MOF-Derived Cu₂O/Cu Nanospheres Anchored in Nitrogen-Doped Hollow Porous Carbon Framework for Increasing the Selectivity and Activity of Electrochemical CO₂-to-Formate Conversion

Copper-based metal–organic frameworks (MOFs) and their derivatives have been used for CO2 electroreduction; however, they still have obvious drawbacks like poor selectivity and durability. Here, Cu_btc (btc = benzene-1,3,5-tricarboxylate)-derived Cu2O/Cu anchored in a nitrogen-doped porous carbon framework (Cu2O/Cu@NC) was prepared for CO2 electroreduction. Cu2O/Cu@NC-800 (carbonizing Cu_btc at 800 °C) produced formate and ethanol concurrently with an overpotential as low as ∼380 mV. However, it exhibited higher selectivity toward formate against ethanol, with the maximum formate faradaic efficiencies of 70.5% at −0.68 V vs a reversible hydrogen electrode (RHE), which was 1.79 and 1.84 times higher than that of Cu2O/Cu@NC-700 and Cu2O/Cu@NC-900. This superior performance remained stable for over 30 h. The enhancement in activity and selectivity was attributed to (i) a higher Cu content and well-dispersed Cu2O/Cu nanoparticles inside the carbon frameworks, which provided abundant active reaction sites, and (ii) a higher content of N doped into the Cu2O/Cu lattice to possibly facilitate *OCHO generation. These findings provided a convenient strategy to enhance the activity and selectivity of catalysts for efficient CO2 electroreduction.