六方晶型ZnIn2S4光催化材料的设计合成及其无助催化剂产氢机制研究

Co-catalysts with high price and complicated fabrication is one of the bottlenecks for the practical application of photocatalysis hydrogen evolution. Therefore, exploring photocatalysts without introducing co-catalysts, which could also exhibit high photocatalytic activity, becomes a significant subject. To date, it has been reported that hexagonal ZnIn2S4 is a suitable photocatalyst for hydrogen evolution without co-catalysts. However, its catalytic activity is relatively low, and the mechanism and procedure for such reaction are also unclear. In this project, we will firstly harness density functional theory (DFT) to identify the active sites and facets for photocatalysis hydrogen evolution reaction in hexagonal ZnIn2S4. And according to the calculation results, we will design and synthesize ZnIn2S4 samples with active facets exposed by hydrothermal method，and the sample size will also be optimized to improve the separation and migration of electron-hole pairs. By this means, the photocatalytic activity of achieved samples could be enhanced. Then the process and mechanism of photocatalysis hydrogen evolution for hexagonal ZnIn2S4 without adding co-catalysts are unveiled by investigating the separation and migration of photo-generated charge carriers in the synthesized ZnIn2S4. On the other hand, we will continue choosing appropriate transition metal atoms to substitute Zn atoms according to the DFT calculation results, which could tune the active sites in ZnIn2S4 efficiently. Thus, the photocatalytic activity of samples prepared by impregnation-calcination method could be further enhanced. The project results will push forward the developments and applications of hexagonal metal sulfides in photocatalysis field.

价格昂贵、制备工艺复杂的助催化剂是制约光催化产氢应用的瓶颈问题之一，因此探索自身具有优异产氢性能的光催化材料已成为该领域的一个重要发展方向。目前，已有利用六方晶型ZnIn2S4在无助催化剂条件下进行光催化产氢的报道，但其催化活性较低，且催化反应过程和机理尚不清楚。故本项目拟利用密度泛函理论（DFT）确定六方晶型ZnIn2S4光催化产氢的反应位点和活性晶面，设计合成具有活性晶面暴露的ZnIn2S4，并通过三维尺寸优化提高电子-空穴对的分离和迁移能力，从而增强其产氢活性。然后，研究ZnIn2S4内部光生载流子分离和迁移等科学问题，揭示其无助催化剂光催化产氢的反应过程和机理。另一方面，继续利用DFT计算筛选合适的过渡金属原子，并采用溶液浸渍-退火法制备金属原子取代锌原子的ZnIn2S4，实现产氢位点的调控，进一步提高其光催化活性。本项目的研究成果将推动六方晶型金属硫化物在光催化领域的发展和应用。

光催化分解水产氢是一种转换储存太阳能的绿色化学方法，也是解决能源短缺和环境污染问题的有效途径。本项目主要围绕六方晶型ZnIn2S4光催化材料的设计合成、产氢过程和机制展开，具体研究成果如下：（1）晶面调控提高ZnIn2S4光催化产氢活性。理论计算发现位于（110）晶面上的S原子的G_H^°仅为-0.16 eV，可作为光催化产氢的位点。我们通过加入柠檬酸钠，成功地获得了厚度仅为3-4 nm且具有更多（110）晶面暴露的ZnIn2S4纳米片。该纳米片的光催化产氢速率达到1.93 mmol g-1 h-1。（Appl. Catal. B: Environ. 2020, 265, 1186160）。（2）异原子掺杂提高ZnIn2S4光催化产氢活性。之前的计算表明ZnIn2S4（006）晶面上的S原子不具有产氢活性。但是用Ni原子取代Zn原子后，其周围S原子的G_H^°由-1.59 eV提高到了-0.25 eV。接着我们制备了Ni原子掺杂的ZnIn2S4，其产氢性能提高了3.2倍，可达4.22 mmol g-1 h-1。（J. Mater. Chem. A 2020, 8, 13376）。（3）表面凸起状Pt单原子提高ZnIn2S4光催化产氢活性。我们利用光沉积在ZnIn2S4表面制备了凸起状的Pt单原子来模拟颗粒催化剂中的棱和角。与传统的缺陷限域单原子相比，凸起状结构的单原子能够在其周围富集更多的氢气，提高传质过程。当Pt的质量分数仅为0.3%时，ZnIn2S4的光催化产氢活性能够达到17.5 mmol g-1 h-1，是纯ZnIn2S4的17.8倍。接着，我们把Pt-ZIS制备成薄膜，发现在光照下可以产生明显的气泡，证明了该光催化剂未来大规模使用的可能性。（Nat. Commun. 2022, 13, 1287, 高被引，热点论文）。此外，我们还将ZnIn2S4与其他半导体材料（如TiO2，WO3）复合，探究了其作为光阳极时的电荷迁移过程。相关论文发表在Electrochim. Acta（2020, 361, 137017），Surfaces and Interfaces （2021, 26, 101323），CrystEngComm（2021, 23, 1777）。