Abstract
Zn/Cu electrocatalysts were synthesized by the electrodeposition method with various bath compositions and deposition times. X-ray diffraction results confirmed the presence of (101) and (002) lattice structures for all the deposited Zn nanoparticles. However, a bulky (hexagonal) structure with particle size in the range of 1–10 μm was obtained from a high-Zn-concentration bath, whereas a fern-like dendritic structure was produced using a low Zn concentration. A larger particle size of Zn dendrites could also be obtained when Cu2+ ions were added to the high-Zn-concentration bath. The catalysts were tested in the electrochemical reduction of CO2 (CO2RR) using an H-cell type reactor under ambient conditions. Despite the different sizes/shapes, the CO2RR products obtained on the nanostructured Zn catalysts depended largely on their morphologies. All the dendritic structures led to high CO production rates, while the bulky Zn structure produced formate as the major product, with limited amounts of gaseous CO and H2. The highest CO/H2 production rate ratio of 4.7 and a stable CO production rate of 3.55 μmol/min were obtained over the dendritic structure of the Zn/Cu–Na200 catalyst at −1.6 V vs. Ag/AgCl during 4 h CO2RR. The dissolution and re-deposition of Zn nanoparticles occurred but did not affect the activity and selectivity in the CO2RR of the electrodeposited Zn catalysts. The present results show the possibilities to enhance the activity and to control the selectivity of CO2RR products on nanostructured Zn catalysts.
Highlights
Removal of CO2, the principal greenhouse gas, from the atmosphere is critical in order to avoid climate disasters caused by global warming
A fern-like dendritic structure of Zn nanoparticles was obtained on Zn/Cu–Na60 and Zn/Cu–Na200, as shown in Figure 2c,d, respectively
Zn/Cu and Zn and Cu on Cu foil (ZnCu/Cu) electrocatalysts were prepared via the electrodeposition method with various bath compositions and deposition times
Summary
Removal of CO2 , the principal greenhouse gas, from the atmosphere is critical in order to avoid climate disasters caused by global warming. Carbon monoxide (CO) is an interesting product of this process because it can be used as a reactant for the Fischer–Tropsch process to produce hydrocarbon fuels and chemicals [5,6] It can be separated from liquid electrolytes. A metal foil or plate is used as a cathode (working electrode) in the electrochemical reduction of CO2 , but this exhibits low efficiency and selectivity toward CO production [14,15,16]. Cu foil (Zn/Cu) and electrodeposition of Zn and Cu on Cu foil (ZnCu/Cu) in an electrodeposition solution consisting of NaCl (Zn/Cu-Na, ZnCu/Cu-Na) or HCl (Zn/Cu-H, ZnCu/Cu-H) with different deposition times These catalysts were evaluated in the electrochemical reduction of CO2 to higher-value chemicals. The morphology, surface composition, and crystalline structure of these catalysts were investigated by scanning electron microscopy–energy dispersive X-ray spectroscopy (SEM-EDX) and X-ray diffraction (XRD)
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