Advanced redox (uni yr3) write the half equations ...?

(NO3)- + 2H+ + e- --> NO2 + H2O

2(NO3)- + 4H+ +2e- --> N2O4 +2H2O

Nitrogen Dioxide and Dinitrogen Tetroxide are in equilibrium, lower temperatures and higher pressures favour Dinitrogen Tetroxide.

N2O4 + 2H+ + 2e- --> 2H+ 2(NO2)- (Protons can be omitted)

2(NO2)- + 6H+ + 2e- --> N2O + 3H2O

N2O + 2H+ + 2e- --> N2 + H2O

Overall Reaction...

2(NO3)- + 12H+ + 8e- --> N2 + 6H2O

Of Course most Nitric acid reactions tend to produce NO or NO2, although it always appears as if NO2 is being produced because NO oxidises rapidly in air.