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Abstract A green physical route for producing novel multifunctional polyvinyl alcohol/kappa-carrageenan alkaline gel polymer electrolyte is developed, which is based on double-network physical cross-linked hydrogel. The alkaline gel polymer electrolyte has excellent tensile stress (2.22 MPa), stretchability (12.43 mm/mm) and ionic conductivity (0.21 S/cm). In this study, KOH is served as not only ionic donator but also cross-linking agent. A supercapacitor is assembled from polyvinyl alcohol/kappa-carrageenan alkaline gel polymer electrolyte and activated carbon electrodes, which exhibits ideal electrochemistry behavior. The electrode specific capacitance is 470 F/g at 0.5 A/g, and retains above 95% after 2000 charge/discharge cycles. Additionally, the electrochemical performance of supercapacitor under different tensile deformations (≤200%), bending angles (0–230°) and temperatures (≥-40 °C) displays a slightly reduction, indicating that the supercapacitor possesses good flexibility and low temperature resistance. These findings are desirable for applications in supercapacitor devices of flexibility or low working temperature. Graphical abstract Image 1 Highlights • KOH playing two roles of ionic donator and cross-linking agent in the AGPE. • Outstanding tensile property and ionic conductivity of PVA/carrageenan AGPE. • Superior properties of supercapacitor under deformation and low temperature. [ABSTRACT FROM AUTHOR]

Compared with traditional microbial fuel cells, the microfluidic microbial fuel cells have higher performance and energy efficiency due to their co-laminar flow characteristic and micro-scale structure. However, there are very few numerical studies on microfluidic microbial fuel cells, which makes it difficult to study the operating mechanism. In this study, a three-dimensional numerical model is developed to characterize and predict the comprehensive performance of a biofilm-based Y-typed microfluidic microbial fuel cell. Multiple physical fields, containing the bioelectrochemical reaction kinetics, mass transport, hydrodynamics and thermal equilibrium, are coupled in this model to investigate the effects of various parameters on cell performance. The model reliability is validated through the previous experiment. Simulation results reveal the non-linear performance trend of microfluidic microbial fuel cells with the augment of temperature. In addition, high fuel concentration can cause the substrate inhibition phenomenon and affect bacterial activity. Model applicability for different parametric analyses is emphasized by exploring the effect of ionic strength on cell performance. Finally, considering the catholyte diffusion, optimization strategies for energy efficiency are presented. The proposed numerical model can be helpful for the experimental guidance and optimal design of microfluidic microbial fuel cells. [Display omitted] • The first three-dimensional model for microfluidic microbial fuel cell is proposed. • Hydrodynamics and thermal equilibrium are coupled together. • Effects of temperature on anode reaction and catholyte property are considered. • Fuel utilization and exergy efficiency are introduced to evaluate performances. [ABSTRACT FROM AUTHOR]

Under the dual pressure of energy consumption and environmental pollution, mankind hopes to develop clean and renewable alternative energy, and the rapid development of fuel cells meets people's demand for energy-efficient power systems. The emergence of portable micro energy systems represented by microfluidic fuel cells, such as paper-based microfluidic fuel cells, has greatly enriched the means of medical detection to better cope with the threat of disease transmission. In this work, the numerical simulation method is innovatively introduced to study the paper-based microfluidic fuel cells. Both transient and steady-state modes are employed to demonstrate the whole operation process of the paper-based microfluidic fuel cell. In addition, the different structural parameters, including electrode spacing, the distance between electrode and inlet, channel thickness, and electrode length, are also investigated their influence mechanisms on cell performance. Results show that the increase of most structural parameters decreases cell output power in different degrees. Even on the premise that increasing channel thickness has a positive impact on the output power, the fuel utilization still shows a downward trend. These conclusions provide theoretical support and reference for future optimization work and accelerate the development of microfluidic fuel cells. • Numerical simulation is employed to study paper-based microfluidic fuel cell. • The effects of structure parameters on cell performance are discussed. • Through fuel concentration distribution to reveal cell performance mechanism. • Fuel utilization is used to evaluate energy efficiency. [ABSTRACT FROM AUTHOR]