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Instruments / Technical Area	Publication Details	Published	Actions
	Spatial profiling of a Pd/Al2O3 catalyst during selective ammonia oxidation Donato Decarolis , Adam H. Clark , Tommaso Pellegrinelli , Maarten Nachtegaal , Evan Lynch , C. Richard A. Catlow , Emma K. Gibson , Alexandre Goguet , Peter P. Wells Acs Catalysis 50, 2141 - 2149 DOI: 10.1021/acscatal.0c05356 Open Access Show Abstract ▼ Abstract: The utilization of operando spectroscopy has allowed us to watch the dynamic nature of supported metal nanoparticles. However, the realization that subtle changes to environmental conditions affect the form of the catalyst necessitates that we assess the structure of the catalyst across the reactant/product gradient that exists across a fixed bed reactor. In this study, we have performed spatial profiling of a Pd/Al2O3 catalyst during NH3 oxidation, simultaneously collecting mass spectrometry and X-ray absorption spectroscopy data at discrete axial positions along the length of the catalyst bed. The spatial analysis has provided unique insights into the structure–activity relationships that govern selective NH3 oxidation—(i) our data is consistent with the presence of PdNx after the spectroscopic signatures for bulk PdNx disappear and that there is a direct correlation to the presence of this structure and the selectivity toward N2; (ii) at high temperatures, ≥400 °C, we propose that there are two simultaneous reaction pathways—the oxidation of NH3 to NOx by PdO and the subsequent catalytic reduction of NOx by NH3 to produce N2. The results in this study confirm the structural and catalytic diversity that exists during catalysis and the need for such an understanding if improvements to important emission control technologies, such as the selective catalytic oxidation of NH3, are to be made.	Feb 2021
B07-C-Versatile Soft X-ray beamline: Ambient Pressure XPS and NEXAFS B18-Core EXAFS I20-EDE-Energy Dispersive EXAFS (EDE) I20-Scanning-X-ray spectroscopy (XAS/XES)	The electronic structure, surface properties, and in situ N2O decomposition of mechanochemically synthesised LaMnO3 Rachel H. Blackmore , Maria Elena Rivas , George F. Tierney , Khaled M. H. Mohammed , Donato Decarolis , Shusaku Hayama , Federica Venturini , Georg Held , Rosa Arrigo , Monica Amboage , Pip Hellier , Evan Lynch , Mahrez Amri , Marianna Casavola , Tugce Eralp Erden , Paul Collier , Peter P. Wells Physical Chemistry Chemical Physics 6 DOI: 10.1039/D0CP00793E Diamond Proposal Number(s): [20129, 20200, 22063, 15151] Open Access Show Abstract ▼ Abstract: The use of mechanochemistry to prepare catalytic materials is of significant interest; it offers an environmentally beneficial, solvent-free, route and produces highly complex structures of mixed amorphous and crystalline phases. This study reports on the effect of milling atmosphere, either air or argon, on mechanochemically prepared LaMnO3 and the catalytic performance towards N2O decomposition (deN2O). In this work, high energy resolution fluorescence detection (HERFD), X-ray absorption near edge structure (XANES), X-ray emission, and X-ray photoelectron spectroscopy (XPS) have been used to probe the electronic structural properties of the mechanochemically prepared materials. Moreover, in situ studies using near ambient pressure (NAP)-XPS, to follow the materials during catalysis, and high pressure energy dispersive EXAFS studies, to mimic the preparation conditions, have also been performed. The studies show that there are clear differences between the air and argon milled samples, with the most pronounced changes observed using NAP-XPS. The XPS results find increased levels of active adsorbed oxygen species, linked to the presence of surface oxide vacancies, for the sample prepared in argon. Furthermore, the argon milled LaMnO3 shows improved catalytic activity towards deN2O at lower temperatures compared to the air milled and sol–gel synthesised LaMnO3. Assessing this improved catalytic behaviour during deN2O of argon milled LaMnO3 by in situ NAP-XPS suggests increased interaction of N2O at room temperature within the O 1s region. This study further demonstrates the complexity of mechanochemically prepared materials and through careful choice of characterisation methods how their properties can be understood.	Jun 2020

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