利用太阳光催化分解水制氢，可以将间歇性的太阳能资源转化为可储存、无污染的氢能，是人类梦寐以求的解决能源紧缺问题的一条重要途径。提高太阳光分解水效率的关键，在于获得高效稳定的可见光响应光催化材料和设计适于规模应用的光解水反应体系。D4型光电化学分解水体系利用串联式双半导体层吸收不同波段的太阳光，极大拓宽了半导体材料的选择范围，是提高能量转换效率的理想途径。本项目拟将氧化物优良的光催化性能与纳米阵列的有序结构有机结合，构筑具有串联式双光吸收层结构的氧化物纳米阵列光阳极，满足D4型光解水的要求。通过系统研究光阳极的微观结构和光电化学性能之间的关系，阐明D4型光解水反应的电荷转移机理，探索界面深能级存在的实验证据并分析其对光诱导电荷的有效分离和传输的作用机理。通过纳米阵列光阳极的精细设计，获得提高太阳光吸收和光生电子-空穴对利用率的有效途径，构建高效、稳定的太阳能光解水制氢体系。

Using solar energy to split water into hydrogen and oxygen is one of the most important ways to solve the problem of energy shortage, which can convert the intermittent solar energy to the storable and clean hydrogen energy. To address the challenges limiting the efficiency of solar-driven water splitting, one should not only design a water-splitting system suitable for large scale practical applications, but also develop stable and efficient photocatalytic materials, which possess controllable geometric structure and can absorb the visible light in the solar spectrum. A D4 photoelectrochemical (PEC) water-splitting scheme is a promising solution. In the D4 approach, a tandem dual-absorber of semiconductors requires four photons to produce one molecule of H2 and can harvest complementary portions of the solar spectrum to generate sufficient PEC potential for water splitting. The flexibility of material choices, along with the use of visible wavelengths for energy conversion, makes "D4 PEC water splitting scheme" one of the most promising directions for solar-to-fuel conversion. In the project, we are going to fabricate nanoarray photoanodes with a tandem dual-absorber of oxide semiconductors, and investigate the relationship between the microstructure and the photoelectrochemical properties by combining optical, electrical and photoelectrochemical analysis techniques. Such photoanodes can possess the advantages of the excellent photocatalytic properties of oxide semiconductors and highly-order structure of the nanoarrays. We will also study the interfacial charge transfer behavior and its dependence on the interfacial structures by varying the electrode surface nature and the dual-absorber interconnect. Furthermore, we try to explore whether or not there are deep levels on the interface and understand their effects on the visible-light absorption and charge transport. Our purpose is to find an effective method to improve the solar-to-hydrogen conversion efficiency of the nanoarray photoanodes, and finally achieve stable and efficient D4 PEC water splitting using solar energy.