X-ray absorption spectroscopy was performed at Diamond Light Source, UK, at B18, through proposal SP30647 (August 2022) for the Pd/Al2O3, Pd/TiO2 and Pd/In2O3/Al2O3 species. Data was collected at the Pd and In K-edges in transmission mode using a QEXAFS setup with fast scanning Si(311) crystal monochromators. The time resolution here was roughly 90 seconds per spectrum. Samples were packed into an in-house custom-made capillary system designed and constructed by Diamond Light Source. 50 mg of 200-300 μm catalyst particles were packed between 3 cm of quartz wool.

DRIFTS measurements were performed on a Bruker VERTEX 80 system, with a custom-built high-pressure dome, capable of holding 25 bar of pressure within a high pressure chamber DiffusIRTM PIKE Technologies accessory. Argon and a 25% CO2/75% H2 mixture gas were delivered through high pressure EL-FLOW® Bronkhorst mass-flow controllers, into an in-house custom-made gas manifold. 30 mg of sample was used for the measurements. Initially, the sample was reduced in 25 mL/min of 25% H2 and 75 % Ar. The system was heated to 300 °C at a ramp rate of 5 °C/min and held for 1 hour. The samples were then cooled to 30 °C and either pressurised to 20 bar with 30 mL/min of 75% H2 and 25 % CO2 for the 20 bar measurements or kept at atmospheric pressure for the 1 bar measurements. Once the intended final pressure was reached, the system was heated at 10 °C/min, while holding at 50, 100, 150, 175, 200, 225, 250, 275 and 300 °C for 30 minutes for spectra to be collected. Mass-spectrometry data was collected throughout to observe the evolution of different species, using a Pfeiffer OmniStar.