Semi-artificial photosynthetic system based on TiO2/Chlorophyll composite and microalgae for N2 fixation.

In a TiO 2 /Chlorophyll and microalgae hybrid semi-artificial photosynthetic system, Q 0 is proved as electron relay that helps electron transmission from abiotic component to microalgae for amplifying N 2 fixation ability. Furthermore, TiO 2 /Chlorophyll is applied as anode material and microalgae is dispersed in catholyte, as for building a microbial photo-electrolysis cells that can produce 122.62 μg/h of ammonia. [Display omitted] • TiO 2 /Chlorophyll annealed at 400 °C shows visible light response catalysis. • The photogenerated electrons of the TiO 2 -400 °C are captured by Chl-400 °C. • Q 0 effectively relays photogenerated electron from Chl-400 °C to microalgae. • In the material-cell system, the activity of nitrogenase increased by 5.90 times. • The top ammonia content was up to 122.62 μg/h, determined by an ammonia assay kit. Significant process has been made on the development of semi-artificial photosynthesis catering to the production of H 2 – and CO 2 – derived value-added products. But there are little reports on the application of semi-artificial photosynthetic system to nitrogen fixation areas. In this study we report the successful and highly efficient N 2 fixation in one step at room temperature and ambient pressure by constructing new semi-artificial photosynthetic systems based on material-cell hybrids and microbial photo-electrolysis cells (MPECs). Improved TiO 2 /Chlorophyll composite that annealed at 400 °C was selected as electron donator to replenish additional electrons to Nostoc commune Vauch microalgae cell for N 2 fixation. Ubiquinone-0 (2,3-dimethoxy-5-methyl-1,4-benzoquinone, Q 0) was selected as electron relay that guarantees efficient transmission of electrons from abiotic material to microalgae cells. Determined by an ammonia assay kit, at constant concentration of microalgae, the constructed material-cell hybrid system photosynthetically synthesized 40.67 μM/h ammonia, while H-shape MPECs synthesized 132.70 μM/h, 19.23 times higher than that produced by pure microalgae. Using 15N 2 as the reduction gas, the constructed H-shape MPECs photosynthetically synthesized 28.37 μM/h 15NH 4 +, 2.80 time higher than that of the MPECs without Q 0 as electron relay. [ABSTRACT FROM AUTHOR]