Twenty years of making inorganic ultrafine fibers via electrospinning and sol–gel techniques I: an update on catalysis, photocatalysis, and adsorption R&D opportunities

For the past three decades, research interest in electrospinning (ES) has grown exponentially. Twenty years ago, the initial reports on the utilization of this rather simple ultrafine fiber-forming method in combination with a widely established materials chemistry tool known as sol–gel (SG) and without the aid of electrospun organic fibers as templates (or fiber-forming sacrificial polymers) were published in the open literature. In parallel, several groups right around the same time also proposed the use of long-chain organic polymers in SG formulations to facilitate their spinnability into ultrafine fibers. Since then, the number of research articles exploring SG-ES to produce inorganic fibers with submicron diameters has also grown steadily, resulting in several identifiable R&D sub-fields. Relatively recent advances in ES scalability have now made it even more attractive for exploring potential commercial applications. This review is an attempt to provide readers with a comprehensive overview of SG-ES work done in the areas of metal oxide catalysis, photocatalysis, and adsorption. It does not focus on devices having a catalytic function, such as fuel cells and sensors, but on materials whose end goal is to be used as catalysts or sorbents. A number of potentially valuable opportunities and recommendations are also offered.