N/S-Co-Doped Porous Carbon Sheets Derived from Bagasse as High-Performance Anode Materials for Sodium-Ion Batteries

Synthesis of Low-Cost and High-Performance Dual-Atom Doped Carbon-Based Materials with a Simple Green Route as Anodes for Sodium-Ion Batteries

Sodium-ion batteries (SIBs) are promising alternatives to replace lithium-ion batteries as future energy storage batteries because of their abundant sodium resources, low cost, and high charging efficiency. In order to match the high energy capacity and density, designing an atomically doped carbonous material as the anode is presently one of the important strategies to commercialize SIBs. In this work, we report the preparation of high-performance dual-atom-doped carbon (C) materials using low-cost corn starch and thiourea (CH4N2S) as the precursors. The electronegativity and radii of the doped atoms and C are different, which can vary the embedding properties of sodium ions (Na+) into/on C. As sulfur (S) can effectively expand the layer spacing, it provides more channels for embedding and de-embedding Na+. The synergistic effect of N and S co-doping can remarkably boost the performance of SIBs. The capacity is preserved at 400 mAh g -1 after 200 cycles at 500 mA g-1; more notably, the initial Coulombic efficiency is 81%. Even at a high rate of high current of 10 A g-1, the cell capacity can still reach 170 mAh g-1. More importantly, after 3000 cycles at 1 A g-1, the capacity decay is less than 0.003% per cycle, which demonstrates its excellent electrochemical performance. These results indicate that high-performance carbon materials can be prepared using low-cost corn starch and thiourea.

Dual-Heteroatom-Doped Reduced Graphene Oxide Sheets Conjoined CoNi-Based Carbide and Sulfide Nanoparticles for Efficient Oxygen Evolution Reaction

Intensive research is being conducted into highly efficient and cheap nanoscale materials for the electrocatalytic oxidation of water. In this context, we built heterostructures of multilayered CoNi-cyanide bridged coordination (CoNi-CP) nanosheets and graphene oxide (GO) sheets (CoNi-CP/GO) as a source for heterostructured functional electrodes. The layered CoNi-CP/GO hybrid components heated in nitrogen gas (N₂) at 450 °C yield CoNi-based carbide (CoNi-C) through thermal decomposition of CoNi-CP, while GO is converted into reduced GO (rGO) to finally form a CoNi-C/rGO-450 composite. The CoNi-C/rGO-450 composite shows a reasonable efficiency for oxygen evolution reaction (OER) through water oxidations in alkaline solution. Meanwhile, regulated annealing of CoNi-CP/GO in N₂ with thiourea at 450 and 550 °C produces CoNi-based sulfide (CoNi-S) rather than CoNi-C between rGO sheets co-doped by nitrogen (N) and sulfur (S) heteroatoms (NS-rGO) to form CoNi-S/NS-rGO-450 and CoNi-S/NS-rGO-550 composites, respectively. The CoNi-S/NS-rGO-550 shows the best efficiency for electrocatalytic OER among all electrodes with an overpotential of 290 mV at 10 mA cm^-2 and a Tafel slope of 79.5 mV dec^-1. By applying the iR compensation to remove resistance of the solution (2.1 Ω), the performance is further improved to achieve a current density of 10 mA cm^-2 at an overpotential of 274 mV with a Tafel slope of 70.5 mV dec^-1. This result is expected to be a promising electrocatalyst compared to the currently used electrocatalysts and a step for fuel cell applications in the future.

Layer-by-Layer Motif Heteroarchitecturing of N,S-Codoped Reduced Graphene Oxide-Wrapped Ni/NiS Nanoparticles for the Electrochemical Oxidation of Water

A new heterostructured material is synthesized with lamellar arrangements in nanoscale precision through an innovative synthetic approach. The self-assembled Ni-based cyano-bridged coordination polymer flakes (Ni-CP) and graphene oxide (GO) nanosheets with a layered morphology (Ni-CP/GO) are used as precursors for the synthesis of multicomponent hybrid materials. Annealing of Ni-CP/GO in nitrogen at 450 °C allows the formation of Ni₃ C/rGO nanocomposites. Grinding Ni-CP/GO and thiourea and annealing under the same conditions produces N,S-codoped reduced GO-wrapped NiS₂ flakes (NiS₂ /NS-rGO). Interestingly, further heating up to 550 °C allows the phase transformation of NiS₂ into NiS accompanied by the formation of a face-centered cubic (FCC-Ni) metal phase between NS-rGO layers (FCC-Ni-NiS/NS-rGO). Among all the materials, the resulting FCC-Ni-NiS/NS-rGO exhibits good electrocatalytic activity and stability toward the oxygen evolution reaction (OER) owing to the synergistic effect of multiphases, the well-designed alternating layered structures on the nanoscale with abundant active sites.

V3S4 Nanosheets Anchored on N, S Co-Doped Graphene with Pseudocapacitive Effect for Fast and Durable Lithium Storage

Construction of a suitable hybrid structure has been considered an important approach to address the defects of metal sulfide anode materials. V₃S₄ nanosheets anchored on an N, S co-coped graphene (VS/NSG) aerogel were successfully fabricated by an efficient self-assembled strategy. During the heat treatment process, decomposition, sulfuration and N, S co-doping occurred. This hybrid structure was not only endowed with an enhanced capability to buffer the volume expansion, but also improved electron conductivity as a result of the conductive network that had been constructed. The dominating pseudocapacitive contribution (57.78% at 1 mV s⁻¹) enhanced the electrochemical performance effectively. When serving as anode material for lithium ion batteries, VS/NSG exhibits excellent lithium storage properties, including high rate capacity (480 and 330 mAh g⁻¹ at 5 and 10 A g⁻¹, respectively) and stable cyclic performance (692 mAh g⁻¹ after 400 cycles at 2 A g⁻¹).