Sulfolane-Based Flame-Retardant Electrolyte for High-Voltage Sodium-Ion Batteries.

Sodium-ion batteries hold great promise as next-generation energy storage systems. However, the high instability of the electrode/electrolyte interphase during cycling has seriously hindered the development of SIBs. In particular, an unstable cathode-electrolyte interphase (CEI) leads to successive electrolyte side reactions, transition metal leaching and rapid capacity decay, which tends to be exacerbated under high-voltage conditions. Therefore, constructing dense and stable CEIs are crucial for high-performance SIBs. This work reports localized high-concentration electrolyte by incorporating a highly oxidation-resistant sulfolane solvent with non-solvent diluent 1H, 1H, 5H-octafluoropentyl-1, 1, 2, 2-tetrafluoroethyl ether, which exhibited excellent oxidative stability and was able to form thin, dense and homogeneous CEI. The excellent CEI enabled the O3-type layered oxide cathode NaNi1/3Mn1/3Fe1/3O2 (NaNMF) to achieve stable cycling, with a capacity retention of 79.48% after 300 cycles at 1 C and 81.15% after 400 cycles at 2 C with a high charging voltage of 4.2 V. In addition, its nonflammable nature enhances the safety of SIBs. This work provides a viable pathway for the application of sulfolane-based electrolytes on SIBs and the design of next-generation high-voltage electrolytes.

Structural Regulation Enables High Interfacial Functionality for Ni-Rich Single-Crystalline Cathodes.

Ni-rich single-crystalline layered cathodes have garnered significant attention due to their high energy density and thermal stability. However, they experience severe capacity degradation caused by lattice strain and interfacial side reactions during practical applications. In this study, an effective yttrium modification method is employed to stabilize the structure of Ni-rich single-crystalline LiNi0.83Mn0.05Co0.12O2 (SC-NMC83) to solve these issues. This innovative approach successfully immobilizes oxygen within the material, preventing crack formation while simultaneously broadening the diffusion path of Li+. The yttrium-modified sample (SC-NMC83-Y) exhibits a superior capacity retention compared to the SC-NMC83 sample, with values of 90% and 76.1% after 100 cycles, respectively. This work demonstrates the promising potential of a doping strategy for Ni-rich single-crystalline cathodes and paves a pathway for its practical implementation, such as all-solid-state batteries.

Harnessing the Synergistic Interplay between Atomic-scale Vacancies and Ligand Effect to Optimize the Oxygen Reduction Activity and Tolerance Performance.

Defect engineering is an effective strategy for regulating the electrocatalysis of nanomaterials, yet it is seldom considered for modulating Pt-based electrocatalysts for the oxygen reduction reaction (ORR). In this study, we designed Ni-doped vacancy-rich Pt nanoparticles anchored on nitrogen-doped graphene (Vac-NiPt NPs/NG) with a low Pt loading of 3.5 wt.% and a Ni/Pt ratio of 0.038:1. Physical characterizations confirmed the presence of abundant atomic-scale vacancies in the Pt NPs induces long-range lattice distortions, and the Ni dopant generates a ligand effect resulting in electronic transfer from Ni to Pt. Experimental results and theoretical calculations indicated that atomic-scale vacancies mainly contributed the tolerance performances towards CO and CH3OH, the ligand effect derived from a tiny of Ni dopant accelerated the transformation from *O to *OH species, thereby improved the ORR activity without compromising the tolerance capabilities. Benefiting from the synergistic interplay between atomic-scale vacancies and ligand effect, as-prepared Vac-NiPt NPs/NG exhibited improved ORR activity, sufficient tolerance capabilities, and excellent durability. This study offers a new avenue for modulating the electrocatalytic activity of metal-based nanomaterials.

N-Doped Graphene Supported Cu Single Atoms: Highly Efficient Recyclable Catalyst for Enhanced C-N Coupling Reactions.

Heterogenization of homogeneous catalysis through supported single-atom catalysts (SACs) provided a feasible solution to recycling catalysts while keeping its efficiency in chemical synthesis. In this work, Cu SACs anchored on N-doped graphene (Cu SACs/NG) were prepared and first used for C-N coupling reactions. During the preparation, Cu-N-C structures, including Cu-N4 moieties, were formed in a one-step pyrolysis method. As-prepared Cu SACs/NG exhibited excellent catalytic activity toward C-N coupling reactions with a broad scope of substrates and showed outstanding performance of recycling. Compared with Cu nanoparticles (Cu NPs/NG), the advantages of single-atom catalysts were validated via experimental and theoretical calculations. The enhanced performances were attributed to increasing the number of active sites and increasing the intrinsic activity of each active site. This work provides an alternative synthetic strategy for fabricating atomically dispersed SACs and represents a significant advance for coupling reactions.

Constructing robust polymer/two-dimensional Ti3C2TX solid-state electrolyte interphase via in-situ polymerization for high-capacity long-life and dendrite-free lithium metal anodes.

We constructed an artificial polymer/two-dimensional Ti3C2TX (MXene) solid electrolyte interphase (SEI) on a Li metal surface via an in-situ polymerization strategy. The polymer layer provides excellent interface contact and outstanding adaptability for the volume expansion of Li metal, decreasing interface impedance. On the other hand, the two-dimensional MXene with a low Li nucleation energy barrier is beneficial for uniform Li deposition and restraint of interfacial side reactions. In this work, a dense and durable MXene-integrated SEI between the Li metal anode and solid-state electrolyte (SSE) interface is constructed to render the Li/SSE/Li cell to maintain a stable polarization voltage of approximately 50 mV at a capacity of 0.50 mAh cm-2 for over 1000 h. It enables the Li/SSE/LiFePO4 cell to deliver a capacity of 130.1 mAh g-1 at 1C with a capacity retention of 91.4% after 900 cycles. Therefore, we believe that this facile in-situ polymerization method for constructing a layer of polymer/MXene SEI at the interface between Li metal anodes and SSE can promote the practical applications of Li metal batteries.

Correction: Cu2O template synthesis of high-performance PtCu alloy yolk-shell cube catalysts for direct methanol fuel cells.

Correction for 'Cu2O template synthesis of high-performance PtCu alloy yolk-shell cube catalysts for direct methanol fuel cells' by Sheng-Hua Ye et al., Chem. Commun., 2014, 50, 12337-12340, DOI: 10.1039/C4CC04108A.

Construction of tetrahedral CoO4 vacancies for activating the high oxygen evolution activity of Co3-xO4-δ porous nanosheet arrays.

This study presents low-crystalline and non-stoichiometric cobalt oxide (Co3-xO4-δ) porous nanosheet arrays (PNAs) grown on carbon fiber cloth (CFC) (Co3-xO4-δ PNAs/CFC) by a facile in situ anodic oxidation strategy. We firstly verified that the above prepared low crystalline cobalt oxide contained tetrahedral CoO4 vacancies, resulting in the creation of O vacancies at adjacent octahedral CoO6 sites, allowing the generation of tetragonal-pyramidal CoO5 sites which were regarded as active sites and being accessible for the oxygen evolution reaction (OER) with different reaction mechanisms compared to that of traditional CoO6 sites in high-crystalline and stoichiometric Co3O4, thus endowing Co3-xO4-δ PNAs/CFC with significantly improved OER activity and superior stability compared to their crystalline counterparts (Co3O4 PNAs/CFC), as illustrated by experiments and density functional theory (DFT) calculations. This study will open up a new approach for the synthesis of defect-rich materials and provide new insight into the structure-property relationship of OER catalysts.

Activating CoOOH Porous Nanosheet Arrays by Partial Iron Substitution for Efficient Oxygen Evolution Reaction.

Iron-substituted CoOOH porous nanosheet arrays grown on carbon fiber cloth (denoted as Fex Co1-x OOH PNSAs/CFC, 0≤x≤0.33) with 3D hierarchical structures are synthesized by in situ anodic oxidation of α-Co(OH)2 NSAs/CFC in solution of 0.01 m (NH4 )2 Fe(SO4 )2 . X-ray absorption fine spectra (XAFS) demonstrate that CoO6 octahedral structure in CoOOH can be partially substituted by FeO6 octahedrons during the transformation from α-Co(OH)2 to Fex Co1-x OOH, and this is confirmed for the first time in this study. The content of Fe in Fex Co1-x OOH, no more than 1/3 of Co, can be controlled by adjusting the in situ anodic oxidation time. Fe0.33 Co0.67 OOH PNSAs/CFC shows superior OER electrocatalytic performance, with a low overpotential of 266 mV at 10 mA cm-2 , small Tafel slope of 30 mV dec-1 , and high durability.

Silica-Polypyrrole Hybrids as High-Performance Metal-Free Electrocatalysts for the Hydrogen Evolution Reaction in Neutral Media.

Constructing inorganic-organic hybrids with superior properties in terms of water adsorption and activation will lead to catalysts with significantly enhanced electrocatalytic activity in the hydrogen evolution reaction (HER) in environmentally benign neutral media. Herein, we report SiO2 -polypyrrole (PPy) hybrid nanotubes supported on carbon fibers (CFs) (SiO2 /PPy NTs-CFs) as inexpensive and high-performance electrocatalysts for the HER in neutral media. Because of the strong electronic interactions between SiO2 and PPy, the SiO2 uniquely serves as the centers for water adsorption and activation, and accordingly promotes the HER. The metal-free SiO2 /PPy NTs-CFs displayed high catalytic activity in the HER in neutral media, such as a low onset potential and small Tafel slope, as well as excellent long-term durability.

Design and Synthesis of FeOOH/CeO2 Heterolayered Nanotube Electrocatalysts for the Oxygen Evolution Reaction.

FeOOH/CeO2 heterolayered nanotubes supported on Ni foam as efficient oxygen evolution electrocatalysts are reported. The hybrid structure can obviously promote the catalytic performance for the oxygen evolution reaction, such as low onset potential, high electroactivity, and excellent long-term durability. This study provides a new route to the design and fabrication of electrocatalysts with high electroactivity and durability for oxygen evolution.

FeOOH/Co/FeOOH Hybrid Nanotube Arrays as High-Performance Electrocatalysts for the Oxygen Evolution Reaction.

Herein, we developed FeOOH/Co/FeOOH hybrid nanotube arrays (HNTAs) supported on Ni foams for oxygen evolution reaction (OER). The inner Co metal cores serve as highly conductive layers to provide reliable electronic transmission, and can overcome the poor electrical conductivity of FeOOH efficiently. DFT calculations demonstrate the strong electronic interactions between Co and FeOOH in the FeOOH/Co/FeOOH HNTAs, and the hybrid structure can lower the energy barriers of intermediates and thus promote the catalytic reactions. The FeOOH/Co/FeOOH HNTAs exhibit high electrocatalytic performance for OER, such as low onset potential, small Tafel slope, and excellent long-term durability, and they are promising electrocatalysts for OER in alkaline solution.

Retraction Notice: Research on Algorithm of Extracting PPG Signal for Detecting Atrial Fibrillation based on Probability Density Function.

[This retracts the article on p. 179 in vol. 9 PMC6407308.].

Co(OH)2 @PANI Hybrid Nanosheets with 3D Networks as High-Performance Electrocatalysts for Hydrogen Evolution Reaction.

Hybrid electrocatalysts with excellent electrocatalytic activity for hydrogen reduction are fabricated using an efficient and facile electrochemical route. The electronic and synergistic effects between Co(OH)2 and polyaniline (PANI) in the composite structure are the key factors that generate the high electrocatalytic activity and excellent stability. A highly efficient, non-precious metal-based flexible electrocatalyst for high-performance electrocatalysts is shown, which reveals a novel route for the design and synthesis of electrocatalysts.

Asymmetric Paper Supercapacitor Based on Amorphous Porous Mn3O4 Negative Electrode and Ni(OH)2 Positive Electrode: A Novel and High-Performance Flexible Electrochemical Energy Storage Device.

Here we synthesize novel asymmetric all-solid-state paper supercapacitors (APSCs) based on amorphous porous Mn3O4 grown on conducting paper (NGP) (Mn3O4/NGP) negative electrode and Ni(OH)2 grown on NGP (Ni(OH)2/NGP) as positive electrode, and they have attracted intensive research interest owing to their outstanding properties such as being flexible, ultrathin, and lightweight. The fabricated APSCs exhibit a high areal Csp of 3.05 F/cm3 and superior cycling stability. The novel asymmetric APSCs also exhibit high energy density of 0.35 mW h/cm3, high power density of 32.5 mW/cm3, and superior cycling performance (<17% capacitance loss after 12,000 cycles at a high scan rate of 100 mV/s). This work shows the first example of amorphous porous metal oxide/NGP electrodes for the asymmetric APSCs, and these systems hold great potential for future flexible electronic devices.

Research on Algorithm of Extracting PPG Signal for Detecting Atrial Fibrillation based on Probability Density Function.

The paper introduced a new method based on probability density function (PDF) and phase space diagram method for photoplethysmography (PPG) signal extracting. In the paper, PPG information was generated from human fingertips by smartphones. The pulse wave period was then separated and reconstructed into probability density function (PDF) by the phase space diagram algorithm. The difference between normal sinus rhythm (NSR) and atrial fibrillation (AF) was finally found by skewness of the PDF. The results of the present study demonstrates that the new method is vividly viable for detecting AF on the smartphone.