Ultra-small Cu nanoparticles embedded in N-doped carbon arrays for electrocatalytic CO2 reduction reaction in dimethylformamide

Abstract

The development of heterogeneous catalysts with a well-defined micro structure to promote their activity and stability for electrocatalytic CO2 reduction has been shown to be a promising strategy. In this work, Cu nanoparticles (∼ 4 nm in diameter) embedded in N-doped carbon (Cu@NC) arrays were fabricated by thermal decomposition of copper tetracyanoquinodimethane (CuTCNQ) under N2. Compared to polycrystalline copper electrodes, the Cu@NC arrays provide a significantly improved number of catalytically active sites. This resulted in a 0.7 V positive shift in onset potential, producing a catalytic current density an order magnitude larger at a potential of–2.7 V vs. Fc/Fc+ (Fc = ferrocene) in dimethylformamide (DMF). By controlling the water content in the DMF solvent, the CO2 reduction product distribution can be tuned. Under optimal conditions (0.5 vol% water), 64% HCOO–, 20% CO, and 13% H2 were obtained. The Cu@NC arrays exhibited excellent catalytic stability with only a 0.5% decrease in the steady-state catalytic current during 6 h of electrolysis. The three-dimensional (3D) array structure of the Cu@NC was demonstrated to be effective for improving the catalytic activity of copper based catalysts while maintaining long-term catalytic stability.