光电极表面态的静态结构与时间分辨动力学和频光谱研究

Surface States of Photoelectrodes by Surface-Specific Steady-State and Time-Resolved Sum Frequency Spectroscopies

在光催化或光电催化反应过程中,光电极的表面态扮演着重要的角色,影响着电荷的产生、分离和利用过程,从而很大程度上决定了光电极的催化性能,通常用于研究光电极表面态以改进其性能的方法是间接的、非表面特异性的以及需要超高真空条件下进行的方法,无法获得真实条件下的表面态信息。电子和频光谱和电子二次谐波等非线性光学方法具有表面特异性,可以在各种条件下实现表界面系统的原位研究.本研究介绍了表面态的重要性及其与催化性能的密切关系,概述研究半导体表面态、电场和载流子动力学的方法,并重点介绍了界面特异性光谱方法在该领域的最新贡献.包括通过相位信息提取带电表面态的宽带外插法电子二次谐波技术,提供表面态动力学信息的时间分辨电子和频光谱技术和探索表面态耦合的二维电子和频光谱技术,这些非线性光学方法的进一步发展将实现对光电极表面态和界面电子特性的多角度原位表征,提供对表面态及表面电荷转移过程更深层次的理解,以启发未来光催化和光电催化材料的研究和改进.

The surface states of photoelectrodes as catalysts heavily influence their performance in photocatalysis and photoelectrocatalysis applications.These catalysts are necessary for developing robust solutions to the climate and global energy crises by promoting CO2 reduction,N2 reduction,contaminant degradation,and water splitting.The semiconductors that can fill this role are beholden as photoelectrodes to the processes of charge generation,separation,and utilization,which are in turn products of surface states,surface electric fields,and surface carrier dynamics.Methods which are typically used for studying these processes to improve semiconductors are indirect,invasive,not surface specific,not practical under ambient conditions,or a combination thereof.Recently,nonlinear optical processes such as electronic sum-frequency generation(ESFG)and second-harmonic generation(ESHG)have gained popularity in investigations of semiconductor catalysts systems.Such techniques possess many advantages of in-situ analysis,interfacial specificity,non-invasiveness,as well as the ability to be used under any conditions.In this review,we detail the importance of surface states and their intimate relationship with catalytic performance,outline methods to investigate semiconductor surface states,electric fields,and carrier dynamics and highlight recent contributions to the field through interface-specific spectroscopy.We will also discuss how the recent development of heterodyne-detected ESHG(HD-ESHG)was used to extract charged surface states through phase information,time-resolved ESFG(TR-ESFG)to obtain in-situ dynamic process monitoring,and two-dimensional ESFG(2D-ESFG)to explore surface state couplings,and how further advancements in spectroscopic technology can fill in knowledge gaps to accelerate photoelectrocatalyst utilization.We believe that this work will provide a valuable summary of the importance of semiconductor surface states and interfacial electronic properties,inform a broad audience of the capabilities of nonlinear optical techniques,and inspire future original approaches to improving photocatalytic and photoelectrocatalytic devices.