Surface engineering of Au nanostructures for plasmon-enhanced electrochemical reduction of N2 and CO2 into urea in the visible-NIR region

• The capture and utilization of CO 2 is crucial for climate change mitigation. • A plasmon-enhanced photoelectrochemical process for CO 2 and N 2 into urea was proposed. • The plasmonic Au nanostructures are tuned to maximize CO 2 and N 2 PEC reduction activity. • A PEC system based on Au nanosheets yielded higher urea (of 98.5 µg urea mg cat -1 h −1 ) and FE of 22.7% The photoelectrochemical reduction of CO 2 and N 2 (N 2 CO 2 RR) is a promising method of producing urea under ambient conditions since highly active and stable electrocatalysts are desired. Plasmonic metals have attracted considerable attention due to their enhanced electrochemical activity at visible and near-infrared wavelengths (NIR). Herein, the morphology of Au was tuned to spherical nanoparticles, nanorods, and nanosheets by utilizing a variety of structure-directing agents. Among them, Au nanosheets (Au NSs) can absorb a broad spectrum of NIR wavelengths, enabling electrochemical reduction of N 2 into NH 3 , with high yield rates and higher Faradic efficiency (FE) than most of the N 2 RR results reported. In addition, a distal associative pathway for N 2 RR into NH 3 has been established over Au NSs. Additionally, the Au NSs photocathode demonstrates high stability over a period of 10 consecutive runs. In addition, this work provides a guide to fabricating highly stable photocathodes that convert N 2 and CO 2 into urea. Au NSs photocathode achieves a maximum urea yield rate of 98.5 µg urea mg cat -1 h −1 and FE of 22.7% at −0.7 V vs. RHE. Results show that the N 2 and CO 2 is the primary factor for urea production, whereas reducing NO 3 – and HCO 3 – contributes significantly to the total urea yield rate. Density functional theory calculations (DFT) reveal that Au NSs play a crucial role in promoting N 2 and CO 2 adsorption, activation, and stimulating the coupling reaction between C-N to form urea by the distal mechanism. As a result, this work opens up the possibility of developing hybrid catalytic systems for simultaneously reducing nitrate-containing wastewater and CO 2 , thus producing urea-rich treated water for agricultural use and achieving carbon neutrality.