Enhanced nitrate reduction via the Ag–Cu–P catalyst for sustainable ammonia generation under ambient conditions

Abstract

The production of ammonia under ambient conditions has been a long-standing challenge for the chemical industry. The electroreduction of nitrate presents a promising solution for nitrate wastewater treatment and decentralized ammonia production. However, traditional Ag-based catalysts suffer from nitrate-to-nitrite conversion, leading to toxicity concerns and hampering ammonia preparation. In this study, we synthesized an innovative Ag–Cu–P catalyst that effectively tunes the d-band centre and electronic structure. The catalyst exhibited a remarkable NH₄⁺ yield rate of 566.30 μmol cm⁻² h⁻¹ at −0.3 V (vs. RHE), reducing nitrite content to below the drinking water standard. Characterization results revealed a distinctive fern leaf-like morphology, providing an expanded active surface area. The challenge of facile nitrate conversion to nitrite on Ag-based catalysts has been addressed through the implementation of electronic structure modulation in this work. Theoretical calculations confirmed the substantial reduction in the energy barrier by modulating the d-band centre and electronic structure, facilitating the conversion of nitrite to ammonia. The regulation and analysis of d-band centres yielded valuable insights for catalyst material design. Meanwhile, direct evidence for potential intermediates has also been presented through in situ spectroscopy. These findings hold significant potential for practical applications, such as enhanced wastewater treatment and decentralized ammonia production, and provide support in the pressing need for sustainable ammonia synthesis under ambient conditions.