Convenient Synthesis of 5,5′-azotetrazolate Energetic Salts through Electrochemical Oxidative-Coupling of 5-amino-1H-tetrazole Under Mild Conditions

In the synthesis of 5,5'-azotetrazolate energetic salts, the key reaction is the oxidative-coupling of 5-amino-1H-tetrazole (5AT). But in the conventional KMnO4 oxidation method for 5AT coupling, it suffers from several issues in high energy consumption, insufficient security and inconvenient purification. Here, an electrochemical approach for the oxidative-coupling of 5AT into 5,5'-azotetrazolate under mild conditions is reported. The electrochemical oxidative-coupling of 5AT can be achieved on several precious-metal (Pt, Au, Ag) and transition-metal (Fe, Co, Ni, Cu, Mo, W) electrodes in alkaline electrolyte. The oxidative-coupling of 5AT on Pt electrode was mainly initiated by hydroxyl radical intermediates that formed during the electrocatalytic oxidation of water on Pt, whereas on Ni electrode the oxidative-coupling of 5AT was initiated via direct electrooxidation on the Ni surface without mediation by intermediate species. Due to the convenience of this electrochemical method, yields of up to 10 g of 5,5'-azotetrazolate salt could be easily afforded.