强化光生电荷分离的α-Fe2O3/NG/MOx核壳异质结构光电极材料的可控制备及其水解制氢性能研究

α-Fe2O3 has emerged as a photoanode material in the photoelectrochemical (PEC) water splitting because its favorable optical bandgap (2.1 eV),excellent chemical stability, natural abundance, and low cost. However, the short lifetime of photogenerated charge carriers and short hole diffusion length as well as large requisite oxygen evolving overpotential of α-Fe2O3 material lead to electron−hole recombination, thus decreasing the PEC efficiency, which limits its practical applications. In this proposal, we plan to synthesize core-shell heterostructural α-Fe2O3/NG/MOx (NG for N-doped graphene, M for transition metal elements) photoanode composites through aqueous solution method using FTO glass as the matrix. First, both the inter-coupling heterojunctions among α-Fe2O3/NG/MOx and the nanosize effects are expected to promote photoexcited electron−hole separation which can minimize electron−hole recombination and enhance the photocurrent. Second, the photoanode overpotential can be reduced by dual chemical modified function of NG and MOx, therefore further improving the PEC efficiency for water splitting. The physical and chemical experimental measurements will be applied to investigate the relationship between the structure， morphology and PEC performance of the α-Fe2O3/NG/MOx composites. We will also elucidate the coupling mechanism among α-Fe2O3/NG/MOx composites, the nanosize effects on improving the PEC properties of the material, and the photoelectro-catalytic mechanism, so as to obtain the basic principles for preparation and modification of α-Fe2O3 materials. Our study will provide experimental guidence and theoretical basis for the development and application of novel α-Fe2O3 photoanode materials.

α-Fe2O3作为光解水用光电极材料，具有合适的禁带宽度（2.1eV），优异的化学稳定性及廉价易得等优点，但其较短的光生载流子寿命、光生空穴传输距离及较高的析氧过电位,导致其实际光电制氢效率低，有碍其实际应用。本项目拟采用液相法导向合成具有核壳异质结构的α-Fe2O3/NG/MOx（NG为N掺杂石墨烯，M为过渡金属）复合光电极材料。基于α-Fe2O3/NG/MOx性能耦合与纳米尺寸效应，增强其光生电子、空穴分离效率，并利用NG与MOx的双重化学修饰降低析氧过电位，提高其光解水制氢效率。采用现代物理、化学研究方法研究其结构、形貌与光电催化性能之间的关系，阐明α-Fe2O3/NG/MOx性能耦合机制、纳米尺寸效应改善材料性能的机理与材料的光电催化反应原理，从而获得α-Fe2O3材料的制备原理及性能优化机理，为高性能α-Fe2O3光电极材料的研发及应用提供理论基础和技术依据。

α-Fe2O3作为光解水用光电极材料，具有合适的禁带宽度（2.1eV），优异的化学稳定性及廉价易得等优点，但其较短的光生载流子寿命、光生空穴传输距离及较高的析氧过电位,导致其实际光电制氢效率低，有碍其实际应用。本项目针对α-Fe2O3光阳极较短的光生载流子寿命、光生空穴传输距离及较高的析氧过电位等缺点，设计合成了：（a）多孔氧化铁纳米阵列光阳极材料；（b）过渡金属磷化物修饰的氧化铁纳米阵列光阳极材料；（c）过渡金属硼化物修饰的氧化铁纳米阵列光阳极材料；以及（d）过渡金属化合物纳米结构材料几类光/电催化材料。本研究采用XRD、Raman、SEM、TEM、EDS、XPS等结构表征，结合相关的光、电化学表征手段，得出以下结论：（a）揭示多孔氧化铁纳米阵列的性能优化机制；（b）首次将过渡金属硼化物、磷化物与氧化铁光阳极耦合，促进了光电催化性能，并验证了其性能耦合机制；（c）首次发现多相异质结对电催化析氧的促进作用；（d）首次发现了电催化活化可以明显促进过渡金属磷化物的析氧催化性能；（e）首次发现过渡金属硼化物中硼在析氧过程中的作用机制，硼在电解液中的部分溶解可以明显提升材料的析氧催化性能。上述结论验证了光、电催化材料的结构与性能之间的关系，揭示了其性能耦合机制和光电催化性能提升原理，为高性能光电极材料的研发提供了重要的理论基础和技术依据。