Formation and exploration of polymorphism in WO3 nanostructures for improved catalytic and chemical sensing performance

Abstract

Nowadays, the development of functional sensing materials to detect gaseous and volatile organic compounds is of great importance for health and the environment. Doping and functionalization of semiconductor materials, as well as the synthesis of composites, are the most considered methods to improve their sensing performance. In this respect, polymorphic transitions in semiconductor metal oxides and subsequent structural changes offer alternative and efficient strategies to tune the kinetics of redox reactions at their surface. Thus, the polymorphism in transition oxide nanostructures can lead to a significant improvement in their catalytic properties. Here, monoclinic/orthorhombic polymorphic WO₃ nanomaterials are synthesized by the precipitation method. Experimental studies and theoretical modeling of the prepared structures are carried out. The results indicate that the composition of the solvent is a crucial factor in the formation and shape of WO₃ nanoparticles. The use of polyethylene glycol as a surfactant increases the degree of structural disorder, suppresses the formation of hydrates, and affects the oxygen content in WO₃. These effects, in combination with the formation of monoclinic/orthorhombic n–n junctions in the WO₃ polymorph, dramatically increase its sensitivity to acetone molecules. In particular, the response of the synthesized WO₃ polymorph is up to 8 times greater compared to the single-phase monoclinic structure. Hence, appropriate modification of the WO₃ crystal structure and formation of monoclinic/orthorhombic junctions in the nanomaterial can significantly improve its sensing performance to acetone without using dopants, mixture materials, or catalytic layers. The performed experimental studies and theoretical modeling to describe the influence of monoclinic/orthorhombic polymorphism on the sensing performance of WO₃ are important and may provide new insights into its applications in monitoring systems and heterogeneous catalysis.