An investigation into polymer blending, plasticization and cross-linking effect on the performance of chitosan-based composite proton exchange membranes for microbial fuel cell applications

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%.

A sustainable and eco-friendly approach for environmental and energy management using biopolymers chitosan, lignin and cellulose - A review

Biopolymers are a naturally occurring alternative to synthetic polymers that are linked by covalent bonds, which includes cellular components such as proteins, nucleotides, lipids, and polysaccharides. Based on the extensive literature review it was found that chitosan, lignin, and cellulose were predominantly used in the energy and environmental sectors. Due to their vast array of qualities, including the adsorption, flocculation, anticoagulation, and furthermore, have made them useful for treating wastewater and pollutant removal. Chitosan and lignin have been used as a proton exchange membrane in the energy storage device of fuel cells. As these biopolymers develop strong coordination connections with metal surfaces, they act as an anticorrosive agent, which inhibiting the corrosion. Besides, there are a lot of recent developments in the application of biopolymers for energy and environmental fields. The present review provides a concise summary of recent developments in membrane-based biopolymers role in energy and environmental field. In addition, this review is drawn to a conclusion with a discussion of future trends in the real application of biopolymers in a variety of different industries, as well as the financial significance of these future trends.

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.

Fabrication of Cellulose Acetate-Based Proton Exchange Membrane with Sulfonated SiO2 and Plasticizers for Microbial Fuel Cell Applications

Developing a hybrid composite polymer membrane with desired functional and intrinsic properties has gained significant consideration in the fabrication of proton exchange membranes for microbial fuel cell applications. Among the different polymers, a naturally derived cellulose biopolymer has excellent benefits over synthetic polymers derived from petrochemical byproducts. However, the inferior physicochemical, thermal, and mechanical properties of biopolymers limit their benefits. In this study, we developed a new hybrid polymer composite of a semi-synthetic cellulose acetate (CA) polymer derivate incorporated with inorganic silica (SiO₂) nanoparticles, with or without a sulfonation (-SO₃H) functional group (sSiO₂). The excellent composite membrane formation was further improved by adding a plasticizer (glycerol (G)) and optimized by varying the SiO₂ concentration in the polymer membrane matrix. The composite membrane's effectively improved physicochemical properties (water uptake, swelling ratio, proton conductivity, and ion exchange capacity) were identified because of the intramolecular bonding between the cellulose acetate, SiO₂, and plasticizer. The proton (H⁺) transfer properties were exhibited in the composite membrane by incorporating sSiO₂. The composite CAG-2% sSiO₂ membrane exhibited a higher proton conductivity (6.4 mS/cm) than the pristine CA membrane. The homogeneous incorporation of SiO₂ inorganic additives in the polymer matrix provided excellent mechanical properties. Due to the enhancement of the physicochemical, thermal, and mechanical properties, CAG-sSiO₂ can effectively be considered an eco-friendly, low-cost, and efficient proton exchange membrane for enhancing MFC performance.

Moisture-Enabled Germination of Heat-Activated Bacillus Endospores for Rapid and Practical Bioelectricity Generation: Toward Portable, Storable Bacteria-Powered Biobatteries

Small-scale battery-like microbial fuel cells (MFCs) are a promising alternative power source for future low-power electronics. Controllable microbial electrocatalytic activity in a miniaturized MFC with unlimited biodegradable energy resources would enable simple power generation in various environmental settings. However, the short shelf-life of living biocatalysts, few ways to activate the stored biocatalysts, and extremely low electrocatalytic capabilities render the miniature MFCs unsuitable for practical use. Here, heat-activated Bacillus subtilis spores are revolutionarily used as a dormant biocatalyst that can survive storage and rapidly germinate when exposed to special nutrients that are preloaded in the device. A microporous, graphene hydrogel allows the adsorption of moisture from the air, moves the nutrients to the spores, and triggers their germination for power generation. In particular, forming a CuO-hydrogel anode and an Ag₂ O-hydrogel cathode promotes superior electrocatalytic activities leading to an exceptionally high electrical performance in the MFC. The battery-type MFC device is readily activated by moisture harvesting, producing a maximum power density of 0.4 mW cm^-2 and a maximum current density of 2.2 mA cm^-2 . The MFC configuration is readily stackable in series and a three-MFC pack produces enough power for several low-power applications, demonstrating its practical feasibility as a sole power source.

Effect of Sulfonated Inorganic Additives Incorporated Hybrid Composite Polymer Membranes on Enhancing the Performance of Microbial Fuel Cells

Microbial fuel cells (MFCs) provide considerable benefits in the energy and environmental sectors for producing bioenergy during bioremediation. Recently, new hybrid composite membranes with inorganic additives have been considered for MFC application to replace the high cost of commercial membranes and improve the performances of cost-effective polymers, such as MFC membranes. The homogeneous impregnation of inorganic additives in the polymer matrix effectively enhances the physicochemical, thermal, and mechanical stabilities and prevents the crossover of substrate and oxygen through polymer membranes. However, the typical incorporation of inorganic additives in the membrane decreases the proton conductivity and ion exchange capacity. In this critical review, we systematically explained the impact of sulfonated inorganic additives (such as (sulfonated) sSiO₂, sTiO₂, sFe₃O₄, and s-graphene oxide) on different kinds of hybrid polymers (such as PFSA, PVDF, SPEEK, SPAEK, SSEBS, and PBI) membrane for MFC applications. The membrane mechanism and interaction between the polymers and sulfonated inorganic additives are explained. The impact of sulfonated inorganic additives on polymer membranes is highlighted based on the physicochemical, mechanical, and MFC performances. The core understandings in this review can provide vital direction for future development.