Study: Plasmonic copper nanowires boost nitrate reduction efficiency

The electrocatalytic nitrate reduction reaction (NO₃RR) has attracted the attention of researchers for its significant value in ammonia synthesis and effluent treatment. Plasmon-assisted electrocatalysis provides a powerful strategy for efficient conversion of solar energy to chemical energy by combining solar light with an electrochemical bias on the plasmonic metal nanostructures.

Unfortunately, the electrocatalytic performance of plasmon-assisted NO₃RR using gold (Au) catalysts, a typical plasmonic metal, exhibits ultra-low yields for ammonia synthesis due to the worst intrinsic catalytic activity of Au for NO₃RR. The metallic Cu displays both excellent catalytic performance for NO₃RR and plasmonic resonance adsorption. However, no research has focused on the plasmon-assisted NO₃RR on Cu photoelectrodes until now.

A recent study in the Chinese Journal of Catalysis sheds light on this topic.

Professor Yuchao Zhang's group from the Institute of Chemistry, Chinese Academy of Sciences has found that the plasmonic excitation of Cu nanowires (Cu NWs) dramatically enhances the NO₃RR performance. The current density of NO₃RR was enhanced by 27.66 mA cm^–2 (a 3-fold enhancement) under simulated solar irradiation at 328 K compared with that in the dark at 298 K.

In addition, the current density retained 88% of its initial value under plasmonic excitation after 400 cycles of the cyclic voltammetry (CV) tests, in contrast to the 43% decay in the dark. The faradaic efficiency (FE) reached nearly 100%, with the potential ranging from −0.2 to −0.4 V vs. RHE, and a high NH₃ yield rate of 1.37 mmol h⁻¹ cm⁻² was achieved at −0.2 V vs. RHE.

The team discovered that the enhanced performance derived from the accelerated rate-limiting desorption of NH₃, which contributed to the plasmon induced photoelectric and thermal effects on Cu photoelectrode. The plasmon-assisted strategy was also versatile for other Cu-based nanostructures and revealed the great potential for promoting the NO₃RR performance by introducing thermal and light irradiation.