A study was made of the overpotential and product selectivity characteristics of the high temperature solid electrolyte fuel cellIt was found that is the primary oxidation product, although significant amounts of by‐product are also formed due to the catalytic reaction between and on Pt. The influence of this side reaction can be minimized under optimal operating conditions and yields of exceeding 60% can be achieved. Two dimensionless numbers have been identified which govern product selectivity and power output. The cell is a promising candidate for the cogeneration of electric energy and nitric acid.