金属/四元硫族半导体异质纳米晶的水相可控合成与光催化分解水性能研究

Photocatalytic H2 evolution from water splitting is one of the most promising protocols for addressing current world-wide energy and environmental issues. In this project, we aim to establish a novel method for aqueous controllable synthesis of metal (Au, Ag)/quaternary chalcogenide semiconductor (I2-II-IV-VI4) hybrid nanocrystals (abbreviated as HNCs), and investigate their enormous potential in creation of green and efficient catalysts toward photocatalytic H2 evolution. In specific, on the basis of the aqueous cation exchange-enabled nonepitaxial growth strategy, by elaborately engineering the thermodynamics and kinetics of synthesis reaction, we will attempt to develop a method that can realize the synthesis and modulation (compositional, structural and morphological) of metal/I2-II-IV-VI4 HNCs in the aqueous environment; Detailed measurements will be performed on obtained HNCs to determine their activity, stability and quantum yield in photocatalytic H2 evolution reaction. These results will be used to verify the advantages of aqueous synthesis of metal/I2-II-IV-VI4 HNCs with regard to their applications in photocatalytic water splitting, and more importantly, to study the impacts of compositional and structural parameters of metal/I2-II-IV-VI4 HNCs on metal/semiconductor coupling and their photocatalytic performance. By combining ultrafast spectroscopy and theoretical simulation, we will further probe into the transfer dynamics of photogenerated charge and energy at the metal//I2-II-IV-VI4 interface, and the underlying mechanism for plasmon-enhanced photocatalysis over metal/I2-II-IV-VI4 HNCs. In this way, we envision that valuable information will be acquired to direct the optimization of the aqueous synthesis method, and to assist in the development of environmentally friendly photocatalysts featuring high solar spectrum utilization efficiency and high solar-to-hydrogen conversion efficiency.

光催化分解水产氢是从根本上解决能源与环境问题的一项重要途径。本项目拟在水相中建立金属/I2-II-IV-VI4四元硫族半导体异质纳米晶的合成方法，发展绿色、高效的光解水产氢催化材料：采用水相阳离子交换非外延生长原理，通过调变合成反应的热力学与动力学条件，探索金属/I2-II-IV-VI4异质纳米晶的水相合成与调控方法；测试所合成材料光解水产氢的效率与稳定性，验证水相合成体系的优势，并系统考察材料的组成、纳米结构对金属/I2-II-IV-VI4半导体耦合与光催化性能的影响规律；结合超快光谱与计算模拟深入研究光生电荷与能量在金属/I2-II-IV-VI4异质界面的转移机制，以及金属表面等离子共振增强I2-II-IV-VI4光催化活性的微观机理，为进一步优化金属/I2-II-IV-VI4异质纳米晶的水相合成方法，构建高太阳能光谱利用效率、高太阳能-化学能转化效率的环境友好型光催化剂提供指导。

多元硫族半导体作为宽光谱响应、高吸收系数、带宽可调、无毒无害的光电材料，有望替代其二元组份材料，对于发展绿色、高效的光解水制氢催化剂具有十分重要的研究意义，构建金属/多元硫族半导体异质光催化体系是提高光电催化分解水制氢性能的一个重要突破点。然而，金属与多元硫族半导体间较大的晶格失配度是制约金属/多元硫族半导体异质纳米晶合成的一大障碍。本项目首先采用阳离子交换非外延生长法合成策略，在水相中合成了Au@SnxSy核壳纳米晶，并将该方法拓展至金属/四元半导体异质纳米晶体系，在水相中制备了Au@Ag2ZnSnS4（Au@AZTS）核壳纳米晶，对其形貌、尺寸进行精确调控，并对其光电催化产氢性能及构效关系规律进行了研究。主要研究内容与研究结果如下：.1..采用水相阳离子交换非外延生长方法，利用不同磷配体与Ag+配位的反应活性差别，分别采用TBP和TOP为阳离子交换过程中的配体合成了Au@Sn2S3和Au@SnS2两种核壳纳米晶，并对二者进行了光吸收及光电响应测试。该二元体系的研究结果为合成Au@AZTS四元核壳纳米晶提供了有价值的理论指导。.2..将水相阳离子交换非外延生长方法拓展到金属/四元半导体异质纳米晶体系，在水相中合成了Au@AZTS核壳纳米晶，内核与壳层均呈现良好的结晶性，二者之间有清晰的界面，为光生载流子有效分离与传输提供了有利条件。利用阳离子交换法的独特优势，实现了Au@AZTS核壳纳米晶尺寸与形貌的精确调控及其在可见光范围内的宽光谱响应；采用Au核尺寸、形貌及AZTS壳层厚度不同的样品进行光电催化产氢性能测试，结果显示Au@AZTS（38.0±1.3/9.1±1.0 nm）具有最好的光电响应性能；以上研究结果证实通过调控异质纳米晶的尺寸、形貌调节等离子体-激子耦合效率，能够为发展具有宽太阳能光谱响应、高量子产率、对环境友好的新型光电催化分解水产氢催化材料提供一种有效途径。