全氮化物光/电催化剂复合电极的构建及其太阳能分解水机理研究

It is crucial to explore efficient semiconductor photoanodes with narrow band gaps for their practical application in photoelectrocatalytic water splitting. Some nitrides, such as Ta3N5 and InGaN, are very promising photoanode materials due to their suitable band gaps and band positions, and long diffusion length of minority carriers. However, low photo-voltage in these nitride photoanodes limits their practical applications. If oxygen species on the surfaces of nitride photoanodes are higher, the photovoltages will be lower. In this proposal, some efficient transition metal (Fe, Co, Ni, Mn, Cr and so on) nitride electrocatalysts for oxygen evolution reaction will be coated on the surfaces of Ta3N5 and InGaN photoanodes, to construct all-nitride photocatalyst/electrocatalyst composite photoanodes, which can decrease oxygen concentration on the surfaces of Ta3N5 and InGaN and improve the nitride photoelectrodes’s efficiency. Moreover, activation method and mechanism of all-nitride composite photoanodes will be further investigated. The effects of composition, thickness and resistance of nitride electrocatalysts on the photovoltages will be studied in details. With theoretical calculations, adsorption of H2O on the surfaces and photo-generated charge transfer at the interfaces of composite photoanodes will also be analysed. This study will provide some scientific and experimental bases for research to design and develop efficient nitride photoelectrocatalysts.

开发高效窄带隙半导体光阳极是实现太阳能光电催化分解水制氢的关键。一些金属氮化物光阳极，如Ta3N5和InGaN等，具有合适的带隙和导价带位置以及少数载流子扩散距离长等优势，是非常有潜力的光阳极材料。然而，这些氮化物光阳极低的光生电压限制了它们的实际应用。氮化物光阳极表面氧物种越高，会导致其光生电压越低。本项目拟将高活性过渡金属（Fe、Co、Ni、Mn、Cr等）氮化物析氧电催化剂担载在Ta3N5或InGaN等光催化电极表面，构筑全氮化物光/电复合电极，阻止氮化物光催化剂表面引入氧物种，从而提高其光电压。此外，通过研究阐明全氮化物光/电催化剂复合电极的激活方法与机理。研究氮化物电催化剂的成分、厚度、导电性等对复合电极光电压的影响规律。结合理论计算，研究全氮化物光/电催化剂复合电极界面水的吸附行为与光生电荷传输机制。本研究将为设计和开发高效氮化物光电催化材料提供实验基础和理论支持。

光电化学电池是一种太阳能低成本存储的有效方法。针对太阳能转化效率低与界面电荷传输机制不清等关键问题，本项目开展了半导体光电极的表界面电荷传输机制、性能提升方法以及高效全器件构筑等方面的研究。主要研究结果如下：（1）发现了半导体/催化材料、半导体/储能材料、半导体/电解液、半导体/半导体等界面广泛存在可逆的电子离子耦合传输行为，提出了法拉第结新概念和新理论。该理论的提出改变了对固体表界面只存在电子传输的传统认知，具有原创性。（2）提出了氧化还原电位窗口是描述法拉第结界面电荷转移性质的关键参数。通过调控电位窗口显著提高了法拉第结电极的光电压，通过调节半导体表面法拉第层的羟基含量，提高了光电极太阳能分解水光电流。（3）发明了基于法拉第结的两端口太阳能充电全器件，实现了可循环的无偏压光充电-暗放电，并提出了两端口太阳能充电器件无偏压工作的构筑原则。此外，发现了法拉第结太阳能充电器件具有光电压记忆效应的新特性并阐明了其机理。.在本项目的资助下，项目负责人共发表了包括Nat. Commun.（2）、Angew. Chem. Int. Ed.、Natl. Sci. Rev.、Chem. Sci.等期刊在内的论文10篇，申请了中国发明专利3项，培养了研究生8名，圆满完成预期研究目标。