Emerging techniques for the in situ analysis of reaction intermediates on photo-electrochemical interfaces

Abstract

Using light excitation to perform uphill chemical reactions is an attractive strategy for powering alternative energy sources, producing renewable fuels, and providing efficient methods for environmental remediation. In particular, photoelectrochemical reactions at wide-bandgap semiconducting electrodes and their colloidal particles have been thoroughly studied for the last 40 years. Although materials such as TiO₂, SrTiO₃, and ZnO among others have found a myriad of applications, from dye-sensitized solar cells to formulations for self-cleaning street pavement, many questions still remain regarding their surface reaction mechanisms. The need to understand these systems in situ and in operando schemes has become invigorated by the interest in plasmonics, co-catalysts, and bandgap engineering for enhancing their performance. Thus, elucidating the impact of these technologies on the photogenerated surface chemical intermediates can reveal relevant mechanistic differences. Do the reactivities and properties of reactive oxygen species depend on the wavelength of excitation on engineered materials? What is the impact of metal deposits and defects on the formation and properties of surface species? Are there any recent developments in techniques that could shed new light on new materials interactions at the nanoscale? In this review, we seek to provide a fresh perspective on existing and emerging in situ analytical methods applied to semiconducting photocatalysts for answering these and other modern aspects of surface intermediates.