Graphdiyne-Stabilized Cobalt Oxyhydroxide Quantum Dots for Efficient Nitrate-to-Ammonia Electrocatalysis

The electrocatalytic nitrate reduction reaction (NtRR) offers a sustainable and promising alternative to the energy-intensive Haber-Bosch process for ambient ammonia (NH₃) synthesis. However, its practical application is limited by sluggish reaction kinetics and low selectivity due to competing side reactions. Herein, we demonstrate the in situ transformation of cobalt oxyhydroxide (CoOOH) nanosheets into a well-defined quantum dot (QD) architecture induced by a graphdiyne (CoOOH@GDY). Experiments combined with theoretical results demonstrate that the noninteger charge transfer between sp-C and Co atoms at the interface enables precise electronic modulation, the formation of abundant low-coordination sites and grain boundaries, optimized adsorption ability for reaction intermediates, and high intrinsic catalytic activity. As a result, the obtained CoOOH@GDY electrocatalyst exhibited exceptional NtRR performance, achieving a remarkable Faradaic efficiency of 98.01%, a high NH₃ yield rate of 1644 µmol h^-1 cm^-2 in 1 M KOH with 0.1 M NO₃ ^-, and high operational stability. This work highlights the great potential of GDY-mediated interface engineering for the rational design of high-performance electrocatalysts.