We have identified a new NOx storage/reduction catalyst with the composition of Pt-KNO3 supported on a K-titanate nanobelt (KTN) prepared using hydrothermal method. Isothermal NOx storage experiments at 350 degrees C revealed the highest storage capacity (2.27 mmol/g) ever achieved over 33 wt.% KNO3 impregnated catalyst, and lean-rich cycles could be operated for more than 15 times with maintaining its high storage capacity. The characterization of the spent catalysts revealed that addition of more than 33 wt.% KNO3 caused the gradual destruction of the nanobelt structure during the reaction and the decrease in NOx storage capacity. High temperature operation such as at 500 degrees C also caused the destruction of nanobelt structure. It was demonstrated that the main storage specie of NOx was potassium nitrate. Immigration of K+ from and back to K-rich layers on KTN might be the mechanism for the storage and reduction of NOx on those materials. (C) 2011 Elsevier Inc. All rights reserved.