Understanding CO2 Reduction Catalysts

The need to monitor the synthesis and catalytic performance of materials in-situ and in-operando is of critical importance if we are to find where the barriers to increased catalytic efficiency are, and understand and develop methodologies to circumvent them. Photoelectron spectroscopy (PES) is a widely used multidisciplinary technique widely used to study the composition and chemistry of material surfaces. It is an UHV technique, meaning that it is not possible to investigate the solid-gas interface and consequential reactivity. High-pressure photoelectron spectroscopy (HiPPES) is at the forefront of advanced surface characterization techniques as it now allows the measurement of surface chemistry and physics at near-environmental pressures that are highly relevant for technological applications. Whereas standard photoelectron spectroscopy is performed in the UHV (10-9 mbar) pressure range, HiPPES measurements are performed at pressures greater than 10 mbar. This means that surface reactions can be monitored under highly relevant conditions (e.g. as a function of pressure, temperature, humidity, acidity); in stark contrast to the strongly reducing conditions of a conventional spectrometer which not only provide no dynamic information, but may also actually alter the surface chemistry of the system under study. We aim to use the HiPPES technique to the surface chemistry taking place between copper nanoparticles and CO2. By monitoring the interactions of the gas-solid interface we aim to determine the nature of catalytic active sites, and propose evidence-based mechanisms for the reduction of CO2 on copper. We will study the surface chemistry as a function of temperature, co-adsorbates (such as water and O2) and pH. We hope to understand these nanocatalysts in greater detail, to raise the catalytic efficiency, or to discover new catalysts, thereby enabling the economic viability of carbon capture and utilisation technologies.

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 HiPPES technique, has the potential to have an even greater impact, due to the fact that the surface electronic structure and chemistry of a wide array of different materials, each with their own technological applications can be studied under conditions close to which they operate.

The need to reduce CO2 emissions is of critical importance both environmentally and economically, and there is a pressing need to understand the surface chemistry of CO2 reduction catalysts. The clear beneficiaries of HiPPES measurements are in the industrial/manufacturing sector, with a particular emphasis on businesses operating in the area of catalysis. This could lead to significant improvements in reactor design and lowering catalyst cost, thereby the proposed research technique and will have a direct economic impact.

The research would also have an impact to the planned VERSOX beamline at the Diamond Light Source, and would provide a useful link to the UK Catalysis Hub also located on the Harwell campus. This proposal would seek to coordinate and develop the national capability, and strategy, not only in the HiPPES technique, but also in a wider range of in-situ/in-operando characterization techniques.