SiSe2 for Superior Sulfide Solid Electrolytes and Li-Ion Batteries.

Among the various existing layered compounds, silicon diselenide (SiSe2) possesses diverse chemical and physical properties, owing to its large interlayer spacing and interesting atomic arrangements. Despite the unique properties of layered SiSe2, it has not yet been used in energy applications. Herein, we introduce the synthesis of layered SiSe2 through a facile solid-state synthetic route and demonstrate its versatility as a sulfide solid electrolyte (SE) additive for all-solid-state batteries (ASSBs) and as an anode material for Li-ion batteries (LIBs). Li-argyrodites with various compositions substituted with SiSe2 are synthesized and evaluated as sulfide SEs for ASSBs. SiSe2-substituted Li-argyrodites exhibit high ionic conductivities, low activation energies, and high air stabilities. In addition, when using a sulfide SE, the ASSB full cell exhibits a high discharge/charge capacity of 202/169 mAh g-1 with a high initial Coulombic efficiency (ICE) of 83.7% and stable capacity retention at 1C after 100 cycles. Furthermore, the Li-storage properties of SiSe2 as an anode material for LIBs are evaluated, and its Li-pathway mechanism is explored by using various cutting-edge ex situ analytical tools. Moreover, the SiSe2 nanocomposite anode exhibits a high Li- insertion/extraction capacity of 950/775 mAh g-1, a high ICE of 81.6%, a fast rate capability, and stable capacity retention after 300 cycles. Accordingly, layered SiSe2 and its versatile applications as a sulfide SE additive for ASSBs and an anode material for LIBs are promising candidates in energy storage applications as well as myriad other applications.

Carbon-incorporated Ni2P-Fe2P hollow nanorods as superior electrocatalysts for the oxygen evolution reaction.

A rational design and cost-effective transition metal-based hollow nanostructures are important for sustainable energy materials with high efficiency. This study reports on carbon-incorporated Ni2P-Fe2P hollow nanorods ((Ni,Fe)2P/C HNRs) derived from a self-template approach as efficient electrocatalysts. Initially, a Ni2(BDC)2(DABCO)-MOF (Ni-MOF) is converted to NiFe-PBA hollow nanorods (HNRs) through facile ion exchange which was further converted to (Ni,Fe)2P/C HNRs via a subsequent phosphidation process. The resulting (Ni,Fe)2P/C HNRs exhibit remarkable activity for the oxygen evolution reaction in an alkaline solution requiring a small overpotential of 258 mV to drive a current density of 10 mA cm-2 and long-term stability with little deactivation after 40 h. (Ni,Fe)2P/C HNRs outperform (Ni,Fe)2P/C NPs and commercial RuO2. The unique hollow morphology and interfacial electronic structure substantially increase the active site and charge transfer rate of our electrocatalyst, resulting in excellent OER activity and stability.

CoP2/Fe-CoP2 yolk-shell nanoboxes as efficient electrocatalysts for the oxygen evolution reaction.

The development of an efficient electrocatalyst is an important requirement for water splitting systems to produce clean and sustainable hydrogen fuel. Herein, we synthesized CoP2/Fe-CoP2 yolk-shell nanoboxes (YSBs) as efficient electrocatalysts for the oxygen evolution reaction (OER). Initially, zeolitic imidazolate framework-67/CoFe-Prussian blue analogue (ZIF-67/CoFe-PBA) YSBs were prepared by the reaction of ZIF-67 and [Fe(CN)6]3- ions in the presence of a small amount of water as an etching agent. The size of the CoP2 yolk depends on the amount of water. The heteronanostructure composed of the CoP2 yolk and the FexCo1-xP2 shell with a cubic shape was obtained by phosphidation of ZIF-67/CoFe-PBA YSBs. Benefiting from the unique structure and chemical composition, the CoP2/Fe-CoP2 YSB electrocatalyst has a large specific surface area of 114 m2 g-1 and shows superior electrocatalytic performances for the OER such as a low overpotential of 266 mV, a small Tafel slope value of 68.1 mV dec-1, and excellent cyclic stability.

Voltammetric nonenzymatic sensing of glucose by using a porous nanohybrid composed of CuS@SiO2 spheres and polypyrrole.

Porous spheres of CuS@SiO2 were obtained by deposition of CuS on silica spheres through a one-step chemical method. Subsequently, polypyrrole (PPy) was deposited on the CuS@SiO2 spheres. The formation of the porous spheres was elucidated by control experiments and physical characterizations. The nanohybrid was placed on a glassy carbon electrode (GCE) surface where it displays good electrocatalytic activity in terms of glucose electrooxidation with an optimum at a working potential of 0.55 V (vs. Ag/AgCl) in 0.1 M NaOH solution. The PPy-CuS@SiO2 achieves an extremely high sensitivity (505.3 µA mM-1 cm-2), wide linear range (10 µM-4.2 mM), low detection limit (1.0 µM), short response time (˂ 0.5 s), high selectivity, long-term durability, and reproducibility. The fabricated electrode based on PPy-CuS@SiO2 was further used for the determination of glucose in blood sample with good recoveries. Graphical abstract Schematic representation of the method for fabrication of polypyrrole-coated porous CuS@SiO2 sphere.

Hierarchical Nanoboxes Composed of Co9 S8 -MoS2 Nanosheets as Efficient Electrocatalysts for the Hydrogen Evolution Reaction.

The development of hydrogen evolution catalysts based on nonprecious metals is essential for the practical application of water-splitting devices. Herein, the synthesis of Co9 S8 -MoS2 hierarchical nanoboxes (HNBs) as efficient catalysts for the hydrogen evolution reaction (HER) is reported. The surface of the hollow cubic structure was organized by CoMoS4 nanosheets formed through the reaction of MoS42- and Co2+ released from the cobalt zeolite imidazole framework (ZIF-67) templates under reflux in a mixture of water/ethanol. The formation process for the CoMoS4 HNB structures was characterized by TEM images recorded at various reaction temperatures. The amorphous CoMoS4 HNBs were converted through sequential heat treatments into CoSx -MoS2 and Co9 S8 -MoS2 HNBs. Owing to their unique chemical compositions and structural features, Co9 S8 -MoS2 HNBs have a high specific surface area (124.6 m2 g-1 ) and superior electrocatalytic performances for the HER. The Co9 S8 -MoS2 HNBs exhibit a low overpotential (η10 ) of 106 mV, a low Tafel slope of 51.8 mV dec-1 , and long-term stability in an acidic medium. The electrocatalytic activity of Co9 S8 -MoS2 HNBs is superior to that of recently reported values, and these HNBs prove to be promising candidates for the HER.