In Situ Synthesis of Vanadium Nitride/Carbon Composites via Ice Crystal Template Method-Protonated Chitosan Synergistic Strategy for Supercapacitors

Vanadium nitride (VN) is regarded as a highly promising pseudocapacitive material. However, traditional preparation of VN materials typically requires high-temperature ammonization or complex precursor treatments, which often result in particle agglomeration and are environmentally harmful due to the use of ammonia. To address these challenges, this work proposes an in situ synthesis strategy based on the synergistic effect of the ice crystal template method and protonated chitosan. This methodology includes constructing a three-dimensional porous protonated chitosan aerogel via the ice-templating process, which facilitates uniform vanadium ion distribution through electrostatic interactions between protonated amino groups (NH 3 + ) and vanadate anions (VO 3 – ) in ammonium metavanadate (NH 4 VO 3 ). Subsequently, thermal treatment under nitrogen atmosphere induces carbonization of the chitosan matrix into a conductive network, while the decomposition of amino groups generates NH 3 as a reducing agent, enabling the in situ formation of nanostructured VN. This “one-step” synthesized VN/C composite material (VN/C-800-5 wt %) exhibits a high specific capacitance of 214.7 F g –1 at a current density of 0.5 A g –1, significantly outperforming comparative samples prepared with varying chitosan ratios and sintering temperatures. Furthermore, when configured as an asymmetric supercapacitor (Ni(OH) 2 //VN/C-800-5 wt %) with Ni(OH) 2 as the positive electrode, the device achieves an impressive energy density of 31.36 Wh kg –1 within a 1.6 V voltage window and maintains 92.1% capacitance retention after 10,000 charge–discharge cycles.