Electrosynthesis of Green Urea by co-reduction of N2 and CO2 Using Dual Active Sites of Copper Phthalocyanine Nanotube

Abstract

Green synthesis of urea under ambient conditions by electrochemical co-reduction of N2 and CO2 gases using effective electrocatalyst essentially pushes the conventional two steps (N2 + H2 = NH3 & NH3 + CO2 = CO (NH2)2) industrial process at high temperature and high pressure, to the brink. The single step urea synthesis process has hit a roadblock due to the lack of efficient and economically viable electrocatalyst with multiple active sites for dual reduction of N2 and CO2 gas molecules to urea. Herein, CuPc nanotubes having multiple active sites (such as metal center, Pyrrolic-N3, Pyrrolic-N2, and Pyridinic-N1) are reported to exhibit urea yield of 143.47 µg h-1 mg-1cat and FE of 12.99% at –0.6 V vs RHE by co-reduction of N2 and CO2. Theoretical calculation suggests that Pyridinic-N1 and Cu centers are responsible to form C-N bonds for urea by reduction of N2 to NN* and CO2 to *CO respectively.