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

https://doi.org/10.1016/j.cej.2023.146179

Significant process has been made on the development of semi-artificial photosynthesis catering to the production of H₂– and CO₂– 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 N₂ 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 TiO₂/Chlorophyll composite that annealed at 400 °C was selected as electron donator to replenish additional electrons to Nostoc commune Vauch microalgae cell for N₂ fixation. Ubiquinone-0 (2,3-dimethoxy-5-methyl-1,4-benzoquinone, Q₀) 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 ¹⁵N₂ as the reduction gas, the constructed H-shape MPECs photosynthetically synthesized 28.37 μM/h ¹⁵NH₄⁺, 2.80 time higher than that of the MPECs without Q₀ as electron relay.Significant process has been made on the development of semi-artificial photosynthesis catering to the production of H₂– and CO₂– 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 N₂ 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 TiO₂/Chlorophyll composite that annealed at 400 °C was selected as electron donator to replenish additional electrons to Nostoc commune Vauch microalgae cell for N₂ fixation. Ubiquinone-0 (2,3-dimethoxy-5-methyl-1,4-benzoquinone, Q₀) 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 ¹⁵N₂ as the reduction gas, the constructed H-shape MPECs photosynthetically synthesized 28.37 μM/h ¹⁵NH₄⁺, 2.80 time higher than that of the MPECs without Q₀ as electron relay.