Search Results (838)

To reduce greenhouse gas emissions, fuel cell powertrains represent a promising alternative for heavy-duty transport. Such demanding applications require an extended operational lifespan, which calls for models able to accurately map internal states as a function of system architecture and control strategy. This work presents a pseudo-2D macro-homogeneous proton exchange membrane fuel cell model, discretized along the flow channels, in which the various transport phenomena are resolved between layers but not within their thickness. This choice reflects the model’s purpose: integration into complete system models to support system architecture studies, which requires a suitable trade-off between computation time and representativeness of system-imposed operating conditions. Kulikovsky’s analytical approximation is used to compute the voltage losses in the catalyst layer, preserving an accuracy close to a model with a fully discretized catalyst layer thickness. The model is integrated into a system featuring anode recirculation and no cathode humidification to study the sensitivity of humidity distribution to operating parameters. Simulations show that the anode recirculation rate and the temperature difference between inlet and outlet are the two main operating conditions governing spatial humidity distribution, while coolant inlet temperature, pressure, and cathode stoichiometry predominantly affect the absolute humidity within the stack. Full article

Proton-exchange membrane fuel cell degradation is one of the factors that limit the deployment of this technology in the automotive market. Accelerated Stress Tests (ASTs) are the standard tool for assessing durability during design and development phases, thanks to their shorter duration, but there are concerns about their representativeness of degradation phenomena appearing in real driving conditions. The present study couples a semi-empirical multi-layer degradation model with a validated reduced-order physical model of the cell to evaluate degradation occurring in both kinds of conditions. First, the phenomenological model is used to predict the decay in the polarization curve when running continuous real driving cycle and accelerated stress profiles up to a total of 1000 h. Then, the physical reduced-order model is calibrated to the produced polarization curves at each cumulative time by introducing three degradation factors: two associated with the electrochemical surface area of the anode and cathode catalyst layers, and another one related to the membrane conductivity. Additionally, the results of the physical model are evaluated to identify the occurrence of local conditions that can induce degradation. The results show that a properly designed accelerated stress test provides approximately 10 times faster degradation while maintaining similar degradation factors and physical representativeness. Full article

To enhance the corrosion resistance, adhesion strength, and electrical conductivity of bipolar plates for proton exchange membrane fuel cells (PEMFCs), a duplex surface treatment comprising plasma nitriding (PN) followed by arc ion plating of a TiN coating was applied to 316L stainless steel. The duplex coating exhibited a bilayer structure with a TiN top layer (~1.3 μm) and a nitrided diffusion layer (~9.2 μm). Compared with a single TiN coating, it showed superior corrosion resistance in both cathode and anode environments, with corrosion current densities of 0.069 and 0.422 μA·cm⁻², respectively, and maintained stable performance over 10,000 s of potentiostatic polarization. Its interfacial contact resistance at 140 N·cm⁻² was 7.84 mΩ·cm², below the Department of Energy (DOE) 2025 target of 10 mΩ·cm². The water contact angle also increased, benefiting water management. The nitrided interlayer substantially enhanced the adhesion strength of the TiN coating. These findings confirm that the sequential combination of plasma nitriding and TiN coating is an effective strategy for improving the corrosion resistance, electrical conductivity, and adhesion of stainless steel bipolar plates for PEMFC applications. Full article

A leaf-vein–serpentine composite flow field (L-SFF) is proposed to improve reactant distribution, water management, and electrochemical performance of proton exchange membrane fuel cells (PEMFCs). The L-SFF consists of a main trunk and multilevel branches inspired by coconut palm leaf veins, with a branching angle of 45° and a branch width of 2 mm. Three-dimensional multiphysics models of the traditional serpentine flow field (SPFF), cathode leaf-vein–serpentine flow field (S-LFF), and anode leaf–vein–serpentine flow field (L-SFF) were developed using COMSOL Multiphysics 6.1 to investigate current density, membrane water content, temperature distribution, and power output. Under 0.6 V, 353 K, and 1 bar conditions, the L-SFF achieves a maximum power density of 0.538 W·cm⁻², approximately 2.1% higher than SPFF, with an average anode current density of 7092.0 A·m⁻² and a current-density uniformity index of 0.135. The L-SFF also exhibits improved membrane water distribution, with an average water mole fraction of 0.513, and maintains an average membrane temperature of 356.61 K. Furthermore, the effect of GDL porosity on performance was evaluated. When the GDL porosity decreases from 0.8 to 0.2, the maximum power density decreases from 0.534 to 0.474 W·cm⁻² for SPFF (11.2%) and from 0.547 to 0.489 W·cm⁻² for L-SFF (10.6%), indicating better tolerance to variations in porous transport properties. The results demonstrate that the L-SFF structure enhances reactant transport, water management, and performance stability, providing an effective strategy for PEMFC flow-field optimization. Full article

This proposed study presents an in-situ experimental approach for investigating anode-side water dynamics through detailed analysis of pressure-drop data measured across multiple segments of bipolar plate flow channels. A theoretical model was first developed to predict pressure-drop profiles and liquid-water distribution in parallel multiphase flow channels. Based on the model, a bipolar plate with integrated multi-point pressure sensors was designed to enable real-time, spatially resolved monitoring of gas–liquid dynamics and provide advanced diagnostic capabilities. The proposed system was successfully implemented in a single Proton Exchange Membrane Fuel Cell (PEMFC) with an active area of 282 cm², which allows accurate identification of the timing and location of flooding events during operation. Experimental results showed that inadequate water management can cause flooding under steady-state conditions, while water accumulation is more prominent during startup and load-reduction processes. Additionally, the effects of reactant flow rate, humidity, and circulating water temperature on water distribution within the channels were systematically evaluated. Based on these findings, a closed-loop diagnostic and control framework is proposed by enabling dynamic adjustment of operating parameters according to pressure-drop characteristics for real-time optimization of water management and improved fuel cell performance. Full article

The growing deterioration of water resources and the energy requirements of conventional wastewater treatment technologies have increased interest in systems that combine organic matter removal with bioelectrochemical conversion. This study evaluated a laboratory-scale dual-chamber microbial fuel cell (MFC) operated with real wastewater using Scenedesmus acutus (S. acutus) and a native microbial consortium as anodic biocatalysts at 25 and 30 °C. The system was assessed through continuous monitoring of voltage, pH, temperature, and CH₄, H₂, and CO₂ signals in the anodic headspace, together with physicochemical characterization and chemical oxygen demand (COD) removal. COD removal efficiencies of 33.7 and 30.3% were obtained for S. acutus at 25 and 30 °C, respectively, whereas the native microbial consortium achieved 29.8 and 43.4% removal under the same conditions. The consortium at 30 °C showed the most favorable combination of COD removal and electrical response, whereas S. acutus at 30 °C reached the highest maximum voltage and stored energy, although with greater signal variability. The CH₄, H₂, and CO₂ signals differed among conditions and were consistent with the possible participation of fermentative and methanogenic processes alongside electrogenic activity, although gas production rates and the contribution of individual pathways were not quantified. Overall, the results demonstrate the operational feasibility of the proposed MFC for coupling wastewater treatment with a measurable electrical response and support further evaluation of native microbial consortia as anodic biocatalysts. Full article

Microbial fuel cells (MFCs) are promising bioelectrochemical systems for converting organic matter into electrical energy, but their practical relevance depends on both functional performance and sustainability-oriented viability. This study evaluated the bioelectrochemical behavior of double-chamber MFCs inoculated with kefir, comparing graphene and graphite anodes under fed-batch operation. A total of 33 MFC series were monitored longitudinally through voltage, current, power output, substrate consumption, and oxidation-reduction potential. Under the LED-connected closed-circuit configuration used here, kefir-inoculated reactors exhibited a reproducible electrical response together with near-complete substrate depletion. These findings support kefir as a workable mixed inoculum for comparative reactor operation under the tested conditions, although direct extracellular electron transfer and exclusive microbial causation of the measured signal were not demonstrated. Graphene showed higher early and mean electrical performance than graphite, particularly in power-related metrics, although this advantage decreased over time and did not result in a categorical separation of final batch-level outcomes. In contrast, substrate consumption remained highly similar between anode materials, indicating that the main material effect was expressed in electrochemical translation rather than in overall substrate conversion. Taxonomic profiling supported the presence of a metabolically complementary consortium dominated by lactic acid bacteria, acetic acid bacteria, Gram-negative bacteria, and yeasts. Deterministic sensitivity analysis and Monte Carlo-based LCA/TEA screening further showed that the most sustainable scenario was not necessarily the one with the highest electrical response, highlighting the importance of integrating performance, material burden, and uncertainty in MFC assessment. 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

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

Microbial fuel cells (MFCs) are bio-electrochemical devices that simultaneously treat wastewater and recover energy. However, their power generation performance is limited by the biocatalytic activity of electroactive biofilms. In this study, a low-cost, high-performance electroactive biofilm formation method was developed by replacing conventional constant potential polarization, which needs a fixed-resistance polarization approach. Additionally, alternating intermittent polarization with dual anodes was implemented based on these biofilms to continuously induce electron storage behavior. Experimental results confirmed the feasibility of the proposed fixed-resistance polarization method for biofilm cultivation. Compared with the primary biofilms, the derived biofilms exhibited markedly enhanced startup efficiency and power generation performance. Specifically, the startup time decreased by 24.8% from 44.23 h, while bioenergy conversion efficiency improved from 69.72 ± 3.30% to 91.90 ± 3.51%. These performance enhancements were attributed to the superior electrochemical activity of the derived biofilms, as evidenced by increased maximum current density, higher anode capacitance, and broader electrochemical activity range. These characteristics remained stable throughout the biofilm iteration process. Moreover, dual-anode alternating intermittent polarization successfully induced continuous electron storage behavior, leading to enhanced organic matter removal and energy conversion. Under the optimized conditions, MFCs demonstrated notable improvements in electroactivity. This study revealed the regulatory mechanisms of polarization patterns on biofilm formation and operation, providing an experimental foundation for the large-scale application of MFCs in wastewater treatment and energy recovery. Full article

The development of highly efficient and low-cost electrocatalysts for the urea oxidation reaction (UOR) is crucial for advancing urea fuel cell technologies. In this work, MgZnFe-layered double hydroxide (LDH), LDH/BDC-MOF, and LDH/1,2,4-triazole (LDH/TZ) nanocomposites were successfully synthesized via a simple one-pot co-precipitation method. The structural, morphological, textural, and thermal properties of the prepared materials were investigated using XRD, FTIR, SEM, EDX, BET, and TGA analyses. SEM observations revealed that pristine LDH consisted of stacked thin nanosheets with significant layer aggregation, whereas LDH/BDC-MOF exhibited MOF-pillared structures and LDH/TZ formed a highly porous interconnected three-dimensional network that effectively suppressed nanosheet restacking. BET analysis showed a remarkable enlargement in pore size from 6.7 nm for LDH to 34.5 nm for LDH/TZ. The electrocatalytic performance toward UOR was evaluated by cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy in 1.0 M KOH, containing different urea concentrations. Among all investigated electrodes, LDH/TZ exhibited the highest catalytic activity, delivering anodic current densities of 106, 132, 166, 180, and 202 mA cm⁻² at urea concentrations of 0.2, 0.4, 0.6, 0.8, and 1.0 M, respectively. Furthermore, LDH/TZ displayed a lower onset potential of 0.41 V compared with 0.49 V for LDH/BDC-MOF and 0.56 V for pristine LDH. The enhanced activity was further supported by a high double-layer capacitance of 9.7 μF cm⁻², a large electrochemically active surface area of 0.24 cm², and a low charge-transfer resistance of 2.9 Ω. Chronoamperometric measurements demonstrated excellent durability with a stable current density of approximately 73 mA cm⁻² after 3600 s, while cyclic stability reached 94% after 100 cycles. The superior performance of LDH/TZ is attributed to the synergistic effect of the nitrogen-rich triazole ligand, enlarged pore structure, enhanced active-site exposure, and accelerated charge-transfer kinetics, highlighting its strong potential as an efficient electrocatalyst for direct urea fuel cell applications. Full article

Salt-bridge kefir-derived microbial fuel cells (MFCs) provide a low-cost platform for studying fermentation-linked electrical output, but their behavior is often evaluated through isolated current or voltage traces rather than integrated reactor-state evidence. This study assessed laboratory-scale double-chamber MFCs operated under fed-batch conditions with a kefir-derived mixed consortium and molasses-based substrate. Thirty-three independent reactors, including graphite- and graphene-anode configurations, were monitored from day 0 to day 20, generating 693 reactor-day observations. Electrical, redox, temperature, substrate-related, UV–Vis soluble-phase, baseline sequencing, endpoint SEM, FTIR functional-group evidence, and semimechanistic descriptors were integrated to diagnose reactor evolution and predict fixed-condition current output. Current declined from 0.8985 to 0.1133 mA, residual glucose-equivalent decreased from 5.3124 to 0.0127 g L⁻¹, and the glucose-consumption fraction reached 0.9977. Fixed-condition apparent power decreased from 0.8636 to 0.0856 mW, while cumulative charge and cumulative apparent energy averaged 595.02 C and 456.69 J per reactor. FTIR bands supported carbohydrate/EPS, organic-acid, and proteinaceous-matrix signatures consistent with a fermentation–redox–biofilm cascade. The random-forest model showed strong grouped cross-validation performance (R² = 0.956, RMSE = 0.082 mA, MAE = 0.060 mA, slope = 1.009, r = 0.978). This work supports state-aware current and fixed-condition power-output prediction in kefir-driven MFCs without claiming maximum power-density or complete electrochemical characterization. Full article

Direct methanol fuel cells (DMFCs) have attracted considerable attention recently for various applications ranging from portable ones to transportation. The efficiency of DMFCs depends on the kinetics of anodic and cathodic electrocatalysts. Due to sluggish anodic methanol oxidation reaction (MOR), DMFCs require an effective and bifunctional catalyst for promoting efficient MOR. The state-of-the-art MOR catalysts, such as Pt/C and Pt-Ru/C, have been shown to exhibit reasonable MOR activity; however, the insufficient mass activity and poor stability of carbon-supported catalysts have been a major limitation, requiring an alternative, efficient, electrocatalyst that exhibits high mass and specific activities. In addition, electrocatalysts without any carbon support (self-supported electrocatalysts) further mitigate their poor stability and therefore enhance their durability. In this regard, metal aerogel catalysts, which are entirely composed of metallic networks, recently attained special interest due to their specific advantages over conventional carbon supports, such as high catalyst utilization and improved electronic conductivity and stability. In this review, we systematically reviewed various metal aerogel catalysts developed for MOR since their first discovery in 2009. The metal aerogel demonstrated superior MOR performance relative to carbon-supported commercial catalysts, with enhancements ranging from 2-fold to 22-fold of mass activity. We also statistically compared the mass activity of metal aerogels with traditional carbon-supported, non-carbon-supported, and advanced shape-controlled catalysts and found that metal aerogels exhibited high mass activities compared to other catalyst systems. Therefore, we clearly establish that metal aerogel catalysts possess great potential as efficient MOR catalysts in DMFCs. In addition, we have provided several future research directions and strategies for further development of metal aerogel-integrated DMFC devices. Full article

Solid oxide fuel cell (SOFC) multi-stack systems require well-balanced reactant distribution to ensure stable operation, high efficiency, and long-term reliability. In this work, a 3D CFD framework was constructed for a vertically arranged 4 × 1 kW SOFC multi-stack system to examine the influence of U-type and Z-type manifold configurations on the distribution of mass flow, overall flow uniformity, and local utilization of the reacting gases. The system consists of four 1 kWe-rated planar solid oxide fuel cell stacks, individually rated at 1 kWe and comprising 40-unit cells. Results show that the preferred connection type differs between the cathode and anode sides. At 30% air utilization, the U-type connection provides better cathode-side air distribution, with mass flow uniformities of 0.9485 among the four stacks and 0.91842 among the 160-unit cells, while its local reaction gas utilization rates remain close to the prescribed value of 0.30. In contrast, the Z-type connection shows superior anode-side fuel distribution under all tested fuel utilization rates, with its mass flow uniformity increasing from 0.9740 to 0.9865 as the fuel utilization rate increases from 30% to 80%. At the representative 50% fuel utilization condition, the local reaction gas utilization rates of the Z-type connection are closer to the target value of 0.50 than those of the U-type connection. These findings highlight the greater suitability of the U-type connection for cathode-side reactant supply, whereas the Z-type connection is more effective for anode-side fuel distribution, providing useful guidance for pipeline connection design and flow-field optimization in vertically stacked multi-stack SOFC systems. Full article

Microbial fuel cells (MFCs) are emerging as biomimetic bioelectrochemical systems that emulate naturally occurring microbial electron-transfer pathways for stimulus bioenergy generation and wastewater remediation. In this study, food–vegetable leachate (FVL) and sugarcane bagasse-derived biol were evaluated in combination with carbon fiber (CF) and biochar-modified carbon fiber (BCF) electrodes used as membrane components in MFCs. Four configurations, in duplicate, were constructed by coupling two substrates (biol or FVL) with two membrane types (CF and BCF). All systems exhibited progressive anodic acidification and up to a 55% increase in electrical conductivity. The highest voltage output was achieved in MFC-BL-2 (404.59 mV), followed by MFC-FL-1, driven by synergistic interactions between the substrate and biochar-enhanced conductive networks. MFC-FL-1 also demonstrated superior contaminant removal performance, achieving 60% COD reduction, 36% BOD reduction, and 50% NH₄⁺–N removal. SEM–EDS analysis confirmed that biochar-modified electrodes developed a porous structure and substantially enhanced microbial adhesion. FVL-fed systems formed dispersed electroactive biofilms that facilitated electron transfer, whereas biol-fed systems developed compact biofilms that constrained electron flux. By integrating waste-derived lignocellulosic materials with electroactive microbial consortia, this work advances a biomimetic circular bioengineering platform for sustainable bioelectrochemical recovery and wastewater remediation. Full article