Publisher: Springer Nature

Issue: 2

License: http://www.springer.com/tdm

Publication date(s): 2019/02 (print) 2019/01/28 (online)

Pages: 157-163

Volume: 2 Issue: 2

Journal: Nature Catalysis

Link: http://www.nature.com/articles/s41929-018-0213-3

URL: http://dx.doi.org/10.1038/s41929-018-0213-3

The selective catalytic oxidation of NH₃ to N₂ presents a promising solution for the abatement of unused NH₃-based reductants from diesel exhaust after treatment. Supported Pd nanoparticle catalysts show selectivity to N₂ rather than NO_x, which is investigated in this work. The link between Pd nanoparticle structure and surface reactivity was found using operando X-ray absorption fine structure spectroscopy, diffuse reflectance infrared Fourier-transformed spectroscopy and on-line mass spectrometry. Nitrogen insertion into the metallic Pd nanoparticle structure at low temperatures (<200 °C) was found to be responsible for high N₂ selectivity, whereas the unfavourable formation of NO is linked to adsorbed nitrates, which form at the surface of bulk PdO nanoparticles at high temperatures (>280 °C). Our work demonstrates the ability of combined operando spectroscopy and density functional theory calculations to characterize a previously unidentified PdN_x species, and clarify the selectivity-directing structure of supported Pd catalysts for the selective catalytic oxidation of NH₃ to N₂.