基于ZnO单晶的半导体p-n结光催化剂的构建与产氢机理研究

Achieving efficient separation of photo-generated carriers in nanosized semiconductor photocatalyst is an important prerequisite for its application in clean energy regeneration. Formation of semiconductor heterojunction in nanosized photocatalyst can increase its hydrogen production activity, which is attributed to the built-in electric field formed in the semiconductor, effectively separating the photo-generated electrons and holes. However, due to the small size of nanosized heterojunction photocatalyst, its built-in electric field is difficult to measure, therefore most of the researchers can only qualitatively study the mechanism for photocatalytic hydrogen production by using the concept of heterojunction. Taking the advantage of bulk semiconductor which has measurable electric properties, the applicant intends to deposit P-type ZnCdTe thin film on the surface of n-type ZnO single crystal to form a ZnO single crystal/ ZnCdTe film PN junction which is visible-light response. The strength and width of the built-in electric field in the PN junction can be controlled by using ZnO single crystals with different carrier concentration. By using the newly designed photocatalytic reactor which can effectively inhibit surface reverse reaction, the applicant can systematically investigate the influence of strength and width of built-in electric field on the photocatalytic hydrogen production. From the above study, the applicant can reveal separation and transfer procedures and learn the mechanisms of photo-generated carriers in heterojunction, enhancing the understanding on the mechanism of heterojunction photocatalytic hydrogen production. The work is expected to provide theoretical guidance for the construction of photocatalytic nano-heterostructure.

实现光生载流子高效分离是纳米半导体光催化剂在清洁能源再生方向实用化的一个重要前提。构建半导体异质结可以提高纳米光催化剂产氢活性，因为理论上异质结在半导体内形成内建电场能有效分离光生电子和空穴。然而对于纳米异质结光催化剂，其纳米尺度的内建电场难以观测和调控，大多数研究者只能利用异质结的概念对光催化产氢机理进行定性分析研究。申请人拟利用块材半导体性能可量化测定的优点，通过在n型ZnO单晶表面沉积P型ZnCdTe半导体薄膜，来构建有可见光响应的ZnO单晶/ZnCdTe薄膜PN结。采用申请人设计的能有效抑制异质结表面逆反应的新型光催化反应器，通过选择不同载流子浓度的ZnO单晶调控异质结内建电场的强度和宽度，直接测定并系统研究内建电场强度和宽度对光催化产氢活性的影响，从而揭示异质结中光生载流子分离和传输过程及机制，增强对异质结光催化产氢机理的认识。本工作有望为纳米异质结光催化剂的设计提供理论指导。

实现光生载流子高效分离是纳米半导体光催化剂在清洁能源再生方向实用化的一个重要前提。构建半导体异质结可以提高纳米光催化剂产氢活性，因为理论上异质结在半导体内形成内建电场能有效分离光生电子和空穴。然而对于纳米异质结光催化剂，其纳米尺度的内建电场难以观测和调控，大多数研究者只能利用异质结的概念对光催化产氢机理进行定性分析研究。鉴于此，本项目利用块材半导体物理性能可量化测定的优势，以ZnO单晶为模型材料，成功地在ZnO单晶上构建具有可调控内建电场的异质结（如ZnO/ZnCdTe异质结，ZnO/MgZnO异质结及ZnO/溶液异质结），对异质结内建电场进行有效观测，利用自主搭建的能同步测量多电化学参数的新型光电化学反应装置，首次实验证实了异质结内建电场越强，对光生载流子分离能力越强，对应的光电流越明显。在以上机理研究的指导下，设计开发了一种具有高效产氢性能的新型异质结光催化剂及两种非贵金属助催化剂，丰富了纳米半导体光催化剂研究体系。通过本项目的开展，实验证实了异质结中光生载流子分离和传输规律，有力增强了对异质结光催化产氢机理的认识，能为纳米异质结光催化剂的设计提供有益指导。