D4型光解水氧化物纳米阵列光阳极的制备及电荷转移机理研究

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.

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。

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。.本项目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，构筑了CdS/PbS/TiO2纳米管阵列、锐钛矿/金红石相结TiO2纳米管阵列、CdS/ZnO纳米棒阵列、BiVO4/WO3纳米棒阵列等具有串联式双光吸收层结构的纳米阵列复合光阳极，极大拓宽了光电极的可见光吸收活性。通过第一性原理理论分析与实验表征相结合，系统研究了光阳极的微观结构和光电化学性能之间的关系，研发了原子层沉积技术、低温热处理技术等表面/界面改性方法，深入探究了表/界面性质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，构建出高效、稳定的太阳能光解水制氢体系。其中，经Al2O3表面修饰的CdS/PbS/TiO2纳米管阵列在模拟太阳光激发下，最大光电流密度可以达到5.19 mA/cm2，是单纯TiO2纳米管阵列的52倍，比未经Al2O3修饰的量子点敏化纳米管阵列提高了60%；入射单色光光电转换效率（IPCE）在350 nm处达到最大，为83%，并且在小于450 nm时都大于30%。经两步低温热处理法得到的CdS/ZnO纳米棒阵列光电极展示出极佳的光电流密度，在0.4 VSCE处可达9.16 mA/cm2，是未经热处理光电极的1.75倍；其最大光转换效率增长至4.03 %，比未经热处理的提高了44 %；在350 nm处的IPCE值可以达到约95 %。.截止到2019年1月，在Advanced Materials、Chemical Engineering Journal等国内外重要学术刊物上共发表了22篇学术论文，其中SCI收录论文19篇。已经培养毕业1名博士研究生，8名硕士研究生。科研成果获得海南省科技进步奖一等奖1项和三等奖1项。在国内外学术会议上发表邀请报告9次。