Sulfur-doped NiCo carbonate hydroxide with surface sulfate groups for highly enhanced electro-oxidation of urea

Urchin-like NiCo-based bimetallic hydroxide decorated with DOPO as highly hydrophobic flame retardant for remarkably reducing fire hazard of poly (L-lactic acid)

Designing high-performance flame retardants for poly (L-lactic acid) (PLA) materials and exploring a simple and scalable strategy have been hot topics in research. In this work, a novel and highly efficient flame retardant, that is, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) decorated urchin-like NiCo-based bimetallic hydroxide (NiCo-BH@DOPO), was synthesized and incorporated into PLA to prepare PLA and NiCo-BH@DOPO (PLA/NiCo-BH@DOPO) composite. Benefiting from the DOPO organic modification, NiCo-BH@DOPO had superb hydrophobicity and presented excellent dispersion in the PLA matrix. When 20 wt% NiCo-BH@DOPO was added, the LOI value of PLA/NiCo-BH@DOPO composites reached 33.2 %, passed the V-0 level of UL-94 grade, and its maximum peak heat release rate (PHRR) and total heat release (THR) were reduced by 13.2 % and 17.3 %, respectively, compared with PLA/NiCo-BH composites. Furthermore, the residue of PLA/NiCo-BH@DOPO at 800 °C reached 19.8 wt% and the T10% (temperature at 10 % weight loss) increased by 33 °C. More importantly, the residual PLA/NiCo-BH@DOPO char exhibits a significantly reduced presence of large cracks compared to PLA/NiCo-BH, indicating a more compact formation of residual char. NiCo-BH@DOPO endowed PLA with outstanding flame retardancy, thermal stability and carbonization properties, which were owing to the multi-coordinating effect transition metal (NiCo-BH) catalyzed the char formation to form a char layer barrier and DOPO free radicals captured to inhibit the combustion reaction chain. This investigation provided a facile strategy for the novel multi-function NiCo-based bimetallic hydroxide flame retardant, expanding NiCo-BH potential applications in PLA.

An Fe3+ induced etching and hydrolysis precipitation strategy affords an Fe-Co hydroxide nanotube array toward hybrid water electrolysis

Developing advanced electrocatalysts toward the oxygen evolution reaction (OER) has always been recognized as the key challenge for green hydrogen production via water electrolysis due to the commonly required high OER overpotential. In this work, we report a branched FeCo-based hydroxide nanotube array (Fe-CoCH NT) synthesized by an ambient Fe-modification strategy, which could be used as a monolithic electrode for efficient OER catalysis. Its OER performance was even comparable to that of RuO2 with a low overpotential of 290 mV to attain a current density of 10 mA cm-2 due to its unique branched nanotube array structure and intrinsic high catalytic activity. Moreover, an acid-base hybrid electrolysis system was built based on this catalyst and an FeCo-based phosphide nanotube array electrode. By collecting electrochemical neutralization energy, this system just needs an ultralow cell voltage of 0.97 V to attain a current density of 10 mA cm-2 with a large decrease in energy consumption of 41.9% compared to traditional alkaline water splitting systems.

MOF-derived S-doped NiCo2O4 hollow cubic nanocage for highly efficient electrocatalytic oxygen evolution

Inducing the surface reconstruction of spinels is critical for improving the electrocatalytic oxygen evolution reaction (OER) activity. Herein, S-doped NiCo2O4 hollow cubic nanocage was synthesized by anion etching Metal-Organic Frameworks (MOFs) template and air annealing strategies. The hollow structure possesses a large specific surface area and pore size, facilitating active site exposure and mass transport. S2- doping regulates the electronic structure, reducing the oxidation potential of Ni sites during the OER process, thus promoting the surface reconstruction into γ-NiOOH active species. Meanwhile, S2- doping enhances conductivity, accelerating interfacial charge transfer. As a result, S-NiCo2O4-6 exhibits superior OER activity (262 mV overpotential @ 10 mA cm-2) and stability in 1.0 M KOH solution. Furthermore, 20 % Pt/C‖S-NiCo2O4-6 only needs 1.832 V to achieve 50 mA (the electrochemical active area is 4 cm2) in a homemade anion exchange membrane (AEM) electrolyzer. This work proposes a novel approach for preparing efficient anion-doped spinel-based OER electrocatalysts.

Facile Synthesis of Mesoporous Nanohybrid Two-Dimensional Layered Ni-Cr-S and Reduced Graphene Oxide for High-Performance Hybrid Supercapacitors

This study describes the single-step synthesis of a mesoporous layered nickel-chromium-sulfide (NCS) and its hybridization with single-layered graphene oxide (GO) using a facile, inexpensive chemical method. The conductive GO plays a critical role in improving the physicochemical and electrochemical properties of hybridized NCS/reduced GO (NCSG) materials. The optimized mesoporous nanohybrid NCSG is obtained when hybridized with 20% GO, and this material exhibits a very high specific surface area of 685.84 m2/g compared to 149.37 m2/g for bare NCS, and the pore diameters are 15.81 and 13.85 nm, respectively. The three-fold superior specific capacity of this optimal NCSG (1932 C/g) is demonstrated over NCS (676 C/g) at a current density of 2 A/g. A fabricated hybrid supercapacitor (HSC) reveals a maximum specific capacity of 224 C/g at a 5 A/g current density. The HSC reached an outstanding energy density of 105 Wh/kg with a maximum power density of 11,250 W/kg. A 4% decrement was observed during the cyclic stability study of the HSC over 5000 successive charge-discharge cycles at a 10 A/g current density. These results suggest that the prepared nanohybrid NCSG is an excellent cathode material for gaining a high energy density in an HSC.