Tuning local acid-like microenvironment in layered double hydroxide via “Memory Effect” to enhance the CO2-to-HCOOH electrocatalysis in neutral media

HCOOH has been regarded as a high cost-effectiveness product in electrochemical CO₂ reduction reaction (CO₂RR). However, its industrial application is still restricted by the conversion efficiency and selectivity due to the competitive hydrogen evolution reaction. Herein, by tuning the local microenvironment of layered double hydroxide (LDHs) via its “memory effect” characteristic, we realized the high conversion efficiency of electrochemical CO₂RR towards HCOOH. In-situ spectroscopic show that the obtained LDHs (LDH-RE) show an enhanced surface acidity during whole CO₂RR process compared with the original LDHs, which caused by partial recover of CO₃^2– in the intercalation and the reduction of interlayer spacing, and the results make great contribution to the higher selectivity of HCOOH in neutral media. As a result, LDH-RE achieved a high HCOOH faradaic efficiency of 95.7 % at −1.2 V vs RHE in neutral media. Furthermore, in situ ATR-FTIR and DFT results demonstrate that the formation of *HCOO is the rate-determining step for the generation of HCOOH on the surface of LDH-RE. This work gives a new insight into the LDHs promotor strategy in electrocatalysis fields.