If one is unable to say Hallel (on Chanukah) at Schachris, may be say it in the afternoon?
Yes, it may be said until sunset. Saying hallel should not be pushed off, and it should be said adjacent to davening shacharis. It should be noted that one should not eat before saying hallel, unless the person is weak.
Mishna Megillah 20b, M:B 422-2 Biur Halacha D:H V’korin