In the paper, as published in Joule, the researchers explain how photosynthetic processes can be hijacked to drive technological advances and exposes the limits. To understand how, it is important to know that photosynthesis is the largest solar energy conversion process on Earth. While incredibly abundant, the overall efficiency of photosynthesis is quite low - roughly 1% of the energy of sunlight ends up as metabolic compounds. This is due to numerous bio-electro-chemical transformations that are required to convert and store solar energy in biomass. Capturing the energy from sunlight is also possible directly, by-passing most of the transformation steps by combining only the primary photosynthetic protein complexes with conductive synthetic materials to produce biohybrid devices.
During the research the authors found that the system was nearly 100% efficient under low light conditions, with every absorbed photon turned into electrical energy. Such low light conditions are reminiscent of the protein’s natural habitat, for which they were evolved by nature to operate in efficiently. However, under high-light operating conditions many losses resulted in the efficiency to drop by over 90%. This is comparable with water flowing through a pipe that springs leaks under pressure, whereby the water is representative of electrons and the pressure is the light intensity. The authors uncovered the origin and magnitude of these leaks, devised a method to detect them, and proposed ways to patch them up.
Efficiency and strategies
To conduct the research, the authors triggered and studied photosynthesis outside a biological cell within a model device using combined detection tools. Within the combined detection tool illumination of this biohybrid electrode drives reduction of a strongly reducing cofactor, triggering electrical current flow. This flow between the electrodes was measured using electrochemistry. Crucially, simultaneous measurements using spectroscopy enabled the researchers to discern electron flow at the level of the protein, a more granular view which added a range of information.
The results are important for the biohybrid community to understand where losses in efficiency are occurring and discern strategies to fix them. The research will be important to enable the construction of more efficient bio solar cells, more sensitive biosensors, and more productive biofuel cells that drive a sustainable economy drive by natural photosynthetic proteins. Importantly, the combined detection method can be easily applied for a range of novel biohybrid devices, which will allow a transition from trial-and-error to a learned approach for their improvement.
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Image: Vincent Friebe