摘要
燃煤电厂排放的烟气中含有大量氮氧化物(NO_(x)),太阳能驱动的光催化技术为烟气脱硝提供了近零排放的新途径,但单一光催化脱硝效率有限,为实现燃煤烟气中高浓度NO的有效脱除,亟需开发基于光催化的协同氧化脱硝技术。采用水热法并结合氢气还原处理制备了富含氧空位的TiO_(2)纳米片(Defective TiO_(2),D-TiO_(2))后,利用液相浸渍法将铜氧化物(CuO_(x))负载至D-TiO_(2)表面,制得复合样品CuO_(x)/D-TiO_(2)。利用透射电镜(TEM)、X-射线光电子能谱(XPS)、室温电子顺磁共振(EPR)及紫外-可见漫反射光谱等表征技术对复合催化剂的微观组成和能带结构进行测定分析,结果表明,负载的铜物种为混合价态CuO_(x),CuO_(x)改性未影响D-TiO_(2)的微观形貌,但可使D-TiO_(2)的导带电势负移,增强光生电子的还原能力。以CuO_(x)/D-TiO_(2)作为活化H_(2)O_(2)的催化剂,在模拟太阳光照射下考察CuO_(x)负载量对NO脱除率的影响,并以性能最佳的5%CuO_(x)/D-TiO_(2)为光催化剂,研究模拟烟气流速和NO初始体积分数对脱硝活性的影响。基于密度泛函理论的DFT计算结果表明,氧空位有利于NO吸附与活化,光电化学和EPR测试结果表明,复合CuO_(x)不仅增强了D-TiO_(2)的光生电荷分离效率,同时CuO_(x)作为H_(2)O_(2)分解产生·OH的活性位点,起到了助催化剂的关键作用。自由基猝灭实验结果表明,表面·OH是NO光氧化脱除的主要活性自由基,助催化剂CuO_(x)和氧空位的协同作用使NO脱除率由TiO_(2)的15.1%提升至5%CuO_(x)/D-TiO_(2)的63.8%。同时,将5%CuO_(x)/D-TiO_(2)固载至改性碳纤维(MCF)表面构筑了整体式催化剂CuO_(x)/D-TiO_(2)/MCF,MCF载体的光热效应可将吸收的近红外光转化为热,使CuO_(x)/D-TiO_(2)表面产生局部温升,有效加速光电子界面传输与H_(2)O_(2)分解反应动力学,进一步提升NO脱除率达95.2%。此外,NO光氧化脱除的主要产物是可用于生产氮肥的NO_(3)^(-),�
Flue gas emitted by coal-fired power plants contains a large amount of nitrogen oxides(NO_(x)).Solar energy driven photocatalysis technology provides a novel approach of near-zero emission for flue gas denitrification,however the efficiency of single photocatalytic denitrification is limited.To achieve efficient removal of high concentration NO from coal flue gas,the development of a collaborative oxidation denitrification technology based on photocatalysis is urgently required.Defective TiO_(2)(D-TiO_(2))nanosheets with rich oxygen vacancies were first prepared by the hydrothermal method combined with H_(2)reduction treatment,and then CuO_(x)was loaded onto D-TiO_(2)surface via the liquid phase impregnation approach to synthesize CuO_(x)/D-TiO_(2)nanocomposites.Microscopic composition and energy-band structure of composite catalysts were determined by the transmission electron microscopy(TEM),X-ray photoelectron spectroscopy(XPS),room temperature electron paramagnetic resonance(EPR)and UV-visible diffuse reflection spectroscopy.The results showed that the supported copper species was mixed valence CuO_(x),and the modification of CuO_(x)did not affect the micro-morpho-logy of D-TiO_(2),but enabled its conduction-band potential negative shift,consequently enhancing the reduction ability of photogenerated electrons.CuO_(x)/D-TiO_(2)composites were served as the catalysts to activate H_(2)O_(2),and the effect of CuO_(x)loading amount on NO removal rate was studied under simulated solar light irradiation.By using the optimal 5%CuO_(x)/DTiO_(2)catalyst,the influences of simulated flue gas velocity and initial NO concentration on denitrification activity were in-vestigated.DFT calculation results based on the density functional theory indicated that oxygen vacancies were conduct-ive to NO adsorption and activation.Photoelectrochemical characterization and EPR test results displayed that incorporat-ing CuO_(x)not only promoted the charge separation efficiency of D-TiO_(2),and also played a crucial cocatalyst role as the
作者
杨娟
冷冲冲
张鸽
单启月
丰之翔
YANG Juan;LENG Chongchong;ZHANG Ge;SHAN Qiyue;FENG Zhixiang(School of Safety Science and Engineering,Henan Polytechnic University,Jiaozuo454000,China;State Collaborative Innovation Center of Coal Work Safety and Clean-efficiency Utilization,Jiaozuo454000,China)
出处
《煤炭学报》
EI
CAS
CSCD
北大核心
2024年第4期2099-2114,共16页
Journal of China Coal Society
基金
国家自然科学基金资助项目(52074103,U2004194)
河南省科技攻关重点资助项目(222102320095)。
