"informed him of" is correct and usable in written English.
You can use it when you want to communicate that you have given someone information. For example: I informed him of the change in the meeting time.
A fellow rider informed him of the power issues.
We have informed him of the status of the case.
Fagan went to the trial judge's chambers and informed him of her suspicions.
Fiorito informed him of the skateboard incident, and the coach took it calmly.
Idowu disputed the head coach's assertion that he had informed him of his displeasure.
They informed him of the name change as a kind of honor.
Offerman, 33, reacted angrily when General Manager Mike Port informed him of the decision.
Rankin-Gee, with a bright smile, quickly informed him of their change in plans.
Mr. Levy said a board official had informed him of the policy yesterday morning.
Then the telephone rang, and the president of the Swedish Academy informed him of the prize.
Lamoriello told The Associated Press that Sutter informed him of his decision Monday night.
