In a recent report, ozone was produced with high efficiency in perchloric acid on an anode coated with antimony-doped tin oxide. We report here that high current efficiency can be enhanced if trace amounts of a second dopant, nickel, is present. The effect of composition of the coating in terms of Ni:Sb:Sn was carefully analyzed. The optimum Ni:Sb:Sn ratio, determined to be 1:8:500, was determined giving a corresponding ozone generation current efficiency of over 30% at room temperature. The highest current efficiency was observed at an optimum operating potential of <mml:math display="inline"><mml:mrow><mml:mn>2.2</mml:mn><mml:mspace width="0.3em"></mml:mspace><mml:mi mathvariant="normal">V</mml:mi></mml:mrow></mml:math>2.2V vs <mml:math display="inline"><mml:mrow><mml:mi mathvariant="normal">Ag</mml:mi><mml:mo>∕</mml:mo><mml:mi mathvariant="normal">Ag</mml:mi><mml:mi mathvariant="normal">Cl</mml:mi></mml:mrow></mml:math>Ag∕AgCl . Electrolytic generation of ozone in perchloric acid, sulfuric acid, and phosphoric acid at different concentrations was also studied and compared. In <mml:math display="inline"><mml:mrow><mml:mn>0.1</mml:mn><mml:mspace width="0.3em"></mml:mspace><mml:mi mathvariant="normal">M</mml:mi></mml:mrow></mml:math>0.1M <mml:math display="inline"><mml:mrow><mml:msub><mml:mi mathvariant="normal">H</mml:mi><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub><mml:mi>S</mml:mi><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mrow><mml:mn>4</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>H2SO4 , the ozone concentration reached <mml:math display="inline"><mml:mrow><mml:mn>34</mml:mn><mml:mspace width="0.3em"></mml:mspace><mml:mi>mg</mml:mi><mml:mo>∕</mml:mo><mml:mi mathvariant="normal">L</mml:mi></mml:mrow></mml:math>34mg∕L and a current efficiency of 36.3% could be achieved. This is about the highest current efficiency ever reported for electrolytic generation of ozone in an aqueous medium at room temperature.