A free-standing and flexible phosphorus/nitrogen dual-doped three-dimensional reticular porous carbon frameworks encapsulated cobalt phosphide with superior performance for nitrite detection in drinking water and sausage samples

An assembly and self-template strategy is presented for the synthesis of cobalt phosphide nanoparticles (CoPx, x = 1, 2) embedded into 3D phosphorus/nitrogen co-doped reticular porous carbon frameworks (denoted as CoPx@P,N-RPCs) utilizing polyacrylonitrile (PAN) as the in situ nitrogen doping carbon source and hypophosphite as phosphorus source via hydrothermal method and subsequent phosphorization. The obtained CoPx@ P,N-RPCs nanocomposite possesses the inherent features of both unique 3D porous structure and hierarchical connectivity, providing highly efficient pathways for electron, ion, and mass transport. The unique P,N co-doped carbon network confines nanostructural CoPx into the microstructural carbon network, which prevents them from aggregating, improves the conductivity of CoPx, meanwhile alleviates large volume expansion/contraction effect, thus results in high electrochemical performance and cycling durability. Benefiting from its unique structural advantages, the CoPx@P,N-RPCs nanocomposite exhibits excellent electrochemical performance for nitrite (NO2-) detection with a wide linear range of 10 nM to 1.184 mM, a low detection limit of 5 nM, and a very high stability, which is better than most nitrite sensors reported previously. Importantly, the nitrite level can be determined by the resulting sensor in food and drinking water with excellent recoveries, implying its feasibility for realistic application.