Vacancy engineering mediated hollow structured ZnO/ZnS S-scheme heterojunction for highly efficient photocatalytic H2 production

空位工程调控中空结构ZnO/ZnS S型异质结用于高效光催化产氢

Designing a step-scheme(S-scheme)heterojunction photocatalyst with vacancy engineering is a reliable approach to achieve highly efficient photocatalytic H_(2)production activity.Herein,a hollow ZnO/ZnS S-scheme heterojunction with O and Zn vacancies(VO,Zn-ZnO/ZnS)is rationally constructed via ion-exchange and calcination treatments.In such a photocatalytic system,the hollow structure combined with the introduction of dual vacancies endows the adequate light absorption.Moreover,the O and Zn vacancies serve as the trapping sites for photo-induced electrons and holes,respectively,which are beneficial for promoting the photo-induced carrier separation.Meanwhile,the S-scheme charge transfer mechanism can not only improve the separation and transfer efficiencies of photo-induced carrier but also retain the strong redox capacity.As expected,the optimized VO,Zn-ZnO/ZnS heterojunction exhibits a superior photocatalytic H_(2)production rate of 160.91 mmol g^(-1)h^(-1),approximately 643.6 times and 214.5 times with respect to that obtained on pure ZnO and ZnS,respectively.Simultaneously,the experimental results and density functional theory calculations disclose that the photo-induced carrier transfer pathway follows the S-scheme heterojunction mechanism and the introduction of O and Zn vacancies reduces the surface reaction barrier.This work provides an innovative strategy of vacancy engineering in S-scheme heterojunction for solar-to-fuel energy conversion.

利用太阳能驱动半导体光催化分解水产氢是应对能源短缺和环境污染的有效解决方案之一.ZnO因其成本低、化学稳定性良好和环境友好等优点,在光催化领域备受关注.然而,单一ZnO存在光生载流子易复合和光吸收范围窄的本征缺陷,严重阻碍了其进一步应用.针对这些问题,通过形貌调制、空位引入、S型异质结的构建等策略,可实现光生载流子的有效分离和转移,拓宽光吸收范围,同时保留光催化反应中电子和空穴的强氧化还原能力,从而有效增强光催化性能.本文以溶剂热法合成的中空结构ZnO为基底,通过离子交换和煅烧处理方法制备了具有氧和锌双空位的中空ZnO/ZnS S型异质结光催化剂(V_(O,Zn)-ZnO/ZnS).X射线粉末衍射、拉曼光谱、扫描电镜、透射电镜以及非原位X射线光电子能谱等表征证实了V_(O,Zn)-ZnO/ZnS异质结光催化剂的成功制备.电子顺磁共振光谱测试结果表明,ZnO/ZnS异质结中存在氧和锌双空位.紫外-可见漫反射结果表明,空心结构、双空位的引入以及异质结的构建明显提高了太阳光的利用率.结合莫特-肖特基曲线、X射线光电子能价带谱和紫外光电子能谱等表征结果,确定了ZnO和ZnS的能带结构和费米能级位置.利用光电性能、接触角和表观活化能等分析了V_(O,Zn)-ZnO/ZnS异质结光催化产氢性能提升的原因.密度泛函理论计算、原位X射线光电子能谱和电子自旋共振光谱验证了该异质结的电荷转移路径遵从S型机制.在模拟太阳光照射下,最佳配比的V_(O.)_(Zn)-ZnO/ZnS异质结的最大光催化产氢速率为160.91 mmol g^(-1)h^(-1),分别约为纯ZnO和ZnS的643.6倍和214.5倍.此外,为了提高光催化剂的可回收性和可重复利用性,构建了V_(O,Zn)-ZnO/ZnS异质结水凝胶,仍保持较好的光催化产氢活性.综上所述,在此光催化体系中,空心结构和空位的引入提高了太阳光的利用率.此外,氧和锌空位分别作为光生电子和空穴的捕获位点,有利,于促进光生载流子的分离.同时,S型电荷转移机制不仅提高了光生载流子的分离和转移效率,而且还保持了其强的氧化还原能力.本研究利用空位工程为构建高效S型异质结用于光催化分解水产氢提供了一种新思路.