Synergistic N, S doping in chitin-derived carbon catalysts for efficient nitrate-to-ammonia electroreduction

Abstract

Electrochemical nitrate reduction to ammonia (NO₃RR) represents a promising approach for wastewater treatment while simultaneously offering an alternative to the Haber–Bosch synthesis process. However, current research on metal-free carbon-based catalysts remains limited in scope, exhibits relatively low catalytic performance, and predominantly relies on carbon precursors derived from non-renewable resources. To address these challenges, this study employs chitin and shrimp shells as a precursor to synthesize sulfur–nitrogen co-doped carbon (SNC) catalysts via thiourea doping. At −0.95 V (vs. RHE), the optimized catalyst achieves a faradaic efficiency of 97.6% and an ammonia yield rate of 21 012 μg h⁻¹ mg⁻¹. Characterizations such as high-resolution transmission electron microscopy (HRTEM), powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and in situ attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) have been conducted to elucidate the catalyst structure.