Electrochemical N–N Oxidatively Coupled Dehydrogenation of 3,5-Diamino-1<i>H</i>-1,2,4-triazole for Value-Added Chemicals and Bipolar Hydrogen Production

Electrochemical H₂ production from water favors low-voltage molecular oxidation to replace the oxygen evolution reaction as an energy-saving and value-added approach. However, there exists a mismatch between the high demand for H₂ and slow anodic reactions, restricting practical applications of such hybrid systems. Here, we propose a bipolar H₂ production approach, with anodic H₂ generation from the N-N oxidatively coupled dehydrogenation (OCD) of 3,5-diamino-1<i>H</i>-1,2,4-triazole (DAT), in addition to the cathodic H₂ generation. The system requires relatively low oxidation potentials of 0.872 and 1.108 V vs RHE to reach 10 and 500 mA cm^-2, respectively. The bipolar H₂ production in an H-type electrolyzer requires only 0.946 and 1.129 V to deliver 10 and 100 mA cm^-2, respectively, with the electricity consumption (1.3 kWh per m³ H₂) reduced by 68%, compared with conventional water splitting. Moreover, the process is highly appealing due to the absence of traditional hazardous synthetic conditions of azo compounds at the anode and crossover/mixing of H₂/O₂ in the electrolyzer. A flow-type electrolyzer operates stably at 500 mA cm^-2 for 300 h. Mechanistic studies reveal that the Pt single atom and nanoparticle (Pt_1,n) optimize the adsorption of the S active sites for H₂ production over the Pt_1,n@VS₂ cathodic catalysts. At the anode, the stepwise dehydrogenation of -NH₂ in DAT and then oxidative coupling of -N-N- predominantly form azo compounds while generating H₂. The present report paves a new way for atom-economical bipolar H₂ production from N-N oxidative coupling of aminotriazole and green electrosynthesis of value-added azo chemicals.