【摘要】 光催化产生太阳燃料因其低成本和零碳排放而成为解决能源危机的研究热点,但光激发载流子对的快速体相复合是需要解决的根本问题.本文在钛酸锶（SrTiO₃）纳米纤维上嵌入磷化钴（CoP）和碳化钼（Mo₂C）构筑了双助催化剂体系.与纯SrTiO₃纳米纤维和二元样品相比,双助催化剂体系显著提高了析氢和二氧化碳还原性能.双助催化剂体系有利于有效促进空间电荷分离并提高光催化性能.此外, SrTiO₃与助催化剂之间形成肖特基结,使光激发电子从SrTiO₃快速转移到助催化剂,实现了光激发电子的有效分离并延长了光激发电子寿命.通过原位辐照X射线光电子能谱测试（ISI-XPS）确定了SrTiO₃和助催化剂之间的电子转移路线,根据紫外-可见漫反射光谱（UV-VisDRS）和紫外光电子能谱（UPS）提出了SrTiO₃和助催化剂的能带结构.结果表明,双助催化剂促进了电荷分离并增强了光催化性能.扫描电镜、透射电镜、高分辨透射电镜及其对应的元素分布结果表明,成功构筑了双助催化剂体系,且助催化剂的引入未影响SrTiO₃纳米纤维的结构.SrTiO₃纯样品表现出较低的光催化产氢活性,引入Co P后产氢性能得到提升并在Co P负载量为6%时达到最高.电化学测试、光致发光测试和瞬态光电压测试表明,引入Co P后的复合样品电化学性能得到提升,表现出更及时的电荷分离、更低的起始电位、更低的载流子复合率以及更长的载流子寿命.进一步在SrTiO₃纳米纤维上嵌入CoP和Mo₂C,构筑双助催化剂体系,其光催化产氢活性显著提升.同时,得益于SrTiO₃独特的能带位置,该双催化剂体系也表现出良好的二氧化碳还原性能.采用ISI-XPS, UPS, UV-VisDRS等研究了双助催化剂的催化机理以及电子转移路径.UPS和UV-VisDRS结果表明, SrTiO₃具有较高的功函数, Co P的功函数较低, Mo₂C的功函数位于SrTiO₃和Co P之间,因此电子倾向于从SrTiO₃的导带流向Mo2C再流向CoP,同时形成肖特基势垒使得电子难以流回SrTiO₃,从而实现载流子的及时分离以及延长电子寿命.此外, ISI-XPS的结合能大小变化表明,电子是从SrTiO₃流到Mo2C再流向Co P.综上,本文制备了双助催化剂修饰的SrTiO₃纳米纤维,证明了Co P和Mo2C在改性宽带隙半导体中的作用,并证实了SrTiO₃和助催化剂之间光激发载流子的有效空间分离,探索了光激发电子在双助催化剂体系间的流向,为后续研究提供了理论依据和探索思路.更多还原

【Abstract】 Photocatalytic solar fuel generation is currently a hot topic because of its potential for solving the energy crisis owing to its low cost and zero-carbon emissions. However, the rapid bulk recombination of photoexcited carrier pairs is a fundamental disadvantage. To resolve this problem, we synthesized a dual cocatalysts system of cobalt phosphide（Co P） and molybdenum carbide（Mo₂C）embedded on strontium titanate（Sr TiO₃） nanofibers. Compared with those of pristine SrTiO₃ and binary samples, the dual cocatalysts system（denoted SCM） showed a significant improvement in the hydrogen evolution and CO₂ reduction performance. Further, the structure of SCM effectively promoted spatial charge separation and enhanced the photocatalytic performance. In addition, the Schottky junction formed between the SrTiO₃ and cocatalysts enabled the rapid transfer of photoexcited electrons from SrTiO₃ to the cocatalysts, resulting in effective separation and prolonged photoexcited electron lifetimes. The electron migration route between SrTiO₃ and the cocatalysts was determined by in situ irradiation X-ray spectroscopy, and band structures of Sr TiO₃ and the cocatalysts are proposed based on results obtained from UV-vis diffraction reflection spectroscopy and ultraviolet photoelectron spectroscopy measurements. On the basis of our results, the dual cocatalysts unambiguously boosts charge separation and enhances photocatalytic performance. In summary, we have investigated the flux of photoexcited electrons in a dual cocatalysts system and provided a theoretical basis and ideas for subsequent research.更多还原