Look up classic ADHD coping mechanisms. Others have mentioned some in this thread like studying with someone (body doubling) or enforcing a schedule. One big reason procrastination works is that the stress/adrenaline acts like a stimulant that is one of the normal medications for ADHD that helps you focus.
One other suggestion is to study when well rested (first or second thing in the morning). ADHD symptoms can be exacerbated by being tired.