氧空位对M//M'Ox型复合半导体异质界面结构及光催化作用机制的调控作用

Design and development of photocatalysts with excellent performances are a bottleneck problem urgent need to be resolved at present for photocatalysis science field. Based on the strategy of heterojunction, we suggest a novel idea to construct active interface structure and increase photocatalytic efficiency by modifying the heterojunction interface state via changing composition of surface structure of two pure components with nanocrystallization, forming cluster, creating oxygen vacancies and lattice defect, location doping of surface atoms, etc. The precious metal M (such as Pd, Pt, and Au etc.) modified metal oxide semiconductors M'Ox (such as TiO2, ZnO, and WO3, etc.) would be selected as model photocatalysts. Research contents include to prepare controllably novel photocatalyst M//M'Ox containing the dipole heterointerface induced by oxygen vacancies, to characterize systematically features and polarized states of the heterojunction interface structure, to value detailedly the photocatalytic behaviors of materials for photoreforming methanol, photosplitting water or photoreducting carbon dioxides. According to these researches, we would make clear nature of the effect of heterojunction interface structure on the photocatalysis of material, establish a theory model of photocatalysis based on the heterojunction interface structure effect, develop the new design principle and method of photocatalyst by synergetic heterojunction and defect effects, and hereby prepare more efficient photocatalyst. This research proposal will have considerable value for enriching photocatalytic theory, and acquiring highly efficient photocatalyst.

设计制备高效光催化剂是光催化领域迫切需要突破的瓶颈问题。项目基于异质结策略，提出采用纳米化、团簇化、制造表面缺陷或空位、局域表面原子掺杂等方法，改变复合材料组元的化学组成和表面结构来调控两物相接触界面的状态，进而通过构建高活性界面结构来调控复合材料光催化作用机制并提高光催化效率的复合光催化剂设计新思路。拟选简单且有应用前景的贵金属M（Pd、Pt、Au等）修饰半导体金属氧化物M'Ox（TiO2、ZnO、WO3）作为模型光催化剂，构建高活性的含氧空位诱导极化界面的M//M'Ox，表征界面结构和极化状态，评价材料对甲醇重整、水分解制氢或CO2还原等光催化性能，阐明异质界面影响光催化性能的微观作用本质，建立界面结构光催化作用理论模型，发展基于异质结和缺陷协同作用的光催化剂材料设计制备科学原理和方法，并开发出更加高效的光催化材料。研究对于丰富光催化理论和创制高效光催化剂具有重要科学和实际意义。

本项目针对光催化产氢和CO2转化过程的低反应效率和产物选择性等问题，基于异质结原理，采用纳米化、团簇化、制造表面缺陷、表面局域掺杂等策略，通过改变复合材料组元的化学组成和表面结构，调控两物相接触界面结的状态，构建高活性界面结构，我们设计合成了十几个结构新颖、性能优异的光催化剂。例如，通过简单光沉积法得到Pt颗粒尺寸在2.2-2.7 nm的Pt//TiO2对甲醇光催化重整产氢有高达1.97 mol·g−1·h−1的稳定产氢速率。相比于常规Pt/TiO2，该新型光催化剂的单光子氢气收率从0.041提高到1.28，光量子效率从4.1%提高到89.2%。Pt//TiO2的高活性归因于金属Pt与半导体TiO2界面稳定束缚着高浓度的氧空位,光生电子和空穴分别聚集在Pt颗粒及其与TiO2的接界处，而非分别发生在Pt和TiO2表面。这种光和热催化协同达到一个光子产生1.28个氢分子的超高氢释放效率，据此提出了极化异质结作用新机制。另外，把金属Pt或Ni12P5植入金红石和锐钛矿异相结的界面制备出TiO2(A)/Pt/TiO2(R)或TiO2(A)/Ni12P5/TiO2(R)复合催化剂。该新结构能显著提升光催化重整甲醇制氢活性，据此提出串联异质结作用机制。通过自组装技术制备出了3D-SiC@2D-MoS2纳米花，其可使CO2与H2O全转化生成计量比的CH4和O2。研究表明，该催化剂具有由具有更负导带电位和高电子迁移率的SiC纳米晶与具有更正价带电势和高空穴迁移率的MoS2纳米片构成的特殊Z-型异质结构，实现的强氧化还原能力和强迁移率的联合，从而提升了光催化还原与氧化性能。这些新型界面结构光催化剂及其作用机制模型，不仅为开发高效光催化剂提供新思路，而且为认识和理解作用机理提供理论依据。本项目在包括PNAS、JACS、Nat. Commun、Sci. Bull.等重要期刊发表学术论文38篇。