Carbon Nanotube-Templated Synthesis of Covalent Porphyrin Network for Oxygen Reduction Reaction

Abstract

The development of innovative techniques for the functionalization of carbon nanotubes that preserve their exceptional quality, while robustly enriching their properties, is a central issue for their integration in applications. In this work, we describe the formation of a covalent network of porphyrins around MWNT surfaces. The approach is based on the adsorption of cobalt(II) meso-tetraethynylporphyrins on the nanotube sidewalls followed by the dimerization of the triple bonds via Hay-coupling; during the reaction, the nanotube acts as a template for the formation of the polymeric layer. The material shows an increased stability resulting from the cooperative effect of the multiple π-stacking interactions between the porphyrins and the nanotube and by the covalent links between the porphyrins. The nanotube hybrids were fully characterized and tested as the supported catalyst for the oxygen reduction reaction (ORR) in a series of electrochemical measurements under acidic conditions. Compared to similar systems in which monomeric porphyrins are simply physisorbed, MWNT-CoP hybrids showed a higher ORR activity associated with a number of exchanged electrons close to four, corresponding to the complete reduction of oxygen into water.

N-doped carbon nanotubes containing a high concentration of single iron atoms for efficient oxygen reduction

“…Figure 2a shows the highresolution N1s peaks of the CNT@Fe-N-PC and reference samples of iron phthalocyanine and PPy. Only one N 1s peak at~398.7 eV can be observed for iron phthalocyanine, which originates from either Fe-N x or pyridinic N because of the small difference in binding energy between Fe-N x and pyridinic N. 31,32 Two separate N1s peaks were observed for PPy, which can be attributed to pyrrolic N (399.7 eV) and oxidized N (406.5 eV). The fitted peaks of the CNT@Fe-N-PC at 398.7 and 401.0 eV can be assigned to Fe-N x (or pyridinic N, 23.7%) and graphitic N (76.3%), respectively.…”

Metal–Organic‐Framework‐Derived Dual Metal‐ and Nitrogen‐Doped Carbon as Efficient and Robust Oxygen Reduction Reaction Catalysts for Microbial Fuel Cells

“…However, it is still challenging to achieve satisfying ORR performance with these inexpensive catalysts due to the sluggish kinetics of ORR. It was shown recently that modification of the nonmetal heteroatom doped carbon with transition metal species could promote its ORR activity to a level comparable to that of Pt‐based catalyst 17, 18, 19, 20, 21. Although the detailed mechanism for this performance enhancement is not clearly understood yet,22, 23 these results clearly outlined the potential of the metal and nonmetal heteroatom codoped carbon for the development of high performance and low cost ORR catalyst.…”

Natural Hematite as a Low-Cost and Earth-Abundant Cathode Material for Performance Improvement of Microbial Fuel Cells

“…In recent years, the synthesis of electrocatalysts containing non-precious metals (e.g., Fe and Co) have been extensively investigated in MFCs for improving cathodic reactivity. Promising results in terms of oxygen reduction reaction activity were non-precious metals linked with organics N 4 -chelating ligands and their polymeric derivatives [7][8][9][10], such as metals tetramethoxyphenylporphyrin (TMPP), CoTMPP, FeCoTMPP, ClFeTMPP, and metals phthalocyanine (Pc), FePc, CoPc, CoNPc, FeCuPc, etc. [11][12][13][14][15][16][17].…”