A Mediator-Free Integrated Chemical System for Efficient Solar Energy Conversion Using Thylakoid Membrane-Based Composite Film

Abstract

There are numerous attempts to mimic or directly utilize photosynthetic light reactions taking place in a thylakoid membrane to convert solar energy to electricity as they provide highly efficient electron transfer mechanisms. In this study, we develop a mediator-free integrated system in which whole thylakoid membranes are incorporated into polyaniline and reduced graphene oxide. Each component plays its own role in electron transfer from thylakoid to the electrode. Polyaniline acts like a molecular wire that has access to reaction centers from which it takes electrons, delivering them to reduced graphene oxide and eventually to the electrode. Graphene oxide needs to be electrochemically reduced due to its low electrical conductivity. Lacking any component causes smaller photocurrent than when all three components are present. System optimization between graphene oxide, polyaniline, and the number of potential cycling is made for the enhanced photocurrent. The maximum power density of 10.5 μW cm−2 with current density of 24.7 μA cm−2 under one sun illumination is achieved. The turnover frequency is calculated to be 0.3 water molecule per photosystem II per second. This result shows the possibility of using whole thylakoid membranes as a solar energy conversion unit with proper means of electron transfer.