Electrochemical Carbon Dioxide Reduction on Femtosecond Laser-Processed Copper Electrodes: Effect on the Liquid Products by Structuring and Doping

Abstract

A femtosecond laser process is presented increasing the surface area of copper electrocatalysts for an electrochemical CO2 reduction reaction (CO2RR). The laser treatment allows us to tune the surface morphology and the chemical composition of the copper electrocatalysts. This tunability is used to correlate the role of the surface area and catalyst dopants with the selectivity of the CO2RR. The liquid products of the CO2RR are monitored through ex situ nuclear magnetic resonance spectroscopy. The products’ distribution shows that the electrode surface area plays a key role in the electrochemical conversion of CO2 into multicarbon liquid products. We show that sulfur dopants boost the production of formate. Remarkably, by co-doping sulfur and fluoride, we show that the chalcogenide dopant counteracts the known boosting effect of fluoride to convert CO2 into multicarbon products. Oxygen doping in the range of 2–19 atom % does not significantly affect the distribution of liquid products from CO2 electroreduction. In a broad perspective, this work highlights the potential of the femtosecond laser process to fine-tune surfaces to produce photo- and electrocatalyst materials.

Enhanced Performance of Laser‐Structured Copper Electrodes Towards Electrocatalytic Hydrogenation of Furfural

“…The periodicity of the pattern is more pronounced on the strongly structured samples without (StS) or with nickel (StS−Ni) in the lowest SEM magnification micrographs of Figure 1b and c. Large conical spikes‐like structures are arranged in a comb‐like structure vertically to the laser scan direction and energy dispersive X‐ray (EDX) spectroscopy analysis confirmed the presence of nickel alloying. They are covered with a cauliflower‐like porous substructure similar as observed in the earlier works [34,37] . As revealed by the laser scanning microscopy (LSM) measurements shown in Figure 1d, the conical structures are about 50–70 μm high and dimples and holes are about 110 μm in depth.…”

“…They are covered with a cauliflowerlike porous substructure similar as observed in the earlier works. [34,37] As revealed by the laser scanning microscopy (LSM) measurements shown in Figure 1d, the conical structures are about 50-70 μm high and dimples and holes are about 110 μm in depth. Also, the differences between the samples with or without the nickel incorporation are rather small.…”

“…[32] It is an ablation process and parts of the ablation plume are re-solidified on the surface, which also enables the incorporation of functional elements into the solid surface within the process environment. [33,34] This is a scalable approach and facilitates the enhancement of active surface area with micrometer-sized particles by forming porous layers. [35] The surface enhancement in turn changes the corresponding conditions at the reaction sites and thereby, the performance of the electrochemical reactions is improved.…”

“…An emerging and alternate appealing technique to structure the catalyst materials at varying length scales is laser materials processing, especially with laser pulse widths in the femtosecond range [32] . It is an ablation process and parts of the ablation plume are re‐solidified on the surface, which also enables the incorporation of functional elements into the solid surface within the process environment [33,34] . This is a scalable approach and facilitates the enhancement of active surface area with micrometer‐sized particles by forming porous layers [35] .…”

Highly‐Efficient CO2 Electromethanation with Extremely Low Overpotentials on Pt/C Catalysts: Strategic Design of Multi‐Potential‐Step Method

“…Electrocatalysts, such as Au, Ag, Cu, etc., are well known as popular choices for experimental designs due to their CO 2 reduction activity, [3–27] although, these metals require high overpotentials. The overpotentials of $${\ge }$$ 0.3 V, $${\ge }$$ 0.6 V, and $${\ge }$$ 0.9 V are required for Au, Ag, and Cu electrocatalysts, respectively [28] .…”