Selective electroreduction of CO2 to formate on 3D [100] Pb dendrites with nanometer-sized needle-like tips

Abstract

Honeycomb porous Pb films with a dendrite-like secondary structure growing along the [100]-axis were prepared by Dynamic Hydrogen Bubble Templating (DHBT) and used for the electroreduction of CO₂. Detailed physicochemical characterization of the porous films revealed that the thickness (up to 70 μm) and electrochemically active surface area (up to 1500 cm²) of the porous Pb films could be tuned through the current density (varied between −1 and −4 A cm⁻²) and deposition time (varied between 3 and 60 s). The electrochemical activity and stability of the electrodes toward the electroreduction of CO₂ were investigated by linear sweep voltammetry and potentiostatic electrolysis in 1 M KHCO₃ electrolyte at standard pressure and room temperature. The formate production was quantified by UV-visible spectrophotometry. The faradaic efficiency for formate was larger than 90% for electrodes with electrochemical surface areas above 500 cm² and it was attributed to an increased fraction of the [100] surfaces. The porous Pb film deposited at −4.0 A cm⁻² and 40 seconds proved to be a highly active and stable electrode, with a partial current density (j_formate) of −7.5 mA cm⁻² and a faradaic efficiency of 97% for formate at an overpotential of −0.99 V after 6 hours of electrolysis.