2021 Ghorai Scalable Production of Cobalt Phthalocyanine Nanotubes – Eﬃcient and Robust Hollow Electrocatalyst for Ammonia Synthesis at Room Temperature
Electrocatalytic ammonia (NH3 )synthesis through the nitrogen reduction reaction (NRR) under ambient
conditions presents a promising alternative to the famous century-old Haber−Bosch process. Designing and developing a high-performance electrocatalyst is a compelling necessity for electrochemical NRR. Speciﬁc transition metal based nano-structured catalysts are potential candidates for this purpose
owing to their attributes such as higher actives sites, speciﬁcity as well as selectivity and electron transfer, etc. However, due to the lack of a well-organized morphology, lower activity, selectivity, and stability of the electrocatalysts make them ineﬀective at producing a high NH3 yield rate and Faradaic eﬃciency (FE) for further development. In this work, stable β-cobalt phthalocyanine (CoPc) nanotubes (NTs) have been synthesized by a scalable solvothermal method for electrochemical NRR. The chemically synthesized CoPc NTs show excellent electrochemical NRR due to high speciﬁc area, greater number of exposed active sites, and speciﬁc selectivity of the catalyst. As a result, CoPc NTs produced a higher NH3 yield of 107.9 μgh−1 mg −1cat and FE of 27.7% in 0.1 M HCl at −0.3 V vs RHE. The density functional theory calculations conﬁrm that the Co center in CoPc is the main active site responsible for electrochemical NRR. This work demonstrates the development of hollow nanostructured electrocatalysts in large scale for N2 ﬁxation to NH3.