Large-Pore Mesoporous CeO_2-ZrO_2 Solid Solutions with In-Pore Confined Pt Nanoparticles for Enhanced CO Oxidation

摘要

Active and stable catalysts are highly desired for converting harmful substances (e.g., CO, NO_x) in exhaust gases of vehicles into safe gases at low exhaust temperatures. Here, a solvent evaporation-induced co-assembly process is employed to design ordered mesoporous Ce_xZr_(1?x)O_2 (0 ≤ x ≤ 1) solid solutions by using high-molecular-weight poly(ethylene oxide)-blockpolystyrene as the template. The obtained mesoporous Ce_xZr_(1?x)O_2 possesses high surface area (60-100 m~2 g~(?1)) and large pore size (12-15 nm), enabling its great capacity in stably immobilizing Pt nanoparticles (4.0 nm) without blocking pore channels. The obtained mesoporous Pt/Ce_(0.8)Zr_(0.2)O_2 catalyst exhibits superior CO oxidation activity with a very low T100 value of 130 °C (temperature of 100% CO conversion) and excellent stability due to the rich lattice oxygen vacancies in the Ce_(0.8)Zr_(0.2)O_2 framework. The simulated catalytic evaluations of CO oxidation combined with various characterizations reveal that the intrinsic high surface oxygen mobility and well-interconnected pore structure of the mesoporous Pt/Ce_(0.8)Zr_(0.2)O_2 catalyst are responsible for the remarkable catalytic efficiency. Additionally, compared with mesoporous Pt/ Ce_xZr_(1?x)O_(2-s) with small pore size (3.8 nm), ordered mesoporous Pt/Ce_xZr_(1?x)O_2 not only facilitates the mass diffusion of reactants and products, but also provides abundant anchoring sites for Pt nanoparticles and numerous exposed catalytically active interfaces for efficient heterogeneous catalysis.