A Highly Dispersed Cobalt Electrocatalyst with Electron-Deficient Centers Induced by Boron toward Enhanced Adsorption and Electrocatalysis for Room-Temperature Sodium-Sulfur Batteries.

As vitally prospective candidates for next-generation energy storage systems, room-temperature sodium-sulfur (RT-Na/S) batteries continue to face obstacles in practical implementation due to the severe shuttle effect of sodium polysulfides and sluggish S conversion kinetics. Herein, the study proposes a novel approach involving the design of a B, N co-doped carbon nanotube loaded with highly dispersed and electron-deficient cobalt (Co@BNC) as a highly conductive host for S, aiming to enhance adsorption and catalyze redox reactions. Crucially, the pivotal roles of the carbon substrate in prompting the electrocatalytic activity of Co are elucidated. The experiments and density functional theory (DFT) calculations both demonstrate that after B doping, stronger chemical adsorption toward polysulfides (NaPSs), lower polarization, faster S conversion kinetics, and more complete S transformation are achieved. Therefore, the as-assembled RT-Na/S batteries with S/Co@BNC deliver a high reversible capacity of 626 mAh g-1 over 100 cycles at 0.1 C and excellent durability (416 mAh g-1 over 600 cycles at 0.5 C). Even at 2 C, the capacity retention remains at 61.8%, exhibiting an outstanding rate performance. This work offers a systematic way to develop a novel Co electrocatalyst for RT-Na/S batteries, which can also be effectively applied to other transition metallic electrocatalysts.

P-doped porous carbon from camellia shell for high-performance room temperature sodium-sulfur batteries.

Room-temperature sodium-sulfur batteries are still hampered by severe shuttle effects and sluggish kinetics. Most of the sulfur hosts require high cost and complex synthesis process. Herein, a facile method is proposed to prepare a phosphorous doped porous carbon (CSBP) with abundant defect sites from camellia shell by oxidation pretreatment combined with H3PO4activation. The pretreatment can introduce pores and adjust the structure of biochar precursor, which facilitates the further activation of H3PO4and effectively avoids the occurrence of large agglomeration. Profiting from the synergistic effects of physical confinement and doping effect, the prepared CSBP/S cathode delivers a high reversible capacity of 804 mAh g-1after 100 cycles at 0.1 C and still maintains an outstanding capacity of 458 mAh g-1after 500 cycles at 0.5 C (1 C = 1675 mA g-1). This work provides new insights into the rational design of the microstructures of carbon hosts for high-performance room temperature sodium-sulfur batteries.

Room-temperature assembled 3D macro-porous Ti3C2Tx/RGO hybrid hydrogel and the application as the self-standing electrode for sodium-ion storage.

Assembling two-dimensional (2D) MXene nanosheets into monolithic three-dimensional (3D) structures is an efficient pathway to transfer the nanoscale properties to practical applications. Nevertheless, the majority of the preparation schemes described in the literature are carried out at relatively high temperatures, which inevitably leads to the notorious high-temperature oxidation issue of MXenes. Preparing MXene-based hydrogels at lower temperatures or even room temperature is of great research importance. In this study, we report a novel and efficient room-temperature gelation method for fabricating 3D macro-porous Ti3C2Tx MXene/reduced graphene oxide (RGO) hybrid hydrogels, using anhydrous sodium sulfide (Na2S) as the primary reducing agent and l-cysteine as the auxiliary crosslinker. This room-temperature preparation technique successfully prevents the oxidation issue of MXenes and generates porous aerogels with excellent structural robustness after freeze-drying. As the self-standing anode for sodium-ion storage, the optimized 3D Ti3C2Tx MXene/RGO electrode possesses a specific capacity of 152 mAh/g at 0.1 A/g and good cycling stability with no significant capacity degradation after 500 cycles, which is significantly higher than that of the vacuum-filtered MXene film. This work demonstrates a straightforward room-temperature gelation method for constructing 3D MXene-based hydrogels to avoid the oxidation of MXenes, and casts new insight on the mechanism of the graphene oxide (GO)-assisted gelation.

Insight into highly efficient co-removal of p-nitrophenol and lead by nitrogen-functionalized magnetic ordered mesoporous carbon: Performance and modelling.

Highly efficient simultaneous removal of Pb(II) and p-nitrophenol (PNP) contamination from water was accomplished by nitrogen-functionalized magnetic ordered mesoporous carbon (N-Fe/OMC). The mutual effects and inner mechanisms of their adsorption onto N-Fe/OMC were systematically investigated by sole and binary systems, and thermodynamic, sorption isotherm and adsorption kinetics models. The liquid-film diffusion step might be the rate-limiting step for PNP and Pb(II). The fitting of experimental data with Temkin model indicates that the adsorption process of PNP and Pb(II) involve physisorption and chemisorption. There exist site competition and enhancement of PNP and Pb(II) on the sorption to N-Fe/OMC. Moreover, N-Fe/OMC could be regenerated effectively and recycled by using dilute NaOH and acetone. These demonstrated superior properties of N-Fe/OMC indicate that it could be applied to treatment of wastewaters containing both lead and PNP.