Quantitative discrimination of surface adsorbed NOx species on CeO2 via spectrophotometry for SCR denitration investigation

CeO 2 -based catalysts are widely investigated for selective catalytic reduction (SCR) of NO with NH 3 . Interaction of NO/O 2 with CeO 2 generally produces two surface species, i.e., nitrates and nitrites. However, the explicit quantification of these two species is still unresolved. Herein, we reported that spectrophotometry characterization was effective in determining surface adsorbed NO x species on CeO 2 by measuring the corresponding ions (NO 2 – and NO 3 – ) dissolved in aqueous solution. Experimental results show that both nitrate (–NO 3 ) and nitrite (–NO 2 ) species can be quantitatively evaluated and the accuracy is verified by calibrating with NO x -TPD result. Exclusive transfer of adsorbed NO x from catalyst surface to aqueous solution is confirmed and the dissolution process can be accelerated by ultrasonic treatment. Moreover, useful information related to evolution of surface NO x species under various conditions (O 2 treatment, different adsorption temperature and duration) and over different catalysts (Fe 2 O 3 , MnO 2 and MnO x –CeO 2 ) are provided. The result of present study demonstrates the potential of spectrophotometry for quantitative discrimination of surface NO x species on CeO 2 and other oxide-based materials, which is conducive to mechanism analysis of SCR reaction.