A comprehensive approach was applied to investigate oscillatory CO oxidation over a Pt/Al2O3-based diesel oxidation catalyst with small Pt particles (about 1.5 nm diameter) in a fixed-bed microreactor under relevant reaction conditions by combining spatially and time-resolved operando X-ray absorption spectroscopy, infrared thermography, and online mass spectrometry. The catalyst-bed zone responsible for the oscillatory behavior and the emerging hot spot was identified by means of IR thermography. Oscillations of the Pt oxidation state and the hot spot region evolved simultaneously and moved from the end toward the beginning of the catalyst bed with increasing reaction temperature. The changes in CO oxidation activity during oscillations can be unambiguously correlated with dynamic structural changes of the Pt particles. The applied operando approach is complementary to surface science studies and also studies on model Pt particles. Surface oxidation of small Pt nanoparticles leads to a fast deactivation of the catalyst, which is regenerated in a slow reduction step. The presence of metallic Pt is required for high activity of the catalyst.
Bibliographical noteFunding Information:
KIT and the BMBF projects ‘MatAkt’ and ‘ZeitKatMat’ are gratefully acknowledged for financial support, and SLS (SuperXAS beamline) and ANKA (XAS beamline) for providing beam time. Dr. M. Nachtegaal, Dr. O. Safonova (SLS), and Dr. S. Mangold (ANKA) are gratefully acknowledged for their help and technical support during XAS experiments. FLIR is acknowledged for providing the IR thermography camera and technical assistance. Jan-Dierk Grunwaldt and Ronald Frahm are finally grateful on the fruitful discussions on in situ and operando studies with people at Haldor Topsøe A/S which started with Bjerne Clausen, Alfons Molenbroek, Henrik and Nan Topsøe, Jens Rostrup-Nielsen, and especially inspiring conversations with Haldor Topsøe, who also gave an inspiring talk at HASYLAB.
- CO oxidation
- Heterogeneous catalysis
- Structure-activity relationships