At 14, he's still young; with experience, the vocal part will come. Leading by example is a great foundation -- that will show his teammates that his directons and encouragement are worth listening to.
Having a coach that expects leadership from his catcher would be very valuable (haven't we all had the experience that a coach can use even the exact words we have to our sons....but they don't listen until that someone else says it?). So would having a coach who displays the value he places on the catching position. If you can find such a coach on a travel team or as a private instructor (given that he doesn't have that at hs), go for it.
Otherwise, start with basics. Hustle on and off the field like you own it. Then move on to how to deal with pitchers....which is a lot like dealing with real people with problems (that was for you, Phoenix
). Next might be encouragement to a player that just made an error. Take it one step at a time.
Sometimes we make the mistake of giving our kids general instruction "You need to be a leader". What does that mean? Does he know? Ask him what he thinks it is!
To me, being a leader on the field has nothing to do with the rah-rah stuff. But it has a lot to do with knowing the game, and doing all yu can to keep the team on track to put themselves in the best position to succeed as a unit.