Formation of NiCo2V2O8 yolk – double shell spheres with enhanced lithium storage properties

Complex nanostructures with multi‐components and intricate architectures hold great potential in developing high‐performance electrode materials for lithium‐ion batteries (LIBs). Herein, we demonstrate a facile self‐templating strategy for the synthesis of metal vanadate nanomaterials with complex chemical composition of NiCo2V2O8 and a unique yolk–double shell structure. Starting with the Ni‐Co glycerate spheres, NiCo2V2O8 yolk–double shell spheres are synthesized through an anion‐exchange reaction of Ni‐Co glycerate templates with VO3− ions, followed by an annealing treatment. By virtue of compositional and structural advantages, these NiCo2V2O8 yolk–double shell spheres manifest outstanding lithium storage properties when evaluated as anodes for LIBs. Impressively, an extra‐high reversible capacity of 1228 mAh g−1 can be retained after 500 cycles at a high current density of 1.0 Ag−1.NRF (Natl Research Foundation, S’pore)Accepted versio

Coordination Polyhedra: A Probable Basic Growth Unit in Solution for the Crystal Growth of Inorganic Nonmetallic Nanomaterials?

Learning from the classical crystallization mode and the conventional oriented attachment mode, we demonstrate another understanding of the crystal growth of inorganic nonmetallic nanomaterials in solution from the perspective of coordination polyhedra. A family of beta-Ni(OH)(2) hourglass-like nanostructures is controllably synthesized and chosen to illustrate this understanding, in which the coordination polyhedra of Ni(OH)(6)(4-) are supposed to serve as the basic growth unit to grow these crystals in solution. According to this "coordination polyhedra growth unit" mode, a probable crystal growth mechanism featuring two-stage oriented attachment is put forth. In addition, with this deliberate mode, a series of anisotropic features as well as interesting structural patterns of the as-prepared beta-Ni(OH)(2) nanocrystals have also been successfully explained. The nanocrystal growth mechanism proposed in this paper may be general; for example, it might reflect the actual circumstances of crystallization of certain inorganic nonmetallic nanocrystals in solution

Ordered colloidal clusters constructed by nanocrystals with valence for efficient CO2 photoreduction

The ability to construct discrete colloidal clusters (CCs) as complex as molecular clusters is limited due to the lack of available colloidal building blocks and specific directional bonds. Here, we explore a strategy to organize anisotropic Prussian blue analog nanocrystals (NCs) toward CCs with open and highly ordered structures, experimentally realizing colloidal analogs to zeolitic clathrate structures. The directional interactions are derived from either crystallographic or morphological anisotropy of the NCs and achieved by the interplay of epitaxial growth, oriented attachment, and local packing. We attribute these interparticle interactions to enthalpic and entropic valences that imitate hybridized atomic orbitals of sp3d2 octahedron and sp3d3f cube. Benefiting from the ordered multilevel porous structures, the obtained CCs exhibit greatly enhanced catalytic activity for CO2 photoreduction. Our work offers some fundamental insights into directional bonding among NCs and opens an avenue that promises access to unique CCs with unprecedented structures and applications.Ministry of Education (MOE)National Research Foundation (NRF)Published versionX.W.L. acknowledges the funding support from the National Research Foundation (NRF) of Singapore via the NRF investigatorship (NRF-NRFI2016-04) and the Ministry of Education of Singapore through Academic Research Fund (AcRF) Tier-1 Funding (M4011783, RG5/17) and Tier-2 Funding (M4020386, MOE2017-T2-003)

Construction of single-crystalline Prussian blue analog hollow nanostructures with tailorable topologies

Engineering complex nanostructures, particularly topologically intricate architectures, represents an appealing challenge for chemists and material scientists because such structures often manifest unique properties. Here, we demonstrate the versatility of a self-templated epitaxial growth strategy for construction of single-crystalline hollow nanostructured Prussian blue analogs (PBAs). Specifically, this strategy enables a controllable synthesis of Co-Fe PBA cages, frames, and boxes with diverse geometries by tuning their growth kinetics and thus expands the richness of their topological complexity. As an attempt, the topologies of these structures are identified and discussed. After thermal treatment, the corresponding oxide derivatives with preserved structures exhibit enhanced electrocatalytic activity for the oxygen evolution reaction in alkaline medium, where the frame structures demonstrate the best catalytic performance. Our work may further advance the topology in chemistry and materials science for realizing not only the geometries of the nanostructures but also their topology-dependent catalytic properties

Oriented assembly of anisotropic nanoparticles into frame-like superstructures

It is fascinating but challenging for nanoscientists to organize nanoparticles (NPs) into ordered architectures just as it is for chemists to manipulate atoms and molecules to form functional molecules and supramolecules. We explore a strategy to assemble anisotropic NPs into open frame-like superstructures via oriented attachment (OA), experimentally realizing a nanoscale analog to the bonding behavior in M8L12-type supramolecular cubes. We highlight the role of NP shape in the OA-involved assembly for constructing predictable superstructures. In addition, the frame-like superstructures can retain their basic structure when undergoing postcrystallization of the building blocks as well as annealing for conversion toward functional electrocatalytic materials. Our work enables fundamental insights into directional “bonding” among NPs and adds to the growing body of knowledge for bottom-up assembly of anisotropic NPs into sophisticated functional materials.NRF (Natl Research Foundation, S’pore)Published versio

Formation of Ni-Fe mixed diselenide nanocages as a superior oxygen evolution electrocatalyst

Exploring effective electrocatalysts is a crucial requirement for boosting the efficiency of water splitting to obtain clean fuels. Here, a self-templating strategy is reported to synthesize Ni-Fe mixed diselenide cubic nanocages for the electrocatalytic oxygen evolution reaction (OER). The diselenide nanocages are derived from corresponding Prussian-blue analog nanocages, which are first obtained by treating the nanocube precursor with a site-selective ammonia etchant. The resulting Ni-Fe mixed diselenide nanocages perform as a superior OER electrocatalyst, which affords a current density of 10 mA cm-2 at a small overpotential of 240 mV; a high current density, mass activity, and turnover frequency of 100 mA cm-2 , 1000 A g-1 , and 0.58 s-1 , respectively, at the overpotential of 270 mV; a Tafel slope as small as 24 mV dec-1 ; and excellent stability in alkaline medium.NRF (Natl Research Foundation, S’pore)Accepted versio

Surface engineering toward stable lithium metal anodes

The lithium (Li) metal anode (LMA) is susceptible to failure due to the growth of Li dendrites caused by an unsatisfied solid electrolyte interface (SEI). With this regard, the design of artificial SEIs with improved physicochemical and mechanical properties has been demonstrated to be important to stabilize the LMAs. This review comprehensively summarizes current efficient strategies and key progresses in surface engineering for constructing protective layers to serve as the artificial SEIs, including pretreating the LMAs with the reagents situated in different primary states of matter (solid, liquid, and gas) or using some peculiar pathways (plasma, for example). The fundamental characterization tools for studying the protective layers on the LMAs are also briefly introduced. Last, strategic guidance for the deliberate design of surface engineering is provided, and the current challenges, opportunities, and possible future directions of these strategies for the development of LMAs in practical applications are discussed.Published versionThis work is supported by the funding of the National Key R&D Program of China (2022YFB2502000), the “Leading Innovative and Entrepreneur Team Introduction Program of Zhejiang” (2020R01002), and the National Natural Science Foundation of China (grant nos. 52225208, 51972285, and U21A20174)

Coordination Polyhedra: A Probable Basic Growth Unit in Solution for the Crystal Growth of Inorganic Nonmetallic Nanomaterials?

Learning from the classical crystallization mode and the conventional oriented attachment mode, we demonstrate another understanding of the crystal growth of inorganic nonmetallic nanomaterials in solution from the perspective of coordination polyhedra. A family of β-Ni­(OH)₂ hourglass-like nanostructures is controllably synthesized and chosen to illustrate this understanding, in which the coordination polyhedra of Ni­(OH)₆^4– are supposed to serve as the basic growth unit to grow these crystals in solution. According to this “coordination polyhedra growth unit” mode, a probable crystal growth mechanism featuring two-stage oriented attachment is put forth. In addition, with this deliberate mode, a series of anisotropic features as well as interesting structural patterns of the as-prepared β-Ni­(OH)₂ nanocrystals have also been successfully explained. The nanocrystal growth mechanism proposed in this paper may be general; for example, it might reflect the actual circumstances of crystallization of certain inorganic nonmetallic nanocrystals in solution

Pearson’s Principle Inspired Generalized Strategy for the Fabrication of Metal Hydroxide and Oxide Nanocages

Designing a general route for rational synthesis of a series or families of nanomaterials for emerging applications has become more and more fascinating and vital in the view of nanoscience and nanotechnology. Herein, we explore a general strategy for fabricating uniform nanocages of metal hydroxides (MHs) and metal oxides (MOs). A template-assisted route inspired by Pearson’s hard and soft acid–base (HSAB) principle was employed for synthesizing MH nanocages via meticulous selection of the coordinating etchant as well as optimization of the reaction conditions. The concept of “coordinating etching” is successfully achieved in this work. This unique route shows potential in designing well-defined and high-quality MH nanocages with varying components, shell thicknesses, shapes, and sizes at room temperature. Consequently, porous MO nanocages can be obtained readily just through appropriate thermal treament of the respective MH nanocages. The overall strategy present in this work extends the application of the HSAB principle in nanoscience and offers a unqiue clue for rational fabrication of hollow (porous) and/or amorphous structures on the nanoscale, where these nanocages may present promising potential for various applications

Construction of hierarchical Co–Fe oxyphosphide microtubes for electrocatalytic overall water splitting

Development of efficient electrocatalysts is a crucial requirement to build water splitting systems for the production of clean and sustainable fuels. This goal could be achieved by fine‐tuning the composition and structure of the electrocatalytic materials. Here, a facile self‐templated synthetic strategy is developed for the fabrication of hierarchical Co–Fe oxyphosphide microtubes (MTs). Fe‐based metal–organic compound microrods are first synthesized as the self‐sacrificing template. Afterward, the Fe‐based precursors are converted into hierarchical Co–Fe layered double hydroxide MTs through a hydrothermal approach, which are then transformed into the hierarchical Co–Fe oxyphosphide MTs by a phosphidation treatment. Benefiting from the synergistic effect of the compositions and the advantages of the hierarchical hollow structure, the obtained electrocatalyst exhibits enhanced performance for overall water splitting.NRF (Natl Research Foundation, S’pore)MOE (Min. of Education, S’pore)Published versio