Potential-Modulated Selective Electrosynthesis of Azo-Tetrazole Energetic Compounds via a Co₂P Nanowire-Based Cathode

The electrochemical synthesis of azo-bridged nitrogen-rich heterocyclic compounds has emerged as a promising strategy in the field of energetic materials due to its efficiency and controllability. Here, we present an innovative and environmentally benign electrocatalytic strategy employing cobalt phosphide (Co₂P) nanowire arrays as cathodic catalysts for the safe and efficient synthesis of sodium 5,5'-azo-tetrazole under mild electrochemical conditions. Notably, the Co₂P catalyst drives the reaction at a low potential of -0.4 V (vs Hg/HgO), which benefits from its unique needle-like morphology that optimizes electron transport pathways and active site distribution. By adjustment of the applied potential and reaction time, the yield of the reductive coupling can be effectively controlled. A detailed mechanistic pathway has been elucidated for the cathodic reductive coupling of sodium 5-nitrotetrazole mediated by Co₂P electrodes. Electrochemical reduction at -0.6 V (vs Hg/HgO) and -0.8 V (vs Hg/HgO) yields a tunable mixture of sodium 5,5'-azo-tetrazole and its azoxy derivative, whereas exclusive generation of sodium 5,5'-azo-tetrazole is achieved at -1 V (vs Hg/HgO) through precise modulation of electron transfer kinetics. This voltage-gated synthesis paradigm establishes a novel electrochemical methodology for the programmable assembly of nitrogen-rich heterocyclic frameworks, offering unprecedented control over azo-linkage formation in energetic material design.