High photocurrent generation by photosystem I on artificial interfaces composed of π-system-modified graphene

Photosystem I (PSI) is a key component of the oxygenic photosynthetic electron transport chain because of its light-induced charge separation and electron transfer (ET) capabilities. We report the fabrication of an efficient graphene-biohybrid light-harvesting electrode consisting of cyanobacterial trimeric PSI complexes immobilized onto π-system-modified graphene electrodes. Based on the strong interaction between conjugated aromatic compounds and the graphene material via π–π-stacking, we have designed a simple but smart platform to fabricate light-driven photoelectrochemical devices. Due to the possibility of surface property adaptation and the excellent conductivity of graphene, the modified biohybrid electrodes exhibit a well-defined photoelectrochemical response. In particular, the PSI–graphene electrode applying pyrene butyric acid NHS ester displays a very high photocurrent output of 23 μA cm−2 already at the open circuit potential which can be further increased by an overpotential and the use of an electron acceptor (methyl viologen) under air saturation up to 135 μA cm−2. Comparing the graphene–PSI biohybrid systems based on different π-system-modifiers reveals that the pyrene derivatives result in higher current outputs compared to the anthracene derivatives and that the covalent fixation during immobilization appears more efficient compared to simple adsorption. Interestingly, the pyrene-based PSI electrodes also display a nearly unidirectional photocurrent generation, establishing the feasibility of conjoining these nanomaterials as potential constructs in next-generation photovoltaic devices.