No abstract

The emergence of biopolymers as polymer electrolyte membrane for non-Nafion used fuel cell application in recent years was an impactful finding. This review gives a different approach to researchers, by exposing the characterization analysis perspectives of developed materials from biomass sourcesalginates, carrageenan, cellulose, chitosan and polyhydroxyalkanoates. Their membrane performances are proven in this work through chemistry understandings, hence assuring a clear picture to gain information of these biopolymers' behavior as PEM. These five bio-precursor materials are believed to perform as high potential PEM alternatives, thus this study appeared to be an insightful guidance to the industry replacing high cost Nafion membrane to a lower cost membrane sources for future massive production economically benign. HIGHLIGHTS• Biopolymers are one of the promising natural sources to be utilized as the essential PEM in fuel cell • These biopolymers to be highlighted in this review are alginates, chitosan, carrageenan, cellulose and starch • Electronic biopolymers like carbon composites, hydrogels, nucleic acid, polyester, polysaccharide and protein imposed great features with their abundant functional groups, strong electrical conductivity, excellent ion conduction, versatility and stability

Summary This study discusses three conductive materials—carbon nanotube, graphene oxide, and montmorillonite which recently being used as fillers in membranes of fuel cell application and commonly hybridized with polymers as the matrix. The polymer electrolyte membrane fuel cell (PEMFC) is using a polymer‐based membrane as the electrolyte, which might require filler or functionalization to enhance their cell performance. This review provides brief information for the researcher who insists on improving the current PEM using these potential fillers, specified with required values of membrane properties measurement. It also entails the special features of the nanofillers concerning their chemical structure and electrochemical properties based on recent studies. As electricity is generated from an external fuel source, the membranes that are used should be more than 0.1 S/cm of proton conductivity, low fuel permeability (< 1.37 x 10−6 cm2/s), cheap, and high stability in dry and wet condition. PEM is widely being utilized together with filler(s) incorporated as a purpose to overcome recent drawbacks encountered by the commercial Nafion membrane solely. Hence, the fillers embedded in the membrane are necessarily to have the promising characteristics, acknowledging the potential performances of three conductive nanofillers of (a) carbon nanotubes which is well‐known of its electrical conducting potential with three cylindrical design, (b) graphene oxide which is a reactive carbonaceous material with its multifunctional groups and (c) montmorillonite which is one of the clay types that has tetrahedral and octahedral layers of alumina‐silicates for producing better hybrid polymer electrolyte membrane. Highlights Carbon nanotube, graphene oxide, and montmorillonite are highly promising conductive fillers with outstanding cell performances based on previous studies. Carbon nanotube, graphene oxide, and montmorillonite are chosen as incorporated fillers recently due to their rolling up direction (chirality vector of graphene sheet), reactive functional groups attached on the carbon atoms and ionic multilayers of the tetrahedral and octahedral sheet, respectively. High proton conductivity, low electronic conductivity, low fuel permeability, low water transport, low production cost, and high mechanical stability in both dry and wet condition are properties that should be portrayed by a good hybrid membrane.

Nafion is a commercial membrane that is widely used in direct methanol fuel cells (DMFC) but has critical constraints such as being expensive and having high methanol crossover. Efforts to find alternative membranes are actively being carried out, including in this study, which looks at producing a Sodium Alginate/Poly (Vinyl Alcohol) (SA/PVA) blended membrane with modification by montmorillonite (MMT) as an inorganic filler. The content of MMT in SA/PVA-based membranes varied in the range of 2.0–20 wt% according to the solvent casting method implemented. The presence of MMT was seen to be most optimal at a content of 10 wt%, achieving the highest proton conductivity and the lowest methanol uptake of 9.38 mScm−1 and 89.28% at ambient temperature, respectively. The good thermal stability, optimum water absorption, and low methanol uptake of the SA/PVA-MMT membrane were achieved with the presence of MMT due to the strong electrostatic attraction between H+, H3O+, and −OH ions of the sodium alginate and PVA polymer matrices. The homogeneous dispersion of MMT at 10 wt% and the hydrophilic properties possessed by MMT contribute to an efficient proton transport channel in SA/PVA-MMT membranes. The increase in MMT content makes the membrane more hydrophilic. This shows that the loading of 10 wt% MMT is very helpful from the point of view of sufficient water intake to activate proton transfer. Thus, the membrane produced in this study has great potential as an alternative membrane with a much cheaper cost and competent future performance.

This study reports the effect of plasticizers namely isopropanol, polyethylene glycol, maltitol and spermidine on the properties of the sodium alginate composite membrane. The concentration of each potential plasticizer was set at minimum to execute performance. Properties of sodium alginate were studied through characterization studies - Field Emission Scanning Electron Microscope (FESEM) to observe on the morphology structure. The membrane performance is also seen through water uptake and swelling ratio tests. Isopropanol produced better plasticizer with the lowest water uptake of 575.53% and less hydrophilic compared to spermidine (1268.46%), polyethylene glycol (1014.30%) and maltitol (595.82%). Further study may require copolymerization to support polyol for ensuring structure firmness. This study proven the plasticizers could enhance membrane’s flexibility in DMFC and becoming a promising choice of additives for better alginate-based membrane establishment.