掺杂钨酸亚锡薄膜光电解水光阳极的光电化学性能研究

Photoelectrochemical (PEC) water splitting provides a cost-effective route for solar hydrogen production with potential strategic applications. One of the most challenging topics in the area is to develop high performance photoanodic materials operating at low applied bias, i.e., between 0.2~0.7 V vs. RHE. As a group of promising candidates, Sn(II)-based oxides are attractive photoanodic semiconductors with bandgaps (1.5~2.5 eV) narrower than most of the conventional binary oxides and the better band positions for the electrochemical step. SnWO4 is one of the relatively more popular one among them, because of its good performance for the photodegradation of pollutants. However, due to the lack of suitable methods for preparing high quality thin film and the chemical instability of Sn(II), its application in PEC water splitting is rarely reported. Herein we propose to investigate alpha-SnWO4, one of its phase with better carrier transportation kinetics, for photoanodes to address aforementioned challenge. .Particularly, this project will clarify how the variables in the preparation impacts the physical properties, and thereafter the photoelectrochemical behaviors. We will develop reliable and efficient procedure for preparing uniform doped alpha-SnWO4 oxide thin film and the surface modification protocols for the electrodes. The detailed relationship between the synthesis condition, and more importantly the structure and the properties of the film, will be associated with the photoanode performance. By combing multiple spectral and electrochemical characterizations, the impact of nanoscale geometric parameters, crystalline orientation and other features of the SnWO4 film will be optimized using photocurrent and onset potential as the benchmark. The internal and intrinsic factors which determine the charge carrier transportation in the bulk will be addressed. The morphology, crystal defects and doping will be comprehensively studied to unveil how the carrier transportation kinetics was impacted. Based on the observation with various doped films at different dopant concentration, we will deduce the correlation between the dopant and performance, bridged by the understanding of the electronic structure and charge carrier kinetics. Furthermore, we would introduce mild deposition techniques for depositing multi-functional surface modification layers or multi-layers to improve the PEC properties and to reach out the long-term stability of over tens of hours. The influences of each component will be carefully evaluated and balanced to maximize the photocurrent, as well as to gain a better onset potential and good stability. This project will also use SnWO4 as a paradigm to generalize the methodology and empirical principle for synthesis chemistry and doping towards other Sn(II)-based oxides thin films, together with the nanostructure optimization and electrode assembly.

光电解水制氢是一种具有重要前景的低成本制氢技术，长寿命、低偏压、高效的光阳极材料是该领域现阶段核心挑战之一。本项目旨在发掘Sn(II)三元氧化物作为新型阳极材料应对上述挑战的潜力，通过研究其光电性能和半导体材料制备技术的关系，寻找突破现有性能指标的可行方案。此类半导体具有比传统氧化物更窄的带隙以及适宜的带边位置，但一直较为缺乏可靠易行的薄膜材料制备方案，遑论形貌、缺陷工程开发。本项目以α-钨酸亚锡为代表，开发其高品质薄膜制备工艺，发展其缺陷控制、掺杂方法及优化技术；结合多种光谱表征和光电化学分析技术，分析光电极厚度、多孔性、形貌、晶体取向等特征并进行针对性优化；通过光阳极性能与不同掺杂离子种类、浓度相关性，寻求光电极内部电荷传输关键限制性物理机理以释放其潜力；同时合理选择、优化温和的表面修饰技术，合理配置表面与体相能级，综合设计优化全系统性能，开发高效、稳定的薄膜光阳极。

光电解水制氢具有重要前景，其系统受制于长寿命、低偏压、高效的光阳极材料这一核心挑战。本项目探索钨酸亚锡这一新型阳极材料以应对上述挑战的潜力，寻找突破现有光电材料瓶颈的可能性。本项目以α-钨酸亚锡为核心材料，开展了一系列对其物理、化学性质的深入探索，开发其高品质薄膜制备工艺，发展其缺陷控制、掺杂方法及优化技术；并结合多种光谱表征和光电化学分析技术，分析光电极厚度、多孔性、形貌、晶体取向等特征对光电催化特性的核心影响；通过光阳极性能与衍生材料化学组成等相关性，初步阐释了二价锡材料内部电荷传输关键限制性机理；同时，开发了相应的温和的表面修饰技术，并对其水氧化过程及电极稳定化的机理进行了探讨。