Cu–Al Layered Double Hydroxides as Precursors to Operando-Formed Dendritic Cu for Electrochemical CO 2 Reduction

High Resolution Image Download MS PowerPoint Slide The electrochemical reduction of CO 2 to valuable chemicals and fuels is a promising strategy for mitigating climate change, but it requires the development of efficient and selective catalysts. We report the synthesis and characterization of a series of Cu x Al 1 -layered double hydroxides (LDH) ( x = 1, 1.5, 2, 3), yielding a robust structural model of Cu 1 Al 1 -LDH. Combining structural, elemental, and thermal investigations leads to a precise determination of the LDH’s compositions as well as an understanding of the thermal decomposition of the LDHs into (mixed-) metal oxides. During the electrochemical CO 2 reduction reaction (CO 2 RR), we observe an operando reduction to catalytically active copper dendrites. The Cu:Al ratio is found to play a crucial role in determining the size and activity of these dendrites, enabling a tunable catalyst system with Faradaic efficiencies (FEs) for formic acid (HCOOH) reaching up to 30.5% and FE for syngas (hydrogen and carbon monoxide) of up to 72%. This study demonstrates the potential of CuAl-LDH phase engineering as a cheap and easily accessible pathway for the development of efficient electrochemical CO 2 reduction catalysts.