Enhanced surface functionality and microbial fuel cell performance of chitosan membranes through phosphorylation

Proton conductivity and dielectric studies on chitosan/polyvinyl alcohol blend electrolytes: Synergistic improvements with ionic liquid and graphene oxide

This study investigates the impact of ionic liquid, 1-methylimidazolium tetrafluoroborate (IL) and graphene oxide (GO) on the performance of chitosan/polyvinyl alcohol (CS/PVA)-based composite electrolytes. Fourier-transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) confirm the successful incorporation of IL and GO, affecting the structural and morphological properties of the electrolytes. Thermogravimetric analysis (TGA) reveals enhanced thermal stability in GO-doped samples, with increased residual weight at high temperatures, while IL addition leads to higher initial weight loss due to its hygroscopic nature. Ionic conductivity measurements demonstrate that the CS/PVA/IL-GO(4.0) composite achieves the highest proton conductivity of 1.76 × 10-3 S/m at 300 K and 1 MHz, surpassing other samples and aligning with top values reported in literature. Dielectric studies show a significant increase in dielectric constant to 9.55 × 104 at 300 K and 20 Hz for CS/PVA/IL-GO(4.0), attributed to enhanced dipole alignment and polarization effects. The loss tangent analysis indicates the shortest relaxation time of 2.07 × 10-4 s for CS/PVA/IL-GO(4.0), correlating with its superior proton conductivity. These findings highlight the potential of CS/PVA/IL-GO electrolytes for advanced energy storage and conversion applications, suggesting further research into GO dispersion and long-term stability for optimized performance in practical devices.

Improved Proton Conductivity of Chitosan-Based Composite Proton Exchange Membrane Reinforced by Modified GO Inorganic Nanofillers

Non-fluorinated chitosan-based proton exchange membranes (PEMs) have been attracting considerable interest due to their environmental friendliness and relatively low cost. However, low proton conductivity and poor physicochemical properties have limited their application in fuel cells. In this work, a reinforced nanofiller (sulfonated CS/GO, S-CS/GO) is accomplished, for the first time, via a facile amidation and sulfonation reaction. Novel chitosan-based composite PEMs are successfully constructed by the incorporation of the nanofiller into the chitosan matrix. Additionally, the effects of the type and amount of the nanofillers on physicochemical and electrochemical properties are further investigated. It is demonstrated that the chitosan-based composite PEMs incorporating an appropriate amount of the nanofillers (9 wt.%) exhibit good membrane-forming ability, physicochemical properties, improved proton conductivity, and low methanol permeability even under a high temperature and low humidity environment. When the incorporated amounts of S-CS/GO are 9 wt.%, the proton conductivity of the composite PEMs was up to 0.032 S/cm but methanol permeability was decreased to 1.42 × 10-7 cm2/s. Compared to a pristine CS membrane, the tensile strength of the composite membrane is improved by 98% and the methanol permeability is reduced by 51%.

From single-chamber to multi-anodic microbial fuel cells: A review

Microbial fuel cells (MFCs) present a promising solution for wastewater treatment with the added benefits of energy generation, less sludge production and less energy consumption. MFCs have demonstrated high efficiency in the degradation of diverse types of wastewater. Nevertheless, the relatively low power density exhibited by MFCs has imposed certain restrictions on their widespread implementation. Consequently, the need for modification of MFC technology led to the development of stack and multi-chambered MFCs. The modified variations exhibit enhanced scalability and demonstrate greater reliability in terms of power output compared to traditional MFCs. In the present review article, different components of MFCs such as anode, cathode, microbial community and membrane have been reviewed and the advancement in design for better scalability of MFCs has been addressed, emphasizing the benefits associated with stacked and multi-anodic MFCs for enhanced performance. Finally, an update of previous large-scale MFC system applications is presented.

Composite proton exchange membrane for fuel cells based on chitosan modified by acid-base amphoteric nanoparticles

Currently, achieving a simultaneous improvement in proton conductivity and mechanical properties is a key challenge in using chitosan (CS) as a proton exchange membrane (PEM) substrate in direct methanol fuel cells (DMFCs). Herein, a novel nanofiller-zwitterionic molecule, (3-(3-aminopropyl) dimethylammonio) propane-1-sulfonate, ADPS)-modified polydopamine (PDA) (PDA-ADPS) was synthesized by the Michael addition reaction and was incorporated into a CS matrix to prepare CS/PDA-ADPS composite membranes. PDA-ADPS, which contains an acid-based ion pair can create new proton conduction channels in the composite membrane, improving proton conductivity. The proton conductivity of the CS/PDA-ADPS composite membrane was as high as 38.4 mS cm-1 at 80 °C. Moreover, due to the excellent compatibility and dispersibility of PDA-ADPS in the CS matrix, the obtained CS/PDA-ADPS composite membranes exhibited favorable mechanical properties. Such outstanding proton conductivity and mechanical properties guarantee good performance of the composite membranes in fuel cells. The peak power density of the CS/PDA-ADPS composite membranes was 30.2 mW cm-2 at 70 °C. This work provides a new strategy for fabricating high-performance CS based PEMs for DMFCs.

Investigating the Sulfonated Chitosan/Polyvinylidene Fluoride-Based Proton Exchange Membrane with fSiO2 as Filler in Microbial Fuel Cells

Chitosan (CS), a promising potential biopolymer with exquisite biocompatibility, economic viability, hydrophilicity, and chemical modifications, has drawn interest as an alternative material for proton exchange membrane (PEM) fabrication. However, CS in its original form exhibited low proton conductivity and mechanical stability, restricting its usage in PEM development. In this work, chitosan was functionalized (sulfonic acid (-SO3H) groups)) to enhance proton conductivity. The sulfonated chitosan (sCS) was blended with polyvinylidene fluoride (PVDF) polymer, along with the incorporation of functionalized SiO2 (-OH groups), for fabricating chitosan-based composite proton exchange membranes to enhance microbial fuel cell (MFC) performances. The results show that adding functionalized inorganic fillers (fSiO2) into the membrane enhances the mechanical, thermal, and anti-biofouling behavior. From the results, the PVDF/sCS/fSiO2 composite membrane exhibited enhanced proton conductivity 1.0644 × 10-2 S cm-1 at room temperature and increased IEC and mechanical and chemical stability. Furthermore, this study presents a revolutionary way to generate environmentally friendly natural polymer-based membrane materials for developing PEM candidates for enhanced MFC performances in generating bioelectricity and wastewater treatment.

Chemical modifications in the structure of marine polysaccharide as serviceable food processing and preservation assistant: A review

Marine polysaccharides are a kind of natural polysaccharides which isolated and extracted from marine organisms. Now some marine polysaccharides, such as chitosan, sodium alginate and agar, have been proven to exhibit antibacterial, antioxidant functions and biocompatibility, which are often used to preserve food or improve the physicochemical properties of food. However, they still have the defects of unsatisfactory preservation effect and biological activity, which can be remedied by its modification. Chemical modification is the most effective of all modification methods. The advances in common chemical modification methods of chitosan, sodium alginate, agar and other marine polysaccharides and research progress of modified products in food processing and preservation were summarized, and the influence of additional reaction conditions on the existence of chemical modification sites of polysaccharides was discussed. The modification of functional groups in natural marine polysaccharides leads to the change of molecular structure, which can improve the physical, chemical and biological properties of marine polysaccharides. Chemically modified products have been used in various fields of food applications, such as food preservatives, food additives, food packaging, and food processing aids. In general, chemical modification has excellent potential for food processing and preservation, which can improve the function of marine polysaccharides.

Natural biopolymers as proton conductors in bioelectronics

Bioelectronic devices sense or deliver information at the interface between living systems and electronics by converting biological signals into electronic signals and vice-versa. Biological signals are typically carried by ions and small molecules. As such, ion conducting materials are ideal candidates in bioelectronics for an optimal interface. Among these materials, ion conducting polymers that are able to uptake water are particularly interesting because, in addition to ionic conductivity, their mechanical properties can closely match the ones of living tissue. In this review, we focus on a specific subset of ion-conducting polymers: proton (H⁺ ) conductors that are naturally derived. We first provide a brief introduction of the proton conduction mechanism, and then outline the chemical structure and properties of representative proton-conducting natural biopolymers: polysaccharides (chitosan and glycosaminoglycans), peptides and proteins, and melanin. We then highlight examples of using these biopolymers in bioelectronic devices. We conclude with current challenges and future prospects for broader use of natural biopolymers as proton conductors in bioelectronics and potential translational applications.

Review of Chitosan-Based Polymers as Proton Exchange Membranes and Roles of Chitosan-Supported Ionic Liquids

Perfluorosulphonic acid-based membranes such as Nafion are widely used in fuel cell applications. However, these membranes have several drawbacks, including high expense, non-eco-friendliness, and low proton conductivity under anhydrous conditions. Biopolymer-based membranes, such as chitosan (CS), cellulose, and carrageenan, are popular. They have been introduced and are being studied as alternative materials for enhancing fuel cell performance, because they are environmentally friendly and economical. Modifications that will enhance the proton conductivity of biopolymer-based membranes have been performed. Ionic liquids, which are good electrolytes, are studied for their potential to improve the ionic conductivity and thermal stability of fuel cell applications. This review summarizes the development and evolution of CS biopolymer-based membranes and ionic liquids in fuel cell applications over the past decade. It also focuses on the improved performances of fuel cell applications using biopolymer-based membranes and ionic liquids as promising clean energy.

Characterization of a new composite membrane for point of need paper-based micro-scale microbial fuel cell analytical devices

Microbial fuel cells (MFCs) can evolve in a viable technology if environmentally sound materials are developed and became available at low cost for these devices. This is especially important not only for the designing of large wastewater treatment systems, but also for the fabrication of low-cost, single-use devices. In this work we synthesized membranes by a simple procedure involving easily-biodegradable and economic materials such as poly (vinyl alcohol) (PVA), chitosan (CS) and the composite PVA:CS. Membranes were chemical and physically characterized and compared to Nafion^®. Performance was studied using the membrane as separator in a typical H-Type MFCs showing that PVA:CS membrane outperform Nafion^® 4 times (power production) while being 75 times more economic. We found that performance in MFC depends over interactions among several membrane characteristics such as oxygen permeability and ion conductivity. Moreover, we design a paper-based micro-scale MFC, which was used as a toxicity assay using 16 μL samples containing formaldehyde as a model toxicant. The PVA:CS membrane presented here can offer low environmental impact and become a very interesting option for point of need single-use analytical devices, especially in low-income countries where burning is used as disposal method, and toxic fluoride fumes (from Nafion^®) can be released to the environment.

Advanced redox flow fuel cell using ferric chloride as main catalyst for complete conversion from carbohydrates to electricity

Liquid catalyzed fuel cell (LCFC) is a kind of redox flow fuel cell directly converting carbohydrates to electricity. To improve its efficiency, ferric chloride (FeCl₃) was introduced as main catalyst. As mono catalyst, phosphomolybdic acid (PMo₁₂) was much better than phosphotungstic acid (PW₁₂) and FeCl₃ was intermediate between them. Compared with PMo₁₂ at the optimal dose of 0.30 mol/L, the combination of FeCl₃ (1.00 mol/L) and PW₁₂ (0.06 mol/L) achieved similar power output from glucose (2.59 mW/cm²) or starch (1.57 mW/cm²), and even improved the maximum power density by 57% from 0.46 to 0.72 mW/cm² when using cellulose as the fuel. Long-term continuous operation of the LCFC indicated that carbohydrates can be hydrolyzed to glucose and then oxidized stepwise to carbon dioxide. At the latter stage, there was a linear relationship between the electron transfer number from glucose to catalyst and the subsequent cell performance. Based on these findings, the contribution of FeCl₃ to LCFC should be derived from the accelerated hydrolysis and oxidation of carbohydrates and the enhanced electron transfer from glucose to anode. The addition of FeCl₃ reduced the usage of polyoxometalates by 80%, and the replacement implied that LCFC can be operated less toxically and more economically.

Simultaneous wastewater treatment and bioelectricity production in microbial fuel cells using cross-linked chitosan-graphene oxide mixed-matrix membranes

Microbial fuel cells (MFCs) are emerging technology for wastewater treatment by chemical oxygen demand (COD) reduction and simultaneous bioelectricity production. Fabrication of an effective proton exchange membrane (PEM) is a vital component for MFC performance. In this work, green chitosan-based (CS) PEMs were fabricated with graphene oxide (GO) as filler material (CS-GO) and cross-linked with phosphoric acid (CS-GO-P(24)) or sulfuric acid (CS-GO-S(24)) to determine their effect on PEM properties. Interrogation of the physicochemical, thermal, and mechanical properties of the cross-linked CS-GO PEMs demonstrated that ionic cross-linking based on the incorporation of PO₄^3- groups in the CS-GO mixed-matrix composites, when compared with sulfuric acid cross-linking commonly used in proton exchange membrane fuel cell (PEMFC) studies, generated additional density of ionic cluster domains, rendered enhanced sorption properties, and augmented the thermal and mechanical stability of the composite structure. Consequently, bioelectricity performance analysis in MFC application showed that CS-GO-P(24) membrane produced 135% higher power density than the CS-GO-S(24) MFC system. Simultaneously, 89.52% COD removal of primary clarifier municipal wastewater was achieved in the MFC operated with the CS-GO-P(24) membrane.

Influence of Pectin as a green polymer electrolyte on the transport properties of Chitosan-Pectin membranes

Novel blend membranes have been prepared from Chitosan (CH), Pectin (PEC) and their mixtures. The obtained samples were cross-linked and sulfonated before characterization. The results show that CH/PEC membranes display structural changes on the chemical and physical properties as a function of composition. DSC analysis reveals an endothermic peak due to the scission of the ionic pairs between carboxylic groups and ammonium groups, which produces a strong change on physical properties such as methanol permeability and proton conductivity. The methanol permeability decreases with the amount of Pectin from (4.24±0.04)×10^-6cm²/s for pure Chitosan membrane to (1.51±0.03)×10^-6cm²/s for blend CH/PEC membranes when the amount of Pectin is 50% (v/v). The proton conductivities of the blend membranes follow a similar behavior. For a pure CH membrane the conductivity is 2.44×10^-3S/cm, decreasing with pectin content until the composition 50/50 (v/v), in which the conductivity drops almost one order of magnitude.