Preparation and Formation Mechanism of Porous Polyurea by Reaction of Toluene Diisocyanate with Water and Its Application as Adsorbent for Anionic Dye Removal

A novel and easy one-step protocol for preparation of a new porous material, polyurea （PPU）, is reported, which is accomplished through a precipitation polymerization of toluene diisocyanate （TDI） in mixed solvent of H20-acetone without need for surfactant and porogen. Effects of TDI concentration, mechanical stirring, solvent composition and TDI addition rate on PPU structure are studied. Surface morphology and pore structure of PPU are characterized by scanning electron microscopy and Hg intrusion. Chemical structure of the PPU polymer is investigated using NMR, XRD and FTIR. Mechanism of pore formation is discussed. The obtained PPU is used as adsorbent for anionic dyes adsorption investigation. Two anionic dyes, remazol brilliant blue R and acid fuchsine, are tested. The results indicate that the as-prepared PPU is of high performance in dye adsorption and recycled use. This study provided therefore a facile route to the preparation of a novel and attractive adsorbent candidate for removal of anionic dyes from wastewaters.

Immobilization of cobalt oxide nanoparticles on porous nitrogen-doped carbon as electrocatalyst for oxygen evolution

Highly efficient and robust electrocatalysts have been in urgent demand for oxygen evolution reaction(OER).For this purpose,high-cost carbon materials,such as graphene and carbon nanotubes,have been used as supports to metal oxides to enhance their catalytic activity.We report here a new Co_(3)O_(4)-based catalyst with nitrogen-doped porous carbon material as the support,prepared by pyrolysis of porous polyurea(PU) with Co(NO_(3))_(2)immobilized on its surface.To this end,PU was first synthesized,without any additive,through a very simple one-step precipitation polymerization of toluene diisocyanate in a binary mixture of H2O-acetone at room temperature.By immersing PU in an aqueous solution of Co(NO_(3))_(2)at room temperature,a cobalt coordinated polymer composite,Co(NO_(3))_(2)/PU,was obtained,which was heated at 500℃ in air for 2 h to get a hybrid,Co_(3)O_(4)/NC,consisting of Co_(3)O_(4)nanocrystals and sp2-hybridized N-doped carbon.Using this Co_(3)O_(4)/NC as a catalyst in OER,a current density of10 mA·cm^(-2)was readily achieved with a low overpotential of 293 mV with a Tafel slope of87 mV·dec^(-1),a high catalytic activity.This high performance was well retained after 1000 recycled uses,demonstrating its good durability.This work provides therefore a facile yet simple pathway to fabrication of a new transition metal oxides-based N-doped carbon catalyst for OER with high performance.