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%. 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