To enhance nitrogen photofixation more effectively, Fe-doped TiO2 nanoparticles with highly exposed (101) facets were prepared successfully by two-step hydrothermal method. The quantum yield of nitrogen photofixation in the presence of ethanol as scavenger can be significantly enhanced to 18.27×10-2m-2 which is 3.84 times higher than pristine TiO2. The electrochemical properties of the photocatalyst reveal that the improvement of photocatalytic activity can be attributed to the enhancement of charge carrier's concentration and photocurrent density by the optimal doping of Fe3+. The electron spin-resonance spectroscopy demonstrates the generation of active radicals such as O2- and OH in the nitrogen photofixation. The quantum yields of nitrogen photofixation depend on the partial pressure of nitrogen in the reaction. A systematic experimental investigation companying with periodic density functional theory calculation into the intermediates reveals the intrinsic electron transfer pathways and the mechanism of nitrogen photofixation. The entire reduction process of 1molN2 to 2mol NH3 with consumption of 6mol electrons on TiO2 is similar to the traditional biological nitrogen fixation process. The proposed electron transfer mechanism may be useful to other applications, which use semiconductor materials as photocatalysts.
Bibliographical noteFunding Information:
This work has been partially supported by National Nature Science Foundation of China (Grant Nos. 51178412 and 51278456 ), and Zhejiang Provincial Education Department Scientific Research Projects (Grant No. Z201122663 ).
- Density functional theory
- Electrochemical impedance spectroscopy
- Electron transfer
- Photocatalytic reduction
- Titanate nanotube