A Cu14(dppy)7(dmbt)3 cluster of chelating structure for enhanced electrocatalytic nitrogen reduction to ammonia

Abstract

The urgent demand for sustainable ecosystems is driving the transition from the energy-intensive Haber–Bosch process to electrocatalytic nitrogen reduction reaction (ENRR), facilitating sustainable ammonia production through renewable energy. In this study, we synthesised a Cu₁₄(dppy)₇(dmbt)₃ nanocluster (Cu₁₄ NC) and investigated it as a high-efficiency ENRR catalyst by supporting it on graphene. These graphene-supported Cu₁₄ NCs (Cu₁₄ G) achieve an outstanding ammonia yield of 3.58 μg h⁻¹ cm⁻² with a faradaic efficiency (FE) of 55.96% at a low overpotential of −0.8 V vs. RHE in 0.1 M KOH (H-cell setup). Notably, the Cu₁₄ G NCs completely suppress hydrazine formation and surpass the performance of Cu₁₄ NCs on TiO₂, CeO₂, graphene oxide, MXene, or unsupported alternatives. Furthermore, the Cu₁₄ G catalyst exhibits exceptional long-term stability. The enhanced performance arises from graphene's superior conductivity and its robust contacts with the chelating structured Cu₁₄ NCs, which stabilise essential intermediates, facilitate charge transfer, and inhibit the competing hydrogen evolution pathway. These findings underscore the capacity of copper cluster catalysts to transform nitrogen fixation, facilitating decentralised, sustainable ammonia production.