Imogolite Nanotubes and Their Permanently Polarized Bifunctional Surfaces for Photocatalytic Hydrogen Production

Abstract

To date, imogolite nanotubes (INTs) have been primarily used for environmental applications such as dye and pollutant degradation. However, imogolite's well-defined porous structure and distinctive electro-optical properties have prompted interest in the system's potential for energy-relevant chemical reactions. The imogolite structure leads to a permanent intrawall polarization arising from the presence of bifunctional surfaces at the inner and outer tube walls. Density functional theory simulations suggest such bifunctionality to encompass also spatially separated band edges. Altogether, these elements make INTs appealing candidates for facilitating chemical conversion reactions. Despite their potential, the exploitation of imogolite's features for photocatalysis is at its infancy, thence relatively unexplored. This perspective overviews the basic physical-chemical and optoelectronical properties of imogolite nanotubes, emphasizing their role as wide bandgap insulator. Imogolite nanotubes have multifaceted properties that could lead to beneficial outcomes in energy-related applications. This work illustrates two case studies demonstrating a step-forward on photocatalytic hydrogen production achieved through atomic doping or metal co-catalyst. INTs exhibit potential in energy conversion and storage, due to their ability to accommodate functions such as enhancing charge separation and influencing the chemical potentials of interacting species. Yet, tapping into potential for energy-relevant application needs further experimental research, computational, and theoretical analysis.