Multi-Dimensional Ni@TiN/CNT Heterostructure with Tandem Catalysis for Efficient Electrochemical Nitrite Reduction to Ammonia

Electrochemical nitrite reduction reaction (NO2RR) is considered as a sustainable ammonia (NH3) synthesis strategy. However, there are still significant challenges in designing efficient NO2RR catalysts. Here, carbon nanotube (CNT) encapsulated Ni nanoparticles (NPs) loaded on MXene-derived TiN (Ni@TiN/CNT) heterostructure is constructed by combining molten salt etching strategy and chemical vapor deposition. Ni@TiN/CNT exhibits excellent NH3 yield rate (15.6 mg h−1 mgcat.−1), Faradaic efficiency (95.6%) and record cycle stability (NO2RR performance is virtually unattenuated after 60 cycles) at −0.7 V versus reversible hydrogen electrode (vs. RHE). In addition, the Zn-nitrite battery with Ni@TiN/CNT as the cathode shows high power density (9.6 mW cm−2) and NH3 synthesis performance. Combining validation experiments and density functional theory calculations reveal that Ni@TiN/CNT follows the tandem catalytic mechanism. The TiN site preferentially adsorbs and activates NO2−, while the Ni site provides abundant active hydrogen for the subsequent reduction process. Meanwhile, the chainmail structure of CNT prevents the oxidation and leaching of active sites, thereby significantly enhancing the stability of Ni@TiN/CNT. This work provides a new inspiration for the preparation of durable and efficient NO2RR electrocatalysts with tandem catalytic sites.