Please see the Certification and Training section found here.
This is the most pertinent part.
'There is no officially recognised Selenium certification available,
and the project developers strongly believe that certification is of no real benefit
to individuals or the industry. We have not authorized anyone to offer "official"
Selenium certification and anyone who claims to offer it is misusing the Selenium
project's trademark.'
Tread carefully with anyone offering certification. I'm certain there are paid trainings offered from many places (although I've never used anything other than classes on Pluralsight that covered things I already knew), but there is also a lot of freely available information on the internet to help learn how to use Selenium.
Best wishes on your Selenium explorations!