膜状光催化剂界面电子隧穿层的构筑和作用

Membrane photocatalytic systems combined membrane separation technology and photocatalysis, making the photocatalytic reaction and separation of the products occur simultaneously. Thus, membrane photocatalytic systems become the promising approach to industrialization of photocatalysis. Separation of the photo-induced charge carriers in the membrane-like photocatalyst (MPC) and the following transfer of the charges in each interface to the co-catalysts are the prerequisites not only for processing the photocatalytic reactions, but also for the separation of the reduction and oxidization products. Because of the large contact barrier, the built-in filed hinders the transfer of photogenerated electrons at the MPC-co-catalyst of reduction, which becomes the key step influencing the photocatalytic reaction and separation of the products. In order to reduce the energy dissipation for photogenerated electrons passing through the built-in fields near the co-catalyst of reduction, here, we propose to construct the tunneling interlayer by selectively doping of the photocatalyst. The formed tunneling interlays sandwiched between photocatalyst and co-catalyst of reduction can facilitate electron transfer through the interface and reduce the energy consumption. In this project, we will selectively dope several common photocatalysts (TiO2, CdS, BiVO4) with related foreign elements to form tunneling interlayers connected to co-catalyst of reduction (CoSx, NiSx, CuS, and Pt). Combining with photo-driven hydrogen generation in water-ethanol systems; we will investigate the effect of certain factors, such as the density and distribution of electronic doping, the construction of tunneling interlayers on the energy dissipation and photocatalytic performance. Our research will provides certain fundamentally important guidelines for development of efficient membrane-like photocatalysts.

光催化膜反应体系集化学反应和膜分离功能于一体，无需依赖导电基底和外电路对光生电荷的收集和传导即可实现氧化-还原产物的分离，是一条理想的光催化实际放大运用途径。在该体系中，光生电子-空穴在膜状光催化剂（MPC）中的传输以及在各自界面上的转移不仅是光催化反应的基本前提，更是实现产物分离的必要条件。光生电子在MPC与还原助催化剂界面间的转移由于受到内建电势场的阻碍作用，成为决定体系性能的关键因素。我们在理论模拟的基础上，提出采用选择性高浓度掺杂的方式，在MPC与还原助催化剂之间构筑电子隧穿层来降低界面电子转移能耗。并采用（光）电化学方法考察隧穿层的电子掺杂浓度等因素与界面电子转移行为和能耗之间的调变关系。基于此，我们选取一些常见的光催化剂和产氢助催化剂，设计相应的MPC，考察并阐明隧穿层中电子掺杂浓度及其分布、隧穿层的构造等因素对光催化性能促进作用的机制，为高性能MPC的设计提供必要的理论依据。

半导体—金属界面电子转移是光催化反应的速率控制步骤。本项目通过理论模拟与实验相结合的方式，提出在半导体表面构筑超薄的电子媒介层，将界面电子转移由高能耗的热电子发射与势阱态辅助的电荷复合相并联的方式转变为低能耗的电子隧穿，促进光生电荷的空间分离，提高入射光子的利用效率。本项目提出的，通过半导体表面电子态调控促进以势阱态辅助电荷复合为主导的界面电子转移的同时，还能好抑制半导体中光生电子的泄露。此外，本项目还提出通过能带调控，在降低界面电子转移能耗的同时，为助催化剂的广泛选择提供了重要的理论支撑。在本项目的研究过程中，我们提出了基于开路电位衰减的理论和技术，提出了运用于光催化剂中半导体—金属界面电子转移时间常数测试的双通道开路电位衰减法。该方法不仅明确了半导体—金属界面电子转移高达亚秒—秒级别的时间尺度比目前普遍报道的值大6-12个数量级，也意味着比光催化反应中其他反应步骤慢100倍以上；同时也为该领域提供了一种可靠的测试方法，为光催化领域认识这一速率控制步骤提供了有力依据。本项目提出的方案可以将直接太阳光催化的光子利用效率提高~60倍。本项目关于界面电子转移及其能耗的研究，在光催化领域属于罕见；其能耗的降低方案不仅可以为高性能光催化剂的设计提供很好的理论支撑，同时也可以为金属—半导体接触广泛应用的电子工业，如半导体元器件的设计提供必要界面电子转移理论基础。