二维g-C3N4基纳米异质结的构建及光催化还原CO2性能研究

Aiming at the low utilization and conversion efficiency of solar light during photocatalytic reduction CO2 over graphene-like carbon nitride (g-C3N4), the combination of two-dimensional g-C3N4 nanosheets and layered metal sulfides is proposed to prepare nano-heterojunction photocatalysts, which will be coupled with metal nanoparticles to construct an efficient CO2 photocatalytic reduction system by enhancing the nano-heterojunction photocatalytic activity using the surface plasmon resonance effect from the metal nanoparticles. The purpose of this study is to design and synthesis a series of metal nanoparticles modified two-dimensional metal sulfides/g-C3N4 nano-heterojunction photocatalysts. The effort will be devote to the controllable preparation of g-C3N4 nanosheets, metal sulfides nanosheets and metal nanoparticles, and regulating their element components, structures and photoproperties by exploring effective synthesis methods. In addition, the coupling mechanism of metal nanoparticles and metal sulfides with g-C3N4 nanosheet will be investigated under the assistance of time resolved spectrometry and theoretical calculation. Meanwhile, the photocatalysis mechanism will be investigated to obtain a new method and strategy to solve the low efficiency during photocatalytic reduction CO2 and establish the macro-kinetic model. Great progress will be made in this research from micro scale two dimensional materials to macro reactor. The completion of this research will be of great significance for the basic research and technology application of two dimensional photocatalytic nanomaterials.

针对石墨相氮化碳光催化还原CO2反应过程可见光利用率低和量子效率低的问题，提出将二维g-C3N4纳米片与层状金属硫化物复合制备二维纳米异质结，再和纳米金属耦合,形成表面等离子体增强的二维纳米异质结光催化剂，实现g-C3N4高效光催化还原CO2的研究思路。旨在设计合成一系列纳米金属耦合的硫化物/g-C3N4二维纳米异质结催化剂，重点探索单层g-C3N4纳米片、硫化物纳米片及纳米金属的可控制备与复合，实现对复合材料二维形貌、元素组成、光学性能的调控；借助时间分辨光谱和理论计算等手段，弄清纳米金属-硫化物/g-C3N4二维纳米异质结的光电耦合机制，研究光催化反应机理，获得控制光催化过程的新策略和新方法，有效地解决光催化还原CO2效率低的难题；建立宏观动力学模型，从二维纳米异质结光催化微观尺度到宏观反应器研究，取得重要进展。本项目研究结果对二维纳米光催化材料的基础研究和技术应用具有重要意义。

项目针对石墨相氮化碳光催化反应过程可见光利用率低和量子效率低的问题，将二维g-C3N4纳米片与层状硫化物复合后再耦合纳米金属获得金属-半导体/g-C3N4基二维纳米异质结光催化剂，实现了太阳光高效光催化还原CO2和光解水制氢的研究目标。优化建立了基于高温煅烧法、液相剥离法、原位水热法和微波辅助化学还原法的纳米金属-层状硫化物/g-C3N4二维纳米异质结的普适性复合途径，重点围绕MoS2/g-C3N4、Bi2MoO6/g-C3N4、WS2/Ag/g-C3N4等二维纳米异质结的构建、晶型结构、元素组成、光学及光电特性、光解水制氢性能及反应机理等开展了系列研究。主要成果如下：1）以三聚氰胺为前驱体，高温煅烧后在酸中剥离获得单层g-C3N4；2）实现了MoS2、WS2、Bi2MoO6等二维纳米片在g-C3N4表面的原位生长以及Au、Ag纳米颗粒有效分散于半导体异质结上，促进了可见光高效捕获和光生载流子的有效分离，从而提高g-C3N4纳米片的光催化性能；3）提出了半导体-半导体异质结、表面金属-半导体肖特基结和金属表面等离子体效应协同光催化增强机制；4）探索得到过渡金属磷化物、氧化物/g-C3N4高效光催化体系，Ni2P/g-C3N4、NiCoP/g-C3N4、NiCo2O4/g-C3N4实现了高效光解水制氢。项目的开展有效增强了g-C3N4光催化活性，提高了光能利用效率，对推动构建二维异质结复合光催化技术在能源与环境领域的基础研究和技术应用有重要意义。