Electrochemical reduction of CO2 (CO2RR) is expected to play a key role among the various strategies being explored to limit global warming. In this scenario, Layered Double Hydroxides (LDHs) are emerging as a promising class of electrocatalysts to replace the most used noble metals. In this work three Zn-Al LDH with different Zn2+/Al3+ ratio were synthesized and characterized by means of XRD, STEM-EDX and HR-TEM. Their suitability for CO2RR to CO was assessed by means of a custom-made three-compartment cell, showing an increase in CO selectivity by decreasing the Zn2+/Al3+ ratio. The CO2 interaction with the samples was firstly characterized by means of volumetric adsorption measurements, exhibiting an increase in capture capacity by decreasing the Zn2+/Al3+ ratio. The evolution of the samples in interaction with a CO2-saturated liquid flow was then deeply investigated by means of in-situ ATR-IR spectroscopy. The samples displayed a different evolution in the vibrational region of the carbonate-like species (1800–1200 cm−1). To better discriminate the different carbonate cyclohexane was also employed. A definitive assignment of the main IR bands of the carbonate was carried out by studying the spectral behavior of the different bands observed in the ATR-IR experiments and by comparing these results with the existing literature. Interestingly, Zn-Al 1:2 LDH, the most efficient electrocatalyst for CO2RR, is also the sole sample exhibiting a higher monodentate to total bidentate carbonates ratio, suggesting that the existence of a higher content of low coordination oxygen anions with stronger basic character can influence the final catalytic activity. © 2024 The Authors

This work was supported by 4AirCRAFT project under the strategic international cooperation between Europe and Japan. 4AirCRAFT has received funding from the European Union’s Horizon 2020 research and innovation programme (No 101022633) and Japan Science and Technology Agency (JST) (No JPMJSC2102). We acknowledge the Hercules fund 'Direct electron detector for soft matter TEM' from Flemish Government for the purchase of the K2 DED. MC, MD, NGP, MS, SB, VC and FB acknowledge support from the Project CH4.0 under the MUR program "Dipartimenti di Eccellenza 2023–2027" (CUP: D13C22003520001)

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