honestly, i think you already have your idea. use your setup: a kid has an upcoming chemistry exam that he is studying quite seriously to pass.
then make an inciting incident: an experiment he is working on goes wrong and:
a) he turns into altered being with super powers.
b) he creates an altered being with super powers... and is potentially wild/evil.
c) he creates a potion that temporarily increases his intelligence, but makes him forget long term memories as a side effect.
create whatever fits your style and preference. push your protagonist up a tree, then start sawing.
to break an art block, i'd recommend just going with a limited one-shot for your possible story. at least until you're done with your chemistry studies. good luck with both! 
