氢溢流引发颜色变化的核心过程：

1. 氢气解离：Pt等贵金属催化剂将H₂分子裂解为H原子

2. 氢溢流：H原子迁移到WO₃表面

3. 注入与变色：H原子注入WO₃晶格，W⁶⁺被还原为W⁵⁺，形成蓝色HₓWO₃

4. 可逆漂白：通入O₂时，HₓWO₃被氧化，恢复原色

这一颜色变化本质上是氢原子进入WO₃晶格后引发的价态变化和结构相变（单斜→四方），肉眼即可直接观察。

To check for the spillover, we used WO3 to diagnose the activation of molecular hydrogen in the various catalysts, because the spilled-over hydrogen migrates and readily reacts with the yellow WO3 to form dark blue HxWO3.  As shown in the photographs in Figure, the WO3 alone exhibited an unchanged color after hydrogen treatment. In contrast, the Rh@HZSM-5 gave the darkest color of the tungsten species after hydrogen treatment under mild conditions , demonstrating that hydrogen dissociation and spillover occurred. We infer that the significant spillover should be attributed to the abundant acidic sites on Rh@HZSM-5. After partial ion exchange of protons with K+, Rh@KZSM-5 with reduced acidity also showed the color change, but the resultant color was much lighter than that observed with Rh@HZSM-5.

Product Selectivity Controlled by Nanoporous Environments in Zeolite Crystals Enveloping Rhodium Nanoparticle Catalysts for CO2 Hydrogenation | Journal of the American Chemical Society

https://pubs.acs.org/doi/pdf/10.1021/acsami.6c02154