Synthesis and Photocatalysis of Metal Oxide Aerogels: A Review

Metal oxide aerogels have emerged as a new class of photocatalysts. As a type of 3-dimensional (3D) porous structure, an aerogel owns the characteristics of high specific surface area, tunable pore size, and large pore volume, which can distinguish itself from conventional powder or film counterparts. Such merits allow aerogels to expose more active catalytic sites and support other active cocatalysts. Metal oxide aerogels in a monolithic form also overcome the recycling and separation issues that hinder the application of free-standing powder photocatalysts. This article reviews the typical synthesis methodologies of metal oxide aerogels, including alkoxide hydrolysis and condensation, epoxide assistant, and self-assembly. It also discusses the interfacial charge and mass transfer processes in metal oxide aerogels and correlations among the composition, microstructure, and photocatalytic activity. In addition, this article gives a summary of photocatalytic applications of aerogels in water purification and sterilization, solar water splitting, and gas-phase reactions such as CO2 reduction and CO oxidation. It also discusses the strategies for enhancing the performance of aerogel photocatalysts. In particular, this paper highlights the recent development of plasmonic aerogel photocatalysts.