urge vs urge on

urge is a noun but urge on is not a noun.

Word	Noun	Adjective	Verb	Adverb
urge	Yes	No	Yes	No
urge on	No	No	Yes	No

As verbs, urge and urge on are synonyms defined as:

Other synonyms of urge include exhort, press.

As verbs, urge and urge on are synonyms defined as:

Other synonyms of urge include barrack, cheer, exhort, inspire, pep up, root on.

urge (noun)	urge on (noun)
a strong restless desire
an instinctive motive

urge (verb)	urge on (verb)
force or impel in an indicated direction	force or impel in an indicated direction
spur on or encourage especially by cheers and shouts	spur on or encourage especially by cheers and shouts
push for something