The influence of surface composition of carbon nanotubes on the photobioelectrochemical activity of thylakoid bioanodes mediated by osmium-complex modified redox polymer

A combination of photosynthetic biocatalysts with high surface area conductive materials mediated by an osmium-complex modified redox polymer (OsRP) holds promising features for the development of sustainable "green" systems for solar energy conversion. In this work we performed a comparative study of two types of carbon nanotubes (CNTs) synthesized by pyrolysis of polymeric precursors. Both CNTs were of similar morphology, but had a different surface C/O ratio. The CNTs were utilized as a support for immobilization of thylakoid membranes, electrochemically wired through the OsRP. The photobioanodes based on the CNTs with a higher C/O ratio exhibit a higher maximum photocurrent density of 97.1 ± 8.3 μA cm⁻² at a light intensity of 400 W m⁻² with reduced charge transfer resistance, but had lower operational stability. Our results demonstrate the significance of investigating of electrochemical communication between the photosynthetic component, the redox mediator and the support nanomaterial and may offer new opportunities for designing and optimization of mediated bioelectrochemical systems.