Synergistic photoelectric and thermal effect for efficient nitrate reduction on plasmonic Cu photocathodes

Recently, electrochemical nitrate reduction reaction (NO₃RR) has been intensively explored for the synthesis of ammonia, and copper (Cu) has become one of the most promising materials for NO₃RR. Notably, Cu is an important plasmonic metal that absorbs visible light. The plasmonic effect might have a significant influence on the performance of Cu-catalyzed NO₃RR but has been seldom reported. Herein, we report the synergistic photoelectric and thermal effect for efficient and stable NO₃RR on plasmonic Cu nanowire photocathodes, which is exclusively effective for NO₃RR but has no effect on the competing hydrogen evolution reaction. The faradaic efficiency for ammonia production is nearly 100% within a potential range from –0.2 V to –0.4 V vs. RHE, and a high ammonia yield rate of 1.37 mmol h^–1 cm^–2 is achieved at –0.2 V vs. RHE. Further operando photoelectrochemical studies and theoretical simulations confirm that the plasmonic excitation efficiently accelerates the rate-limiting desorption of NH₃ on Cu surfaces. We further demonstrate the versatility of this strategy to other Cu-based nanostructures.