I agree with ThrustVectoring that you'll probably get more mileage out of implementing something like a GTD system (or at least that doing this will be cheaper and seems like it would complement any additional mileage you get out of nootropics). There are lots of easy behavioral / motivational hacks you can use before you start messing with your neurochemistry, e.g. rewarding your inner pigeon.

I've had some success recently with Beeminding my Pomodoros. It forces me to maintain a minimal level of work per unit time (e.g. recently I was at the MIRI workshop, and even though ordinarily I would have been able to justify not doing anything else during that week I still spent 25 minutes every day working on problem sets for grad school classes) which I'm about to increase.