What does this phrase outside Yue Fei Temple mean? (Characters identified: 乾坤正氣)
The characters are

⿰龺乙⿰土正氣

In modern characters, this would be written as

乾坤正氣


The tricky characters are the first and second, where

The right side of the first character is 「乙」
The right side of the second character is an old way of writing 「申」