Catalysts, catalyst systems, and methods for removing ammonia and/or carbon monoxide in flue gases are provided where ammonia is used with a selective catalytic reduction catalyst for reducing oxides of nitrogen. A dual oxidation catalyst generally comprises an alkali component, a transition metal, and a metal oxide support. This catalyst is also substantially free from precious metal components and effective for substantially simultaneously oxidizing ammonia (NH.sub.3) and carbon monoxide (CO) when placed in an exhaust gas stream. The catalyst is effective to provide low ammonia to nitrogen oxides selectivity.