Three dimensional model of a high temperature PEMFC using PBI doped phosphoric acid membranes. Study of the flow field effect on performance

A three-dimensional isothermal model of a high temperature polymer membrane fuel cell equipped with polybenzimidazole (PBI) membrane is described. All major transport phenomena were taken into account except the species cross-over thought the membrane. The cathode catalyst layer was treated as spherical catalyst agglomerates with porous inter-agglomerate spaces. The inter-agglomerate spaces were filled with a mixture of electrolyte (hot phosphoric acid) and polytetrafluoroethylene (PTFE). This approach proved to be an essential requirement for accurate simulation. In this particular paper the influence of different flow field designs and dimensions on performance was intensely study. Traditional configurations were tested (straight, serpentine, pin-in and interdigitated), and a new designs were proposed. With these new designs we tried to maximize performance by providing homogeneous reactants distribution over the active area keeping low pressure drop and relatively high velocity. The dimension and position of the inlet and outlet manifolds were also analysed. From the obtained results was observed a massive influence of the manifolds position and dimension on performance. This fact leaded to an optimization of the manifolds which can give important guidelines for future bipolar plates production

DNA copy number changes define spatial patterns of heterogeneity in colorectal cancer

Genetic heterogeneity between and within tumours is a major factor determining cancer progression and therapy response. Here we examined DNA sequence and DNA copy-number heterogeneity in colorectal cancer (CRC) by targeted high-depth sequencing of 100 most frequently altered genes. In 97 samples, with primary tumours and matched metastases from 27 patients, we observe inter-tumour concordance for coding mutations; in contrast, gene copy numbers are highly discordant between primary tumours and metastases as validated by fluorescent in situ hybridization. To further investigate intra-tumour heterogeneity, we dissected a single tumour into 68 spatially defined samples and sequenced them separately. We identify evenly distributed coding mutations in APC and TP53 in all tumour areas, yet highly variable gene copy numbers in numerous genes. 3D morpho-molecular reconstruction reveals two clusters with divergent copy number aberrations along the proximal–distal axis indicating that DNA copy number variations are a major source of tumour heterogeneity in CRC

Categorical Dimensions of Human Odor Descriptor Space Revealed by Non-Negative Matrix Factorization

In contrast to most other sensory modalities, the basic perceptual dimensions of olfaction remain unclear. Here, we use non-negative matrix factorization (NMF) – a dimensionality reduction technique – to uncover structure in a panel of odor profiles, with each odor defined as a point in multi-dimensional descriptor space. The properties of NMF are favorable for the analysis of such lexical and perceptual data, and lead to a high-dimensional account of odor space. We further provide evidence that odor dimensions apply categorically. That is, odor space is not occupied homogenously, but rather in a discrete and intrinsically clustered manner. We discuss the potential implications of these results for the neural coding of odors, as well as for developing classifiers on larger datasets that may be useful for predicting perceptual qualities from chemical structures

Entropy generation analysis based on a three-dimensional agglomerate model of an anion exchange membrane fuel cell

\ua9 2019. A three-dimensional agglomerate numerical model has been used to analyse entropy generation in an anion exchange membrane fuel cell. The effects of inlet relative humidity, platinum loading, carbon loading and ionomer volume fraction on entropy generation have been analysed in the present study. The reversible and irreversible heat have been identified as the main sources of entropy production for all the parameters tested. Even though the production of entropy due to Ohmic loss occurs due to both electronic and ionic potentials, the production of entropy as a result of the first is insignificant in comparison to the latter due to the fact that the electronic conductivity is significantly higher in comparison to the ionic diffusivity coefficient. A strong effect of the back diffusion of water has been found on the entropy production due to Ohmic loss, as the hydration of the membrane directly affects the anion transport through the membrane. Water condensation at the anode catalyst layer and gas diffusion layer has been observed in a few cases, giving rise to the entropy generation due to latent heat. Nevertheless, this has been observed to be 1 to 2 orders of magnitude lower in comparison to the entropy generated due to reversible, irreversible and Ohmic heats

Robust poly(p-phenylene oxide) anion exchange membranes reinforced with pore-filling technique for water electrolysis

\ua9 2024 The Authors. Journal of Applied Polymer Science published by Wiley Periodicals LLC. Mechanical robustness and durability are crucial for anion exchange membranes to guarantee the longevity and consistent performance of AEM water electrolysis (AEMWE) systems. In this study, a composite membrane based on the quaternized poly(p-phenylene oxide) (QPPO)/polytetrafluoroethylene (PTFE) was developed. This membrane was fabricated by enhancing the QPPO-based AEM through a pore-filling technique within a porous PTFE structure. The tensile strength of the composite membrane was increased significantly from 16.5 to 31 MPa. The conductivity of the composite membrane was 6.25 mScm−1 lower than 30 mScm−1 of the QPPO-based membrane at 20\ub0C, resulting from the low volume fraction of QPPO in the composite membrane. At 40% RH, the net change mass of the composite membrane is 1.59%, much lower than that of QPPO-based membrane (10.98%) at 40\ub0C. The composite membrane demonstrated a significantly increased lifetime in the working electrolyzer (>200 h) compared with an otherwise identical electrolyzer assembled with a QPPO-based membrane (50 h)

Degradation of QPPO-based anion polymer electrolyte membrane at neutral pH

\ua9 2023 The Royal Society of ChemistryThe chemical stability of anion polymer electrolyte membranes (AEMs) determines the durability of an AEM water electrolyzer (AEMWE). The alkaline stability of AEMs has been widely investigated in the literature. However, the degradation of AEM at neutral pH closer to the practical AEMWE operating condition is neglected, and the degradation mechanism remains unclear. This paper investigated the stability of quaternized poly(p-phenylene oxide) (QPPO)-based AEMs under different conditions, including Fenton solution, H2O2 solution and DI water. The pristine PPO and chloromethylated PPO (ClPPO) showed good chemical stability in the Fenton solution, and only limited weight loss was observed, 2.8% and 1.6%, respectively. QPPO suffered a high mass loss (29%). Besides, QPPO with higher IEC showed a higher mass loss. QPPO-1 (1.7 mmol g−1) lost nearly twice as much mass as QPPO-2 (1.3 mmol g−1). A strong correlation between the degradation rate of IEC and H2O2 concentration was obtained, which implied that the reaction order is above 1. A long-term oxidative stability test at pH neutral condition was also conducted by immersing the membrane in DI at 60 \ub0C water for 10 months. The membrane breaks into pieces after the degradation test. The possible degradation mechanism is that oxygen or OH˙ radicals attack the methyl group on the rearranged ylide, forming aldehyde or carboxyl attached to the CH2 group

Membraneless water electrolysis enabled by flow and porous electrode design for bubble separation

\ua9 2025. Intensification of water electrolysers is essential to lower the cost of green hydrogen. In this study we design and test a novel alkaline water electrolyser operating without a separator diaphragm (membraneless), using instead a convective flow barrier between electrodes, saving material and energy cost. For the first time, high-speed imaging has confirmed conditions required for a clear electrode gap, with bubble separation up to high current density >4 A cm−2. This design was enabled through computational fluid dynamics simulations (OpenFOAM) developed for coupling ionic and kinetic charge transport in the electrolyte and electrodes with the insulating effect of bubble two-phase flow. A pseudo-2D, 3D-printed transparent electrolyser cells validated the fluid flow vectors using particle image velocimetry of bubbles, as well as tracking bubble transport inside the cell. The simulated current density distribution on the electrodes, along with the two-phase flow simulations showed membraneless separation of bubbles was possible and later proven in the experiments using an inactive porous barrier layer with pore diameter of <51μm. Modelling at larger scale detailed that two-phase flow of bubbles effects charge-transfer instead of ohmic transport in this system. Theoretical single-phase flow and transport models predict at 50 cm scale it can operate at low current density with low crossover

Review of next generation hydrogen production from offshore wind using water electrolysis

\ua9 2023 The Author(s)Hydrogen produced using renewable energy from offshore wind provides a versatile method of energy storage and power-to-gas concepts. However, few dedicated floating offshore electrolyser facilities currently exist and therefore conditions of the offshore environment on hydrogen production cost and efficiency remain uncertain. Therefore, this review focuses on the conversion of electrical energy to hydrogen, using water electrolysis located in offshore areas. The challenges associated with the remote locations, fluctuating power and harsh conditions are highlighted and recommendations for future electrolysis system designs are suggested. The latest research in polymer electrolyte membrane, alkaline and membraneless electrolysis are evaluated in order to understand their capital costs, efficiency and current research status for achieving scaled manufacturing to the GW scale required in the next three decades. Operating fundamentals that govern the performance of each device are investigated and future recommendations of research specifically for the integration of water electrolysers with offshore wind turbines is presented

Enhancing the physicochemical properties of nickel cobaltite catalyst for oxygen evolution reaction in anion exchange membrane water electrolyzers

\ua9 The Author(s) 2024. Hierarchical hollow urchin-like nickel cobaltite (NiCo2O4) was synthesized using a two-step hydrothermal method. The effects of metal composition and surfactant addition on the morphology, structure, and electrochemical performance toward oxygen evolution reaction (OER) were investigated. The addition of cetyltrimethylammonium bromide (CTAB) reduced particle aggregation, resulting in a higher electrochemical active surface area and electrical conductivity. Lowering the Ni content from 1.0 to 0.25 did not alter the morphology and structure of the product to any extent. However, the crystallite size slightly increased. Among the spinels with different Ni and Co compositions, NiCo2O4 exhibited a superior OER electrocatalytic activity, achieving a 380 mV overpotential at 10 mA/cm2 current density. It also delivered a good performance in an anion exchange membrane water electrolyzer (AEMWE) using 1 M NaOH at 60 \ub0C, reaching a current density of about 420 mA/cm2 at a cell voltage of 1.95 V