The novel catalysts of truncated polyhedron Pt nanoparticles supported on three-dimensionally ordered macroporous oxides (Mn, Fe, Co, Ni, Cu) with nanoporous walls for soot combustion

Abstract

Three-dimensionally ordered macroporous (3DOM) transition metal oxides (TMO) (Mn, Fe, Co, Ni, Cu) with nanoporous walls were synthesized by the surfactant (P123)-assisted colloidal crystal template (CCT) method, and 3DOM TMO-supported truncated polyhedron Pt nanoparticle catalysts were prepared by the gas bubbling-assisted membrane reduction (GBMR) method. All the catalysts possessed well-defined 3DOM nanostructure with small interconnected pore windows (∼80nm). The nanopores with the size of ∼6nm and truncated polyhedron Pt nanoparticles with the sizes of 2.9–3.5nm are highly dispersed on the inner walls of uniform macropores. 3DOM Pt/TMO catalysts with nanoporous walls exhibit the large total pore volume (∼3.4mlg−1), the high porosity (>91%) and surface area (36–40m2g−1). 3DOM structure improves the contact efficiency between catalyst and soot, and the strong metal (Pt)–support (TMO) interaction is favorable for the improvement of reducibility and for increasing the amount of active oxygen species. Among all of 3DOM Pt/TMO catalysts with nanoporous walls, Fe- and Co-based catalysts with the moderate reducibility exhibited higher catalytic activity for diesel soot combustion in contrast to the others. For instance, the T50 of 3DOM Pt/Fe2O3 and Pt/Co3O4 catalysts are 358 and 351°C, respectively. And the nanopores on the inner walls of 3DOM Pt/TMO catalysts remarkably improve the SCO2 for soot oxidation, and it is nearly 100% in a wide temperature range (200–450°C). The excellent performance of the catalysts for soot combustion might be due to the factors including unique 3DOM structure with nanoporous walls, highly active component (Pt), large surface area, and the moderate reducibility of the materials. The materials consist of 3DOM supports with nanoporous walls and metal nanoparticle active sites may be the potential practical applications in the catalytic oxidation of diesel soot particles.