Doping Modification Of Metal Oxide Semiconductor And Its N₂ Photofixiation Performance

The traditional ammonia synthesis industry needs to be revolved due to its high pollution and energy consumption,and the current urgencies of mitigating climate change and energy shortage have promoted us to seek more efficient approach to the ammonia synthesis under mild conditions.Herein,the metal ion doping modification strategy was used to metal oxide semiconductors for improvng the N₂ photofixation profermance.The main conclusions are summarized as follows:?1?By using Sr?NO₃?₂,Ti?OC₄H₉?₄ and Fe?NO₃?₃ as raw materials,a series of Fe-doped SrTiO₃ nanomaterials(Fe_xSr_1-xTiO₃)were synthesized via a hydrothermal process.It was found that the Fe_xSr_1-xTiO₃ products with x>0.10 will transform into composites containing Fe-doped SrTiO₃ and?-Fe₂O₃ nanocrystals,which would act as charge recombination sites,and thus causes a decreased N₂ photofixation activity.Also,the Fe-doped sites can not only chemisorb and activate the N₂ molecules,but also promote the charge separation efficiency,and thus significantly improve the N₂ photofixation ability.The highest N₂ photofixation activity with an average NH₃ production activity is 30.1?mol g^-1 h^-1,which is 3.2 times higher than that of the single SrTiO₃.The present results provide new insights into the significance of Fe-doping strategy for efficiently promoting the N₂ photofixation ability.?2?A series of Mn-doped sea-urchin-like monoclinic W₁₈O₄₉ mictrospheres were synthesized via a facile solvothermal process.It was found that the Mn²⁺ions in the monoclinic W₁₈O₄₉ intervene the formation of microsphere-like morphology of W₁₈O₄₉,but it does not change the growth orientation of nanorods and the multilevelled structure,which lead to the decrease of specific surface area.Moreover,it is firstly found that Mn²⁺-doped sites in W₁₈O₄₉can not only act as chemisorption and activation centers of N₂ and H₂O molecules,but also facilitate the photoinduced charge separation and migration in Mn-W₁₈O₄₉,and thus cause an efficiently enhanced N₂ photofixation ability under full spectrum or visible light irradiation.The highest NH₃ production activity is 97.9?mol g^-1 h^-1 under full spectrum irradiation,which is 2.3 times higher than that of the single W₁₈O₄₉.The present results pave new way to the design and synthesis of high-performance,easily available materials for N₂ photofixation.