Using synchrotron radiation to understand mechanochemically-prepared catalysts

Authors: Peter Wells (University of Southampton; Diamond Light Source)
Co-authored by industrial partner: No

Type: Diamond Annual Review Highlight

State: Published (Approved)
Published: July 2021
Diamond Proposal Number(s): 20129 , 20200 , 22063 , 15151

Abstract: The commercial catalysts currently used to remove polluting gases from vehicle exhausts rely on expensive precious metals, with demand continually growing. Preparing these catalysts often requires solvents, waste treatment and elevated temperatures, all with an environmental cost. One solution is to investigate the use of an alternative, more abundant material. LaMnO has shown promising catalytic behaviour and is made by physically mixing two solid reactants. The catalytic activity of materials is highly dependent on how they are produced. In this work, researchers synthesised LaMnO3 by a novel method, ball milling, to improve its catalytic properties. To replicate or optimise the final material structure, it is vital to investigate the chemical steps occurring within the ball mill. However, the ball mill setup makes it difficult to perform real-time analysis. Therefore, the research team replicated the conditions experienced within the ball mill by applying extreme pressures to the starting materials. Using Diamond Light Source’s Energy Dispersive EXAFS beamline (I20-EDE) meant they could monitor how the structure changes with increasing pressure, using X-ray Absorption Fine Structure (XAFS) measurements in real-time. This beamline setup also allowed them to use a specialised high-pressure cell. They used complementary measurements on Diamond’s Versatile Soft X-ray (VerSoX) beamline (B07) to study the surface properties of the materials during catalysis. Beamline I20-Scanning was used to look at electronic structure. For industrial companies researching ball milling as an alternative production route, i.e. for autocatalysis or battery materials, this research highlights that though the preparation route produces beneficial properties at a lower environmental cost, understanding its underlying chemistry is hugely challenging.

Journal Keywords: Mechanochemistry; N2O decomposition; Perovskite; Catalysis; XAS; in situ NAP-XPS

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)

Added On: 26/11/2021 13:52

Discipline Tags:

Physical Chemistry Catalysis Chemistry Inorganic Chemistry

Technical Tags:

Spectroscopy X-ray Absorption Spectroscopy (XAS) X-ray Emission Spectroscopy (XES) X-ray Photoelectron Spectroscopy (XPS) Energy Dispersive EXAFS (EDE) High Energy Resolution Fluorescence Detected XAS (HERFD-XAS) Near Ambient Pressure XPS (NAP-XPS)