In certain chemical reactions, catalysts can be used to decrease the activation energy of those reactions. For example, platinum is a catalyst for hydrogen/oxygen reactions, so, therefore, the resulting gases have more energy leading to a higher ISP. Right?
If so, then I understand why there aren't platinum catalysts in the reaction chamber of the engine as it would melt the platinum. However, what would be the issue with suspending the platinum within the hydrogen fuel to form a colloid, therefore removing that aspect of the problem?
The video linked is an interesting watch too