The decisive factor of hollow spherical network morphology of Nd_1-xCe_xCo_1-yCu_yO_3±δ perovskites towards soot oxidation

The perovskites Nd_1-xCe_xCo_1-yCu_yO₃ (x = 0–0.05, y = 0–0.1) have been synthesized using PVP-assisted sol–gel method and applied for soot oxidation reactions. XRD technique reveals the formation of orthorhombic phase with crystal volume of around ~ 214 ų and crystal size of ~ 25–40 nm. The interconnected nanoparticles with hollow spherical network morphology of particles are observed for the samples NdCoO₃ (NC1) and Nd_0.98Ce_0.02Co_0.95Cu_0.05O₃ (NC2) with particle sizes of around 300–500 nm. The samples experienced a charge transfer from ligand (O²⁻) to cobalt cation in UV region (210–260 nm) and also observed broad absorption bands in the visible region (380–600 nm). In addition, the bandgap energy of NC2 showed the lowest value (4.21 eV); as well as surface morphological advantage promoted the transport of surface-chemisorbed oxygen species in the inner and outer surface of catalysts surface due to the reducibility of the catalyst with the soot (O2x-O2x-+O2-=0.90). Furthermore, XPS results evidenced the higher content of Co²⁺ cation upon substitution of Ce/Cu into NC1, which successively formed more amount of O_β-oxygen species. Remarkably, the perovskite NC2 showed the lowest soot oxidation temperature (T_50% = 434 °C) among the investigated perovskites. Besides, the spherically networked morphology of NC2/NC1 samples also decided the soot oxidation process.