Coupled Experimental and Computational Investigation of Interfaces in Multicomponent Photoelectrodes for Solar Water Splitting

太阳能裂解水为生产氢气提供了一条可持续和对环境无害的路线，用作清洁燃料来源。这就是为什么低成本、高效率的太阳能水分离是重大的科学挑战之一。将水与阳光分离的一种方法是使用光电化学电池(PEC)，但这些设备的效率还不够高，无法实际使用。该项目研究了优化PEC部分的方法：催化剂和保护层，它们是高效和可持续的太阳能水分离的关键组件。它还研究了半导体电极，这些电极收集太阳能，然后产生和传输用于制氢的电荷。PEC的整体性能不仅受到这些单独部件的整体性能的影响，而且还受到它们之间形成的界面的影响。然而，研究与水分裂有关的界面的困难阻碍了他们的研究。在这个项目中，威斯康星大学麦迪逊分校的KYoung-Shin Choi博士和芝加哥大学的Giulia Galli博士结合了实验和计算研究，以了解和控制具有代表性的PEC系统-钒酸铋光阳极及其与其他金属氧化物的界面性质。该项目使人们有可能制定总体战略，在PEC的不同部分之间建立最佳接口，以加强太阳能水的分裂。崔博士和加利博士还在开设实验和计算相结合的教程，教该领域的研究人员如何最好地比较计算结果和实验结果。最后，他们正在创建和维护一个网站，其中包含世界各地的研究人员可以访问和使用的PECs的有用数据。在光电化学电池(PEC)中，除了收集太阳能并产生/传输电荷载体的半导体电极外，催化剂和保护层是高效和可持续地分解太阳能的关键组件。多组分光电极的整体性能不仅受各组分的整体性质的影响，还受它们之间形成的界面的影响。这些界面的特性可以很大程度上影响电荷传输特性和复合损失，从而决定到达电极表面参与水分解反应的电荷载流子的数量。到目前为止，由于大量的实验和计算挑战，对与水分裂相关的界面的原子和电子结构的系统研究非常少见。在这个项目中，崔博士和加利博士通过实验和计算相结合的研究，建立了对界面原子和电子结构对光电化学性质影响的一般和基本的理解。为了阐明界面-光电化学性质之间的关系，以BiVO4基光阳极为代表的多组分光电极体系，构建了一系列半导体/析氧催化剂(OEC)、半导体/保护层和保护层/OEC界面，并用具有系统变化表面端面的单晶和多晶BiVO4电极进行了检测。原子水平上对界面-光电化学性质关系的了解使人们有可能设计出在光子吸收剂、保护材料和催化剂之间构建最佳界面的一般策略，以增强太阳能水的分解。这项拟议的工作还为社区提供了有效的实验-计算耦合策略，用于研究复杂的、不同种类的界面。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Solar water splitting provides a sustainable and environmentally benign route for the production of hydrogen gas for use as a clean fuel source. This is why low cost and efficient solar water splitting is one of the grand scientific challenges. One way to split water with sunlight is with a photoelectrochemical cell (PEC), but these devices are not yet efficient enough for practical use. This project examines methods of optimizing parts of the PEC: the catalyst and protection layers that are key components for efficient and sustainable solar water splitting. It also examines the semiconductor electrodes that harvest solar energy, then generate and transport the electrical charge used for hydrogen generation. The overall performance of a PEC is affected not only by the bulk properties of these individual parts, but also by the interfaces formed between them. However, the difficulty of studying the interfaces relevant to water splitting have stood in the way of their study. In this project, Dr. Kyoung-Shin Choi of the University of Wisconsin - Madison and Dr. Giulia Galli of the University of Chicago combine experimental and computational studies to understand and control interfacial properties of a representative PEC system - bismuth vanadate-based photoanodes and their interfaces with other metal oxides. This project makes it possible to devise general strategies to construct optimal interfaces between the different parts of a PEC to enhance solar water splitting. Dr. Choi and Dr. Galli are also setting up combined experimental-computational tutorials to teach researchers in the field how to best compare computational and experimental results. Finally, they are creating and maintaining a website that contains useful data on PECs that can be accessed and used by researchers worldwide.In a photoelectrochemical cell (PEC), in addition to semiconductor electrodes that harvest solar energy and generate/transport charge carriers, catalyst and protection layers are key components for efficient and sustainable solar water splitting. The overall performance of multicomponent photoelectrodes is affected not only by the bulk properties of the individual constituents but also by the interfaces formed between them. The characteristics of these interfaces can considerably affect the charge transport properties and recombination loss, thus determining the number of charge carriers reaching the electrode surface to participate in water splitting reactions. To date, systematic studies of the atomic and electronic structures of interfaces relevant to water splitting have been extremely rare, due to numerous experimental and computational challenges. In this project, Dr. Choi and Dr. Galli are establishing a general and fundamental understanding of the effect of interfacial atomic and electronic structures on photoelectrochemical properties by combining experimental and computational studies. In order to elucidate interface-photoelectrochemical property relationships, BiVO4-based photoanodes are used as a representative multicomponent photoelectrode system, and a series of semiconductor/oxygen evolution catalyst (OEC), semiconductor/protection layer, and protection layer/OEC interfaces are constructed and examined by using single crystal and polycrystal BiVO4 electrodes with systematically varied surface terminations. An atomic level understanding of interface-photoelectrochemical property relationships makes it possible to devise general strategies to construct optimal interfaces among photon absorbers, protective materials, and catalysts to enhance solar water splitting. The proposed work also provides the community with validated coupled experimental-computational strategies for studying complex, heterogeneous interfaces.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.