Solution Processed Hafnia Nanoaggregates: Influence of Surface Oxygen on Catalytic Soot Oxidation

Hafnium dioxide (HfO2) nanoaggregates are synthesized by sol-gel and hydrothermal routes followed by hydrogen annealing at different time durations. The proposed study aims to explore the effect of hydrogen annealing time on the properties of HfO2 and also envisage the catalytic soot oxidation using HfO2 nanoaggregates. It is observed that annealing under a hydrogen atmosphere brought about substantial changes in certain attributes such as chemical and textural properties with marginal changes in some other properties like optical activity and band gap. The pristine HfO2 without hydrogen annealing showed a lower ignition temperature, whereas hydrogen annealed HfO2 for 2 h showed the best catalytic performance characterized by the soot combustion temperature (T50) in contrast to samples prepared at longer duration because of the higher surface adsorbed oxygen species in its widely distributed pores.