The Potential of Polyurethane Bio-based Solid Polymer Electrolyte for Photoelectrochemical Cell Application

A photoelectrochemical cell was developed from bio-based polyurethane (PU), solid poly-mer electrolyte with lithium iodide as conducting material. At the initial stage, PU pre-polymer was prepared via prepolymerization technique by reacting palm kernel oil-basedmonoester-OH (PKO-p) and 2,4'-methylene diphenyl diisocyanate (2,4'-MDI). The poly-urethane electrolyte film was then prepared by inclusion of varying amount of lithiumiodide (LiI) via solution casting technique. The formation of urethane linkages (NHCObackbone) and the chemical interaction between segmented polyurethane and lithium ionfrom LiI salts were confirmed by ATR-FTIR technique. Thermal studies carried out by TGA have proven the occurrence of polymer-salt complexation. Structural analysis by XRD has revealed that polyurethane electrolytes with 25 wt.% LiI reduced the semi-crystallinecharacteristics of plasticized polyurethane. The SEM morphological observation on the fractured film indicated the absence of phase separation. The ionic conductivity increased with the addition of 25 wt.% LiI resulted in the highest conductivity of 7.6x10^-4 S cm^-1. The temperature dependence conductivity of the electrolytes obeyed the Arrhenius law with the pre-exponential factor, s0 of 2.4x10^-3 S cm^-1 and activation energy, Ea of 0.11 eV. A dye-sensitized solar cell of FTO/TiO2-dye/PU-LiI-I2 /Pt give a response under light in-tensity of 100 mW cm^-2 indicated the photovoltaic effect with the Jsc of 0.06 mA cm^-2 and Voc of 0.14 V respectively. These properties exhibited promising potentials for photo-electrochemical cell giving the focus on bio-based polymer electrolyte.