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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]

Through the chelation effect of 1,10-phenanthroline and the spatial confinement effect of polydopamine-derived nitrogen-doped hollow carbon spheres, sub-nanometer-scale copper active species were constructed, which realized the electrochemical reduction of nitrate to ammonia in a complex water environment and purified nitrate wastewater. [Display omitted] • Double confinement mechanism realizes sub-nanometer-scale copper preparation. • Ammonia yield rate and FE as high as 21413.5 μg h−1 mg cat. −1 and 92.07%, respectively. • CuCN/NHCSs can efficiently catalyze eNitRR in complex water environments. • Nitrate hazard concentration can be reduced below the limit value of WHO and US EPA. Electrochemical-nitrate-reduction-reaction (eNitRR) ammonia synthesis shows the vision of green ammonia synthesis and is also an effective way to purify nitrate wastewater. In this study, the complex of 1,10-phenanthroline and Cu2+ was adsorbed on the surface of polydopamine-derived nitrogen-doped-hollow-carbon-spheres, and sub-nanometer-scale copper species (CuCN/NHCSs) were obtained after heat treatment. Using CuCN/NHCSs as catalyst, the ammonia yield rate and Faradaic efficiency of eNitRR reached 21413.5 μg h−1 mg cat. −1 (−1.1 V vs RHE) and 91.08% (−0.9 V vs RHE), respectively. CuCN/NHCSs still have high catalytic activity for eNitRR even in complex water environments (such as acidity, alkalinity, coexisting ions). In the face of low concentration of nitrate in natural sewage, CuCN/NHCSs as a catalyst can reduce the concentration of NO 3 − to below the limits set by WHO and US EPA within 10 h, and achieve effective purification of nitrate sewage. DFT calculations show that both single-atom Cu sites and Cu atom cluster sites on NHCSs can promote the electrochemical conversion of NO 3 − to ammonia, so minimizing copper sites can maximize the unit activity. Furthermore, the simultaneous anchoring of Cu atom clusters and single-atom Cu in the carbon matrix is beneficial to lower the energy barrier of the potential-determining step of eNitRR. [ABSTRACT FROM AUTHOR]