Hydrogen Power Project

At my high school we all have to complete a senior project of our choice in order to graduate. In entails a paper, presentation, and a product that it took at least 12 hours to create. I thought an exploration of using hydrogen as a fuel source would be a cool project. I thought I could send an electric current through water to harvest the O2 and the H2 (electrolysis). I could then combust the H2 i made and make a simple engine to create mechanical energy.

Does any body have any comments or advice on this project? I especially want advice on creating the engine. I want to make something relatively simple, the simplest I could think of would be a pinwheel kinda deal where the expanding gas would simply spin a pinwheel, but a piston design would be great if I could build it cheaply.