Electrochemical Reduction CO2 to Formate on Cuxo Electrode

Abstract

In recent years, CO2 conversion using electrochemical catalysis approaches has attracted great attention due to its several advantages such as the controllable electrode potentials, reaction temperature and the recycled supporting electrolytes1. But the low performance of the electrocatalysts (i.e., low catalytic activity and insufficient stability) hinders its practical application1. Cu have been explored to catalyze CO2 electroreduction due to its low cost, abundant reserve and reasonable overall Faradaic efficiency towards fuel production(e.g. CO, CH4, C2H4, formate, alcohols)2. However, the energetic efficiency of Cu is limited by the large overpotential (>0.7 V) required for CO2 reduction to outcompete H2O reduction3. Furthermore, Cu electrode rapidly lose their CO2 reduction activity2. Achieving efficient Cu-catalyzed CO2 reduction requires preparing Cu particles whose surfaces have active sites that are different from those on the surface of a metallic Cu electrode4. Here, we prepared CuxO particles by a simple one-step hydrothermal synthesis, and applied them to the gas diffusion electrode, these electrodes exhibited good electrochemical performance of high catalytic activity and high selectivity. The CuxO were prepared using a simple hydrothermal method as follows: 0.04 mol Cupric Acetate Monohydrate and 0.02mol hexamethylenetetramine were mixed under stirring to form a homogeneous solution. Then the mixture was transferred into a 100 mL stainless-steel autoclave and heated at 180℃ for 2 h. Then the precipitate was collected by centrifugation, washed with deionized water and absolute ethanol for several times, until the pH was neutral, finally dried at oven at 85℃ for 12h. The crystal structure of the product was characterized by XRD and SEM. The catalyst electrode was prepared by CuXO powder bonded with Nafion solution and isopropanol, and spread over the gas diffusion layer (GDL). The catalytic activity of CuXO nanocatlyst supported on GDL as the cathode electrode was measured using cyclic voltammetry (CV) and linear sweep voltammetry (LSV) in 0.5M KHCO3 aqueous solution saturated with both N2 and CO2, respectively. Figure 1 shows the CV curves on the CuxO/GDL electrode. It can be seen that the anodic peaks between 0V~ 0.85V and the cathodic peak between -0.6V~ 0.25V. The onset potential in 0.5M KHCO3 solution saturated with CO2 was found to be at 0.20 V, which is 250 mV more positive than that under N2 ( 0 V). At an potential of -1.25V, the current density in CO2-saturated 0.5M KHCO3 reached 17.1 mAcm-2 (Fig. 1). All the above reults indicates that participation of CO2 reduction contributes to the enhancement of cathodic current.