Au-modified Cu2O nanocubes for light-enhanced nitrate electroreduction to ammonia

Abstract

As an alternative to the traditional ammonia (NH₃) synthesis method, the electrochemical reduction reaction of nitrate (NO₃⁻RR) for NH₃ production not only mitigates nitrate pollution but also yields economically valuable NH₃. Cu₂O nanomaterials exhibit excellent catalytic activity for NO₃⁻RR with low cost and are beneficial for the rate-limiting step (NO₃⁻ to NO₂⁻). In this work, Au-modified Cu₂O nanocubes (Au/Cu₂O NCs) were synthesized and used as an efficient NO₃⁻RR electrocatalyst for NH₃ production. At −0.75 V potential (relative to the reversible hydrogen electrode, RHE), Au/Cu₂O NCs reach 39.79 mg h⁻¹ mg_cat⁻¹ in NH₃ yield and a faradaic efficiency of 92.93%. Furthermore, the localized surface plasmon resonance (LSPR) characteristics of Au and a narrow band gap of Cu₂O can generate plasma and photoexcited electrons, which can efficiently utilize visible light to accelerate NO₃⁻RR. Indeed, the synergistic effect between Au and Cu₂O can result in an increased NH₃ yield of 57.3 mg h⁻¹ mg_cat⁻¹ under external light conditions for NO₃⁻RR, 1.44 times higher than that without light.