Ruthenium Anchored Laser-Induced Graphene as Binder-Free and Free-Standing Electrode for Selective Electrosynthesis of Ammonia from Nitrate

Abstract

Developing effective electrocatalysts for the nitrate reduction reaction (NO₃RR) is a promising alternative to conventional industrial ammonia (NH₃) synthesis. Herein, starting from a flexible laser-induced graphene (LIG) film with hierarchical and interconnected macroporous architecture, a binder-free and free-standing Ru-modified LIG electrode (Ru-LIG) is fabricated for electrocatalytic NO₃RR via a facile electrodeposition method. The relationship between the laser-scribing parameters and the NO₃RR performance of Ru-LIG electrodes is studied in-depth. At -0.59 V_RHE, the Ru-LIG electrode exhibited the optimal and stable NO₃RR performance (NH₃ yield rate of 655.9 µg cm^-2 h^-1 with NH₃ Faradaic efficiency of up to 93.7%) under a laser defocus setting of +2 mm and an applied laser power of 4.8 W, outperforming most of the reported NO₃RR electrodes operated under similar conditions. The optimized laser-scribing parameters promoted the surface properties of LIG with increased graphitization degree and decreased charge-transfer resistance, leading to synergistically improved Ru electrodeposition with more exposed NO₃RR active sites. This work not only provides a new insight to enhance the electrocatalytic NO₃RR performance of LIG-based electrodes via the coordination with metal electrocatalysts as well as identification of the critical laser-scribing parameters but also will inspire the rational design of future advanced laser-induced electrocatalysts for NO₃RR.

Keywords: ammonia; electrocatalysis; laser‐induced graphene; nitrate reduction reaction; ruthenium.