Modulating Surface-Active Hydrogen for Facilitating Nitrate-to-Ammonia Electroreduction on Layered Double Hydroxides Nanosheets

Abstract

Electrocatalytic nitrate (NO3−) reduction reaction (NitRR) to valuable ammonia (NH3) presents a promising alternative strategy to the conventional Haber-Bosch process, yet suffers from low Faradaic efficiency (FE) and limited NH3 yield due to the sluggish multi-electron/proton transfer steps involved. Here, NiCuFe-layered double hydroxides (NiCuFe-LDHs) nanosheets with abundant metal Ni and Cu sites are synthesized for facilitating NO3−-to-NH3 electroreduction with a large NH3 yield of 1.64 mmol h−1 cm−2, NH3 FE of 94.8% and high stability for 15 cycles. Computational and theoretical analysis reveals the NitRR pathway and elucidates that the Cu and Ni sites act as the primary center for NO3−adsorption and activation. Meanwhile, the Ni site effectively modulates the adsorption and dissociation of H2O to provide sufficient H*, thus enhancing the NitRR activity of NiCuFe-LDHs nanosheets. Consequently, the Zn-NO3− battery utilizing NiCuFe-LDHs nanosheets as the cathode delivers a high FE of 85.8%, a large NH3 yield of 1.63 mmol h−1 cm−2, and a remarkable power density of 12.4 mW cm−2, outperforming most previous reports, which enable the simultaneous NO3− pollutants removal, NH3 production, and electricity output. This work offers a promising strategy for designing and synthesizing efficient electrocatalysts for NO3− removal and value-added NH3 production.