Manipulating wettability of catalytic surface for improving ammonia production from electrochemical nitrogen reduction

An electrochemical nitrogen reduction reaction (ENRR) is considered a promising alternative for the traditional Haber-Bosch process. In this study, we present a method for improving the ENRR by controlling the wettability of the catalyst surface, suppressing the hydrogen evolution reaction (HER) while facilitating N-2 adsorption. Reduced-graphene oxide (rGO) with a hydrophobic surface property and a contact angle (C.A.) of 59 degrees was synthesized through a high-density atmospheric plasma deposition. Two other hydrophilic and superhydrophobic surfaces with a C.A. of 15 degrees and 150 degrees were developed through additional argon plasma and heat treatment of as-deposited rGO, respectively. The ENRR results showed that the ammonia yield and Faradaic efficiency tended to increase with increasing hydrophobicity. Electrochemical measurements reveal that superhydrophobic rGO achieves a higher Faradaic efficiency (5.73 %) at similar to 0.1 V (vs RHE) and a higher NH3 yield (9.77 lg h(-1) cm(-2)) at similar to 0.4 V (vs RHE) in a 0.1 M KOH electrolyte. In addition, the computational fluid dynamics simulation confirmed that the amount of time the N-2 gas remains on the surface could increase by improving the hydrophobicity of the catalytic surface. This study inspires the development of the rGO electrocatalyst through surface wettability modification for boosting ammonia electrosynthesis.

Automated summary

This study presents a method for improving the electrochemical nitrogen reduction reaction (ENRR) by controlling the wettability of the catalyst surface to suppress hydrogen evolution reaction (HER) and facilitate N2 adsorption. It was found that increasing the hydrophobicity of the surface led to higher ammonia yield and Faradaic efficiency. Computational fluid dynamics simulation confirmed that improving the hydrophobicity of the catalytic surface increased the amount of time N2 gas stayed on the surface.