Engineering Interfacial Water Activation via Synergistic Defect and Aggregate Carbon Dots Layer for Efficient Nitrate-to-Ammonia Electrocatalysis

Abstract

Ammonia synthesis from nitrate via electrocatalysis offers a sustainable alternative to the energy-intensive Haber–Bosch process, yet achieving high efficiency is challenging due to sluggish multi-electron transfer and unstable intermediates. Here, we report a TaON@CL hybrid electrocatalyst (CL denotes an aggregate carbon dots–derived carbon layer), which integrates oxygen vacancy-rich TaON with the carbon layer to synergistically engineer interfacial water activation and electron transfer, leveraging a sustainable and waste-valorizing carbon source. The defect-engineered TaON@CL enhances nitrate adsorption and stabilizes key hydrogenated intermediates, while concurrently promoting interfacial charge transfer, lowering the free energy requirement of the rate determine step (RDS), and facilitating water activation at the catalyst–electrolyte interface. This synergistic design achieves an NH3 yield of 2843.1 mmol gcat.−1 h−1 with 86.4% Faradaic efficiency. Operando attenuated total reflection surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS), transient photovoltage (TPV) analysis, and density functional theory (DFT) calculations collectively reveal that the defect-engineered TaON and biomass-derived carbon layer act cooperatively to enhance interfacial water activation, facilitate electron transfer, and lower the rate-determining energy barrier, thereby establishing the mechanistic basis for the catalyst’s high activity and selectivity.