Cu-Pd bimetallic clusters with a Cu/Pd atomic ratio of 2 supported on active carbon (AC) ([Cu-2-Pd](cluster)/AC) selectively hydrogenated nitrate ions in water to harmless compounds, including N-2 and N2O (> 99% selectivity), and the formation of NH3 was suppressed to tolerable levels (<.5 ppm). The activity and selectivity of [Cu-2-Pd](cluster)/AC were superior to that of conventionally prepared Cu-Pd/AC. [Cu-2-Pd](cluster)/AC showed stationary conversion and selectivity from the onset of the reaction and remained active for up to 110 h.