the transition from active mixed-control behaviour to a passivated interfacial regime. Density functional theory calculations suggest that elementary water activation and hydrogen-forming steps at Bi sites are intrinsically feasible, implying that the experimentally observed overpotentials originate primarily from transport, interfacial resistance and chloride-driven passivation rather than from an unfavourable molecular reaction pathway. These findings provide a mechanistic framework for understanding Bi-based Prussian blue analogue electrodes in non-purified saline electrochemical systems and highlight the dual role of chloride as both a charge-compensating electrolyte species and a passivating reactant. Full article

With the rapid development of grid-scale energy storage, aqueous polysulfide/iodide redox flow batteries (SIFBs) have attracted extensive attention owing to their low cost, high safety, and suitable output voltage. However, the sluggish redox kinetics of iodine and polysulfide couples and the severe shuttle effect seriously restrict their performance. Here, an ultrathin nanoflower-like CuCo₂S₄ electrocatalyst supported on graphite felt (GF) is rationally designed and synthesized via a hydrothermal method combined with high-temperature sulfurization. Benefiting from the unique open nanoflower structure, abundant multivalent metal sites, and strong Cu–Co bimetallic synergy, the as-prepared CuCo₂S₄ exhibits excellent adsorption capacity for polysulfide and polyiodide intermediates, small redox peak potential separation, and low charge transfer resistance. When applied in SIFBs, the CuCo₂S₄ electrode delivers a remarkably low voltage gap of 0.29 V at 20 mA cm⁻², stable energy efficiency of 62–66% over 50 cycles, and superior long-term cycling stability with high energy efficiency above 70% after 400 cycles. This work provides an effective strategy for constructing high-efficiency bifunctional electrocatalysts toward high-performance and long-life SIFBs for large-scale energy storage applications. Full article

The conversion of bio-waste into functional energy materials provides a robust platform for addressing both environmental and energy challenges. In this paper, discarded absorbent pads are transformed into carbon-rich frameworks, which is followed by the fabrication of composites through the incorporation of Cu₄SnS₄ (CSS) for dual electrochemical applications. Integrating CSS into the waste-derived carbon matrix induces strong synergistic effects, improving electrical conductivity, increasing active-site availability, and accelerating charge-transfer kinetics. Comprehensive physicochemical analyses confirmed the successful formation of a well-integrated heterostructure composite with favorable structural and surface characteristics. Electrochemical evaluations further demonstrated that CSS-modified carbon exhibits superior bifunctional performance. In a two-electrode configuration, the composite delivers an energy density of 12.08 Wh kg⁻¹ at a power density of 250 W kg⁻¹ along with excellent cycling stability in supercapacitor applications. As an electrocatalyst, it achieves a low overpotential of 268 mV at −10 mA cm⁻² and a small Tafel slope of 75 mV dec⁻¹, reflecting efficient reaction kinetics. The strong durability observed in both systems underscores the structural integrity and long-term operational stability of the material. Overall, this paper advances a sustainable waste-to-resource strategy for fabricating multifunctional carbon-based composites, offering a promising platform for integrated energy-storage and hydrogen-generation technologies. Full article

Self-powered integrated electrochemical systems require electrode materials that can simultaneously provide energy storage and sensing functions. Boron-doped diamond (BDD) electrodes have good chemical stability and a wide potential window, but their small specific surface area and slow interfacial charge transfer limit their use in such bifunctional applications. In this work, we prepared a three-dimensional porous BDD scaffold on titanium foam by hot-filament chemical vapor deposition, and then grew polypyrrole (PPy) layers on the scaffold by in situ oxidative polymerization. The polymerization time was varied from 8 to 20 h. The BDD/PPy composite obtained after 12 h showed an areal capacitance of 398.6 ± 15.2 mF/cm² at 1 mA/cm², which is about 5.8 times that of the porous BDD alone (67.9 mF/cm²). Its charge transfer resistance (R_ct) was as low as 1.3 ± 0.1 Ω, among the lowest reported for BDD-based electrodes. The porous BDD framework provides ion diffusion pathways, while the PPy layer introduces pseudocapacitance. X-ray photoelectron spectroscopy reveals that the PPy layer contains pyrrolic –NH– groups, which are known to chelate various water pollutants (e.g., heavy metal ions and organic molecules). Based on these surface properties and the low R_ct, we suggest that this composite may have theoretical potential for preconcentrating and detecting multiple pollutants. This work demonstrates a way to improve the capacitance of BDD-based electrodes and may serve as a starting point for future exploration in integrated energy-sensing devices after experimental validation. Full article

Seawater zinc–air batteries (SZABs) stand out as promising candidates for marine and offshore energy supply. However, their practical implementation is greatly restricted by tardy oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) kinetics at the air cathode, severe chloride ion-induced catalyst corrosion, and structural deterioration of traditional binder-containing electrodes in seawater media. Herein, we design and fabricate a binder-free integrated electrode consisting of carbon-supported iron phthalocyanine- modified star-like cobalt sulfide arrays directly grown on nickel foam. The optimal catalyst (0.3FePc-C/CoS) integrates the respective advantages of Fe single atoms and cobalt sulfide, exhibiting excellent ORR and OER activity, delivering a prominent half-wave potential of 0.89 V versus RHE, and exhibiting a low OER overpotential of 160 mV at 50 mA cm⁻² and robust stability in seawater. As a self-supported air cathode, the 0.3FePc-C/CoS-based battery attains a favorable open-circuit voltage reaching 1.48 V, prominent peak power density (126.4 mW cm⁻²), small charge–discharge potential polarization (0.52 V), excellent energy efficiency (68.8%) and extraordinary long-term cycling durability (>360 h). This work not only discloses a feasible synergistic modulation strategy for constructing high-performance bifunctional electrocatalysts but also provides a valuable reference for developing corrosion-resistant integrated air electrodes toward practical marine energy storage applications. Full article

Microbial fuel cells (MFCs) are promising bioelectrochemical systems for simultaneous wastewater treatment and energy recovery. However, their practical application is still limited by insufficient power output and weak transient energy-supply capability under fluctuating operational conditions. Herein, a bifunctional CF/MXene/FeS composite anode was fabricated through a one-step hydrothermal strategy to simultaneously enhance electricity generation and capacitive charge storage in MFCs. Unlike conventional bioanode modifications that primarily target conductivity enhancement alone, the constructed hierarchical composite integrates conductive MXene nanosheets and electroactive FeS phases to synergistically improve extracellular electron transfer and interfacial charge-storage behavior. The modified electrode exhibited enhanced surface roughness, abundant electroactive sites, and improved biofilm-supporting interfaces. Benefiting from the integrated conductive and electroactive composite framework, the CF/MXene/FeS anode achieved a maximum power density of 1.69 W/m², which was 70.7% higher than that of pristine CF, together with an increased open-circuit voltage of 0.711 V. In addition, the composite electrode delivered a high total charge density of 13,192.09 C/m² under the C900/D900 condition. Microbial community analysis further revealed substantial enrichment of electroactive bacteria, with the relative abundance of Geobacter increasing from 0.0058% to 22.84%. This work provides a promising strategy for integrating electricity generation and transient energy storage in bioelectrochemical systems, offering potential applications for energy-buffered MFCs under fluctuating power-demand conditions. Full article

Achieving efficient overall water splitting with non-precious metal catalysts remains a significant challenge due to the sluggish kinetics of both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). Herein, we report a nickel–iron bimetallic doped geopolymer electrocatalyst (Ni_0.9Fe_0.1-GP) fabricated via a one-step alkali activation method on 316L stainless steel. Structural characterizations reveal that Fe³⁺ incorporation alters the distribution of Na⁺ and Ni²⁺ within the geopolymer network and modulates the Ni electronic structure. Electrochemical measurements show that Ni_0.9Fe_0.1-GP delivers an HER overpotential of 332.42 mV and an OER overpotential of 227.31 mV at 10 mA cm⁻², outperforming Ni-GP and bare 316L SS. The practical operating voltage of Ni_0.9Fe_0.1-GP is 1.81 V, while the two-electrode electrolyzer delivers a comparable current density at 1.90 V (after accounting for uncompensated system resistances). Long-term stability tests demonstrate the superior durability of Ni_0.9Fe_0.1-GP during HER, OER, and overall water splitting. Mechanistic studies reveal the dual role of Fe³⁺: substantially increasing the electrochemical active surface area (ECSA) while modulating the Ni electronic structure, and improving structural stability through strong chemical anchoring within the geopolymer network. This work provides new insights into cost-effective bifunctional electrocatalysts and expands the application of geopolymers as functional catalytic supports for water splitting. Full article

Developing bifunctional non-noble metal electrocatalysts with high activity, stability, and cost-effectiveness is essential for large-scale sustainable water splitting, yet remains challenging. Herein, 2P-FeCoNi-MOF was synthesized via hydrothermal reaction of FeCoNi-LDH followed by phosphidation. Its layered structure, integrated with 3D nickel foam, creates a hierarchical porous architecture that increases surface area and accelerates electron transport. Synergistic effects among Fe, Co, Ni in the trimetallic phosphides, together with an amorphous carbon layer, boost catalytic performance. Moreover, superhydrophilic and superaerophobic surfaces enhance mass transfer. In 1 M KOH, 2P-FeCoNi-MOF achieves low overpotentials of 70 mV for HER and 225 mV for OER at 10 mA cm⁻², with excellent stability for 100 h at 100 mA cm⁻². For the overall water splitting, it requires only 1.54 V to reach 10 mA cm⁻² and maintains stability for 100 h at 100 mA cm⁻². Therefore, this study provides a new approach for the preparation of high-performance self-supported non-noble metal-based electrocatalysts for water splitting. Full article

The functional valorization of waste fabrics, particularly their conversion into flexible low-cost, high-performance electrodes, holds significant promise for resource sustainability and the development of advanced energy technologies. Here, a NiB/Cu/polyester fabric (PF) composite electrode was fabricated via two-step electroless plating on waste PF and was demonstrated as a bifunctional electrocatalyst for methanol oxidation (MOR) and urea oxidation (UOR). The morphology, crystal structure, surface chemical state, and wettability of the electrodes were characterized using SEM, TEM, XRD, XPS, and contact angle measurements. The Cu interlayer critically enhanced interfacial wettability, intrinsic catalytic activity and stability. At 0.8 V, the NiB/Cu/PF electrode delivered average current densities of 312 mA·cm⁻² for MOR and 288 mA·cm⁻² for UOR, outperforming NiB/PF by 27.9% and 9.1%, respectively. After 2000 accelerated degradation cycles with electrolyte renewal, MOR and UOR activities were retained at 91.6% and 105.0%, respectively. Remarkably, the Cu interlayer conferred exceptional mechanical–electrochemical robustness: following 100 sequential bending and twisting deformations, current density retention ranged from 84.6% to 96.7% across multiple test configurations. The Cu interlayer acted as a flexible stress buffer during mechanical deformation, effectively improving the adhesion between the coating and the substrate. Full article