Search Results (2,331)

Reactions between nitrogen-containing compounds and free chlorine in swimming pools produce several undesirable by-products, with trichloramine (TCA) being especially problematic due to its odor and hazardous properties, causing respiratory symptoms and skin and eye irritation for swimmers and personnel. To address this issue, this study investigates electrochemical oxidation as a potential technique for reducing TCA concentrations in various pool water environments. Specifically, the results show that electrolysis, using a mixed metal oxide (MMO) electrode as the anode, affects the amount of free chlorine and significantly reduces TCA in synthetic pool water containing urea and sodium hypochlorite. This approach is further validated in large-scale systems with real swimming pool water. In two long-term experiments, TCA released from the pool water falls from a baseline of 1.42 mg/m³ to 0.94 mg/m³ in a 680 m³ pool, a reduction of 34% ($p<0.001$), and from 0.77 mg/m³ to 0.35 mg/m³ in an 85 m³ pool, a reduction of 55% ($p<0.001$). Water from a third pool was used to map the potential dependence. Importantly, the anode potential is critical for TCA reduction, with 1.8 V vs. RHE identified as optimal and a working window of 1.7–1.9 V. The system operates at approximately 1 A/m² and 2 W/m². Overall, this electrolysis process reduces the trichloramine burden of swimming pool water, which is expected to lower airborne trichloramine in swimming halls and thereby improve conditions for users and personnel. Full article

External corrosion of buried ferrous water mains remains the dominant driver of structural failure in aging water distribution networks, yet the mechanisms linking soil physical and chemical heterogeneity to corrosion kinetics and product phase evolution have not previously been synthesized into a unified critical framework. This review evaluates three partially competing accounts of electrochemical degradation—anodic dissolution coupled to oxygen reduction within porous rust layers, redox cycling of iron oxide phases driven by seasonal soil moisture fluctuations, and microbially influenced corrosion (MIC) mediated by direct extracellular electron transfer (EMIC) and chemical metabolite pathways (M-MIC)—and assesses the weight of evidence for each. We demonstrate that corrosion products retain electrochemical activity long after formation, functioning as dynamic redox mediators that continue the reactions responsible for their own growth: the reduction of lepidocrocite under anoxic conditions regenerates Fe²⁺ ions that sustain anodic dissolution and catalyze oxygen reduction, while repeated soil moisture cycles drive the irreversible transformation of γ-FeOOH to Fe₃O₄, which fundamentally alters the conductivity and cathodic capacity of the rust layer. The widely cited universal critical-moisture threshold of 65% water-holding capacity (WHC) is evaluated and found to be a single-point approximation contradicted by texture-resolved experimental data that show the critical degree of saturation ranges from S_r ≈ 0.5 in sand to S_r ≈ 0.8 in clay. Modern machine learning analyses of field corrosion databases confirm that chloride content, pH, pipe-to-soil potential, and water content are the four highest-ranked predictors of maximum pit depth, consistent with the mechanistic framework developed here. The classical cathodic depolarization model of SRB-driven corrosion is evaluated against EMIC evidence and found insufficient: measured pure-culture SRB corrosion current densities range from 14 to 135 µA cm⁻², not the milliampere-level values reported in some earlier reviews. An explicit research agenda is proposed to address the five most consequential unresolved mechanistic questions. Full article

A CT-80 coiled tubing fractured at the gooseneck during retrieval after a 2.5 h treatment with 15% HCl under high-temperature bottom-hole conditions (196 °C). The failure was investigated by dimensional measurements, metallography, Vickers microhardness testing, SEM/EDS, and FT-IR spectroscopy. Pronounced corrosion asymmetry was observed. Cumulative external wall loss reached 1.196 mm, compared with 0.292 mm on the inner wall, while the wall loss attributed to the final operation was approximately twelve times greater externally than internally. These findings suggest two different exposure histories: predominantly uniform attack of the outer wall during backflow of spent, inhibitor-depleted acid, and localized pitting of the inner wall under incomplete inhibitor coverage. EDS mapping identified Sb-rich deposits around inner-wall pits. In combination with the relevant literature, this distribution is consistent with a possible Sb–Fe galvanic effect that may have promoted local anodic dissolution, although galvanic coupling was not measured directly. The FT-IR spectra were consistent with iron oxides/oxyhydroxides, carbonate-containing scale, sulfate-bearing products on the outer surface, and thin organic residues rather than a continuous inhibitor film. Microhardness increased from 229 HV1 in the new tubing to 243.4 HV1 at the fracture location; this increase may reflect limited hydrogen uptake together with service-induced strain hardening or residual stresses. Fractography showed necking and dimpled microvoid coalescence, supporting a predominantly ductile overload mechanism in the corrosion-thinned section. A limited contribution of hydrogen to ductility loss cannot be excluded because the hydrogen content was not quantified. Full article

Interconnector geometry strongly affects gas transport, polarization loss, and pressure drop in planar solid oxide fuel cells (SOFCs). In this study, four interconnector configurations were investigated for an anode-supported planar SOFC, including one conventional straight-rib interconnector and three connected-rib interconnectors, namely circular-rib (CI), rectangular-rib (RI), and triangular-rib (TI) designs. A three-dimensional multi-physics model coupling electric field, flow field, species transport, and temperature field was established and validated against experimental polarization data of the conventional straight-rib cell. To ensure a fair comparison, all interconnectors were designed with the same interconnector–electrode contact area. The effects of rib configuration on electrical performance, overpotential components, reactant distribution, velocity distribution, and pressure drop were systematically analyzed. At 800 °C, the peak power densities of CI-SOFC, RI-SOFC, and TI-SOFC increased by 4.9%, 9.7%, and 11.7%, respectively, compared with SI-SOFC. The connected-rib interconnectors mainly reduced cathode-side activation and concentration overpotentials by improving oxygen redistribution beneath the ribs. Among the four configurations, the TI-SOFC showed the highest power density and the strongest under-rib transport enhancement, while the RI-SOFC provided a better compromise between flow uniformity and pressure drop. Full article

Plasmonic nanostructures offer a practical solution for solar-to-thermal conversion, yet simultaneously achieving ultra-broadband absorption, scalable fabrication, and long-term stability using earth-abundant aluminum remains difficult. In this work, we present a three-dimensional (3D) crown-like aluminum nanostructure absorber that achieves an experimental average absorption of 92% across the solar spectrum (200–2500 nm), with only 1.9% degradation in average absorption over 24 months. The structure is fabricated via a scalable anodic aluminum oxide (AAO) template-assisted method, enabling large-area production without costly lithography and exhibiting broad fabrication tolerance to deposition-thickness variations. Electromagnetic simulations and structure analysis reveal that the ultra-broadband absorption arises from three synergistic mechanisms: multi-mode electric resonances, magnetic resonance behavior within the metal–dielectric–metal architecture, and a graded-refractive-index profile. Proof-of-concept photothermal experiments under simulated sunlight offer experimental confirmation of the absorber’s solar-to-thermal conversion capability, showing substantially enhanced solar-to-thermal energy utilization compared to pure-water references. This work provides a scalable, durable, and cost-effective platform for ultra-broadband solar absorption and solar-to-thermal conversion, and offers a viable design strategy for plasmonic absorbers based on earth-abundant materials. Full article

Slow reaction kinetics of the hydrogen oxidation reaction (HOR) and hydrogen evolution reaction (HER) under alkaline conditions limits the performance of anion exchange membrane fuel cells and water electrolysers (AEMFC and AEMWE). Consequently, high loadings of PGM metal-based compounds such as Pd-CeO₂ and PtRu are required to obtain competitive performance. The amount of precious metals present can be reduced by exploiting interaction with an active support material that tunes both hydrogen desorption and hydroxyl adsorption, processes that are key descriptors of HOR activity. In this work, NiWO_3−xC is prepared, composed of oxygen-deficient tungsten oxide (WO_3−x) doped with Ni nanoparticles and mixed with conductive carbon (50:50 wt%). This material is decorated with Pd nanoparticles (6.6 wt% Pd loading). Structural analysis (XRD, XPS, and HR-TEM/STEM) confirm a hybrid morphology of Pd nanoparticles deposited on both the Ni and W portions of the support. The HOR and HER activity was studied using electrochemical tests and compared to the performance of both a Pd/C standard with equivalent Pd loading (6.9 wt%) and the NiWO_3−xC support. The Pd-normalized exchange current densities for the HOR (I⁰) are 18.7 A g_Pd⁻¹ for Pd/NiWO_3−xC and 3.21 A g⁻¹ for Pd/C. The enhanced HOR activity of Pd/NiWO_3−xC translates to high power densities in AEM fuel cell tests with this catalyst applied to the anode electrode (up to 0.9 W cm⁻²). Full article

When metal oxides are employed as anodes in lithium-ion batteries, their practical application is often constrained by sluggish reaction kinetics. Structure optimization and heterointerface regulation are effective strategies for improving the aforementioned issue. Herein, a series of Co₃O₄/ZnCo₂O₄ heterostructured materials with hollow structures is prepared. The effects of the two-phase ratio on the interfacial activity and electrochemical performance are systematically investigated. Among them, the optimized Co₃O₄/ZnCo₂O₄-2 material exhibits enhanced interfacial interactions and abundant oxygen vacancies, which optimize the local electronic environment and facilitate charge transfer. Electrochemical test results indicate that the Co₃O₄/ZnCo₂O₄-2 anode maintains a reversible capacity of 582.4 mAh g⁻¹ after 1000 cycles at 1 A g⁻¹, demonstrating good cycling stability. Furthermore, the full cell assembled with a LiFePO₄ cathode maintains a discharge capacity of 115.9 mAh g⁻¹ after 100 cycles at 0.2 C, validating the practical application potential of the material. This work reveals the key role of interface regulation in boosting Li⁺ diffusion kinetics of transition metal oxides, providing new insights for the rational design of heterostructured anodes. Full article

Selective laser melting (SLM) can effectively suppress metallurgical defects inherent to conventional manufacturing; however, subsequent aging treatments essential for engineering applications introduce secondary precipitates that alter the electrochemical homogeneity of the matrix. The underlying mechanism by which such precipitation behavior governs corrosion resistance remains elusive. In this study, a Fe-30Mn-8Al-1.5C-2.5Ni steel was investigated to elucidate the corrosion morphology and electrochemical behavior of the as-built, 450 °C-aged, and 750 °C-aged specimens during immersion in a 3.5 wt.% NaCl solution. The results demonstrate that the inherent Mn microsegregation and high-density subgrain boundaries induced by SLM trigger preferential localized anodic dissolution on the surface of the as-built sample, culminating in the formation of a loose, porous manganese oxide product layer. Aging treatment at 450 °C induces extensive precipitation of κ-carbides within grain interiors and along grain boundaries, accompanied by localized depletion of Al and Mn at the phase interfaces. A pronounced micro-galvanic coupling established between the κ-carbides and the adjacent Al-depleted zones directly compromises the continuity of the passive film, thereby further deteriorating the corrosion resistance. In contrast, aging at 750 °C relieves the residual stress and eliminates the as-built elemental microsegregation. The resulting compositional homogenization of the matrix reduces the localized electrochemical driving force, which promotes a uniform reaction of Al at the surface to construct a continuous, compact Al-rich passive film, thereby sustaining the highest charge-transfer resistance during long-term immersion. This work elucidates the correlation among the intrinsic defects of SLM, aging-induced solute-depleted zones, κ-carbide precipitation, and localized micro-galvanic corrosion, providing a fundamental basis for tailoring the microstructure and corrosion resistance of additively manufactured lightweight steels. Full article

A strategy combining imprinting with anode oxidation is proposed for preparing an aluminum template with a negative compound-eye array. Injection compression molding with the aluminum template mounted on the mold cavity surface is applied to fabricate polystyrene replicas with a biomimetic compound-eye array on their surfaces. It is demonstrated that orderly microlenses and dense nanopillars with average diameters of approximately 225 μm and 63 nm, respectively, are formed on the polystyrene replicas. The polystyrene replica surfaces with the compound-eye array exhibit both hydrophobicity, with a water contact angle of 151 ± 2° and a rolling angle of 4 ± 1°, and excellent antireflectivity, showing an average reflectance of approximately 4% across the 400–1000 nm wavelength range. The microlens and nanopillar structures on the PS replicas are therefore key to achieving both hydrophobicity and antireflectivity simultaneously. The proposed fast mass-replication approach, which combines imprinting, anode oxidation, and injection compression molding, offers an efficient route for producing bioinspired compound-eye arrays. This strategy shows potential for applications in optoelectronics, photovoltaics, and self-cleaning optical surfaces. Full article

The economic viability of circular biorefineries is fundamentally constrained by the energetic and thermodynamic limits of conventional downstream processing. This critical review examines the paradigm shift toward electro-driven membrane separations, establishing them not merely as alternative filtration devices, but as active, programmable electrochemical interfaces. Moving beyond classical bulk-desalination models, the analysis elucidates the complex reactive-transport physics governing bio-based chemical recovery, where localized pH modulation, electrostatic gating, and field-induced speciation dictate molecular discrimination. The manuscript critically benchmarks the inescapable macro-scale thermodynamic tradeoff among interfacial selectivity, volumetric productivity, and specific energy consumption (kWh/kg). Furthermore, it evaluates the integration of active 2D nanoconfined materials (e.g., MXenes) and rigorously critiques the severe performance degradation modes—specifically electro-biologically coupled fouling and anodic oxidation—that paralyze industrial scale-up. Ultimately, this review outlines a strategic mandate for the fully electrified biorefinery, where continuous in situ product recovery, artificial intelligence-guided module design, and autonomous cyber-physical control systems converge to eliminate legacy thermal unit operations and seamlessly integrate biomanufacturing with decarbonized electrical grids. Full article

Ti₃C₂T_x MXene is an attractive conductive scaffold for lithium-ion battery anodes owing to its two-dimensional structure, hydrophilic surface chemistry, and tunable interlayer spacing; however, pristine MXene generally exhibits moderate lithium-storage capacity and suffers from restacking-induced loss of accessible active sites. In this study, Ti₃C₂T_x MXene@ZnO composites were prepared by growing ZnO on Ti₃C₂T_x MXene nanosheets with controlled growth times of 1, 2, and 3 h. The materials were characterized by FE-SEM, XRD, and N₂ adsorption–desorption measurements, and their electrochemical performance was evaluated in CR2032-type half-cells. Structural analyses showed that MZ-2h exhibited a more uniform distribution of ZnO particles, increased MXene interlayer spacing, and the highest BET surface area (42.77 m² g⁻¹) and total pore volume (0.1027 cm³ g⁻¹), whereas excessive ZnO growth for 3 h caused particle aggregation and reduced pore accessibility. Electrochemical measurements showed that MZ-2h delivered the best rate capability, maintaining 182.4 mAh g⁻¹ at 0.2 C and 48.0 mAh g⁻¹ at 5 C, together with the highest second-cycle Coulombic efficiency of 88.4%. These results demonstrate that controlling ZnO growth time is an effective strategy for balancing ZnO-derived lithium-storage contribution, particle dispersion, pore accessibility, and the MXene-based framework in Ti₃C₂T_x MXene-based hybrid anodes. 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

Gold cyanidation remains one of the most important hydrometallurgical processes in the mining industry. Gold dissolution kinetics and cyanide consumption are governed by coupled anodic–cathodic electrochemical reactions and influenced by pulp pH, particle size, cyanide concentration, mineralogy, and solution chemistry. Despite extensive studies on individual additives in gold cyanide leaching, a coherent synthesis of oxidants and leaching accelerants in modern gold cyanidation remains lacking. The main purpose of this paper is to present a critical review of the literature on leaching accelerants and oxidants used to enhance gold cyanide leaching kinetics and reduce cyanide consumption. The literature highlights that iron sulfide minerals, found in gold ores, can significantly increase cyanide and oxidant consumption through increased oxidant demand, surface passivation, and galvanic interactions that suppress gold dissolution kinetics. This review article summarises the leaching accelerants used, where lead nitrate plays a central role in gold cyanide leaching, and emphasises that its effectiveness is associated with suppression of sulfide-related passivation and favourable modification of surface electrochemistry of gold. The synergistic effects of leaching accelerants with different oxidants on leaching performance are also assessed, with emphasis on their electrochemical roles. Full article

Dye-sensitized solar cells (DSSCs), belonging to the third generation, are highlighted for their low production cost compared to other photovoltaic technologies. These cells are composed of a cathode, an electrolyte, and an anode, commonly using TiO₂. This work aims to produce and characterize CeO₂, SnO₂, and ZrO₂ oxides as substitutes for TiO₂ in DSSCs. The semiconductor oxides were synthesized using the Pechini methodology and applied as the anode of the system. The device was assembled in a sandwich configuration, with an anode and cathode (graphene), an active area of 0.2 cm², and an electrolyte containing the I₃⁻/3I⁻ redox pair. The techniques employed included scanning electron microscopy (SEM), dynamic light scattering (DLS), X-ray diffraction (XRD), UV-Vis spectroscopy, open-circuit potential curves and electrochemical impedance spectroscopy (EIS). The oxides exhibited good crystallization with non-defined morphology. The obtained band gap values were 2.8 eV, 3.0 eV, 3.1 eV, and 4.8 eV for CeO₂, TiO₂, SnO₂, and ZrO₂, respectively. In DSSCs, these oxides showed photosensitivity, generating potential when exposed to light with TiO₂-based cell exhibited the lowest charge transfer resistance (R_ct = 57.8 kΩ). This comparative framework establishes a preliminary screening of the intrinsic interfacial charge transfer and recombination kinetics of alternative standalone photoanodes, serving as a baseline for future device optimization. Full article

Electrocoagulation (EC) is a promising technology for hypereutrophic wastewater treatment, yet reactor geometry, electrode passivation, and energy inefficiency remain key limitations. This study developed a graphene oxide–phosphomolybdate (GO–POM) composite cathode integrated into an asymmetric electrode configuration (anode:cathode area ratio = 1:10) to simultaneously address charge-transfer resistance, passivation, and energy consumption in the EC treatment of Lake Mariut wastewater (Cairo, Egypt). The GO–POM composite exhibited a charge-transfer resistance of 2.34 ± 0.09 Ω·cm², significantly lower than that of a graphite rod (4.12 ± 0.31 Ω·cm²), carbon felt (3.28 ± 0.24 Ω·cm²), and SS316 (6.84 ± 0.45 Ω·cm²). Under optimized conditions (j = 10 mA/cm², pH 6.0, 60 min), the asymmetric GO–POM system achieved 92.2 ± 1.8% TOC removal with a specific energy consumption of 4.4 ± 0.3 kWh/m³—a 37% reduction compared to the symmetric conventional baseline (6.1 ± 0.4 kWh/m³). The treated effluent met the discharge limits set by Egyptian Law 48/1982 for COD, BOD, and TSS. Preliminary techno-economic and life-cycle analyses identified Al electrode consumption as the dominant cost and carbon driver, with a solar-powered continuous-flow operation as the priority pathway for further energy reduction. Full article