This has been done ad nauseum. But...
Pre FP Hal had feats to match the best heralds, Thor included. But it's a matchup issue. Mjolnir's energy soak is among the best in all of comics, and he can redirect and amplify it to serve his purposes. Even a good GL can't overcome that when the matchup is so close even before such issues.
Anyway, Pym makes a good point here that it's not just about weapons.
Even without Mjolnir, Thor is a Class 100+ character with a fair degree of super-durability, weather powers, vast experience and more. There is that 60 seconds rule, but it's gonna be quite a challenge for Hal to separate Thor from Mjolnir for that long...