Effects of different crystal phases of WO3 and their three-dimensional hierarchical structures on hydrogen gasochromic properties

Self-assembled three-dimensional tungsten trioxide (WO 3 ) structures were synthesized using a low-cost hydrothermal process. By adjusting the pH of the precursor solution, monoclinic WO 3 (m-WO 3 ) and hexagonal WO 3 (h-WO 3 ) were fabricated. The morphology, structure, chemical composition, and gasochromic properties of both WO 3 phases were systematically characterized. The results showed that, compared to m-WO 3 sensors, h-WO 3 sensors exhibited a faster response time (23.43 s) and higher contrast (ΔE = 6.88) to 1 % hydrogen at room temperature. Furthermore, first-principles calculations based on density functional theory (DFT) not only explained the excellent sensing performance of h-WO 3 but also refined the understanding of the gasochromic mechanism of WO 3 . The combination of experimental and theoretical studies provides a detailed explanation of the differences in gasochromic properties between the two WO 3 crystal phases. h-WO₃ possesses a unique intracrystalline tunnel structure, which provides more adsorption sites and enables faster electron transport. This work offers a feasible strategy for designing novel hydrogen sensors and holds practical significance for hydrogen leak detection and traceability.