沥青路面g-C3N4基光催化复合材料制备及可见光催化降解氮氧化物性能研究

Aiming at the serious problem of air pollution caused by automobile exhaust emission, a kind of C3N4 based visible-light photocatalytic material is prepared and used on asphalt pavement to achieve the effective degradation of tail gas pollutants. Firstly, g-C3N4 photocatalytic materials are prepared and then complexed by the nano TiO2 materials to improve the photocatalytic activity. Molecular simulation software is used for modeling the molecular structure of compound light catalyst. The compound modification mechanism of photocatalyst is studied by the calculation and analysis of the energy band structure and the electron density of the catalyst and the simulation of reaction process. Secondly, the photocatalytic composite is compound to emulsified asphalt in form of dispersion liquid. The microporous structure will be formed after the demulsification of emulsified asphalt, which could increase the contact area between photocatalytic materials and pollution gas, visible light, so as to improve the efficiency of photocatalytic degradation. At the same time, the compatibility and molecular interaction between g-C3N4/TiO2 and asphalt materials are analyzed by means of microscopic characterization and the influence of the performance of the two is also studied. using the mixed material design method of the common micro surfacing to form asphalt mixture specimens where the light catalytic emulsified asphalt is used as binder, and then the degradation effect of nitrogen oxides in the tail gas is evaluated. Finally, a test road is paved and its degradation effect and durability is evaluated .

针对汽车尾气排放导致大气污染愈发严重的问题，项目拟开发一种石墨相氮化物（g-C3N4）可见光催化材料并应用于沥青路面，以实现对尾气污染物的有效降解。首先研制g-C3N4光催化材料，与纳米TiO2进行半导体复合以提高光催化活性。利用分子模拟软件对复合光催化剂分子结构进行建模，通过对催化剂晶体能带结构、电子密度计算分析和反应过程的模拟，研究光催化剂半导体复合改性机理。其次以分散液形式将复合半导体与乳化沥青共混，通过乳化沥青破乳后形成的微孔结构，增大光催化材料与污染气体、可见光的接触面积，提高光催化降解效率，同时通过微观表征手段分析g-C3N4/TiO2与沥青材料的相容性及分子间作用，研究两者间的性能影响。采用普通微表处混合料设计方法，以光催化乳化沥青为粘结料成型混合料试件，评价其对尾气中氮氧化物(NOx)的降解效果。最后进行光催化路面试铺，跟踪评测评价其降解效果及耐久性。

以纳米二氧化钛（TiO2）为典型代表的光催化剂被广泛用于环境治理领域，但是TiO2较大的禁带宽度及低量子利用率等问题影响了其使用效果。项目选择g-C3N4和TiO2复合，以期拓宽TiO2的可见光响应范围和提高它的光催化活性，采用分子模拟技术和材料表征手段从原子和微观尺度探究g-C3N4/TiO2的光催化活性增强机制。选取具有较多孔系结构的碎石封层作为载体制备光催化降解试件，探索g-C3N4/TiO2光催化材料在沥青路面上对NO的降解效果。. 首先以三聚氰胺和锐钛矿型商用TiO2为原材料，采用超声辅助高温一步固相法合成g-C3N4/TiO2复合光催化剂，以NO为目标污染物，其降解效率为评价指标，研究质量配比、煅烧温度和时间对样品光催化活性的影响。结果表明，NO降解效率均呈先快速上升后缓慢下降直至平缓的趋势。利用微观表征手段研究了复合样品和单体材料的结构和光学性质。发现g-C3N4和TiO2的晶相结构在合成过程中并未受到破坏，但TiO2的结晶度降低；g-C3N4的存在改善了TiO2的团聚现象，引入的N-Ti配位键使复合物中TiO2的电子结构发生改变，窄化了禁带宽度，扩宽了可见光响应范围。. 其次基于第一性原理计算了g-C3N4/TiO2纳米异质结的电子结构。结果表明，g-C3N4(001)/TiO2(001)异质结为间接带隙半导体；异质结的形成造成了电子大面积的弥散分布，复合体系比单体材料更趋于稳定；界面相互作用使得电子从g-C3N4(001)转移到TiO2(001)表面，而空穴留在g-C3N4(001)表面，该过程在界面间形成一个内极化电场，有利于抑制光生电子和空穴的复合，延长光生载流子寿命，从而增强光催化活性。. 最后选择单层碎石封层作为载体，设计g-C3N4/TiO2的三种添加方式和5种掺量，研究不同添加方式和掺量对NO降解效率的影响。分析表明，g-C3N4/TiO2材料用于单层碎石封层的最佳方案为：采用在沥青表面撒布光催化材料的方法成型试件，光催化剂用量占沥青质量的4%（92g/m2）。对不同掺量下试件的集料脱落率进行评价，发现随着掺量增加，集料脱落率逐渐增大，当掺量为4%时集料脱落率为22.66%，与目前对碎石封层集料脱落率的研究相比，满足路用性能要求。