甘油供电子太阳光催化固氮为高效叶面肥体系构建及其电子转移机制

Recently, with the rapidly increased production of biodiesel, there are a large amount of glycerol wastewater (byproducts) generated, which are difficult to be disposed and utilized. The high efficient and environmental friendly foliar fertilizer has broad demand in agriculture field. As a result, the project team tries to construct a novel system of solar photocatalytic nitrogen fixation for efficient foliar fertilizer with glycerol as electron donor, based on previously firm foundation of photocatalytic nitrogen fixation research. The ultimate goal of this project is to achieve waste recycling and cleaning production process..In this work, much effort will be devoted to solve the problem of low utilization efficiency of solar-excited electrons and low quantum yield of nitrogen fixation in the novel system. The project team employs strategy of energy band modulation and catalyst modification to enhance the solar light absorption and accelerate electrons transfer therefore. Moreover, coupling homogeneous photocatalytic nitrogen fixation pathway with heterogeneous reaction significantly improves photocatalytic nitrogen fixation rate. Density functional theory (DFT) calculation and isotope tracer technique will be used to investigate the generation of high reducibility free radicals which is important in homogeneous nitrogen fixation pathway. Environmental and efficient nitrogen fixation photocatalysts will be selected to evaluate the effect of foliar nitrogenous fertilizer..Physical and chemical characterization methods, such as quadrupole-time of flight mass spectrometry, DFT calculations, in situ fourier infrared technique will be used to investigate the C, N elements balance, radicals formation mechanism, and pathways of nitrogen fixation. Therefore, the electron transfer mechanism of nitrogen fixation can be revealed..Consequently, this research will devote to constructing theory and technical system of solar photocatalytic nitrogen fixation for efficient and environmental foliar fertilizer with glycerol as electron donor.

针对生物柴油副产甘油废水产生量大、处理和利用困难，农业生产中高效环保叶面肥市场需求广阔的现状，申请人基于良好的光催化固氮研究基础，提出构建甘油供电子太阳光催化固氮为高效叶面肥体系，以实现废物资源化、全过程清洁化的目的。.太阳光催化固氮具有电子利用效率不高、量子产率低的问题，本申请通过催化剂能带调配与修饰改性等手段，拓展催化剂吸收光谱，加速光生电子迁移，构建太阳发激发电子空穴高效分离体系。同时辅以化学计算、同位素示踪，关注强还原自由基的生成，研究甘油在催化剂表面的非均相固氮反应路径、溶液中均相固氮反应路径，提高光催化固氮效率。筛选出环境友好、固氮高效的催化剂，评估叶面固氮效果。基于现代材料物理和化学表征手段，结合电子顺磁共振、四极杆飞行时间质谱、原位傅立叶红外等，探明体系碳、氮平衡、自由基生成及电子迁移，揭示体系的电子转移机制,构建甘油供电子太阳光催化固氮为高效、环保叶面肥技术与理论体系。

光催化固氮技术可在温和条件下实现氮元素固定，被视为潜在环境友好型氮肥生产方式。传统半导体光催化剂存在可见光响应低、光生载流子复合率高以及稳定性差等缺点，限制了光催化固氮技术的发展。为此，针对性优化固氮光催化剂，构建高效光催化还原固氮体系意义重大。.该项目将光催化固氮技术与叶面施肥方式有机耦合，通过对光催化产氢半反应界面电子能垒及电子迁移机制的探索，为光催化固氮反应奠定理论基础；通过筛选匹配光催化固氮需求的催化剂能带结构及电子传递途径，构建原位光催化固氮体系；结合多元醇牺牲剂捕集空穴，构建高效叶面氮肥体系。制备出O-g-C3N4、Cu/TiO2、Cu、C/ZnO等多种高效固氮光催化剂，总结出催化剂界面电子转移路径及固氮反应机理，形成了光催化叶面氮肥评价体系。.课题采用微波水热法、煅烧法等制备出Cu/TiO2（负载）、Cu、C/ZnO（负载）、O-g-C3N4催化剂（掺杂）等环境友好型高效固氮光催化剂，通过表面负载金属、非金属元素以及掺杂等方式，利用界面电荷转移机制加快光生电子空穴对分离，拓展电子转移路径，降低表面反应能垒，实现电子蓄积，从而提高电流密度，提高光催化固氮速率。对于Cu/TiO2，Cu/TiO2(1.0wt%)的光催化固氮效率最高，达到6.78 mmol·g-1·h-1，是原始TiO2（1.13 mmol·g-1·h-1）催化剂的6.00倍。对于Cu、C/ZnO，当Cu负载量为3.0wt%时，所得催化剂的产氨效率最优为4.96 mmol·g-1·h-1，为原始ZnO催化剂(0.61 mmol·g-1·h-1)的8.13倍。对于O-g-C3N4，当过氧化氢溶液浓度为10%时，制备所得OCN-10的产氨效率最高(3.98 mmol·g-1·h-1)，为原始g-C3N4 (0.64 mmol·g-1·h-1)的6.24倍。.课题在制备高效固氮光催化剂基础上，结合易降解小分子有机醇类牺牲剂构建环保型原位产氨叶面肥体系。通过太阳光下模拟叶片固氮效果实验及典型作物施用实验，证明该体系除具有缓释肥效外，还具有保水性强、安全性好等特点，高度适配干旱地区农业生产用肥需求。本叶面肥体系尤其适用于非食叶型农作物、景观植物等，显示出良好实用价值及极高规模化、商业化应用潜力。