Ni(II)-Incorporated Porphyrin-Based Conjugated Porous Polymer Derived from 2,6-Diformyl-4-methylphenol as a Catalyst for the Urea Oxidation Reaction.

The urea oxidation reaction (UOR) is an excellent alternative to the sluggish oxygen evolution reaction (OER) as an anode reaction for hydrogen generation via electrochemical water splitting. Here, a porphyrin-based conjugated porous polymer (CPP) has been developed through the polycondensation reaction of 2,6-diformyl-4-methylphenol and pyrrole (DMP-POR). The nickel(II) complex of this conjugated polymer Ni-DMP-POR shows efficient UOR in an alkaline medium. The as-synthesized materials were characterized by solid-state C CP-MAS, thermogravimetric analysis (TGA), Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The porous property of the materials was characterized by N adsorption/desorption isotherms at 77 K. Both DMP-POR and Ni-DMP-POR showed excellent thermal stability. The Ni-DMP-POR exhibits very good UOR in 1 M KOH and 0.33 M urea with an overpotential of 260 mV at 10 mA cm and a Tafel slope of 48 mV dec. The catalyst also shows excellent chronoamperometric and chronopotentiometric stability, suggesting its future scope in sustainable hydrogen production from wastewater resources.