硫缺陷型硫化物光催化剂的制备及其可见光催化性能

发布时间：2018-03-23 17:19

本文选题：硫化物　切入点：硫缺陷　出处：《华侨大学》2016年硕士论文

【摘要】：近年来,半导体材料因在能源转化和污染治理方面具有潜在应用前景而备受瞩目。金属硫化物凭借其良好的可见光响应、适宜的能带结构、原料丰富、制备简单等优点,已成为半导体材料研究的重中之重。尽管如此,CdS、ZnIn_2S_4、CdIn_2S_4等金属硫化物仍面临着光生电子-空穴对易复合、比表面积小等关键问题,而且硫化物在光、电化学反应过程中容易光腐蚀,其活性与稳定性的提高亟待解决。本文首先以CdS为研究对象,采用NaBH4固相还原-HF表面修饰方法,在CdS中引入了硫缺陷和氟离子。利用NaBH4强还原性,使用热还原法在三元硫化物ZnIn_2S_4和CdIn_2S_4结构中成功地引入S缺陷,制备了系列硫缺陷型ZnIn_2S_4-x和CdIn_2S_(4-x),拓展了该还原法的运用范围和研究对象。利用X射线衍射(XRD)、Raman光谱、X射线光电子能谱(XPS)、物理吸附-脱附、紫外-可见漫发射光谱(UV-vis DRS)、荧光光谱(PL)和光电化学等技术对催化剂的晶体结构、表面化学状态、硫缺陷的种类及含量、比表面积、孔径分布、光吸收性能、能带结构和光生载流子的分离效率等性质进行了系统地表征和深入地分析。系统、全面地考察了催化剂可见光催化分解水制氢的性能。主要的研究内容和结果如下:(1)硫缺陷的引入降低了CdS导带底的位置,CdS的禁带宽度缩小,可见光的吸收范围增大,表面光生载流子的分离效率升高,可见光催化制氢活性明显增强,275℃条件下制得的CdS-R2性能最佳,其光催化产氢效率为4.2 mmol?h~(-1)?g~(-1),是纯CdS的3.2倍,但是该CdS-R2的光稳定性较差,反应4 h后逐渐失活;氟离子表面修饰后,CdS-R2-F3催化剂的活性稳定性显著提高,而且,氟离子的电子诱导作用有利于催化剂表面光生载流子的有效分离,进一步提高了光催化剂的性能。与CdS-R2相比,氟修饰的CdS-R2-F3的产氢效率达6.0 mmol?h~(-1)?g~(-1),反应的催化效率提高了42.9%,且反应进行了20 h后,催化剂依然保持良好的活性稳定性。(2)NaBH_4固相还原后,ZnIn_2S_4晶格中部分Zn-S键和In-S键同时断裂,产生硫缺陷态,导致ZnIn_2S_4-x的导带位置下降,催化剂的可见光利用率升高、光生载流子分离效率显著增强,ZnIn_2S_(4-x)可见光催化制氢的效率相应地提高,275℃条件下制得的ZnIn_2S_4-x性能最佳,其光催化制氢效率为13.2 mmol?h~(-1)?g~(-1),是纯ZnIn_2S_4(4.5 mmol?h~(-1)?g~(-1))的2.9倍,反应进行15h后,催化剂保持着稳定的制氢效率。(3)通过NaBH4固相还原法调控CdIn_2S_(4-x)晶相中硫缺陷的含量,同样可实现CdIn_2S_(4-x)能带结构的微调,在CdIn_2S_(4-x)结构中引入硫缺陷,增强了催化剂的可见光吸收范围和能力,提高了表面光生电子、空穴的分离效率,提高了CdIn_2S_(4-x)可见光催化性能。结果表明:CdIn_2S_(4-x)的最佳热还原温度为300℃,与纯的CdIn_2S_4相比,硫缺陷CdIn_2S_4光催化剂制备氢效率(1.1mmol·h~(-1)·g~(-1))提高了1.1倍,且反应18 h后活性仍保持稳定。
[Abstract]:In recent years, semiconductor materials have potential applications in energy conversion and pollution control has attracted attention. The metal sulfides with its good response to visible light, the band structure, suitable abundant raw materials, simple preparation and the like, has become a priority among priorities of semiconductor materials research. However, CdS, ZnIn_2S_4. CdIn_2S_4 and other metal sulfide still faces the photogenerated electron hole pairs easy recombination surface of small area of key issues, and in the light of sulfide, corrosion to light in the electrochemical reaction, the activity and stability improvement. This paper takes CdS as the research object, using NaBH4 solid phase reduction of -HF surface modification method. Sulfur defects and fluorine ion is introduced in CdS. By using NaBH4 strong reduction, using thermal reduction method successfully introduced S defects in three yuan ZnIn_2S_4 sulfide and CdIn_2S_4 structure, a series of sulfur defective preparation ZnIn_2S_4-x and CdIn_2S_ (4-x), to expand the scope of application and the research object of the reduction method. By using X ray diffraction (XRD), Raman spectra, X ray photoelectron spectroscopy (XPS), adsorption desorption, UV Vis spectra, fluorescence spectra (UV-vis DRS) (PL) crystal structure photoelectric and Chemical Technology of catalyst, surface chemical state, sulfur content and types of defects, specific surface area, pore size distribution, light absorption and separation efficiency properties of band structure and optical carriers were systematically characterized and analyzed deeply. The system, comprehensive study of the performance of the catalyst under visible light catalytic decomposition of water to hydrogen. The main research contents and results are as follows: (1) the introduction of sulfur defects reduced CdS the bottom of the conduction band position, the band gap of CdS is reduced, the visible light absorption range increases, increasing the separation efficiency of photogenerated carrier surface, visible light photocatalytic activity for hydrogen generation Enhanced 275 C prepared under the condition of optimum CdS-R2 performance, the photocatalytic hydrogen production rate was 4.2 mmol? H~ (-1)? G~ (-1), is 3.2 times that of pure CdS, but the CdS-R2 light stability is poor, 4 h reaction gradually after inactivation; fluoride ion surface modification, activity the stability of CdS-R2-F3 catalyst is significantly improved, and electron induced effects of fluoride is beneficial to effective separation of photogenerated carrier catalyst surface, to further improve the performance of photocatalysts. Compared with CdS-R2, the efficiency of hydrogen production of fluorine modified CdS-R2-F3 6 mmol? H~ (-1)? G~ (-1), catalytic reaction efficiency the increase of 42.9%, and the reaction is 20 h, the catalyst still maintain good activity stability. (2) NaBH_4 solid phase reduction, ZnIn_2S_4 lattice Zn-S In-S bond and fracture, produce sulfur defect state, leading to ZnIn_2S_4-x conduction band position rate decline, rising by visible light The high separation efficiency of photogenerated carriers significantly enhanced ZnIn_2S_ (4-x) efficiency of visible light photocatalytic hydrogen production increased 275, C prepared under the condition of optimum ZnIn_2S_4-x performance, the photocatalytic efficiency of hydrogen production was 13.2 mmol? H~ (-1)? G~ (-1), pure ZnIn_2S_4 (4.5 mmol? H~ (-1)? G~ (-1)) 2.9 times, after 15h reaction, the catalyst maintained a stable hydrogen production efficiency. (3) the regulation of CdIn_2S_ by NaBH4 solid phase reduction method (4-x) content in crystal phase sulfur defects, also can achieve CdIn_2S_ (4-x) band structure tuning in CdIn_2S_ (4-x) the introduction of sulfur the defect structure, enhance the absorption ability and range of visible light, improves the surface separation efficiency of photogenerated electrons and holes, improved CdIn_2S_ (4-x) visible light catalytic performance. The results showed that CdIn_2S_ (4-x) temperature is 300 DEG C the best thermal reduction, compared with pure CdIn_2S_4, sulfur deficient CdIn_2S_4 light catalyst for preparing hydrogen The efficiency (1.1mmol. H~ (-1). G~ (-1)) increased by 1.1 times, and the activity remained stable after the reaction of 18 h.

【学位授予单位】：华侨大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：O643.36

【相似文献】