Chitosan capped noble metal doped CeO2 nanomaterial: Synthesis, and their enhanced catalytic activities

Chitosan (Ch) capped Ch-CeO2, Ch-CeO2/Ag, Ch-CeO2/Pd and Ch-CeO2/Ag/Pd nanomaterials were fabricated using seedless and metal displacement plating method. The Ce4+ ions first formed complex with Ch through amino and hydroxyl groups and then reduced in presence of NaOH and molecular oxygen at higher temperature. Ch-Ag+ and Ch-Pd2+ complexes adsorbed on the surface of Ch-CeO2 and reduced under potential deposition. Ninhydrin reaction test was conducted to confirm the presence of chitosan on the surface of NMs. The catalytic efficiency was increases markedly with incorporating noble metal into Ch-CeO2 NMs. Ch-CeO2/Ag/Pd exhibits higher catalytic performance towards hydrogen generation due to the narrow band gap (2.65 eV) and smaller work function of CeO2 (phi = 2.8 eV) than that of Ag-0 (phi = 4.6 ev) and Pd-0 (phi = 5.2 eV). Hydrogen generation rates increases with temperature and activation energies were found to be 632, 60.3, 56.2 and 53.0 kJ/mot for Ch-CeO2, Ch-CeO2/Ag, Ch-CeO2/Pd, and Ch-CeO2/Ag/Pd, respectively. CeO2/Ag/Pd shows better catalytic efficiency due to the strong interaction between Ag/Pd metal and active support CeO2. The photocatalytic rates drastically inhibited with scavengers, demonstrate that the reactive radical oxygen species (HO center dot and O-2(-)center dot), holes (h(+)) and electrons (e(-)) played major role in the NaBH4 hydrolysis. (C) 2020 Elsevier B.V. All rights reserved.

Automated summary

Chitosan-capped CeO2 nanomaterials with noble metal composites were fabricated, showing significantly improved catalytic efficiency. CeO2/Ag/Pd exhibited the best catalytic performance, while reactive oxygen species and holes played major roles in the NaBH4 hydrolysis process.