• Effect of NaBH 4 chemical etching on the reducibility of CeO 2 nanorods. • CO adsorption band for polydentate carbonate is found from in situ DRITFS as a result of NaBH 4 etching. • Surface defects obtained by NaHB 4 chemical etching are critical to strong TM (TM-transition metals: Cu, Co, Ni, Fe, Mn)-CeO 2 interactions, therefore resulting in the improved low temperature catalytic activity. In this work, hydrothermally synthesized CeO 2 nanorods (CeO 2 NR) were chemically etched by strong reducing agent NaBH 4 with 0.6~30 wt% addition, and further transition metal (TM) oxides (TM: Cu, Co, Ni, Fe and Mn) were loaded on the surface modified 6 wt% NaBH 4 CeO 2 NR powder (mCeO 2 NR) to prepare mCeO 2 NR supported TM oxide catalysts. Both mCeO 2 NR supports (treated by 0.6–30 wt% NaBH 4 ) and mCeO 2 NR supported TM oxide catalysts were employed to investigate the effect of chemical etching on their surface structure, CO adsorption, CO 2 desorption and catalytic performance. Compared with pristine CeO 2 NR, one strong CO adsorption band for polydentate carbonate is found from in situ DRITFS as a result of NaBH 4 etching, which can explain the enhanced low temperature reducibility and catalytic performance of mCeO 2 NR supports and mCeO 2 NR supported TM oxide catalysts. The vibrational band signals of bicarbonate, monodentate/bidentate/polydentate carbonate and bridged carbonate are detected in all mCeO 2 NR supported TM catalysts and the effect of CO adsorption mode on CO oxidation activity is discussed.