A Facility for Ambient Pressure Photoelectron Spectroscopy (APPES) (R)

Lead Research Organisation: Imperial College London
Department Name: Materials


For over 50 years, x-ray photoelectron spectroscopy (XPS) has demonstrated itself as an invaluable technique in the study of filled electronic states of solids, as well helping to determine the nature of interactions between solid surfaces and molecular species. Unfortunately there is one main drawback in the technique, that being that typical XPS measurements are performed in ultra high vacuum (UHV) conditions (10-10 mbar), due to the need of minimising the chances of unfavourable collisions occurring before the excited photoelectrons reach the energy analyser. Due to this restraint, studying the surfaces of technologically important materials occurs at a pressure many orders of magnitude lower than the operational conditions of the systems themselves (1-50 bar). Bridging this so-called "Pressure Gap" has remained a significant technological challenge. Very recent developments in electron energy analyser and sample holder design have for the first time allowed photoelectron spectroscopic measurements to be performed in ambient pressures of up to 25 mbar. The opportunity to study "real" surfaces in-situ and in-operando is a step change in the field of photoelectron spectroscopy, and opens a new and vital chapter in the area of surface science.

The ambient pressure photoelectron spectroscopy (APPES) system is a state-of-the-art laboratory-based instrument with capabilities of performing high-energy resolution, low signal-to-noise photoemission measurements in up to 25 mbar ambient pressure with a number of different gases (O2, N2, H2, ethylene, acetylene). The instrument is equipped with a monochromated x-ray source and a high transmission, differentially pumped electron energy analyser. The system is fitted with an in-situ sample cell, which can provide a temperature range of 80 - 1100 K in the ambient atmospheres, permitting in-operando measurements. This specially designed modular in-situ cell, which is fully retractable from the analysis chamber, also allows standard UHV XPS comparative measurements to be performed with ease.

The APPES instrument based at the Department of Materials, Imperial College London will be highly multidisciplinary, covering five broad research themes (i) Energy; (ii) Catalysis; (iii) Electronic Materials; (iv) Biomaterials; (v) Environmental and Heritage Science. The instrument, while hosted at Imperial is engaged in highly collaborative research at a regional, national (including the Diamond Light Source) and international level, with access arrangements also provided through coordination the National XPS Facility (NEXUS) at the University of Newcastle. This new approach to providing wide- reaching access will allow the APPES technique to be fully exploited and generate world-leading cutting edge scientific output.

Planned Impact

Since the first development of x-ray photoelectron spectroscopy (XPS) over 50 years ago, the technique has formed the basis of numerous scientific breakthroughs providing vast economic and societal benefits. The proposed APPES technique, has the potential to have an even greater impact, due to the fact that the surface electronic structure of a wide array of different materials, each with their own technological applications will be be studied under conditions close to which they operate.

The obvious beneficiary of APPES measurements is in the commercial private sector, with emphasis on businesses operating in all the identified research themes. For example, Johnson-Matthey who work within the area of catalysis, could utilise the technique for understanding how catalysts behave in near-operational conditions. This could lead to significant improvements in reactor design and lowering catalyst cost, thereby the technique will have a direct economic impact.

The impact to the planned VERSOX beamline at the Diamond Light Source is important to stress. This proposal seeks to help to coordinate and develop the national capability, and strategy, in the APPES technique at a personnel, instrumentation and scientific output level.

There are a number of government agencies who would benefit from this research including the Health Protection Agency (HPA - Biosafety Unit, Decontamination Studies and Molecular Identification Services), the Environment Agency (National Laboratory Service). We would also seek to liaise and seek collaborative research efforts with the National Physical Laboratory (NPL). Understanding how pathogens behave in contact with surgical instruments, without exposing the samples to extreme UHV environments would have great national and international health benefits. One experiment could look at the growth of pathogens under aerobic and anaerobic conditions within a specially designed in-situ high pressure cell.

The APPES technique would also have a great impact on the area of conservation and heritage science, where we have already sought interest in the study of paint pigments from a colleague at Tate Britain. As the instrument is hosted geographically close to many museums (Natural History, Science Museum, V&A) we would seek to establish collaborative research with those institutions. We would also use the Institute of Conservation as a point of contact for planned heritage science research.

At a more specific project level, the Lead Co-I will develop a range of skills including public communication (training by the Royal Society), a well as opportunities to interact with government and policy makers at a national level (again through the Royal Society MP-Scientist pairing scheme).


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Description This grant has allowed the development of the world-leading laboratory-based high-pressure photoelectron spectrometer. We have developed a unique system that allows the measurement of chemistry and physics of surfaces under a gaseous environment - compared to traditional vacuum measurements. The unique high-pressure reaction cell allows precision control of sample environment, thereby allowing controlled and reproducible measurements to be performed. The system has been performing above expectation is is the focal point of 3 EPSRC awards -studying the surface chemistry of solid oxide fuel cells and carbon dioxide reduction catalysts.

In 2020 the system was upgraded to incorporate an angle-resolved photoelectron spectrometer (ARPES), coupled to a high pressure XPS system. This is the first system of its type in the world.
Exploitation Route There are a number of publications in the process of being published based on this work. We have done extensive research to understand the behaviour of gas flow near the sample surface - which is very important to the high-pressure XPS community as knowing exactly the pressure of the surface at the point of measurement, is critical to understanding the surface chemistry. We have implemented a number of upgrades to the system, which will increase the signal-to-noise of spectra and also reducing the time taken to perform experiments, as well as currently attaching a new chamber to the system for preparation of single crystal surfaces (work done in collaboration with Royal Dutch Shell. All of these activities will be used by the wider (global) photoemission community

We are now currently measuring the O2 interaction with haemoglobin. The first demonstration of this technique on biologically critical proteins.
Sectors Chemicals,Electronics,Energy,Environment,Healthcare,Manufacturing, including Industrial Biotechology,Culture, Heritage, Museums and Collections,Pharmaceuticals and Medical Biotechnology

Description We are happy to begin delivering significant impact in each of the 5 research themes (catalysis, energy materials, electronic materials, biomaterials, environment and heritage science). The theme of catalysis has already secured an EPSRC award to study CO2 reduction catalysts using high-pressure XPS, and two more on SOFCs (energy materials). We discovered the need to use an in-line gas purifier to lower contamination to the ppb levels. This was published in Review of Scientific Instruments in 2017.
Sector Chemicals,Energy,Environment,Manufacturing, including Industrial Biotechology,Culture, Heritage, Museums and Collections
Impact Types Economic

Description EPSRC Strategic Advisory Team for Capital Equipment
Geographic Reach National 
Policy Influence Type Participation in advisory committee
URL http://www.epsrc.ac.uk/research/ourportfolio/themes/researchinfrastructure/strategy/
Description Oral evidence for the report on Scientific Infrastructure to the House of Lords Select Committee for Science and Technology
Geographic Reach National 
Policy Influence Type Gave evidence to a government review
URL http://www.publications.parliament.uk/pa/ld201314/ldselect/ldsctech/76/7602.htm
Description Roadmap for Photoelectron Spectroscopy
Geographic Reach National 
Policy Influence Type Participation in a national consultation
URL https://www.epsrc.ac.uk/funding/calls/capitalroadmapspectroscopy/
Description Energy Resilient Manufacturing
Amount £295,230 (GBP)
Funding ID EP/M013839/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 01/2015 
End 06/2016
Description Experimental Equipment Call
Amount £1,461,911 (GBP)
Funding ID EP/M028291/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 03/2015 
End 03/2016
Description Industrial Funding
Amount £620,000 (GBP)
Organisation Total E & P 
Sector Private
Country United Kingdom
Start 04/2017 
End 04/2019
Description Regenerative Medicine Capital June 2013
Amount £29,500 (GBP)
Funding ID MR/L012677/1 
Organisation Medical Research Council (MRC) 
Sector Public
Country United Kingdom
Start 08/2013 
End 08/2017
Description SUPERGEN Fuel Cells Challenge
Amount £1,076,043 (GBP)
Funding ID EP/M014142/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 03/2015 
End 03/2019
Description SUPERGEN Fuel Cells Challenge
Amount £1,229,672 (GBP)
Funding ID EP/M014304/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 01/2015 
End 12/2017
Description Scienta Omicron 
Organisation Scienta Omicron GmbH
Country Germany 
Sector Private 
PI Contribution Scienta Omicron are the manufacturers of the high pressure XPS instrument, and have provided support in attempting some exciting new experiments.
Collaborator Contribution They have promised to underpin any unintentional damage to the spectrometer caused by the experiments we wish to perform.
Impact We have so far published 4 papers together, with another 2 in preparation.
Start Year 2014
Description Shell 
Organisation Shell Global Solutions International BV
Department Shell Global Solutions UK
Country Netherlands 
Sector Private 
PI Contribution We are currently still designing the new chamber to be added to the high pressure XPS system
Collaborator Contribution Shell have provided funding to allow me to build a new chamber for preparing surfaces for high pressure XPS measurements. The research will be focused on corrosion research of pipeline materials.
Impact Too early for any outputs
Start Year 2015
Description University of Oxford 
Organisation University of Oxford
Department Inorganic Chemistry
Country United Kingdom 
Sector Academic/University 
PI Contribution We are working in collaboration with Charlotte Williams (University of Oxford). At Imperial we will be performing high pressure XPS on industrially relevant catalysts for CO2 reduction to methanol.
Collaborator Contribution Our collaborator in Oxford will be synthesising and testing the performance of these new catalysts.
Impact The publication outputs have been captured in the other submission (EP/M013839/1) for the specific collaborative work on catalysis.
Start Year 2015