Search Results (210)

The valorization of dairy industry by-products and simultaneous energy recovery remain important challenges in sustainable waste management. In this study, waste buttermilk was evaluated as a substrate for bioelectricity generation in a microbial fuel cell (MFC) equipped with a gas diffusion anode (GDE) and non-precious metal cathodes. Three electrode configurations were investigated: GDE/GDE, GDE/Cu–B, and GDE/Ni–Co. Stable operation was achieved for all MFC systems, confirming that waste buttermilk can support electroactive biofilm development. The GDE/Ni–Co configuration exhibited the highest performance, reaching a maximum power density of 25 mW·m⁻², compared to 22 mW·m⁻² and 17 mW·m⁻² for GDE/Cu–B and GDE/GDE, respectively. Coulombic efficiency ranged from 10.83% to 18.82%, depending on the electrode system. A cyclic performance decrease was observed, likely caused by membrane fouling and electrode surface blockage. The results indicate that waste buttermilk can be utilized for simultaneous waste treatment and energy recovery in MFC systems, although further optimization is required to improve long-term stability. Full article

This work presents a comprehensive investigation of the thermal decomposition of nickel oxalate dihydrate as a precursor for the synthesis of porous NiO, with particular emphasis on microstructural formation and evolution. The transformations occurring at successive stages of the reaction were examined using SEM, TEM, N₂ adsorption, TG–DSC–MS, and in situ powder XRD, enabling the mechanisms of pore formation to be elucidated. The decomposition results in the formation of a porous pseudomorph composed of NiO nanoparticles with an average size of approximately 4 nm. This is the first time that the resulting microstructure has been shown to exhibit hierarchical, bimodal porous architecture. During dehydration, macropores are generated as a result of crystal fragmentation into blocks several hundred nanometers in size. Subsequent oxalate decomposition leads to the formation of mesoporous aggregates composed of nanometer-sized particles. The factors governing the parameters of the porous microstructure are analyzed. The resulting NiO, with its hierarchical pore structure, shows significant potential for applications in heterogeneous catalysis, gas sensing, and as electrodes for supercapacitors, lithium-ion batteries, and photoelectrochemical devices, as its macropores facilitate mass transport by reducing diffusion resistance while its mesopores provide a large accessible surface area for adsorption and catalytic reactions. Full article

The main goal of this study was to develop and validate a laboratory-scale prototype of a rechargeable metal hydride (MH)–air battery integrating gas diffusion electrodes (GDEs) and MH electrodes with stable performance over extended operation (>500 h) and repeated charge–discharge cycling (>100 cycles). This work addresses the critical transition from optimized electrode materials to a functioning system by investigating its operation under deep-discharge conditions, a key but still insufficiently explored regime in the context of stationary renewable energy storage. In this respect, this study explicitly targets the practical applicability of the developed system rather than focusing solely on material-level performance. The most efficient electrode materials, previously optimized, were successfully integrated into a single-cell configuration and systematically evaluated under various operating conditions. By determining the limiting current density for stable GDE operation, an appropriate operating window was defined, enabling maximum capacity utilization without compromising electrode integrity. At a current density of 10 mA, the maximum depth of discharge was achieved at a cell voltage of 575 mV, ensuring operation in a regime that limits GDE degradation while maintaining high energy efficiency. In addition, the electrode retains its mechanical stability after operation is interrupted, indicating good structural robustness. Furthermore, the performance of two identical cells connected in series was investigated to assess system scalability. The cells were operated under near-limit conditions and exhibited stable behavior. Overall, the present results confirm that the developed MH–air battery system extends beyond laboratory-scale validation and shows strong potential for implementation in stationary energy storage applications. Full article

Direct methanol fuel cells (DMFCs) offer significant advantages including high energy density and rapid refueling, making them promising power sources for portable electronic products. However, their practical application, particularly in passive systems, is hindered by critical mass transport limitations: water flooding in the cathode and CO₂ bubble blockage in the anode. Herein, a novel dual-gradient patterned wettability current collector (CC) was designed to alleviate this mass transport impedance. The design uniquely integrates wedge-shaped gradients with surface energy gradients to create a unified, self-driven mechanism for efficient water and CO₂ bubble transport at both electrodes. A mathematical model was developed to quantitatively evaluate the effects of the dual-gradient structure. The results confirm that water removal is enhanced when the cathode current collector features a hydrophobic periphery with a dual-gradient patterned wettability interior on the gas-diffusion-layer side and a fully hydrophilic air-side surface, whereas an inverted pattern facilitates anode CO₂ removal. Optimal fabrication parameters on 316 L stainless steel were established by investigating laser scanning conditions and low-surface-energy agent concentrations. The experimental results show that the passive DMFCs incorporating the optimized current collectors delivered marked performance improvements. At 1 mol·L⁻¹ methanol, the novel anode and cathode current collectors increased peak power density by 15.6% and 14.5%, respectively. Electrochemical impedance spectroscopy revealed a 31.4% and 31.9% reduction in mass transfer resistance of the cell with novel anode and cathode current collectors, respectively, confirming improved gas–liquid self-driven efficiency. Furthermore, the new cells exhibited substantially enhanced long-term stability over 18 h of continuous discharge, attributed to the robust wettability achieved via laser–silane modification. Overall, these findings suggest that the proposed dual-gradient wettability design is a promising method for improving internal mass transport, potentially supporting the development of more robust passive DMFCs. Full article

We developed an arbitrary Lagrangian–Eulerian (ALE)-based multiphysics model for evaporation from a contact-line-pinned sessile drop of neat water subject to a vertically oriented sinusoidal alternating current (AC) electric field applied across parallel-plate electrodes. The framework fully couples electrostatics, incompressible flow, heat transfer with evaporative cooling, and transient vapour transport in air, and includes an instantaneous, voltage-controlled electrowetting contact-angle response under constant-contact-radius conditions. Validation against published data shows that the model captures both pinned-droplet evaporation and electrically induced deformation. Because Maxwell traction scales with the squared electric-field magnitude, droplet height and contact angle exhibit a robust 2:1 frequency-doubled response, producing two peak–trough events per voltage period. The resulting periodic deformation drives oscillatory interfacial shear and internal recirculation, yielding a synchronous double-peaked evaporative-flux waveform. Gas-side analysis quantifies a time-varying diffusion-layer thickness via a characteristic diffusion length; two thinning events per period coincide with flux maxima, indicating that AC enhancement is dominated by periodic compression of the vapour boundary layer and reduced gas-side mass-transfer resistance. Increasing voltage amplitude (0–60 kV) strongly accelerates volume loss, while frequency has a secondary effect: the cycle-averaged flux rises from 1 to 10 Hz but decreases slightly at 20 Hz due to phase lag and weaker boundary-layer modulation. Full article

The electrochemical reduction of CO₂ offers a sustainable approach to transforming carbon dioxide into value-added products when powered by renewable energy. However, current electrocatalysts lack efficiency and selectivity, hindering commercial application. Combining tin’s high formate selectivity with copper’s ability to reduce CO₂ via COOH* pathway offers a promising strategy. This synergy mitigates copper’s low selectivity, providing a cost-effective catalyst with enhanced performance over pure Sn-based systems. This work investigates CuSn bimetallic electrocatalysts synthesised by scalable electrodeposition onto gas diffusion layers to boost formate production. Catalytic performance and cell potential were evaluated at current densities ranging from 50 to 200 mA cm⁻² and varying Sn compositions. Catalysts with Sn content below 4% predominantly formed CO and H₂, but smaller particles and improved metal dispersion increased formate production. A catalyst containing 12% Sn achieved a maximum faradaic efficiency (FE) of 52% at 50 mA cm⁻² with an iR-corrected potential of −0.56 V vs. SHE. At 200 mA cm⁻², it exhibited a 30% FE for formate, along with 31% FE for CO and 9.3% FE for H₂, while other gases contributed to less than 4% FE, indicating potential as syngas feedstock. Higher Sn content, combined with smaller, well-distributed particles, effectively suppressed H₂, CO, and other by-products, highlighting a strong dependence of FE on Sn content and bimetallic distribution, demonstrating compositional tuning importance via electrodeposition. Full article

Through-plane electronic transport in porous membrane electrode assembly (MEA) electrodes is governed by the three-dimensional (3D) connectivity of the conducting phase. Here, we quantify the role of the spanning-cluster fraction $P_{\infty }$, defined as the fraction of conducting-phase voxels that belong to the $z$-spanning connected component in a finite reconstructed volume, on effective conductivity using scanning electron microscopy (SEM)-informed 3D reconstructions of four archetypal morphologies: a granular catalyst layer (CL), labeled CL1; a fibrous gas diffusion layer (GDL), labeled GDL1; an open-cell foam (OCF); and a micro-fibrous non-woven (MFM), labeled MFM1. Each morphology is reconstructed on a $150\times 150\times 150$ voxel grid, and $z$-spanning connectivity is identified with a 26-neighbor flood-fill algorithm. Steady-state conduction is solved by a finite-volume method (FVM) with an imposed potential difference between the z-faces and no-flux lateral boundaries. Although all samples exhibit through-thickness connectivity, the normalized conductivity ${\sigma }_{\mathrm{e}\mathrm{f}\mathrm{f}}/{\sigma }_{\mathrm{b}\mathrm{u}\mathrm{l}\mathrm{k}}$ varies widely, from $\approx 0.134$ (MFM1) to $\approx 0.706$ (OCF). The corresponding ${(P}_{\infty },{\sigma }_{eff}/{\sigma }_{bulk})$ pairs are $\left(0.996,\approx 0.306\right)$ for CL1, $\left(0.999,\approx 0.303\right)$ for GDL1, $\left(0.997,\approx 0.706\right)$ for OCF, and $\left(0.901,\approx 0.134\right)$ for MFM1. OCF exhibits the highest response due to vertically coherent channels, whereas MFM1 underperforms due to laminated constrictions; CL1 and GDL1 lie in an intermediate regime with nearly isotropic skeletons. Overall, the results show that while a $z$-spanning connected component is required for measurable conduction, the magnitude of ${\sigma }_{\mathrm{e}\mathrm{f}\mathrm{f}}$ is dictated by percolating-skeleton quality (bottlenecks, cross-sectional constrictions, and pathway alignment) rather than phase amount alone. The proposed descriptors therefore enable percolation-aware screening metrics for designing and comparing MEA-relevant GDL and CL microstructures. Full article

This work presents the development and validation of a 1D finite-volume model for the simulation of planar solid oxide cells (SOCs), developed for integration in more complex systems and process simulations. The model allows to investigate the temperature, composition, and current density profiles along the channel. In this work, the Fick’s equations typically used to calculate the concentration overpotential due to H₂ and H₂O diffusion in the electrode are improved compared to 1D SOC models available in the literature. In particular, the approximate analytical solution of the dusty gas model (DGM) equations allows for a better definition of H₂ and H₂O mixture diffusion coefficients, which are relevant, for instance, in the case of solid oxide fuel cells (SOFCs) fed with reformate gas mixtures. Differently from other 1D models available in the literature, the model developed is validated using experimental SOFC polarization curves covering a wide range of operating conditions in terms of molar fraction of H₂ (21–93%) and H₂O (7–50%) in the fuel, temperature (550–750 °C), and fuel utilization factor (exceeding 90%), demonstrating that 1D SOC models retain a good description of the physical processes occurring within the cell. While this work focuses on a co-flow SOFC configuration, the model can simulate a counter-flow configuration and electrolysis operation without modifying the model equations. Full article

Cellulose nanofibers/metal-organic framework (CNFs/MOF) composites hold promise for energy storage thanks to high porosity, large specific surface area, and inherent flexibility, but their poor conductivity limits applications to environmental remediation and gas adsorption. Herein, flexible CNFs served as substrates for in situ growth of continuous ZIF-8 nanolayers via interfacial synthesis, with a CNFs/ZIF-8 gel network built to enhance structural integrity and flexibility. A novel strategy first regulated the layered pore structure: ZIF-8 in CNFs/ZIF-8 nanofibers was etched in the acidic environment of aniline in situ polymerization, constructing a hierarchical porous architecture with interconnected micropores and mesopores. CNFs/ZIF-8/PANI gel composite membranes were then fabricated. As self-supporting electrodes for symmetric supercapacitors, the composites showed excellent electrochemical performance: 1350 F/g at 1 A/g for the electrode, and the flexible solid-state device delivered a specific capacitance of 220.9 F/g at 0.5 A/g, along with a capacitance retention rate of 74% after 5000 charge–discharge cycles at 10 A/g. The superior performance stems from synergistic hierarchical pore structure regulation via partial MOF sacrificial templating and gel matrix-mediated rapid ion diffusion, offering a feasible approach for high-performance flexible energy storage devices. Full article

The electrocatalytic reduction of CO₂ in the gas phase has been carried out in a PEM type cell. The influence of the support material of the macroporous substrate (MPS) and the binding agent used to join the catalytic layer (CL) with the MPS has been analyzed. Three types of carbon paper used as support for the MPS have been compared and the influence of the use of Nafion^® as a binding agent has been analyzed. Toray 090 and Avcarb P75T have allowed similar results in the CO₂ conversion rate to be obtained, although significant differences are observed regarding the selectivity of the process. Regarding the use of binding agent, it has been observed that it is essential to be able to carry out the electroreduction process and, although its concentration does not seem to greatly affect the rate of CO₂ conversion, it does influence the selectivity of the process. Full article

The electrochemical reduction of CO₂ to ethanol represents a sustainable alternative to recycle CO₂ into a value-added product, yet achieving high selectivity and efficiency remains a challenge. This work explores Cu-based catalysts supported on SiO₂ and ZrO₂, with and without ZnO doping, for ethanol production in a continuous flow-cell system. Gas diffusion electrodes are fabricated using commercial catalysts with varying Cu loadings (5–10%) and ZnO contents (2–3.5%). Comprehensive characterization by XPS confirms the presence of Cu²⁺ and Zn²⁺ species, while SEM reveals that ZnO incorporation improves surface uniformity and aggregate distribution compared to undoped samples. Electrochemical tests demonstrate that 10% Cu on SiO₂ achieves a Faradaic efficiency of 96% for ethanol at −3 mA cm⁻², outperforming both doped catalysts and previously reported materials. However, efficiency declines at higher current densities, indicating a trade-off between selectivity and productivity. ZnO doping enhances C₂⁺ product formation but does not surpass the undoped catalyst in ethanol selectivity. These results underline the importance of catalyst composition, support interactions, and operating conditions, and point to further optimization of electrode architecture and cell configuration to sustain high ethanol yields under industrially relevant conditions. Full article

Hydrogen energy is vital for a clean, low-carbon society, and proton exchange membrane fuel cells (PEMFCs) represent a core technology for the conversion of hydrogen chemical energy into electrical energy. When PEMFC single cells are stacked under assembly force for high power output, their porous electrodes (gas diffusion layers, GDLs; catalyst layers, CLs) undergo compressive deformation, altering internal transport processes and affecting cell performance. However, existing microscale studies on PEMFC porous electrodes insufficiently consider compression (especially in CLs) and have limitations in obtaining compressed microstructures. This study proposes a combined framework from a microstructure perspective. It integrates the finite element method (FEM) with computational fluid dynamics (CFD). It reconstructs microstructures of GDL, CL, and GDL-bipolar plate (BP) interface. FEM simulates elastic compressive deformation, and CFD calculates transport properties (solid zone: heat/charge conduction via Laplace equation; fluid zone: gas diffusion/liquid permeation via Fick’s/Darcy’s law). Validation shows simulated stress–strain curves and transport coefficients match experimental data. Under 2.5 MPa, GDL’s gas diffusivity drops 16.5%, permeability 58.8%, while conductivity rises 2.9-fold; CL compaction increases gas resistance but facilitates electron/proton conduction. This framework effectively investigates compression-induced transport property changes in PEMFC porous electrodes. Full article

A low-cost screen-printed carbon electrode (SPCE) was used to determine gallic acid (GA) in banana wine (BW). Cyclic voltammetry (CV) showed GA oxidation in Phosphate-Buffered Saline (PBS, pH 7.0) with 10% ethanol was diffusion-controlled, forming a quinone species. This supporting electrolyte was applied for calibration using the identified CV and differential-pulsed voltammetry (DPV) peaks, whose low potentials ensured good selectivity and stability. Linearity was obtained between 0.25–5.00 μM GA, suitable for BW analysis. BW was filtered, diluted (1:20) in electrolyte, and analysed via the standard addition method. GA concentrations were 7.369 μM (CV) and 7.570 μM (DPV), with no significant differences. Further validation of the voltammetric procedure using fortified BW confirmed its reliability, with excellent recoveries of 94.41% (CV) and 99.33% (DPV). The SPCE-based voltammetric approach offers a simple, accurate, and low-cost method for GA determination in BW, combining good sensitivity, selectivity, and reproducibility. Full article

The emission of greenhouse gases from fossil fuels creates devastating effects on Earth’s atmosphere. Therefore, a clean energy source is required to fulfill the energy demand. Hydrogen is considered an energy vector, and the production of green hydrogen is a promising approach. Photoelectrochemical (PEC) water splitting is the best approach to produced green hydrogen, but the efficiency is low. To produce hydrogen by PEC splitting water, semiconductor photocatalysts have received an enormous amount of academic research in recent years. A new class of co-catalysts based on transition metals has emerged as a powerful tool for reducing charge transfer barriers and enhancing photoelectrochemical (PEC) efficiency. In this study, copper oxide (CuO) and tin oxide ($Sn{O}_2$) multilayer thin films were prepared by thermal evaporation to create an energy gradient between $Sn{O}_2$ and CuO semiconductors for better charge transfer. To improve the crystallinity and reduce the defects, the prepared films were annealed in a tube furnace at 400 °C, 500 °C, and 600 °C in an argon inert gas environment. XRD results showed that $Sn{O}_2$/CuO-600 °C exhibited strong peaks, indicating the transformation from amorphous to polycrystalline. SEM images showed the transformation of smooth dense film to a granular structure by annealing, which is better for charge transfer from electrode to electrolyte. Optical properties showed that the bandgap was decreased by annealing, which might be diffusion of Cu and Sn atoms at the interface. PEC results showed that the $Sn{O}_2$/CuO-600 °C heterostructure exhibits the solar light-to-hydrogen (STH%) conversion efficiency of 0.25%. Full article

Developing cost-effective and durable electrocatalysts with high hydrogen evolution efficiency remains a critical challenge for sustainable energy conversion. Herein, spinel-type Co₂CuO₄ and Co₃O₄ nanosheet electrodes were fabricated directly on Ni foam via a simple electrodeposition route and evaluated for the alkaline hydrogen evolution reaction (HER) in 1.0 M KOH. Structural and surface analyses confirmed the formation of phase-pure, porous, and highly interconnected nanosheet architectures, where the substitution of Cu²⁺ into the Co₃O₄ lattice induced charge-redistribution and optimized the electronic configuration. The Co₂CuO₄ catalyst exhibited superior activity, requiring an overpotential of 127 mV to achieve 10 mA cm⁻² with a corresponding Tafel slope of 61 mV dec⁻¹, outperforming the Co₃O₄ catalyst (176 mV and 95 mV dec⁻¹). This enhancement arises from improved intrinsic kinetics, higher turnover frequency, and reduced charge-transfer resistance, reflecting an increased density of active sites and enhanced interfacial conductivity. Furthermore, the Co₂CuO₄ catalyst maintained excellent stability for 100 h at both 10 and 500 mA cm⁻², attributed to its strong adhesion and open nanosheet framework, which facilitates efficient gas release and electrolyte diffusion. These findings establish Co₂CuO₄ as a promising and durable HER electrocatalyst for alkaline water electrolysis. Full article