(2) a nitrate N-O stretching mode centered at 1350 cm -1 , increasing in intensity with increasing nitrate concentration; and (3) phosphate bands between ca. 700 and 1200 cm -1 , which decrease slightly with increasing nitrate concentration, suggesting competitive adsorption with nitrate. Similar observations are made for drop-cast SnO2 powder (Figure ). Numerical integration of the nitrate N-O stretching mode (Figure , Figure ) yields increasing intensity with increasing nitrate concentration, followed by a plateau indicative of a nitrate-saturated surface. Integrated intensity of nitrate band (ca. 1200 to 1500 cm -1 ), normalized by the peak nitrate intensity, for CeO2-δ (orange) and SnO2 (black; spectra provided in Figure ).