Atomic Force Microscopy for Solar Fuels Research: An Introductory Review

Although research on solar fuel production via water oxidation, hydrogen evolution, and carbon dioxide reduction (i.e., artificial photosynthesis) has grown tremendously in recent years, practical solar fuel devices remain elusive. For these multi-electron transfer processes to take place efficiently, integrated systems constructed from materials with very different chemical, mechanical, and electrical properties are required. This complicated integration presents numerous challenges, including the need for increased characterization of material surfaces and interfaces for both fundamental studies and device optimization. Atomic force microscopy (AFM) is a powerful tool for surface and interface analysis. Although solar fuel research has frequently utilized the basic AFM function of topographic mapping for routine surface analysis, some researchers have avoided more advanced AFM methodologies due to the complexity of these integrated solar fuel generating systems. This article provides researchers in this area with an introduction to various advanced AFM techniques for mechanical, electrical, and chemical analysis on the nanoscale. It also discusses the possibility of in situ study while providing an outline of the working principles of different AFM application modes.