Research On The Resource Recovery Of Nitrogen-containing Pollutants Driven By Solar Energ

Nitrogen pollution is a major environmental problem in the 21st century.With the continuous growth of global population and per capita food demand,nitrogen production and consumption are increasing,which intensifies the scale of the global nitrogen cycle and leads to increasingly serious global nitrogen emissions.Nitrogen pollution in the environment causes more serious consequences than carbon emissions.It contributes to global warming,affects human health,biodiversity and ozone levels,and ultimately changes the pattern of the natural nitrogen cycle and breaks the environmental nitrogen balance.Meanwhile,the continuous increasing of nitrogen consumption exacerbates the current global energy crisis and resource depletion predicament,and overcoming the negative environmental effects brought by nitrogen pollution,reducing the cost of nitrogen cycling,and accelerating the resource utilization process of nitrogen pollutants are of great significance for alleviating the pressure on global energy and environment.Therefore,this paper aims to construct a reasonable transformation path of green,environmentally friendly and energy saving nitrogen pollutants to energy,focusing on the increasingly serious nitrogen pollution in water and air,develop a photo（electro）catalytic nitrogen pollutants resource utilization system based on solar energy,and rationally design the corresponding photoactive semiconductor materials for urea and nitric oxide resource utilization.The strategies to enhance the resource utilization of nitrogen-containing pollutants were proposed.The main content of this paper is divided into the following four parts:（1）A novel semiconductor/co-catalyst photoanode,Ni₂P cluster-sensitized Ti O₂nanotube array（Ni₂P/Ti O-NTAs）,has been developed for efficient photoelectrocatalytic urea oxidation reaction（PEC-UOR）and simultaneous energy production hydrogen or electricity.Compared with the traditional Ni（OH）₂ cocatalyst,Ni₂P as a cocatalyst showed higher conductivity,and PO₄^3-generated on the surface of Ni₂P promoted the proto-coupled electron transfer process,and accelerated the in-situ formation of Ni³⁺.Meanwhile,one-dimensional nanotubes not only accelerated the enrichment of urea molecules,but also inhibited the adsorption of CO₂ gas and avoided catalyst poisoning.The theoretical mechanism study confirms that Ni₂P/Ti O₂-NTAs significantly reduced the energy barrier of N-H bond dehydrogenation.More importantly,the strong charge transfer pathway between Ni₂P and Ti O₂ interface enhanced the separation of photogenerated electron-hole pairs and the transfer of photogenerated electrons from Ni₂P to Ti O₂,which promotes the simultaneous production of clean energy.（2）In order to further enhance the photoelectrocatalytic oxidation performance of urea,through increasingthe utilization of sunlight for photoactive semiconductors and reducing the energy loss at the interface between semiconductor and co-catalyst in semiconductor/co-catalyst photoanode,we developed a series of La-Ni-based Ruddlesden-Popper phase perovskite materials(La_n+1Ni_nO_3n+1,n=1,2 and 3)for photoelectrocatalytic oxidation of urea and co-production of hydrogen.By adjusting the n value,the band gap of La_n+1Ni_nO_3n+1 catalysts were reduced,and the spectrum absorption range was successfully extended to the near infrared region（λ≥800 nm）.La-Ni-based perovskites were used as photocollection semiconductor and co-catalyst for the urea oxidation,which avoids the existence of interface barrier between semiconductor and co-catalyst,accelerates the separation and transport of electrons and holes,facilitates the diffusion and adsorption of urea molecules on the photoanode surface,and realizes the high efficiency urea oxidation simultaneous hydrogen production for round-the-clock.（3）Based on the current problems of photocatalytic NO oxidation technology,such as low solar energy utilization,easily electron-hole recombination,poor oxidation capacity,and weak adsorption or activation capacity of reactants,we developed g-C₃N₄/Ti O₂ heterojunction functional foam as NO gas purification filter.Under the irradiation of visible light（λ≥400 nm）,the removal rate of NO gas with low concentration was high and the stability was good.The NO gas purification filter composed of g-C₃N₄ and Ti O₂ quantum dots has good adsorption and activation ability of NO,and can provide a large surface area and continuous pores for capturing and oxidizing NO molecules.The result shows that the g-C₃N₄/Ti O₂ quantum dot heterojunction embedded in the foam skeleton reduced the photogenerated carrier recombination efficiency,and it was found that g-C₃N₄/Ti O₂ heterojunction functional foam could effectively inhibit the production of toxic by-product NO₂ and promote the generation of nitrate.（4）Photocatalytic oxidation of NO to nitric acid still bring secondary hazards to the environments.The use of photocatalytic reduction technology to transform NO into ammonia which can be further used is expected to solve this problem.Using Cu₂O as photocatalyst,the reduction activity and selectivity of NO molecule on different crystal surfaces of Cu₂O were investigated experimentally and theoretically.The results show that Cu₂O{100}crystal surface can reduce NO to NH₃ by a direct dissociative pathway.The Cu₂O{111}crystal surface spontaneously reduces NO to NH₃ by an associative dital-N pathway.Thermodynamically,Cu₂O{111}face is more conducive to the reduction of NO to NH₃,but the product selectivity is lower than that on Cu₂O{100}face due to the relatively lower energy barrier of byproducts.Finally,according to the experimental and theoretical results,the synthesis of Cu₂O with mixed faces was guided,and the activity and selectivity of ammonia synthesis were improved,which can be attributed to the improvement of carrier separation efficiency and the synergistic effect between the two facets.