助催化剂与光催化剂晶/界面匹配效应对完全分解水反应影响的研究

Direct overall water splitting with semiconductor-based photocatalysts is one of the most ideal routes for hydrogen production using solar energy. It was already demonstrated that the photocatalytic properties of cocatalyst nanoparticles or semiconductor photocatalysts could be adjusted by exposed facets. However, most researches investigated the role of exposed facets either of photocatalysts or cocatalyst. The essential relationship between the facets match and related interface structure properties of hybrid photocatalyst with the overall water splitting properties, especially under visible light irradiation is poorly understood. More importantly, the essential relationship between the facets match and related interface structure properties of hybrid photocatalyst with the overall water splitting properties, especially under visible light irradiation is poorly understood. The aim of this project is thus to investigate the role of specific facets match between cocatalyst and photocatalysts and the related interface structure properties on overall water splitting reaction and hydrogen or oxygen evolving half reaction. Three semiconductor metal oxide photocatalyst, anatase TiO2, rutile TiO2, and Bi1-xYxVO4, with overall water splitting ability responding to different light intensity and spectrum was selected as photocatalyst. Two noble metal, Pt, cocatalyst mainly works under the principle of formation schottky contact and Au, cocatalyst, works both under the principle of formation schottky contact and surface plasmon resonance was selected as cocatalyst. Specific clean facets match hybrid photocatalysts with related specific interface structure between cocatalyst and photocatalysts will be targeted synthesis and fine characterized by advanced techniques based on traditional and synchrotron X-ray methods. The associated match mechanisms under different scenarios for water splitting will be investigated by monitoring the dynamic structure changes in situ during water splitting by XAS, Δμ XANES and XRD techniques using a continuous-flow reactor and soft X-ray XAS solid-liquid reactor combined with EPR, DFT numerical simulations and other techniques. Rational hybrid photocatalyst design strategy with the ability to achieve overall water splitting under visible light irradiation will be proposed based on the in-depth understanding of facet matching and related specific interface issues.

太阳能光解水反应中，控制合成具有特定暴露晶面的光催化剂或助催化剂为提高反应活性提供了可行的途径，但是目前的研究一般均限于单独研究特定暴露晶面的光催化剂或助催化剂的影响，反应则多关注产氢半反应。本项目提出在完全分解水反应中，通过同时控制主-助催化剂暴露晶面，构建晶/界面结构匹配效应提高反应效率以及实现可见光分解水的思路。项目拟围绕对光强度以及光波段响应能力不同，但均可实现完全分解水的三类光催化剂：锐钛矿相和金红石相TiO2、Bi1-xYxVO4开展工作，控制合成具有特定暴露晶面的光催化剂，在其表面沉积化学态、粒径可控的具有特定暴露晶面的Pt、Au助催化剂，揭示晶/界面匹配效应的完全分解水反应构效关系规律，通过原位X射线吸收谱结合其他研究手段揭示不同光照条件下，晶/界面匹配效应在动力学和热力学方面影响完全分解水反应的机理。项目结果将为构筑高效可见光完全分解水催化剂提供理论依据。

光催化完全分解水（POWS）制氢基于微纳半导体颗粒中的多步串行物理化学过程，在纯水中实现了由间歇性太阳能向稳定化学能的一步转化，被认为是有应用前景的光催化分解水制氢技术之一。固溶体方法可以实现带隙和带边位置的调控，是设计POWS半导体光催化剂的最有效方法之一。但是如何进一步调整这类光催化材料体系的光吸收特性以及载流子动力学特性仍面临挑战。这是由于半导体光催化剂和助催化剂的微晶结构、助催化剂和光催化剂半导体微晶构成的特定界面结构的匹配效应显著影响了该体系的光氢转化效率。本课题组前期基于三元固溶体结构的能带调控作用，通过钇(Y)掺杂形成钒酸铋钇（BixY1-xVO4），使得不能光催化分解纯水的BiVO4在热力学上达到了POWS的要求。本项目进一步围绕该三元固溶体光催化剂BixY1-xVO4开展研究工作。首先精细控制合成了特定晶界面结构模型光催化剂。进一步探索构建了适合表征光催化反应固液界面结构的原位X射线吸收谱、原位拉曼光谱、原位X射线衍射谱等原位研究方法，结合软X射线吸收谱、瞬态吸收光谱以及球差电镜等表征手段系统探究了包括表面结、异质结、绝缘体/半导体限域异质结等特定晶界面结构对光催化完全分解水性能的调控机制。在上述研究基础上，最后将研究拓展至氧化钛及聚合物氮化碳体系。研究显示体系优化的光吸收特性以及光生载流子传输性能促进了POWS产氢活性的提升。项目揭示的光催化剂晶界面匹配性能增强普遍性机制将为后续的高效POWS体系开发和构建提供有益的借鉴和思路。