An exploration on CO faradaic efficiency with catalyst surface wettability ranging from hydrophilic to superhydrophobic

Hydrophobic electrode can facilitate CO2 mass transfer for carbon dioxide electroreduction reaction (CO2ER) in the microchannel reactor. However, 'trade-off' exists because the reaction cannot proceed in the absence of electrolyte. Therefore, effective control of wettability on the surface of the catalyst is significant to achieve efficient CO2ER performance. In this paper, a nanocone-shaped Zn@Ag has been fabricated through a simple two-step preparation process involving the hydrothermal treatment and the galvanic replacement. Further modification of the myristic acid (MA)/stearic acid (SA) layer on the nanocone by the immersion method can extend the interfacial wettability to the superhydrophobic scale. The experimental parameters including the time of three synthesis procedures were adjusted to regulate the dimensions and surface free energy of the nanocone. Consequently, the nanoncone catalyst itself possessed a maximum intrinsic water contact angle (CA) of -114 degrees, while the SA modified catalyst demonstrated an outstanding water repellency with CA of -152 degrees. The relationship between the CO Faradaic efficiency (FECO) and the surface wettability ranging from hydrophilic to superhydrophobic was ultimately explored. The optimal Zn@Ag@MA catalyst with appropriate hydrophobicity can achieve a FECO of 91%, which is nearly 20% higher than the hydrophilic/superhydrophobic counterpart. In situ attenuated total reflectance infrared (ATR-IR) tests verified that the hydrophobic catalyst can enhance CO2 concentration near the surface and promote the selectivity to CO.

Automated summary

Hydrophobic electrode enhances CO2 mass transfer for carbon dioxide electroreduction reaction (CO2ER) in microchannel reactor. Effective control of catalyst surface wettability is crucial to achieve efficient CO2ER performance.