Electrochemical sensors have emerged as a promising platform for the detection of benomyl (BEN) residues due to their fast response and high sensitivity. Nevertheless, their practical application is greatly restricted by the weak electrochemical activity of BEN, electrode surface fouling, and limited detectable concentration range. Herein, a high-performance electrochemical sensor based on graphene (Gr)-modified black phosphorus (BP) composite was fabricated for BEN determination. In this composite, Gr effectively enhanced the conductivity and electroactive surface area (EASA) while stabilizing BP, and BP endowed the modified electrode with excellent antifouling capability. The optimized electrode exhibited high electroactivity and excellent repeatability toward BEN oxidation. Benefiting from these merits, the proposed sensor achieved an ultralow detection limit (3.0 nmol L⁻¹), good repeatability, and outstanding selectivity toward BEN detection. Further assisted by machine learning, a wide linear detection range spanning 10 nmol L⁻¹–100 μmol L⁻¹ is achieved, verifying its robust sensing capacity. Satisfactory recoveries of 90.2–104.1% are obtained in real agricultural sample analysis, confirming its high potential for rapid trace monitoring of BEN residues in agricultural products.
The urgent need for clean and sustainable energy has intensified research into renewable Bioelectrochemical technologies. Here, activated carbon (AC) was derived from coffee husk, an abundant agricultural waste, and combined with polyaniline (PANI) via a one step in situ chemical oxidative polymerization to produce AC/PANI nanocomposites. The synthesized materials were characterized using UV-Vis, SEM–EDS, XRD, FTIR, BET and Raman spectroscopy to investigate its optical, morphological, and structural properties, molecular vibrational states, surface area and structural defects. Electrochemical performance was evaluated using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Electrochemical studies revealed a high specific capacitance of 625Fg-1 at 0.01Vs-1. When employed as an anode in microbial fuel cells (MFCs), the AC/PANI electrode delivered a maximum power density of 136.25 mWm-2 and a current density of 350mAm-2, substantially outperforming PANI (42.88mW/m², 180mAm-2) and AC ( 36.5mWm-2,150mAm-2).The superior performance arises from the synergistic interaction between PANI and the AC matrix, providing efficient charge transport, abundant active sites, and combined pseudo capacitive and electric double layer behavior. These results highlight coffee husk derived AC as a cost-effective, sustainable, and high performance material for enhancing MFC anode functionality and advancing electrochemical energy storage technologies.
The practical application of proton exchange membrane fuel cells (PEMFCs) in aerospace systems is challenged by the corrosion of metallic bipolar plates under highly oxidative, acidic, and hydrothermal conditions. Ag coatings are promising conductive protective layers; however, their long-term corrosion evolution and degradation mechanisms in PEMFC environments remain poorly understood. Herein, the corrosion behavior of electrodeposited Ag coatings on 316L stainless steel was systematically investigated in an accelerated simulated PEMFC environment containing 0.5M H2SO4 and 10 ppm HF at 80°C. Electrochemical measurements, including open-circuit potential, electrochemical impedance spectroscopy, and potentiodynamic polarization, were combined with Scanning electron microscope (SEM), Energy dispersive spectroscopy (EDS), X-Ray Diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) analyses. The results show that the corrosion resistance of the Ag coating changed significantly with immersion time. After 24h, the charge-transfer resistance decreased from 3291 to 1969 Ω·cm2, while the corrosion current density increased from 1.232 × 10-5 to 2.234 × 10-5A/cm2. Surface characterization revealed the gradual development of pores, microcracks, and corrosion products, indicating increasingly severe localized corrosion. The degradation mechanism is closely associated with the evolution and breakdown of the surface protective layer. During the initial stage, the formation of a thin Ag2O-rich film partially suppresses interfacial charge transfer and delays corrosion. With prolonged exposure, however, F- penetrates through coating defects and promotes disruption of the surface film, thereby facilitating localized corrosion and accelerating electrochemical degradation. These findings clarify the corrosion evolution of Ag-coated bipolar plates and provide mechanistic guidance for improving the durability of conductive protective coatings for aerospace PEMFC applications.
This paper presents an investigation of the cathodic process during the electrodeposition of cobalt and CoMo alloys under discharge conditions of various cobalt complexes: [Co(Cit)2]4-, [CoСit(MoO4)]3– and [Co(Cit)(PPi)]5-. The EIS method showed that the [Co(Cit)2]4- complex is not electroactive, has the highest charge transfer resistance and does not exhibit specific adsorption. Electrodeposition of the CoMo alloy becomes possible by adding sodium molybdate in an amount of 0.002-0.02mol·L-1 to the citrate electrolyte due to the formation of mixed-ligand complexes [CoСit(MoO4)]3– and the alloy formation occurs from a solution in which none of the metals deposites individually. The formation of electroactive mixed-ligand complexes [Co(Cit)(PPi)]5- upon addition of pyrophosphate ions to the solution promotes both the electrodeposition of cobalt individually and the efficient deposition of CoMo alloys upon addition of 0.02mol·L-1 МоО42-.
The development of efficient and economical electrocatalysts for the hydrogen evolution reaction (HER) remains crucial for sustainable hydrogen production. In this study, the effect of incorporating graphitic carbon nitride (g-C₃N₄) into cubic ZrO₂ (c-ZrO₂) was systematically investigated to elucidate the material's electrocatalytic activity. The ZrO₂@g-C₃N₄ composites were prepared in various compositions (30-90wt.%) of g-C₃N₄ and characterized by XRD, TGA, FE-SEM, CV, LSV, and EIS. The low-temperature cubic ZrO₂ phase was stabilized at room temperature using XRD, and the crystallite size was 4.0-6.7nm, which was attributed to the effects of interfacial strain and confinement caused by the g-C₃N₄ matrix. The FE-SEM images showed intimate contact between the ZrO₂ nanoparticles and g-C₃N₄ nanosheets, forming a hierarchical porous structure. Importantly, the HER activity of the composite showed a non-monotonic trend with composite loading, being highest for the composite containing 30wt. % g-C₃N₄. It was found that the 30wt.% composite had an overpotential of 1300mV at 10mA/cm2 and exhibited much better charge-transfer kinetics than pure ZrO2. The charge-transfer resistance was found to drop significantly with the incorporation of g-C₃N₄, as indicated by EIS data, due to heterojunction formation and an optimized electron transport pathway. The 90wt.% composite showed good stability and poor catalytic activity, indicating a fundamental balance between access to the active site and its protection. The results indicate that ZrO₂@g-C₃N₄ heterostructures are promising, earth-abundant electrocatalysts and provide important guidelines for optimizing their electrocatalytic performance through loading.
The performance of vanadium redox flow batteries (VRFBs) is critically influenced by the flow-field configuration, which governs electrolyte distribution and mass transport. To overcome the insufficient through-plane mass transfer in conventional designs, this study proposes a novel undulating flow field (UFF) featuring a central inlet, pentagonal channels (narrow top, wide bottom), and multiple transverse channels. Using a three-dimensional coupled multiphysics model and experimental validation, we systematically compare a serpentine flow field (SFF) with three UFF variants. Results show that the UFF improves the uniformity of active species concentration. Specifically, at a flow rate of 130mL·min⁻¹, UFF-11 reduces pressure drop and pumping loss by 55.41% relative to SFF. Under a high current density of 200mA·cm⁻² and a low flow rate of 30mL·min⁻¹, UFF-11 increases discharge capacity by approximately 165 mAh, peak power density by 11.74mW·cm⁻², and energy efficiency by 4.29% compared with SFF. Considering pump consumption, UFF-11 also achieves a substantially higher net system energy efficiency, demonstrating clear advantages under low-flow, high-load conditions. This work provides a new strategy for VRFB flow-field design and optimization.
In this work, CaTiO3, SrTiO3, and BaTiO3 perovskite titanates were synthesized via a sol-gel technique for use as supercapacitor electrodes. The bandgap energies of the produced perovskite titanates was calculated as 3.19 eV for BaTiO₃, 3.22 eV for SrTiO₃, and 3.52 eV for CaTiO₃, confirming the semiconducting nature of the perovskite titanates. The specific surface areas of 19.19 m².g⁻¹ , 18.64 m².g⁻¹ , and 12.20 m².g⁻¹ for BaTiO₃, SrTiO₃, and CaTiO₃, respectively, were measured by BET analysis. The DFT pore-width distribution revealed pore-width modes of 16.68 nm for BaTiO₃, 16.02 nm for SrTiO₃, and 10.68 nm for SrTiO₃. The BaTiO3 sample reveals the highest specific capacitance of 1927.7 F·g−1 at 2 A.g−1 current density, which is much higher than both the SrTiO3 (654 F·g−1) and CaTiO3 (280.3 F·g−1). A similar trend was observed in energy density, with the BaTiO₃ electrode showing the highest energy density of 86.9 Wh.kg−1 and power density of 570 W.−1kg, along with capacitive retention of 56.6% and Coulombic efficiency of 85%, outperforming the SrTiO₃ (29.6 Wh.kg−1) and CaTiO₃ (12.6 Wh.kg−1) electrodes. The EIS analysis confirmed the negligible charge-transfer resistance and lowest equivalent series resistance of BaTiO3 (1.13 Ω), with a Warburg slope exceeding 45° in Nyquist plot, representing its good charge transfer character. BaTiO₃ revealed dual charge storage, with a b-value of 0.344 and a capacitive contribution increasing from 7% to 34% as the scan rate rises from 1 to 50 mV/s. The Bode slope of −0.144 confirms dominant diffusion-controlled storage with a significant capacitive contribution, enhancing its energy and power-density potential.
The electrochemical behaviour of electropolymerized poly (3-aminophenylboronic acid) [P(3-APBA)] is strongly dependent on the conditions under which it is formed. However, a systematic understanding of how electropolymerization parameters collectively govern the electrochemical properties of P(3-APBA) remains limited. In this work, the influence of electrolyte composition, supporting electrolyte concentration, fluoride concentration, monomer concentration, and electrodeposition parameters on the formation and electrochemical characteristics of P(3-APBA) films was systematically investigated. Polymer films were synthesized in hydrochloric acid (HCl), sulfuric acid (H2SO4), and phosphate-buffered saline (PBS) using cyclic voltammetry under controlled potential windows, scan rates, and deposition cycles. The resulting materials were characterized using cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS), while ultraviolet-visible (UV-Vis) and Fourier Transform infrared (FTIR) spectroscopies confirmed polymer formation. The results show that electrolyte chemistry strongly influences polymer growth and electroactivity, with 0.5M HCl producing films that exhibited the highest electroactive charge and the most defined redox transitions. In contrast, PBS-based systems showed significantly reduced electrochemical response, indicating suppressed charge transport and limited electroactive site accessibility. The monomer-to-fluoride ratio of 0.04:0.08M was found to provide optimal balance between polymer formation and electrochemical performance, while a potential window of -0.1 to 1.0V, an end potential of 0.5V, and a scan rate of 20mV/s promoted stable film growth. EIS analysis further revealed reduced charge-transfer resistance (Rct) under optimized conditions, consistent with enhanced electron-transfer kinetics within the polymer film. Collectively, these results demonstrate that electrolyte environment, fluoride-assisted activation, and deposition parameters act synergistically to govern the electrochemical properties of P(3-APBA), establishing a reproducible framework for controlled electropolymerization and electrochemical evaluation of this conducting polymer system.
Photocatalytic water splitting presents a direct and sustainable approach for solar-to-hydrogen conversion. However, inconsistencies in electrochemical evaluations have significantly hindered cross-study comparability and mechanistic understanding. To address this issue, this review critically examines the electrochemical methodologies employed to assess photocatalytic hydrogen evolution, categorizing them into mechanism-oriented diagnostics and performance-oriented evaluations. Mechanism-oriented techniques, such as Mott-Schottky analysis, electrochemical impedance spectroscopy (EIS), and incident photon-to-current efficiency (IPCE), offer quantitative insights into band alignment, carrier density, charge transfer kinetics, and recombination dynamics under illumination. In contrast, performance-oriented approaches, including photocurrent response, linear sweep voltammetry (LSV) with Tafel analysis, and chronoamperometry (CA), quantify hydrogen evolution rates, onset potentials, Faradaic efficiency (FE), and operational stability. Rather than reiterating established principles of instrumentation, this review delves into the application of these techniques within illuminated hydrogen evolution systems, clarifying the physical significance, diagnostic depth, reproducibility, and intrinsic limitations of the extracted parameters. Emphasis is placed on identifying sources of systematic error—such as light miscalibration, reference electrode misconversion, uncompensated resistance, surface heterogeneity, and bubble accumulation-that often distort reported performance metrics. To enhance methodological consistency, a Standardized Benchmarking Protocol for Photocatalytic Hydrogen Evolution is proposed, outlining minimum reporting criteria for illumination calibration, potential conversion to RHE, catalyst normalization, and gas quantification. Furthermore, a dedicated section on Future Perspectives and Challenges discusses emerging operando diagnostics and harmonized validation frameworks designed to bridge laboratory-scale measurements with scalable hydrogen production.
In this work, CaTiO3, SrTiO3, and BaTiO3 perovskite titanates were synthesized via a sol-gel technique for use as supercapacitor electrodes. The bandgap energies of the produced perovskite titanates was calculated as 3.19eV for BaTiO₃, 3.22eV for SrTiO₃, and 3.52eV for CaTiO₃, confirming the semiconducting nature of the perovskite titanates. The specific surface areas of 19.19m².g⁻¹, 18.64m².g⁻¹, and 12.20m².g⁻¹ for BaTiO₃, SrTiO₃, and CaTiO₃, respectively, were measured by BET analysis. The DFT pore-width distribution revealed pore-width modes of 16.68nm for BaTiO₃, 16.02nm for SrTiO₃, and 10.68nm for SrTiO₃. The BaTiO3 sample reveals the highest specific capacitance of 1927.7F·g-1 at 2A.g-1 current density, which is much higher than both the SrTiO3 (654F·g-1) and CaTiO3 (280.3F·g-1). A similar trend was observed in energy density, with the BaTiO₃ electrode showing the highest energy density of 86.9Wh/kg and power density of 570W/kg, along with capacitive retention of 56.6% and Coulombic efficiency of 85%, outperforming the SrTiO₃ (29.6Wh/kg) and CaTiO₃ (12.6Wh/kg) electrodes. The EIS analysis confirmed the negligible charge-transfer resistance and lowest equivalent series resistance of BaTiO3 (1.13 Ω), with a Warburg slope above 45° in Nyquist plot. The charge-storage mechanism of BaTiO3, with a b-value of 0.344, a capacitive contribution of 34%, a steeper slope in the Bode magnitude plot at low frequency, and a stable phase plateau near 0° in the Bode phase plot, showed that surface redox reactions are involved in the charge-storage mechanism for next-generation supercapacitor applications.
The escalating discharge of recalcitrant organic wastewater presents a significant threat to global water security. Electrochemical advanced oxidation processes (EAOPs) have emerged as a promising technology to address this challenge, leveraging the in-situ generation of highly reactive species for effective mineralization of organic pollutants. Central to the efficacy of EAOPs is the electrocatalytic electrode, whose performance dictates the overall efficiency, cost, and practicality of the technology. This review systematically summarizes recent advancements in the design strategies for three major electrode categories: boron-doped diamond (BDD), metal oxides, and sp2-hybridized carbon-based materials. We critically assess rational design approaches—including component regulation, structural design, and surface/interface engineering—to reveal intrinsic structure-performance relationships that enhance degradation efficiency and stability. Recognizing the gap between laboratory innovation and industrial application, this review further addresses critical engineering challenges impeding scale-up, including electrode deactivation mechanisms, reactor configuration optimization, mass transfer limitations, and techno-economic feasibility. Key scale-up parameters are discussed to establish a comprehensive framework for practical implementation. Finally, we outline future research directions, offering guidance for the rational design and application of next-generation electrocatalytic electrodes for organic wastewater treatment.
This study investigated a nano-SiO₂-calcium nitrite composite admixture for suppressing chloride-induced reinforcement corrosion in pre-cracked concrete. Ten mixtures were prepared, including plain cracked concrete, single-admixture mixtures, and five tested composite mixtures. Beam specimens with controlled surface crack widths of 0.20–0.35 mm were exposed to 3.5 wt% NaCl wet-dry cycles for 120 d. The optimized NS2-CN2 mixture, containing 2.0% nano-SiO₂ and 3.0% calcium nitrite by binder mass, increased 90 d compressive strength from 52.9 MPa to 68.9 MPa, reduced total porosity from 15.6% to 9.3%, and lowered the apparent chloride diffusion coefficient from 11.8 × 10⁻¹ ² m²/s to 3.5 × 10⁻¹ ² m²/s. At 120 d, NS2-CN2 shifted the open-circuit potential from −492 mV to −225 mV versus SCE, decreased corrosion current density from 1.82 to 0.114 µA/cm², increased charge-transfer resistance from 7.3 to 125.4 kΩ cm², and reduced gravimetric steel loss by 90.8%. Statistical models showed large group effects for diffusion, corrosion current, charge-transfer resistance, and mass loss, with partial η² values of 0.92–0.97. Nano-SiO₂ mainly improved the transport barrier, whereas calcium nitrite primarily stabilized the passive film. Their joint effect on corrosion current was consistent with multiplicative independence; therefore, the data support complementary protection but not a statistically demonstrated superadditive interaction.
The replacement of platinum as a counter electrode is a major challenge in producing low-cost, stable Dye Sensitised Solar Cells (DSSCs). In this work, a counter electrode fabricated using a simple multilayer deposition of AgNWs, rGO, and PEDOT:PSS was developed as a suitable platinum substitute. The layered structure provided the combined benefits of the high electrical conductivity of AgNWs, the larger surface area and catalytic sites of rGO, and the efficient charge transfer kinetics of PEDOT:PSS. Extensive electrochemical studies, including EIS, CV, and Tafel polarisation, confirmed the faster redox kinetics of the counter electrode. The DSSC fabricated with this counter electrode underwent photovoltaic measurements to evaluate its solar cell efficiency. These results approached those of the conventional Pt counter electrode closely. Photovoltaic studies demonstrated a Jsc of 29.65 ± 2.09 mA/cm2, a Voc of 0.61 ± 0.02 V, and FF of 53.89 ± 1.90%, and an efficiency of 9.72 ± 0.03%, which is comparable to Pt (9.81 ± 0.14%). These findings demonstrate that AgNWs-rGO-PEDOT:PSS has potential as a promising and cost-effective alternative counter electrode for DSSC fabrication.
This work targets the long-standing drawbacks including insufficient precision and laggy real-time responsiveness plaguing online parameter identification and state-of-charge (SOC) prediction based on equivalent circuit models (ECMs) of lithium-ion batteries (LIBs).We propose a chaotic optimization adaptive synchronous control algorithm (CO-ASCA) and an integrated SOC estimation method combining CO-ASCA with extended Kalman filtering (EKF) (CO-ASCA-EKF).First, a first-order RC equivalent circuit model (1RC-ECM) chaotic system was constructed using charge-controlled memristors (CCMS). Second, the chaos optimization adaptive synchronous control algorithm (CO-ASCA) was developed to enable real-time online parameter identification for the 1RC-ECM. Third, a SOC estimation algorithm based on CO-ASCA-EKF was established to achieve precise SOC estimation. Finally, experimental results obtained under conditions of Beijing Dynamic Stress Test (BJDST) at 0°C, the Supplementary Federal Test Procedure (US06) at 25°C, and the Federal Urban Driving Study (FUDS) at 45°C respectively validated the effectiveness of both CO-ASCA and CO-ASCA-EKF algorithms.The test results demonstrate that under BJDST conditions (0°C), CO-ASCA achieves a mean relative error (MRE) of 0.062%, which is 1.578 %age points lower than the sparrow search algorithm (SSA, 1.64%) and 3.108 %age points lower than the Least Squares Support Vector Machine (LS-SVM, 3.17%). CO-ASCA-EKF exhibits an MRE of 0.865% under the same conditions, significantly outperforming both the FFRLS-EKF algorithm (3.795%) and the LSTM algorithm (6.516%). This indicates that both CO-ASCA and CO-ASCA-EKF demonstrate superior real-time performance and robustness.
A key challenge for advanced supercapacitors is the development of high-performance electrode materials that can achieve fast charge transport and a large number of electroactive sites. In this work, a new Mo3Sn@Bi2W2O9 hybrid is synthesized by hydrothermal process to promote the electrochemical properties of Bi2W2O9 by heterostructure engineering. Based on structural characterization, one can conclude that the Mo3Sn and Bi2W2O9 phases are coexisting in the hybrid, with an average crystallite size of 41.3 nm for pristine Bi2W2O9 reduced to 25.3 nm for the hybrid. EDX and elemental mapping of the heterostructure show that it is uniformly distributed in the sample, and the BET analysis reveals that the structure has a larger specific surface area (61.5–69.2 m2 g−1), which create more electrochemically active sites and allows for more diffusion of electrolyte ions. The Mo3Sn@Bi2W2O9 electrode exhibits a high specific capacitance of 411.4 F g−1 at 1 A g−1, about 3.8 times as high as that of pristine Bi2W2O9 (107 F g−1). Moreover, the hybrid electrode also shows decreased charge-transfer resistance and improved ion diffusion, which again indicates the fast electron transfer at the heterointerface. The excellent electrochemical properties are due to the synergy between conductive Mo3Sn and Bi2W2O9 which enhances electrical conductivity, exposes more active sites, and accelerates faradaic reactions. The results show that the Mo3Sn@Bi2W2O9 hybrid could be used as a promising electrode material for next-generation high-performance supercapacitors.
Aluminum alloys are limited in their widespread application within this field due to their relatively poor corrosion and wear resistance. The application of surface protective coatings effectively enhances the corrosion resistance and wear resistance of aluminum alloys. This paper comprehensively reviews recent advances in corrosion- and wear-resistant coatings for aluminum alloy surfaces, with particular emphasis on research achievements associated with one-step (such as anodic oxidation (AO), micro-arc oxidation (MAO), electrodeposition (ED）, and other related one-step techniques) and two-step fabrication methods （Post-treatment following MAO, post-treatment following AO, post-treatment following ED, and other two-step processes). A systematic analysis was performed for each coating preparation method, including its corrosion and wear resistance properties. Additionally, a comparative analysis of the advantages and disadvantages of various preparation methods was conducted, and an outlook on future development trends in this field was presented.
The T6-treated AZ80 magnesium alloy is composed of three phases: α-Mg, Mg17Al12, and Al18Mn19. This study reveals a synergistic corrosion inhibition effect in silane coupling agent-organic ligand systems. Specifically, the dodecyltrimethoxysilane (DTMS)-2-2’bipyridyl (bpy) system exhibits optimal corrosion inhibition performance, achieving an inhibition efficiency of 87.96% as determined by weight loss test. Electrochemical measurement results further indicate that bpy acts as an anodic inhibitor, while DTMS functions as a mixed-type inhibitor. The combined application of these two inhibitors further suppresses the anodic corrosion of AZ80 alloy. The synergistic mechanism between DTMS and bpy is attributed to the formation of a composite film. The protective mechanism of this film originates from two key processes: the formation of a hydrophobic monolayer through silane hydrolysis and cross-linking, and the continuous deposition reaction facilitated by the coordination of bpy with Mg2+. This dual mechanism collectively provides sustained and enhanced anodic protection, thereby significantly improving the corrosion resistance of the AZ80 alloy.
Prestressing steel strands are vulnerable to chloride-assisted corrosion fatigue because localized pits can concentrate cyclic stress before appreciable section loss occurs. This study compared eight surface states, from bare steel to silane/polydopamine (PDA) bilayers grown for 3–24 h, using surface characterization, electrochemical testing, humid chloride aging, and corrosion-fatigue testing. Silane/PDA-12h provided the best overall response, with a thickness of 176.6 ± 15.1 nm, scratch critical load of 6.86 ± 0.88 N, initial |Z|0.01 Hz of 9.11 × 10⁵ Ω cm², and corrosion current density of 0.194 ± 0.069 µA cm⁻². After 56 humid chloride cycles, its maximum pit depth was 17.0 ± 3.7 µm versus 108.8 ± 16.9 µm for bare steel; at a 500 MPa stress range, mean fatigue life increased from 0.35 × 10⁶ to 1.44 × 10⁶ cycles. The 24 h film was thicker but less durable, showing that barrier continuity, resistance to electrolyte uptake, and adhesion are more important than maximum thickness.
A Zr-Modified TESPT coating was prepared on 2618 aluminum alloy by dip-coating under conditions of TESPT 4 vol%, Zr/TESPT molar ratio 1:4, pH 4.0, and 12 h hydrolysis. Electrochemical impedance spectroscopy yielded polarization resistance values of 4.21 × 106 Ω·cm2, 7.53 × 105 Ω·cm2, and 5.91 × 104 Ω·cm2 for the Zr-Modified TESPT, TESPT, and bare alloy, respectively. Potentiodynamic polarization gave corrosion current densities of 1.13 × 10−8 A·cm−2, 2.20 × 10−7 A·cm−2, and 4.20 × 10−6 A·cm−2 for the corresponding specimens. The constant phase element parameter decreased from 3.33 × 10−6 F·cm−2 to 1.78 × 10−8 F·cm−2, with the dispersion exponent n decreasing from 0.921 to 0.909 and then to 0.853. Following 48 h neutral salt spray exposure, the Zr-Modified TESPT appeared intact over the majority of the exposed area, with degradation features observed at the periphery and edges, whereas the TESPT coating exhibited sporadic pitting distributed across the entire surface. XPS detected Zr4+ signals on the coating surface; the assignment of these signals to specific chemical species requires additional spectroscopic investigation. These findings characterize the electrochemical and morphological response under the specific preparation and test conditions employed, and further validation is warranted to establish predictive correlations with long-term field performance.
This study addresses key challenges in traditional liquid organic hydrogen carrier (LOHC) dehydrogenation—such as dependence on high temperatures or precious metal catalysts—and electrode passivation in direct electrosynthesis. Using 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO) and its derivatives as media, we examined the electrocatalytic dehydrogenation of piperazine to pyrazine. Through systematic evaluation of 27 electrolyte systems based on diffusion coefficient (D) and electron transfer rate constant (k⁰), synergistic effects among components were identified. An optimal system of ACN + TBAPF6 + TEMPO was selected for low-concentration piperazine reactions; for higher concentrations (e.g., 0.1 M), a mixed solvent of ACN and water was used to improve solubility. CuCo2O4/NF as dehydrogenation catalyst in this optimized electrolyte was further investigated. The electrocatalyst promotes TEMPO redox cycling and piperazine dehydrogenation, achieving high initial conversion (99.6%) and selectivity (79.9%) at 1.55 V (vs. RHE), along with sustained stability over 288 h (the conversion of 90.9%, the selectivity of 67.8%). Mechanistic studies reveal that 2,2,6,6-tetramethyl-1-oxo-piperidinium (TEMPO⁺) regeneration on CuCo2O4/NF proceeds in two steps, enabling a rapid dynamic redox equilibrium that facilitates homogeneous piperazine oxidation. This dehydrogenation system follows a multi-step EE' pathway.
