Evolution of an Electrochemically Inactive Metal–Organic Framework to Reticulated Porous Carbon Particles with High Supercapacitance

Abstract

An iron-containing porphyrin-based porous metal− organic framework (PPMOF) has been synthesized and subsequently pyrolyzed to obtain the carbon structure with homogeneous distribution of nitrogen. The pyrolysis is carried out at different temperatures and in the presence of two different environments; in argon to obtain PPMOF-Ar-700, PPMOF-Ar-800, and PPMOF-Ar-900, and in nitrogen to obtain PPMOF-N-800. The motivation here is to study the change in the electrochemical properties that take place on conversion of the metal−organic framework to its corresponding carbons. The materials have been characterized by powder X-ray diffraction, nitrogen adsorption/desorption, scanning electron microscopy, Xray photoelectron spectroscopy, and Raman spectroscopy, among others. It was observed that PPMOF almost did not show any electrochemical response and was unstable, whereas the carbonized frameworks showed good supercapacitive behavior and stability. The surface area increases from 353 to 838 m 2 •g −1 , when the pyrolysis gas is switched over from nitrogen to argon. It also results in the formation of uniform smooth spherical particles in PPMOF-Ar-800, in contrast to agglomerated broken particles in PPMOF-N-800. PPMOF-Ar-800 shows a remarkable specific capacitance value of 500 F•g −1 at a current density of 1 A•g −1 which is retained at a high value of 111 F•g −1 at a very high current density of 50 A•g −1 in galvanostatic charge/discharge studies, whereas for PPMOF-N-800, the specific capacitance is 400 F•g −1 at 1 A•g −1 and its discharge time is also shorter than that for PPMOF-Ar-800. This indicates that the pyrolysis environment plays a crucial role in the formation and stabilization of the carbon structures.

B/P-Codoped Porous Carbon Electrode for Supercapacitors with Ultrahigh Energy Density

“…75P (Figure a) suggests the presence of C–N bonding along with the C–C bond (284.3 eV) and the formation of both BC 3 and C–P (285.2 eV) functionalities on its surface. The N 1s spectra on deconvolution (Figure b) give four peaks; two of them are attributed to the presence of pyridinic-N (397.6 eV) and pyrrolic-N (400.7 eV) species, as anticipated . Two additional peaks that appear at 399.5 and 404.1 eV suggest the presence of C–N–B functionality and quaternary-N, respectively .…”

“…Thus, these peaks imply the successful incorporation of B and P in the carbon frameworks. The presence of heteroatoms enhances the pseudocapacitive contribution and the carbon support promotes the EDLC behavior; both processes work synergistically to boost the supercapacitance . As evident from the voltammograms (Figure c), CPSM-0 .…”

“…The first peak at 284.4 eV suggests the formation of the defect-induced C–N bonding along with the C–C bond, whereas the other peak located at 285.4 eV indicates the presence of C–P species in the sample . The deconvoluted spectra of N 1s of the material (Figure S5b) indicate the presence of pyridinic-N (398.1 eV), pyrrolic-N (400.4 eV), and pyridonic-N (399.7 eV) . The O 1s core-level spectra of CPSM-1 .…”

“…Deconvolution of the N 1s signal (Figure S4b) results in four prominent peaks. The peak at 399.0 eV can be assigned to pyridinic-N, 399.8 eV to C–N–B, 401.5 eV to pyrrolic-N, and 403.3 eV to quaternary-N . The pyridinic-N is sp 2 hybridized, whereas the pyrrolic-N is sp 3 hybridized, and the distinct signal for C–N–B indicates the high affinity of nitrogen toward the boron atoms.…”

Ni Single Atom Decorated Porous Hollow Carbon Nanosphere‐Based Electrodes for High Performance Symmetric Solid‐State Supercapacitors

“…The peak at ca. 284.53 eV corresponds to sp 3 hybridized amorphous carbon, appearing due to the presence of CÀ C and CÀ N moieties [45] and that at ca. 285.9 eV to the sp 2 hybridized carbon.…”