Is there any official list of people that Zoro had captured or killed as a pirate hunter? I am wondering, since we all knew from the beginning when Zoro appears in the OP world, he was known as a "Bounty hunter" sometimes called "Pirate hunter Zoro".

Is there any official list of individuals that Zoro had captured or killed when he had that title?
No, there is no known list of pirates Zoro captured or killed during his pirate hunter period. The only known one would be Mr. 7

Zoro learned of Dracule &quot;Hawk-Eye&quot; Mihawk, who currently holds the title of the Greatest Swordsman in the world. He set off to sea, searching for him in order to challenge him to a duel. However, he lost his way, and could not find his way back home. In order to survive on his own, he took on bounties to pay for living expenses. He quickly built a famous reputation for himself as a &quot;Pirate Hunter&quot; in East Blue and even in Grand Line as Baroque Works had heard about him; he was even considered the greatest swordsman of East Blue, after which he met the two bounty hunters, Johnny and Yosaku.
Because of his reputation as a bounty hunter, Zoro was offered a position as a numbered agent within the Baroque Works. He replied with that he would accept only on the condition that he would lead the organization (which they refused). He then killed Mr. 7, the agent who offered him the position, to defend himself. - One Piece Wiki