二维材料MX (M=Ga,In, X=S,Se,Te)光催化分解水的理论研究

Production of hydrogen from photocatalytic water splitting provides an effective solution to the energy shortage and environmental pollution. The key of photocatalytic water splitting is to develop visible-light-driven photocatalysts with high solar energy conversion efficiency. So far, most of photocatalysts have relatively large band gaps which can only response ultraviolet light irradiation, and photogenerated carriers cannot efficiently separate and transport to the surface of photocatalysts for participation in the photocatalytic reactions, resulting in lower photocatalytic efficiency, which severely limit their large-scale practical application. In this project, we will take two-dimensional MX materials as an example to carry out an extensive theoretical study based on density functional theory calculations and molecular dynamics simulations. Our activities including the following three parts: (1) We will manipulate the band structure engineering and optical property of two-dimensional MX by monodoping, codoping with various metal cations and non-metal anions or surface passivation with halogen elements, and provide new strategies of doping for enhanced visible-light photocatalytic activity. (2) We will investigate two-dimensional MX-based van der Waals heterostructures to reveal corresponding microscopic mechanism of band engineering and carrier effective separation. (3) We will modify two-dimensional MX with intrinsic defect to explore the effects of defect on photocatalytic performance for MX materials. These results would provide theoretical basis and guidance for further experimental studies.

利用太阳能光催化分解水产氢是解决能源危机与环境污染问题的有效途径之一，其核心技术是开发高效的可见光响应的光催化剂。目前大部分催化剂的带隙较大，只能吸收紫外光，或者载流子不能有效地分离并迁移到表面参与催化反应，导致光催化效率较低，无法实现大规模应用。本项目拟将采用密度泛函理论和分子动力学模拟等方法，对二维材料MX开展深入的理论研究，包括：1、对MX材料进行各种单掺、共掺以及表面钝化，优化体系的能带结构和光学性质以实现其光催化性能增强；2、研究MX基范德瓦斯异质结，揭示能带调控和载流子有效分离的微观机理；3、对含有本征缺陷的MX材料进行改性，探索本征缺陷对MX材料光催化性能的影响。本项目的实施将为进一步的实验研究提供理论依据和指导。

本项目主要研究二维材料及其修饰改性后的电子结构和光催化分解水性能，并在此基础上探索提高二维材料光催化效率的最优途径。在项目的资助下，基于第一性原理的密度泛函理论计算，开展了以下几个方面的研究：(1)构建Type-Ⅱ型范德瓦尔斯异质结，实现带隙的降低和载流子的有效分离，提高光催化活性；(2)构建二维材料的Janus结构，由于存在内建电场，从而保证材料在窄带隙的情况下仍然能够保持能带匹配，同时促进光生载流子的有效分离和拓展光催化材料的光谱响应范围；(3)理论预测并研究新型二维材料的电子性质，并探索其作为光催化分解水材料的可能性。通过相关的研究，厘清了二维材料MX (M=Ga, In, X=S, Se, Te)的电子结构和光催化性能之间的关联，提出了提高二维材料光催化效率的一般规律。此外，我们从理论上还研究了一些其它材料的电子性质，如自旋与能谷极化、电荷输运、磁激发等。本项目的实施将为进一步的实验研究提供理论依据和指导。相关的研究内容发表在 Journal of Physical Chemistry C、Applied Surface Science、Physical Chemistry Chemical Physics、Physica E等SCI刊物，共 11 篇， 其中第一作者论文 4 篇，后续有 2 篇 SCI 论文将在 2021 年刊出。