| Pacific Rim Symposium on Surfaces, Coatings and Interfaces (PacSurf 2016) | |
| Nanomaterials | Monday Sessions |
| Session NM-MoE |
| Session: | Nanocatalysis |
| Presenter: | Takeshi Fujita, Tohoku University, Japan |
| Correspondent: | Click to Email |
Precious metals (Pt and Pd) are typical materials for heterogeneous exhaust-gas catalysts in automotive systems. During a catalytic reaction in conventional nanoparticulate systems, such as Pt, active nanoparticles (typically less than 5 nm) aggregate, resulting in a significant reduction of performance. In addition, their limited resources and high market-driven prices are principal issues in realizing the path toward a more sustainable society.
Herein, we developed an earth-abundant nanoporous NiCuMnO catalyst by leaching Mn from a CuNiMn precursor. The developed catalyst was catalytically active and durable for NO reduction and CO oxidation. During catalytic reactions, the nanostructure self-transformed into a more active nanostructure; in particular, the Cu/CuO regions derived from the nanostructure were very active, and further significant coarsening was not observed without the loss of activity, as these regions were tangled with a stable nanoporous NiMnO network. The self-transformed nanostructure successfully completed a long-term durability test for NO reduction at 400 °C for 10 days. The in situ TEM under NO reduction clearly provided evidence for the instant reaction-induced self-transformation of the nanostructure. This result demonstrates an important implication of this work: even when nanoporous alloys are coarsened to significantly greater than 100 nm, as long as the metal phase is entangled and sustained within a stable nanoporous network of oxides, geometrically necessary surface defects can be retained as catalytically active sites and further enhanced catalytic performance exhibited because of the metal-oxide interfaces (i.e. perimeter); thus, catalytic activity can be retained with durability.
Although the nanoporous NiCuMnO catalyst requires more improvement at low temperatures, the temperature of the catalyst bed in an automobile system is typically higher than 400 °C, where nanoparticles become significantly unstable. Production of the nanoporous catalysts can be easily scaled up, and they may be a rational alternative to traditional precious-metal catalysts for automotive systems in the near future [1].
References
[1] T. Fujita et al., Adv. Func. Mater. 26 (2016) 1609-1616.