I am building a Rube Goldberg machine for Science Olympiad, and one of the scoring steps is to use light to trigger a chemical reaction, which made me immediately think of the decomposition of hydrogen peroxide, but the only problem is that it doesn't occur fast enough. After doing some research, I realized that manganese oxide, the only catalyst for this reaction that I am aware of, will make the reaction occur without light. So, I am now looking for a catalyst that will speed up the reaction fast enough (to produce enough gas to inflate a balloon), but not lower the activation energy so much that it will occur without light.
Just to clarify, the competition does allow people to ask online, and there is in fact a whole community where people discuss this stuff.