This episode made me wonder if Luffy somehow absorbs logia power form those he encounters.. We've seen him use a fire punch (Red Hawk, Ace) against Hody and now a lightning (Enel) punch against Chinjao.. he even named the attack Thor.. after El Thor.
I guess it's the same kind of thing Kurohige used to steal Shirohige's powers, with the difference that Kurohige knows how to do it.