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.