Preparation and characterization of poly(vinyl alcohol)/sodium alginate blended membrane for alkaline solid polymer electrolytes membrane

Abstract

Novel poly(vinyl alcohol)/sodium alginate membranes (PVASA) are prepared in this study. The PVASA membranes are further treated by chemical crosslinking with glutaraldehyde as a crosslinking agent to get the crosslinked PVASA (PVASA-GA). The thermal property, KOH uptakes, ionic conductivity, and methanol permeability of the PVASA and PVASA-GA membranes are measured. Differential scanning calorimetry, X-ray diffraction, and thermogravimetry analysis are used for the characterization of membranes. It is found that with increasing the content of sodium alginate in the PVASA membrane, the crystallinity and melting point of PVASA decrease. The polymer electrolyte membranes are formed by immersing the various PVASA membranes in KOH solution. The effects of crosslinking time and membrane composition of PVA/SA on ionic conductivity through the polymer electrolyte membrane are studied using AC impedance technique. The ionic conductivity (σ) through the PVASA64 membrane at 25°C, (0.091Scm−1), is higher than the other studies for the different modified PVA membranes. The effect of crosslinking time on methanol permeability is very significant. The methanol permeability (P) of the PVASA-GA membranes is on the order of 10−7cm2s−1. The value of selectivity, (σ/P), for the PVASA82-GA60 membrane is at about 21.50×103Scm−3s1. Alkaline direct methanol fuel cells comprises of PVASA82-GA membrane is assembled and examined. It shows excellent electrochemical performance. The maximum power density of 20.7mWcm−2 is achieved at Ep,max=0.232V with a peak current density (ip,max) of 89.20mAcm−2 at 30°C for the direct methanol fuel cell consisting of PVASA82-GA60 membrane.