Increasing the open-circuit voltage of photoprotein-based photoelectrochemical cells by manipulation of the vacuum potential of the electrolytes

Tan, Swee Ching, Crouch, Lucy I., Mahajan, Sumeet, Jones, Michael R. and Welland, Mark E. (2012) Increasing the open-circuit voltage of photoprotein-based photoelectrochemical cells by manipulation of the vacuum potential of the electrolytes. ACS Nano, 6 (10), 9103-9109. (doi:10.1021/nn303333e).

Abstract

The innately highly efficient light-powered separation of charge that underpins natural photosynthesis can be exploited for applications in photoelectrochemistry by coupling nanoscale protein photoreaction centers to man-made electrodes. Planar photoelectrochemical cells employing purple bacterial reaction centers have been constructed that produce a direct current under continuous illumination and an alternating current in response to discontinuous illumination. The present work explored the basis of the open-circuit voltage (VOC) produced by such cells with reaction center/antenna (RC-LH1) proteins as the photovoltaic component. It was established that an up to 30-fold increase in VOC could be achieved by simple manipulation of the electrolyte connecting the protein to the counter electrode, with an approximately linear relationship being observed between the vacuum potential of the electrolyte and the resulting VOC. We conclude that the VOC of such a cell is dependent on the potential difference between the electrolyte and the photo-oxidized bacteriochlorophylls in the reaction center. The steady-state short-circuit current (JSC) obtained under continuous illumination also varied with different electrolytes by a factor of 6-fold. The findings demonstrate a simple way to boost the voltage output of such protein-based cells into the hundreds of millivolts range typical of dye-sensitized and polymer-blend solar cells, while maintaining or improving the JSC. Possible strategies for further increasing the VOC of such protein-based photoelectrochemical cells through protein engineering are discussed

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Contributors

Author: Sumeet Mahajan

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