Self-Assembling Hollow Carbon Nanobeads into Double-Shell Microspheres as a Hierarchical Sulfur Host for Sustainable Room-Temperature Sodium–Sulfur Batteries

We report the use of passion fruit-like double-carbon-shell porous carbon microspheres (PCMs) as the sulfur substrate in room-temperature sodium-sulfur batteries. The PCMs are covered by microsized carbon shells on the outside and consisted of carbon nanobeads with hollow structure inside, leading to a unique multidimensional scaling double-carbon-shell structure with high electronic conductivity and strengthened mechanical properties. Sulfur is filled inside the PCMs (PCMs-S) and protected by the unique double-carbon-shell, which means the subsequently generated intermediate sodium polysulfide species cannot be exposed to the electrolyte directly and well protected inside. In addition, the inner interconnected porous structure provides room for the volume expansion of sulfur during discharge processes. It is found that the PCMs-S with a 63.6% initial Coulombic efficiency contributed to the 290 mA h g -1 at the current density of 100 mA g -1 after 350 cycles. More importantly, PCMs-S exhibited good rate performance with a capacity of 113 and 56 mA h g -1 at the current densities of 1000 and 2000 mA g -1 , respectively.

Activating Titania for Efficient Electrocatalysis by Vacancy Engineering

Pursuing efficient and low-cost electrocatalysts is crucial for the performance of water–alkali electrolyzers toward water splitting. Earth-abundant transition-metal oxides, in spite of their alluring performances in the oxygen evolution reaction, are thought to be inactive in the hydrogen evolution reaction in alkaline media. Here, we demonstrate that pure TiO2 single crystals, a typical transition-metal oxide, can be activated toward electrocatalytic hydrogen evolution reaction in alkaline media through engineering interfacial oxygen vacancies. Experimental and theoretical results indicate that subsurface oxygen vacancies and low-coordinated Ti ions (Ti3+) can enhance the electrical conductivity and promote electron transfer and hydrogen desorption, which activate reduced TiO2 single crystals in the hydrogen evolution reaction in alkaline media. This study offers a rational route for developing reduced transition-metal oxides for low-cost and highly active hydrogen evolution reaction catalysts, to reali...

Active-Site-Enriched Iron-Doped Nickel/Cobalt Hydroxide Nanosheets for Enhanced Oxygen Evolution Reaction

Highly active, durable, and inexpensive nanostructured catalysts are crucial for achieving efficient and economical electrochemical water splitting. However, developing efficient approaches to further improve the catalytic ability of the well-defined nanostructured catalysts is still a big challenge. Herein, we report a facile and universal cation-exchange process for synthesizing Fe-doped Ni(OH)2 and Co(OH)2 nanosheets with enriched active sites toward enhanced oxygen evolution reaction (OER). In comparison with typical NiFe layered double hydroxide (LDH) nanosteets prepared by the conventional one-pot method, Fe-doped Ni(OH)2 nanosheets evolving from Ni(OH)2 via an Fe3+/Ni2+ cation-exchange process possess nanoporous surfaces with abundant defects. Accordingly, Fe-doped Ni(OH)2 nanosheets exhibit higher electrochemical active surface area (ECSA) and improved surface wettability in comparison to NiFe LDH nanosheets and deliver significantly enhanced catalytic activity over NiFe LDH. Specifically, a low o...

Ultrathin and Edge-Enriched Holey Nitride Nanosheets as Bifunctional Electrocatalysts for the Oxygen and Hydrogen Evolution Reactions

Exploring economically efficient electrocatalysts with good electrocatalytic activity is essential for diverse electrochemical energy devices. Series of ultrathin metallic nickel-based holey nitride nanosheets were designed as bifunctional catalysts for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). They exhibit improved catalytic properties owing to the inherent advantages of their plentiful active reaction sites resulting from the complete exposure of the atoms in the large lateral surfaces and from the edges of pore areas, together with expanded lattice spacing distance. This obtained three-dimensional conductive integral architecture can not only accelerate the electron transportation by the highly orientated crystalline structure but also facilitate the diffusion of intermediate and gases. In terms of the OER electrocatalytic properties, a quite low overpotential (300 mV) is required for the holey two-dimensional (2D) Ni3Fe nitride nanosheets to deliver a current density o...

Iridium–Tungsten Alloy Nanodendrites as pH-Universal Water-Splitting Electrocatalysts

The development of highly efficient and durable electrocatalysts for high-performance overall water-splitting devices is crucial for clean energy conversion. However, the existing electrocatalysts still suffer from low catalytic efficiency, and need a large overpotential to drive the overall water-splitting reactions. Herein, we report an iridium-tungsten alloy with nanodendritic structure (IrW ND) as a new class of high-performance and pH-universal bifunctional electrocatalysts for hydrogen and oxygen evolution catalysis. The IrW ND catalyst presents a hydrogen generation rate ∼2 times higher than that of the commercial Pt/C catalyst in both acid and alkaline media, which is among the most active hydrogen evolution reaction (HER) catalysts yet reported. The density functional theory (DFT) calculations reveal that the high HER intrinsic catalytic activity results from the suitable hydrogen and hydroxyl binding energies, which can accelerate the rate-determining step of the HER in acid and alkaline media. Moreover, the IrW NDs show superb oxygen evolution reaction (OER) activity and much improved stability over Ir. The theoretical calculation demonstrates that alloying Ir metal with W can stabilize the formed active iridium oxide during the OER process and lower the binding energy of reaction intermediates, thus improving the Ir corrosion resistance and OER kinetics. Furthermore, the overall water-splitting devices driven by IrW NDs can work in a wide pH range and achieve a current density of 10 mA cm -2 in acid electrolyte at a low potential of 1.48 V.

Degradation of Highly Alloyed Metal Halide Perovskite Precursor Inks: Mechanism and Storage Solutions

Curtailing Perovskite Processing Limitations via Lamination at the Perovskite/Perovskite Interface

Roll-to-Roll Printing of Perovskite Solar Cells

Efficient Fabrication of Pure, Single-Chain Janus Particles through Their Exclusive Self-Assembly in Mixtures with Their Analogues

We report the first example of the fabrication of pure, single-chain Janus particles (SCJPs). The SCJPs were prepared by double-cross-linking an A- b -B diblock copolymer in a common solvent. Inevitably, the double-cross-linking led to a mixture containing not only SCJPs but also multichain particles and irregular single-chain particles. Under well-controlled conditions, the SCJPs in the mixture self-assemble with high exclusivity to form regularly structured macroscopic assemblies (MAs) with a crystal-like appearance that precipitate from the suspension. Pure SCJPs that are uniform in size, shape and Janus structure were efficiently prepared by collection and dissociation of the MAs. Block copolymers with different structural parameters were successfully used for the exclusive self-assembly (ESA), and pure SCJPs with varied structural parameters were produced, confirming the reliability of the ESA method.

Manipulating the Architecture of Atomically Thin Transition Metal (Hydr)oxides for Enhanced Oxygen Evolution Catalysis

Graphene-like nanomaterials have received tremendous research interest due to their atomic thickness and fascinating properties. Previous studies mainly focus on the modulation of their electronic structures, which undoubtedly optimizes the electronic properties, but is not the only determinant of performance in practical applications. Herein, we propose a generalized strategy to incrementally manipulate the architectures of several atomically thin transition metal (hydr)oxides, and study their effects on catalytic water oxidation. The results demonstrate the obvious superiority of a wrinkled nanosheet architecture in both catalytic activity and durability. For instance, wrinkled Ni(OH) 2 nanosheets display a low overpotential of 358.2 mV at 10 mA cm -2 , a high current density of 187.2 mA cm -2 at 500 mV, a small Tafel slope of 54.4 mV dec -1 , and excellent long-term durability with gradually optimized performance, significantly outperforming other nanosheet architectures and previously reported catalysts. The outstanding catalytic performance is mainly attributable to the 3D porous network structure constructed by wrinkled nanosheets, which not only provides sufficient contact between electrode materials and current collector, but also offers highly accessible channels for facile electrolyte diffusion and efficient O 2 escape. Our study provides a perspective on improving the performance of graphene-like nanomaterials in a wide range of practical applications.