(600o) Pd-Substituted Zinc Stannate As a New Oxygen Storage Material for CO Oxidation

Extensive work from both scientific and engineering fields have been devoted to CO oxidation reaction, in response both pollution control and renewable energy development. This is extensively used reaction that has various industrial applications in automotive catalytic converter and fuel cells. CeO₂, SnO₂, Fe₂O₃, TiO₂, are commonly utilized for their application in CO oxidation. The metal oxides which are reducible have advantages in releasing the lattice oxygen and promoting the CO oxidation. A key factor is that the material should have high oxygen storage capacity at low temperatures and thus a high activity of CO oxidation. In these ionic-substituted oxides, a weakening of “metal-oxygen” bond results in lattice oxygen release at very low temperatures during reaction and that are better as compared to metal dispersed oxides.¹One of the limitations of CO oxidation catalyst is that it shows poor performance in hydrogen rich atmosphere. Many efforts have been focused on preferential CO oxidation catalysts that are inactive towards undesired H₂ oxidation.² Few studies revealed that compared to other oxides, zinc stannate sensors showed high selectivity towards CO in H₂ atmosphere at low temperatures.³ Inspired by these studies, we hypothesize that zinc stannate may be an important material for CO oxidation, which has not been reported so far. In this report, we synthesized new and novel oxygen storage Pd-substituted Zn₂SnO₄ through solution combustion method that exhibits good oxygen storage capacity resulting in a low temperature CO oxidation. Encouragingly, this system showed higher activity towards CO oxidation at low temperatures. Our results indeed indicate that, when Pd is substituted in zinc stannatethe metal-oxygen bond weakens, which benefits the lattice oxygen release.We proposed the mechanism based on reaction rates, both CO and O₂ are competitive for the same adsorption sites, according to the data collected in kinetic regime.

References

1.         Hegde, M.; Madras, G.; Patil, K., Noble metal ionic catalysts. Accounts of chemical research 2009,42(6), 704-712.

2.         Pozdnyakova, O.; Teschner, D.; Wootsch, A.; Kröhnert, J.; Steinhauer, B.; Sauer, H.; Toth, L.; Jentoft, F.; Knop-Gericke, A.; Paál, Z., Preferential CO oxidation in hydrogen (PROX) on ceria-supported catalysts, part I: Oxidation state and surface species on Pt/CeO₂ under reaction conditions. Journal of Catalysis 2006,237(1), 1-16.

3.         Yu, J. H.; Choi, G. M., Selective CO gas detection of Zn₂SnO₄ gas sensor. Journal of electroceramics 2002,8 (3), 249-255.