摘要
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•C2+ partial current density and energy efficiency of Hi-NPC was 510 mA/cm2 and 38 %.•C2+ production rate of Hi-NPC catalyst was doubled than reported in literature.•The ECSA effect was normalized and CO2RR kinetics were identical for the electrodes.•Structural diffusivity verified by ORR was a key point influencing CO2RR behavior.
Hierarchical nanoporous copper (Hi-NPC) is a promising catalyst for carbon dioxide reduction reaction (CO2RR) due to its high surface area and excellent mass transport properties. To evaluate the effect of its architecture, eutectic-phased Cu18Al82 and single-phased Cu33Al67 were potentiostatically dealloyed to produce Hi-NPC and homogeneous nanoporous copper (Ho-NPC), respectively. At a comparable overpotential, the Hi-NPC electrocatalyst exhibited a significantly higher C2+ partial current density (jC2+) in CO2RR, reaching 510 mA/cm2, compared to both Ho-NPC (72 mA/cm2) and Cu electrodes (23 mA/cm2). When the current density was normalized by the electrochemically active surface area, the CO production among three electrodes demonstrated similar electrochemical behavior. However, notable differences were observed in the formation of C2H4 and C2H5OH, which can be attributed to the hierarchical structure of Hi-NPC facilitating C–C coupling to form C2 products. Although the Tafel plot indicated the CO2RR kinetics were identical for all three electrodes, linear sweep voltammetry experiments revealed that Hi-NPC exhibited the steepest current variation slope. Furthermore, the improved diffusivity was further confirmed by conducting oxygen reduction reactions with varying partial O2/N2 flow rates and electrochemical impedance spectroscopies. The hydrophobic properties of the electrode under various CO2RR current densities were also evaluated by water contact angle test.