Engineering the hexagonal/monoclinic phase mixture for balancing stability and gasochromic performance of Pd-decorated WO3-based hydrogen sensor

In the study of WO 3 -based gasochromic materials, the color-change rate and contrast are key indicators for evaluating sensor performance, while long-term stability is equally critical, as it directly determines the service life and reliability of the material in practical applications. In this work, h-WO 3 /m-WO 3 gasochromic materials with a hexagonal–monoclinic mixed-phase structure were successfully synthesized by regulating the annealing temperature. Pd nanoparticles were introduced as essential catalysts to enable room-temperature hydrogen-induced coloration of WO 3 . The Pd–WO 3 –400 sample exhibits excellent response to 1 % hydrogen at room temperature, with a rapid response time of only 13 s and a maximum total color difference (ΔE) of 8.1. Moreover, after one year of cyclic testing, this sample shows the slowest performance degradation, demonstrating outstanding long-term stability. In the mixed-phase structure, the open ionic diffusion channels of the hexagonal phase synergize with the structural stability of the monoclinic phase, while phase interfaces further enhance electron and hydrogen-ion transport. These combined effects significantly improve the gasochromic response. This study provides a strategy for designing gasochromic materials that balance high sensitivity and long-term stability, supporting the practical application of visual hydrogen-leak detection.