Electrocatalytic hydrogenation of nitrogenous heterocyclics using Co-based nanoparticles-embedded N-doped carbon derived from ZIF-67

Electrocatalytic hydrogenation (ECH) has been used as a novel approach for the synthesis of organic compounds. Hence, ZIF-67 was selected as a precursor in this study to synthesize a series of electrodes. The ECH effects were assessed on pyridine and diazines. The results showed a significant influence of carbonization temperature and time on the electrocatalyst activity. A temperature of 400 °C was found not high enough for the synthesis of the electrocatalysts, and a long time of 4 h at 800 °C resulted in damage to the spatial structure of the electrocatalyst. The optimal electrocatalyst was obtained under 800 °C and 2 h (Co/NC-800–2). The polyhedral Co/NC-800–2 (20–200 nm) had the N-doped graphitic-carbon shell with embedded Co/CoN/Co3O4 nanoparticles. The onset potential and overpotential (at 10 mA cm−2) were estimated to respectively 64 and 155 mV versus hydrogen evolution reaction (HER), with a Tafel value of 62 mV dec−1. The ECH on pyridine and diazines revealed a positive correlation between ECH effect and HER activity. Co/NC-800–2 possessed excellent ECH activity toward pyridine and pyrazine at − 0.3 V (vs. RHE). N–Co, pyridinic-N, and graphitic-N acted as active sites during electrocatalysis. The N-doped graphitic-carbon promoted the charge transfer during ECH processes.