Substantial Role of Nitrogen and Sulfur in Quaternary-Atom-Doped Multishelled Carbon Nanospheres for the Oxygen Evolution Reaction

Abstract

The synergy between nitrogen (N) and sulfur (S) in quaternary heteroatom-doped carbons is rarely probed, although these elements can significantly alter the performance of the oxygen evolution reaction (OER). Herein, quaternary heteroatom (N, S, P, O)-doped multishelled carbon (NSPO-C) nanospheres are synthesized from heteroatom-containing poly­(cyclotriphosphazene-codioxo-thiane) (PCD) polymer nanospheres. The contents of these quaternary heteroatoms were controlled via a facile carbonization process. The OER performance was tested, which was found to be related to the N and S contents, and the as-prepared NSPO-C-8 nanosphere anode with optimized contents of N (2.76 wt %) and S (1.52 wt %) showed a maximum OER activity, that is, it required a very low overpotential of 339 mV to obtain a current density of 10 mA cm–2 with a low Tafel slope value (39.40 mV dec–1), which is much lower than its conventional RuO2 (401 mV), 20% Pt/C (566 mV), and PO-C nanosphere (452 mV) counterparts. Higher performance is attributed to the synergy between N and S in the NSPO-C nanospheres, which provides maximum exposure to electroactive sites, while special morphology ensures efficient pathways for fast charge transportation. These findings advocate that polyphosphazene-derived heteroatom-doped carbons are potential candidates to fabricate high-performance devices for water oxidation.

Effective Poly (Cyclotriphosphazene-Co-4,4′-Sulfonyldiphenol)@rGO Sheets for Tetracycline Adsorption: Fabrication, Characterization, Adsorption Kinetics and Thermodynamics

“…The adsorbents that have been successfully used for this purpose including polymeric materials [14], montmorillonite [7], smectite clay [15], alumina [16], diatomite [8] and carbon materials [17,18]. Polyphosphazenes are an important class of organic-inorganic hybrid polymers, comprising nitrogen and phosphorus atoms in a conjugated binding owing to their backbone stability, structural diversity, biocompatibility, biodegradability and ability to form hybrid molecules [19][20][21][22][23][24][25][26][27]. Poly (cyclotriphosphazene-co-4,4-sulfonyldiphenol) (PZS) is a copolymer of hybrid phosphazenes [28] containing an organic-inorganic structure, which makes it a promising candidate with an extensive range of potential applications, e.g., encapsulation [29], catalyst support [30], carbon material precursor [31], electrochemical features [32] and bio-medicinal applications [33].…”

A Review on the Morphologically Controlled Synthesis of Polyphosphazenes for Electrochemical Applications

“…The quaternary‐doped (P, N, O, and S) exhibits excellent OER properties with 339 mV overpotential, smallest Tafel‐slop (39.4 mV/dec) than Pt/C (566 mV) and RuO 2 (401 mV). The better working is a synergetic response of N and S as provides full exposure to active‐sites and superfast charge transfer [4] …”

“…OPs contain ‘P’ and ‘N’ in their inherent‐inorganic backbone and acts as a primary source of co‐doping, whereas the counter‐organic part imparts carbon of diverse nature from aliphatic, aromatic to condensed supramolecular entities [2] . The substituting ligands containing −OH, −NH 2 , −SO 3 and −SH i. e., 4,4‐sulphonyl biphenol (PZS), phloroglucinol, p ‐diaminobenzene, and 4,4‐diamnophenyl‐ether (ODA); induced heteroatoms like oxygen (O) and sulphur (S) to the structure and originates individually ternary‐doped (S, P and N) and (O, P and N), [3] and mutually quaternary‐doped (S, O, N and P), [4] this referred to a carbons doped with extensive non‐metallic counterpart. For high electrochemical performance co‐doped carbon synthesis by utilizing PPNs‐matrices is a most favorite and adopted method overlooked in‐comparison with graphene and reduced graphene‐oxides [5]…”

Tetra‐Heteroatom‐Doped Ultra‐Mesoporous Carbon from Polyphosphazene for High‐Performance Supercapacitors

“…[36] Recently, our group successfully synthesized polyphosphazene derived N, S, P, O-doped multi-shelled carbon nanospheres which exhibited an excellent oxygen evolution reaction activity. [37] Also, N, P, O-doped carbon was successfully obtained from linear poly(diaryloxyphosphazene), and a specific capacitance of 105 F/g was achieved. [38] Besides, our recent study suggested that the introduction of crosslinked structures into the linear polyphosphazene precursors was helpful to maintain structural defects, imperfections of carbons and also increased graphite crystalline region, which benefited for enhancing the electrochemical performance of carbon materials .…”

“…By contrast, the in‐situ doping method is more convenient. For this approach, the doping elements are directly derived from heteroatoms‐rich precursors and exhibit homogeneous distribution in carbon materials [20,32,33] . Therefore, the in‐situ doping method is a facile method to prepare multi‐heteroatom‐doping carbon material.…”