Understanding how electrodeposition conditions govern the interplay between electrocatalytic and enzymatic pathways is crucial for the rational design of dopamine (DA)-sensitive electrochemical biosensors.Herein, a one-step electrodeposition approach was employed to fabricate Pd nanoparticles/tyrosinase/Nafion (Pd-NPs/Tyr/Naf) hybrid layers on screen-printed electrodes. Although the hybrid electrodes prepared at room temperature (20 ± 2 °C) and from an electrolyte pre-heated to 40 ± 5 °C exhibited comparable Pd loading and electroactive surface areas, they displayed distinct electrochemically active facet fingerprints corresponding to fundamentally different dominant crystallographic surface architectures. Consequently, the electrodes showed different redox behavior toward dopamine (DA), the substrate, and enzymatically generated quinone (Q), the reaction product.These findings demonstrate that electrodeposition provides an effective means to control facet populations in hybrid bioelectrocatalytic interfaces and establish a foundation for the development of biosensors with enhanced reaction-pathway selectivity.
The recent analytical model for Damjanović kinetics of the oxygen reduction reaction (ORR) is analyzed. The analysis shows that the number of free sites on the Pt surface depends on the water content of the catalyst layer and the ORR overpotential. Drying the catalyst layer shifts the platinum surface towards a blocking state, whereas a high water content facilitates the electrochemical ORR steps. The effect of Pt surface blocking is also observed at higher overpotentials (currents). Catalyst layer drying or an increase in cell current lead to an increase in the apparent Tafel slope.
The effect of vitrification on the electrochemical behavior of NiTi alloy in simulated physiological media was investigated. A Ni50Ti30Nb20 (at.%) metallic glass (MG) was fabricated by melt spinning and compared with crystalline nitinol. Structural characterization was performed by X-ray diffraction (XRD), while corrosion behavior was evaluated by electrochemical impedance spectroscopy (EIS) and cyclic polarization measurements in Hank's solution and artificial saliva at 37 °C. Ion release was quantified by ICP-MS. XRD patterns confirmed the fully amorphous structure of the metallic glass, whereas crystalline nitinol exhibited B2 and B19′ phases. Electrochemical measurements revealed superior corrosion resistance of the metallic glass, with polarization resistance values up to 2.8 times higher than those of crystalline nitinol. Cyclic polarization curves showed lower corrosion current densities, more noble corrosion potentials, and stable passive behavior for the metallic glass. ICP-MS results demonstrated a reduction of approximately three orders of magnitude in Ni ion release compared to crystalline nitinol. The improved electrochemical performance is attributed to the homogeneous vitreous structure, which promotes the formation of a mixed TiNb oxides that stabilize the protective passive film. These results demonstrate that vitrification is an effective strategy to improve the electrochemical stability of NiTi alloys for biomedical applications.
In the development of sodium secondary batteries, the negative electrode materials face challenges in terms of their reversibility and energy density. In this study, phosphorus was explored as a negative electrode material in all-solid-state sodium batteries combined with stable solid electrolytes, such as Na3BS3 glass, Na3Zr2Si2PO12, and β-alumina. The all-solid-state sodium cells exhibited a capacity of 2000 mAh g−1 and high reversibility for over 100 cycles, with high capacity retention of 99%. Despite significant volume expansion, intimate interfaces between the solid electrolyte and active materials were achieved during charge–discharge cycles, facilitated by the high formability and electronic and ionic conductivity of the produced phosphide. Phosphorus acts as a bifunctional material and serves as both an electrode and an electrolyte component. These promising properties support the use of phosphorus-based negative electrodes with both sulfide and oxide solid electrolytes in all-solid-state sodium batteries, thereby facilitating easier cell fabrication with enhanced capacity and cycle life.
Zinc electrowinning (ZE) is highly sensitive to different impurities in the electrolyte. This study systematically investigates the influence of selenium (Se), a rarely studied trace impurity, on ZE process using electrochemical measurements and electrowinning experiments. The results indicate that Se exerts a concentration-dependent dual effect. On the negative side, Se reduces current efficiency (CE) and increases of specific power consumption (SPC) by inducing cathodic polarization. As the Se concentration increases from 0 to 1.0 mg/L over an 8 h ZE, CE reduces from 81.68% to 68.91%, while SPC increases from 3012 to 3689 kWh/t. Notably, these detrimental effects remain modest at Se ≤ 0.2 mg/L but become pronounced beyond this threshold. On the positive side, Se improves deposit morphology by increasing nucleation overpotential (NOP) and hydrogen evolution overpotential, resulting in grain refinement and a smoother and denser morphology with less nodules. It also marginally enhances cathode corrosion, as reflected in reduced corrosion current density (Icorr) and corrosion potential (Ecorr). No more than 0.2 mg/L is proposed as the practical tolerance limit for stable ZE operation.
Supercapacitors (SCs) offer high power density, rapid charge-discharge capability, and excellent cycling stability; however, their relatively low energy density remains a major limitation for applications requiring sustained energy delivery. Biomass-derived activated carbons have emerged as sustainable, low-cost, and renewable alternatives to conventional carbon electrodes owing to their tunable porous structures and surface chemistry. This review critically analyzes recent advances in biomass-derived activated carbons, with particular emphasis on the synergistic effects of pore architecture and surface chemistry on electrochemical performance. Analysis of the available literature demonstrates that the electrochemical performance of biomass-derived carbons is not governed by specific surface area alone but by pore accessibility and the balance between ultramicropores for charge storage and mesopores for rapid ion transport. Consequently, reported specific capacitances range from approximately 100 to over 600 F g−1, depending on the biomass precursor and synthesis strategy. Furthermore, heteroatom doping, particularly with N, B, S, P, and co-doping strategies, significantly enhances electrical conductivity, electrolyte wettability, charge-transfer kinetics, and pseudocapacitive contributions. Representative studies show that nitrogen doping can nearly double the specific capacitance (e.g., from 178 to 324 F g−1) by improving interfacial electrochemical processes. The present review establishes an integrated structure-property-performance framework linking biomass precursor selection, activation strategy, pore architecture, surface functionality, and electrolyte compatibility, thereby providing practical design guidelines for the rational development of next-generation sustainable supercapacitor electrodes.
Static-boundary continuum simulations of local pH at Mg anodes do not explicitly represent the continuous electrolyte renewal present in flow-assisted scanning ion-selective electrode technique (SIET) measurements. Here, an effective fresh-electrolyte renewal boundary, described by km, is incorporated into a one-dimensional model coupling Mg dissolution, OH− generation associated with the negative difference effect (NDE), carbonate buffering, and Mg(OH)₂ precipitation. The simulations show that km modulates the temporal and spatial evolution of local pH. A representative renewal coefficient on the order of 10−5 m s−1 captures the experimentally observed pH range and spatial decay trend. These results identify boundary-mediated OH− exchange as a key factor shaping local pH under electrolyte-renewal conditions.
Tubular solid oxide fuel cells (T-SOFCs) hold great promise in the portable power supply sector due to its structural advantages, including simple sealing and uniform thermal stress distribution. This paper reviews the configuration of T-SOFCs and advances in stack integration from a structural design perspective. At the level of cell structure, the design characteristics, fabrication processes and performance of tubular cells in various configurations, including circular, flat, corrugated, hollow-fiber, and multi-channel micro-monolithic tubular types. At the stack level, flat-tubular stacks utilize internal ribs to perform dual functions of current distribution and collection, with a 60-cell stack delivering 921 W at 750 °C. Micro-tubular dual-conductor nickel pads shorten the current path through multi-point contact, with a 160-cell stack delivering over 1 kW at 700 °C. A series-segmented single-row sub-stack employs a single-row tubular bundle to achieve quasi-two-dimensional flow control, and when combined with optimized sieve plates, reduces the variation coefficient of gas distribution from 96% to 5.83%. Flat-tubular internal reforming stacks use multi-channel reforming reactors and suppress thermal gradients through internal thermal coupling, enabling stable operation over 400 h at S/C = 1. These structural innovations collectively have propelled tubular SOFCs from single cells to engineered stacks, offering broad application prospects in the future for drone propulsion, emergency power supply and renewable energy integration.
Alkaline hexacyanoferrate (AHCF, ferricyanide in strongly alkaline media, pH ≈ 14) has been widely used since 1962 as an oxidant in catalysis, electroanalysis, and more recently in aqueous redox-flow batteries. However, its oxidative mechanism and chemical stability under strongly alkaline conditions remain poorly understood. Herein, AHCF-mediated oxidation of creatinine (Ctn) was systematically investigated using carbon nanomaterial-modified screen-printed electrodes. Voltammetric and batch injection analyses demonstrated efficient mediated oxidation with good selectivity. Complementary SEM, FTIR, UV–Vis, Raman, ICP-OES, and in situ electrochemical quartz crystal microbalance (EQCM) analyses revealed that AHCF undergoes concurrent decomposition during oxidation. Time-dependent UV–Vis studies showed apparent pseudo-first-order decomposition kinetics with rate constants (kobs) of 1.13 × 10−3 min−1 and 1.73 × 10−3 min−1 in the absence and presence of Ctn, respectively, indicating that Ctn accelerates AHCF decomposition. Cyanide release was verified by the characteristic Prussian blue (PB) formation test, while ICP-OES, in situ EQCM, and electron microscopy confirmed the release and deposition of iron species as nanoscale particles on the carbon surface. In situ mass measurements further suggest the transient formation of high-valent iron–oxo/hydroxo intermediates (Mw ≈ 128 g mol−1), which are proposed to be the actual oxidizing species responsible for substrate transformation rather than ferricyanide itself. The deposited iron species subsequently promote the in situ formation of surface-confined PB molecular electrodes with electrocatalytic activity toward hydrogen peroxide reduction. These findings reveal an overlooked decomposition pathway of AHCF, providing new mechanistic insight into its oxidative behaviour while highlighting important stability and safety considerations for alkaline ferricyanide-based electrochemical systems.
Isomeric-shaped electrodes (ISE) as a circular cone electrode (CCE) and a truncated cone electrode (TCE) sharing the same exposure surface of continuously variable diameters are prepared by sectioning cone blocks of X70 pipeline steel. The uneven distribution of surface magnetic flux density on these ferromagnetic steel ISEs under an external magnetic field was characterized via depth profiling after etching in a sulfuric acid solution. The contribution of this uneven magnetic flux density to locally distributed anodic dissolution and pitting corrosion was electrochemically quantified using the ISEs in a mixed bicarbonate-sulfate solution. Conical specimens (Phi 17.6 mm & times; 11 mm) were ground along the base-parallel and apex-parallel directions to final diameters ranging from Phi 3.2 to 7.2 mm, yielding the two geometries: CCE and TCE. Under potentiostatic polarization, the time required for the CCE to reach a quasi-passive state exceeded that for the TCE by approximately 17-43% depending on size across the tested diameters. The polarized surfaces exhibited a three-layer corrosion structure. Both the severity of anodic dissolution (from severe to mild) and the average pit size (from large to small) aligned well with the magnetic flux density distribution (from high to low), particularly in horizontal directions. Relative to the CCE, the TCE exhibited a decrease in the area percentages of the mild- and severe-corrosion zones by approximately 17% and 10-15%, respectively, while the moderately corroded area increased by approximately 30%.
Accurate monitoring of ketone bodies, particularly β-hydroxybutyrate (BHB), is essential for the management of metabolic disorders and for emerging applications in personalised nutrition and continuous health monitoring. Here, we report a mediator-free electrochemical sensor based on a 3D graphene foam integrated within a microfluidic architecture for the detection of BHB in blood using β-hydroxybutyrate dehydrogenase.The sensor exhibits a linear response across clinically relevant concentrations (0–5 mM), covering normoketotic, ketotic, and diabetic ketoacidosis (DKA)-associated levels, with limits of detection of ∼0.06 mM, enabling detection well below physiological baseline levels. The 3D graphene foam facilitates efficient electron transfer, eliminating the need for conventional redox mediators and simplifying sensor design while exhibiting superior stability and selectivity.Device performance was systematically evaluated across increasing matrix complexity, including artificial blood, human plasma, and whole blood. The platform demonstrated strong resistance to electrochemical interferents such as uric acid and dopamine. Integration into a portable format enabled point-of-care operation, with consistent analytical performance maintained over 7 days.These results establish 3D graphene foam-enabled mediator-free biosensing as a promising strategy for reliable ketone detection in complex biofluids, supporting its potential translation into portable and wearable diagnostic systems.
Anode-free lithium metal batteries (AFLMBs) and LMB with low negative-to-positive (N/P) capacity ratio have attracted considerable interest in recent years due to their potential for high energy density. However, their practical application is hindered by severe lithium dendrite growth and an unstable solid electrolyte interphase (SEI), leading to rapid capacity degradation. Herein, we propose a TiN/Ag@Cu sandwich-structured electrode designed to extend cycle lifespan by introducing a metal/semiconductor heterointerface that regulates lithium-ion transport and nucleation behavior. The electrode architecture comprises a silver-plated copper underlayer (denoted as Ag@Cu) and a titanium nitride (TiN) top layer. The TiN layer serves as a fast Li+-screening channel, effectively blocking parasitic side reactions involving other ions and molecules, while the lithiophilic Ag@Cu alloy interlayer provides nucleation sites that guide uniform lithium deposition. This synergistic design enables homogeneous lithium plating, substantially enhancing cycling stability. With a limited amount of pre-deposited lithium, the sandwich-structured electrode enables symmetric Li/Li cells to operate stably for 1100 h. Moreover, Li/LiFePO₄ full cells with a low N/P ratio of 2 achieve a high capacity-retention of 92.3% after 250 cycles. The proposed multilayer architecture is amenable to continuous, large-scale fabrication via roll-to-roll magnetron sputtering, rendering it compatible with existing industrial production lines and offering a promising strategy to improve the cycling durability of anode-free batteries.
The low oxygen transport capacity of Fe-based cathode materials in kinetics is one of the main challenges in current research. To overcome this limitation, LaBa0.5Sr0.5Fe2-xMgxO5+δ (x = 0, 0.025, 0.05, 0.075, 0.1) cathode materials were synthesized by the sol-gel method to enhance the catalytic activity of the oxygen reduction reaction (ORR). XRD results indicated that the LaBa0.5Sr0.5Fe2-xMgxO5+δ series of cathode materials presented a well-defined tetragonal perovskite structure. With increasing doping levels, the thermal expansion coefficient (TEC) gradually increased, the average ionic valence state increased, accompanied by changes in oxygen transport behavior at elevated temperatures.XPS analysis results showed that partial substitution of Fe by Mg could reduce the activation energy of oxygen adsorption, increase the content of adsorbed oxygen, and improve the ORR catalytic activity of the material. At a doping amount of 0.05, the highest electrical conductivity was observed at 300 °C, with a value of 292.02 S cm−1. The symmetrical cell exhibited the best catalytic performance at 800 °C, with an area-specific resistance (ASR) of 0.0261 Ω cm2 and a peak power density (PPD) of 718.91 mW cm2, demonstrating excellent electrochemical performance. These results suggest that doping with small-ion-radius Mg elements may provide an attractive strategy for the future development of cathode materials.
Tungsten bronze and Wadsley–Roth oxides are promising negative-electrode materials for fast-chargeable lithium-ion batteries because of their rapid solid-state Li+ diffusion and moderate operating potentials. Among them, molybdenum-containing oxides deliver large gravimetric capacities but often suffer from capacity degradation during cycling. In this study, we demonstrate that partial substitution of Mo with W alleviates the capacity fading of tetragonal tungsten bronze Mo3–xWxNb2O14. Mo2WNb2O14 (x = 1) electrodes exhibit higher capacity retention than Mo3Nb2O14 (x = 0) after long-term cycling under fast charge/discharge conditions. Entropic potential measurements revealed that W substitution suppresses hysteresis in the thermodynamic response between Li+ insertion and extraction. Ex situ X-ray diffraction and X-ray absorption spectroscopy confirm reversible crystal and electronic structure evolution, respectively, upon Li+ insertion/extraction. These findings highlight W substitution as an effective strategy for improving the reversibility of Li+ intercalation in molybdenum-based tetragonal tungsten bronze oxides.
Developing cathode materials that combine high electrochemical activity with thermal expansion matching to electrolytes remains a critical challenge for intermediate-temperature solid oxide fuel cells (IT-SOFCs). Herein, we report a dual-site A/B high-entropy doping approach to simultaneously enhance the oxygen reduction reaction (ORR) activity and structural stability of perovskite cathodes. A novel high-entropy material, La0.2Sr0.2Pr0.2Ca0.2Ba0.2Fe0.2Mn0.2Co0.2Ni0.2Ti0.2O3-delta (LSPCBFMCNT), was rationally designed and synthesized. The crystal structure, oxygen vacancy concentration, electrical conductivity, and single-cell performance were systematically investigated using XRD, XPS, O2-TPD, TGA, and electrochemical measurements. LSPCBFMCNT retains a pure cubic perovskite structure (Pm-3m) with excellent chemical compatibility with the GDC buffer layer. Multi-element doping at A/B sites increases the Fe3+, Co3+ ratio and surface adsorbed oxygen content, and elevates oxygen vacancy concentration, thereby greatly enhancing the oxygen reduction reaction (ORR) activity. LSPCBFMCNT shows max electrical conductivity of 448.13 S & sdot;cm-1 at 500 degrees C, with lower activation energy (0.7515 eV) than pristine La0.5Sr0.5FeO3-delta (LSF). Anode-supported single cell with LSPCBFMCNT cathode achieves 1166.31 mW & sdot;cm-2 peak power density and negligible current degradation over 100 h. The findings show that dual-site high-entropy design effectively optimizes both electrochemical performance and structural stability of cathodes.
Iridium oxide (IrO2) is widely regarded as the most active and stable oxygen evolution reaction (OER) catalyst applied in proton exchange membrane water electrolysis (PEMWE). However, the scarcity and high cost substantially hinder its large-scale deployment. In contrast, RuO2 exhibits superior catalytic activity but suffers from insufficient stability under commercially relevant operating conditions. This review provides a critical overview of recent advances in RuO2-based catalysts and their degradation behavior in PEM electrolyzers. Degradation mechanisms are analyzed across multiple length scales, ranging from atomic-scale processes to macroscopic degradation phenomena, including the lattice oxygen oxidation mechanism (LOM), electrochemical dissolution, catalyst layer detachment, and porous transport layer deterioration. In addition, we assess emerging strategies to improve catalyst durability, with particular emphasis on approaches that mitigate bubble-induced catalyst detachment at high current densities and performance loss during dynamic load cycling. Ultimately, this work seeks to bridge fundamental mechanistic understanding and practical design principles for the development of robust Ru-based electrocatalysts.
P2-NaMnO2 layered oxide cathode material of sodium-ion batteries (SIBs) has a specific capacity of more than 200 mAh g−1, but there is a strong Jahn-Teller distortion that leads to structural instability. This work systematically studies the electronic structure properties of P2-NaMnO2 using first-principles calculations. NaMnO2 shows metallic properties that are conducive to electrons transportation. The densities of states, atomic population, and bond-length analysis indicate that Ni-doping suppresses Jahn-Teller distortion mainly through charge compensation involving partial Mn3+ to Mn4+ oxidation and modification of the local crystal-field environment, thereby enhancing the structural stability of the material. However, the charge density difference, electrode potential and diffusion barrier analyses demonstrate that Ni-doping can hinder the migration rate of the material and reduce the electrode potential to a certain extent. Understanding the Jahn-Teller effect of P2-NaMnO2 with Ni-doping at orbital energy levels provide a feasible theoretical basis for the design of cathode materials for SIBs with high energy density.
Anode-free sodium metal batteries (AFSMBs), which eliminate active anode materials and rely on in situ sodium plating on a bare current collector, offer a compelling route toward high-energy-density batteries. However, their practical deployment is fundamentally limited by interfacial instability. In AFSMBs, the solid electrolyte inter-phase (SEI) forms on a metal-free current collector during the initial plating process and continuously evolves upon repeated plating/stripping, rendering the interface highly susceptible to non-uniform deposition, dendrite formation, parasitic reactions and rapid sodium inventory loss. Therefore, rational SEI engineering is crucial for achieving reversible sodium nucleation/deposition and durable cycling. Here, we summarize the central challenges of SEI formation in AFSMBs, highlight recent advances in SEI engineering, and discuss the key design principles for stable interphases, with emphasis on fast Na+ transport, mechanical robustness and low sodium consumption. We further outline future opportunities for advanced operando characterization and synergistic interfacial design to accelerate the development of high-performance AFSMBs.
Electrochemical CO2 reduction to multicarbon (C2+) products offers a promising route to convert carbon emissions into value-added chemicals and fuels using renewable electricity. Among the various catalyst systems investigated, Cu-based materials remain the most effective due to their unique ability to promote C-C coupling and generate diverse C2+ products, including ethylene, ethanol, and acetate. However, achieving high selectivity, activity, and stability remains challenging due to the complex reaction network, competing hydrogen evolution, and the sensitivity of key intermediates to catalyst structure and local reaction environment. This review summarizes recent advances in Cu-based electrocatalysts for CO2-to-C2+ conversion, with a particular focus on four classical catalyst design strategies: heterostructure construction, atomic configuration regulation, alloy engineering, and surface molecular modification. By highlighting their distinct mechanistic roles in tuning intermediate adsorption, C-C coupling, and product pathways, this review provides a concise perspective on rational catalyst design for efficient multicarbon electrosynthesis.
