Only if a substantial amount of potato were stuffed into the barrel. The burst strength of the barrel is so much greater than the potato that the potato will always splash.
Silencers mainly trap the expansion of gas exiting outside the barrel end. A silencer cut in half has a lot of small baffles to divert gas away from the main exit stream. You could make a silencer with a water bottle stuffed with wet tissues.
Preparing the potato by making a hole all the way through it might forestall fragmentation of said potato.
How about that stupid old rumor, from Dick Tracey’s Crimestoppers, that a rubber baby bottle nipple can be used as a silencer?
No, it won’t. The powder gases alone will shred the potato. Even if you used a blank the results would be the same. Suppressors work by slowing the expansion of said gases and cooling them. They work exactly the same way as an automotive muffler. A potato does not do that.