The electronic structure, surface properties, and in situ N2O decomposition of mechanochemically synthesised LaMnO3

DOI: 10.1039/D0CP00793E

Authors: Rachel H. Blackmore (UK Catalysis Hub, Research Complex at Harwell; University of Southampton) , Maria Elena Rivas (Johnson Matthey Technology Centre) , George F. Tierney (UK Catalysis Hub, Research Complex at Harwell; University of Southampton) , Khaled M. H. Mohammed (University of Southampton; Sohag University) , Donato Decarolis (UK Catalysis Hub, Research Complex at Harwell; Cardiff University) , Shusaku Hayama (Diamond Light Source) , Federica Venturini (Diamond Light Source) , Georg Held (Diamond Light Source) , Rosa Arrigo (Diamond Light Source; University of Salford) , Monica Amboage (Diamond Light Source) , Pip Hellier (UK Catalysis Hub, Research Complex at Harwell; Cardiff University) , Evan Lynch (UK Catalysis Hub, Research Complex at Harwell; University of Southampton) , Mahrez Amri (Johnson Matthey Technology Centre) , Marianna Casavola (University of Southampton) , Tugce Eralp Erden (Johnson Matthey Technology Centre) , Paul Collier (Johnson Matthey Technology Centre) , Peter P. Wells (UK Catalysis Hub, Research Complex at Harwell; University of Southampton; Diamond Light Source)
Co-authored by industrial partner: Yes

Type: Journal Paper
Journal: Physical Chemistry Chemical Physics , VOL 6

State: Published (Approved)
Published: June 2020
Diamond Proposal Number(s): 20129 , 20200 , 22063 , 15151

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.

Subject Areas: Chemistry, Materials


Instruments: 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)

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