Porous organic polymer derived metal-free carbon composite as an electrocatalyst for CO2 reduction and water splitting

Abstract A hybrid porous organic polymer (POP) comprising of phenylenediamine, phloroglucinol and triazine was synthesized, carbonized at different temperatures and characterized. Solid state 13C and 15N CP-MAS NMR spectra of the POP showed evidences for the presence of the three moieties in varying composition. Raman analysis of the carbonized samples exhibited varying degrees of graphitization and powder X-ray diffraction (PXRD) analysis showed patterns corresponding to N-doped amorphous carbon. Surface morphological characteristics obtained from SEM and TEM analysis confirm different morphologies with slight variations in the particle size and porosity. Further, the electrocatalytic activities of the prepared metal-free catalysts were evaluated. Sample carbonized at 700 °C (PPT-700) showed excellent catalytic activity towards electrocarboxylation of 4-bromoacetophenone in 0.1 M TBABF4/DMF and OER in 1 M KOH as indicated by their onset potential and current density, whereas the sample calcined at 900 °C (PPT-900) exhibited excellent HER activity in 1 M H2SO4. The catalytic activity of PPT-700 towards electrocarboxylation and OER activity is ascribed to the presence of pyridinic, pyrrolic and quaternary nitrogen's, whereas the presence of pyridinic and pyrrolic nitrogen's are responsible for the enhanced HER activity of PPT-900 sample as evident from XPS.