Substantial Role of Nitrogen and Sulfur in Quaternary-Atom-Doped Multishelled Carbon Nanospheres for the Oxygen Evolution Reaction
Yasir Abbas, Majid Basharat, Wei Liu, Muhammad Shuaib Khan, Shuangkun Zhang, Shafqat Ali, Zhanpeng Wu, Dezhen Wu
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.