Understanding the Site‐Selective Electrocatalytic Co‐Reduction Mechanism for Green Urea Synthesis Using Copper Phthalocyanine Nanotubes
Jit Mukherjee, Sourav Paul, Ashadul Adalder, Samadhan Kapse, Ranjit Thapa, Sumit Mandal, Biswajit Ghorai, Sougata Sarkar, Uttam Kumar Ghorai
Abstract
Abstract Green synthesis of urea under ambient conditions by electrochemical co‐reduction of N 2 and CO 2 gases using effective electrocatalyst essentially pushes the conventional two steps (N 2 + H 2 = NH 3 and NH 3 + CO 2 = CO(NH 2 ) 2 ) industrial process at high temperature and high pressure, to the brink. The single step electrochemical green 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 N 2 and CO 2 gas molecules to urea. Herein, copper phthalocyanine nanotubes (CuPc NTs) having multiple active sites (such as metal center, Pyrrolic‐N3, Pyrrolic‐N2, and Pyridinic‐N1) as an efficient electrocatalyst which exhibits urea yield of 143.47 µg h –1 mg –1 cat and faradaic efficiency of 12.99% at –0.6 V versus reversible hydrogen electrode by co‐reduction of N 2 and CO 2 are reported. Theoretical calculation suggests that Pyridinic‐N1 and Cu centers are responsible to form CN bonds for urea by co‐reduction of N 2 to NN* and CO 2 to *CO, respectively. This study provides the new mechanistic insight about the successful electro‐reduction of dual gases (N 2 and CO 2 ) in a single molecule as well as rational design of efficient noble metal‐free electrocatalyst for the synthesis of green urea.