To gain a more comprehensive understanding of the crystallinity and structure of the WO3@Ti and WO3@Ni, peeled-off partitions of both were analyzed using transmission electron microscopy (TEM) (Figure and). In the WO3 grown on the Ti mesh the TEM images confirmed a highly crystalline nanowire. In contrast, the WO3 grown on the Ni foam substrate displayed small, highly crystalline WO3 particles alongside larger amorphous particles. These larger particles which shrink under the electron beam are indicative of NiO/Ni(OH)2. This observation also explains the absence of NiO/Ni(OH)2 reflections in the XRD patterns, as the amorphous nature of the material does not produce sharp diffraction peaks. The results in The surface, elemental, and chemical composition analysis confirm the successful synthesis of WO3, with its morphology, crystallinity, and purity meeting the desired features. Among the substrates evaluated, the Ti substrate demonstrated excellent characteristics, including high chemical resistivity during hydrothermal treatment. This stability makes Ti an ideal substrate for WO3 deposition as it prevents any undesired interactions that could alter the properties of the WO3 layers. In contrast, Ni substrate exhibited reactivity during the same process, leading to the formation of NiO/Ni(OH)2 alongside WO3. This secondary phase limits the utility of Ni as a substrate for WO3 iontronic application, as the formation of NiO/Ni(OH)2 could degrade the performance and purity of the WO3 layer. Therefore, Ti substrates are preferred over Ni for applications requiring stable WO3 coatings, particularly in hydrothermal environments.