A recent study, carried out in collaboration between CNR, the Universities of Brescia and South-Ukrainian, and Sapienza University of Rome (Departments of Physics and SBAI), introduces a novel strategy to control the kinetics of redox reactions on WO₃ surfaces by exploiting structural polymorphism, without relying on conventional doping or composite-based approaches. We synthesized monoclinic/orthorhombic WO₃ polymorphic nanomaterials through a controlled precipitation process. Experimental characterization, supported by theoretical modeling, revealed that the solvent composition plays a key role in determining both the morphology and the phase evolution of WO₃. The addition of PEG as a surfactant enhance structural disorder, suppress hydrate formation, and modify the oxide lattice. These structural changes enable the development of monoclinic/orthorhombic n–n junctions within the WO₃ nanostructure, thereby improving the gas sensor’s sensitivity.