Graphdiyne Nanostructures Stabilize Molecular Cu Phthalocyanine for Selective Electrochemical Nitrate-to-NH3 Conversion

Abstract

Electrochemical nitrate reduction reaction (eNO3RR) to ammonia (NH3) provides a sustainable route for both NH3 synthesis and nitrate pollutant remediation under ambient conditions. However, the development of efficient catalysts remains challenging due to the complex multielectron reaction pathways and the structural instability of active sites under strongly reducing potentials. Molecular catalysts such as metal phthalocyanines offer well-defined coordination environments for nitrate activation, yet they often suffer from aggregation and irreversible reconstruction during electrocatalysis. Here we report a graphdiyne/graphene (GDY/G) nanostructure-supported molecular catalyst that stabilizes copper phthalocyanine (CuPc) for efficient electrochemical nitrate reduction to NH3. Structural characterizations reveal that the GDY layer enables strong interfacial coupling with CuPc, suppressing molecular aggregation and enhancing catalyst dispersion. At −0.70 V vs RHE, the CuPc/GDY/G catalyst achieves a high NH3 Faradaic efficiency of ∼84% and an exceptional NH3 production rate of 1158 mmol·gcat–1·h–1, markedly outperforming the CuPc/graphene counterpart. Density functional theory calculations show that GDY induces charge redistribution and increases the migration energy barrier of the Cu center, thereby preventing catalyst reconstruction and optimizing the reaction energy landscape. This work demonstrates that carbon-supported nanostructure interfaces can stabilize molecular catalysts under electrochemical conditions and provides a general strategy for designing robust catalysts for nitrate-to-NH3 conversion.