# Investigation of CuAl-layered double hydroxides as efficient electrocatalysts of CO₂ reduction

TARHINI Ali<sup>(a)*</sup>, GUYOT Mélanie<sup>(b)</sup>, COSTENTIN Cyrille<sup>(b)</sup>, CHARDON-NOBLAT Sylvie<sup>(b)</sup>, MOUSTY Christine<sup>(a)</sup>, PREVOT Vanessa<sup>(a)</sup>

(a) Institut de Chimie de Clermont-Ferrand, Clermont-Ferrand (France)

(b) Département de Chimie Moléculaire, Grenoble (France)

* ali.tarhini@etu.uca.fr

The emission of CO₂ by industrial action has a serious impact on our environment which leads us to look for ways to decrease the emitted CO₂ to the atmosphere. The electrochemical conversion of CO₂ (CO₂ER) into other molecules such as CO, HCOOH, CH₃COOH, and CH₄ is one of the many ways to achieve this goal. Not only it will help to reduce pollution, but it will also convert CO₂ to valuable products to use as a feedstock.[1] Recently, efficient copper based electro-catalysts for CO₂ER were prepared from layered double hydroxides (LDH) [2]. Using CuAl-NO₃ LDH prepared by the coprecipitation method and thermal treatments, a morphology control allowed to improve the catalytic activity by tailoring the structure of active sites and increasing the surface area/number of active sites. The resulting catalyst promoted the electrochemical conversion, in galvanostatic conditions, of CO₂ to CO and HCOOH with a faradaic efficiency (FY) up to 42% and 22%, respectively.

In the present work, the influence of the chemical composition of Cu based LDH of both the layer and the interlayer domain on the CO₂ER was studied. Several copper based LDH were synthesized by varying the synthetic method and taking into account the Cu/Al ratio and the interlayer anion (CO₃²⁻, Acetate Ac and dodecylsulfate SDS). The electrochemical behavior of these phases was first studied in cyclic voltammetry in different electrolytes under CO₂ saturated atmosphere in order to put in light their electrocatalytic behavior towards CO₂ER. The experimental parameters were optimized to perform the macroscale electrolyses. Among the different phases tested, Cu₂Al-CO₃ LDH phase prepared by coprecipitation showed the highest faradic yield of HCOOH in 0.5 M KCl, reaching 48%.

<figure><img src="image_1.png" /><figcaption>Figure.1: Faradic yields of HCOOH formation by copper based LDH synthesized by different methods in 0.45 M KHCO₃</figcaption></figure>

The authors would like to thank the French ANR (CALHYCO2 - ANR-19-C05-0015) for their financial support.

## References
[1] H.-R. M. Jhong, S. Ma, P. J. A. Kenis, Curr. Opinion Chem. Eng. 2 (2013) 191-199.

[2] K. Iwase, T. Hirano, I. Honma, ChemSusChem, 15 (2022) 1-6