Hollow carbon nanostructures have inspired numerous interests in areas such as energy conversion/storage, biomedicine, catalysis, and adsorption. Unfortunately, their synthesis mainly relies on template-based routes, which include tedious operating procedures and showed inadequate capability to build complex architectures. Here, by looking into the inner structure of single polymeric nanospheres, we identified the complicated compositional chemistry underneath their uniform shape, and confirmed that nanoparticles themselves stand for an effective and versatile synthetic platform for functional hollow carbon architectures. Using the formation of 3-aminophenol/formaldehyde resin as an example, we were able to tune its growth kinetics by controlling the molecular/environmental variables, forming resin nanospheres with designated styles of inner constitutional inhomogeneity. We confirmed that this intraparticle difference could be well exploited to create a large variety of hollow carbon architectures with desirable structural characters for their applications; for example, high-capacity anode for potassium-ion battery has been demonstrated with the multishelled hollow carbon nanospheres.

Transition-metal phosphides have recently been identified as low-cost and efficient electrocatalysts that are highly active for the hydrogen evolution reaction. Unfortunately, to achieve a controlled phosphidation of nonprecious metals toward a desired nanostructure of metal phosphides, the synthetic processes usually turned complicated, high-cost, and even dangerous due to the reaction chemistry related to different phosphorus sources. It becomes even more challenging when considering the integration of those active metal phosphides with the structural engineering of their conductive matrix toward a favorable architecture for optimized catalytic performance. Herein, we identified that the biomass itself could act as an effective synthetic platform for the construction of supported metal phosphides by recovering its inner phosphorus upon reacting with transition-metals ions, forming well-dispersed, highly active nanoparticles of metal phosphides incorporated in the nanoporous carbon matrix, which promised high catalytic activity in the hydrogen evolution reaction. Our synthetic protocol not only provides a simple and effective strategy for the construction of a large variety of highly active nanoparticles of metal phosphides but also envisions new perspectives on an integrated utilization of the essential ingredients, particularly phosphorus, together with the innate architecture of the existing biomass for the creation of functional nanomaterials toward sustainable energy development.

We report a simple and facile synthetic protocol to prepare an SnO2–C hollow composite, which shows improved battery performance when used as an anode material in lithium ion batteries.

Uniform nanoshells of manganese oxides have been successfully prepared by controlling their growth kinetics in solution. The prepared manganese oxides show promising electrochemical performance when used as an anode material in lithium ion batteries.

P2-type sodium layered oxides NaxMO2 (M = transition metal) are considered as one kind of promising cathode material for sodium-ion batteries because of their known structures, superior electrochemical properties, and their ease of synthesis. The Ni2+/Ni3+ and Ni3+/Ni4+ redox reactions endow the P2–Na2/3Ni1/3Mn2/3O2 electrode with a relatively high operating voltage and high specific capacity. However, the phase transition from P2 to O2 and Na+/vacancy ordering make P2–Na2/3Ni1/3Mn2/3O2 susceptible to severe voltage and capacity decay. Herein, we propose to employ the electrochemically active copper(II) as a unique substituent to stabilize the P2 phase, forming Na0.67Ni0.3−xCuxMn0.7O2 (x = 0, 0.1, 0.2 and 0.3). Our work highlights the importance of Cu(II) in the structural engineering of high performance cathode materials, whose existence can not only stabilize the P2 phase against the notorious phase transition, but also contribute to the rechargeable capacity due to the high potential Cu2+/Cu3+ redox. We identified that the cathode formulated as P2-type Na0.67Ni0.1Cu0.2Mn0.7O2 shows favorable battery performance with much-alleviated structural degradation.

To satisfy the upsurging demand for energy storage in modern society, anode materials which can deliver high capacity have been intensively researched for the next generation lithium ion batteries. Typically, the binary MnCo2O4 with a characteristic coupled metal cations showed promising potential due to its high theoretical capacity and low cost. Here, by means of a well-designed synthesis control, we demonstrated a scalable process to achieve a hierarchical structure of MnCo2O4, which existed as uniform microspheres with embedded mesopores, showing favorable structural characters for high performance during a fast charge/discharge process. Our synthesis highlighted the importance of sodium salicylate as an essential additive to control the precipitation of the two involved metal cations. It was proved that a dual role was played sodium salicylate which cannot only facilitate the formation of microspheric shape, but also act as an effective precursor for the creation of inner mesopores. We confirmed that the hierarchically-structured MnCo2O4 showed outstanding performance when it was tested as an anode material in lithium ion batteries as revealed by its extraordinary cycling stability and high rate capability.

Hollow hybrid microspheres have found great potential in different areas, such as drug delivery, nanoreactors, photonics, and lithium-ion batteries. Here, we report a simple and scalable approach to construct high-quality hollow hybrid microspheres through a previously unexplored growth mechanism. Starting from uniform solid microspheres with low crystallinity, we identified that a hollowing process can happen through the progressive inward crystallization process initiated on the particle surface: the gradual encroachment of the crystallization frontline toward the core leads to the depletion of the center and forms the central cavity. We showed that such a synthetic platform was versatile and can be applicable for a large variety of materials. By using the production of Li4Ti5O12–carbon hollow hybrid microspheres as an example, we demonstrated that high-performance anode materials could be achieved through synthesis and structure control. We expect that our findings offer new perspectives in different areas ranging from materials chemistry, energy storage devices, catalysis, to drug delivery.

Uniform CeO2 nanoshells were successfully prepared by using buffer solution as a unique growth medium. The application of this methodology to construct a yolk–shell structured Au@CeO2 nanocatalyst shows improved performance for the catalytic CO oxidation.

This communication reports that the TiO2@polydopamine nanocomposite with a core–shell structure could be a highly active photocatalyst working under visible light. A very thin layer of polydopamine at around 1 nm was found to be critical for the degradation of Rhodamine B.

By using phthalic acid as a soft template, we showed that it was possible to prepare a microporous aluminum-based material when the precipitation of Al3+ was properly controlled. We also identified that this microporous aluminum-based material could be promising for the removal of fluoride ions in water treatment.

The potential use of cerium selenide (Ce2S3) as a non-toxic pigment has long been plagued by its release of hydrogen sulfide (H2S). Here, it is shown that a uniform nanoshell of zinc oxide (ZnO) can effectively eliminate the released H2S and also improve the thermal stability of Ce2S3. Through a series of investigations, a 40 nm thick ZnO surface coating layer was found to provide full protection for the Ce2S3 core, and this thickness is best for eliminating the release of H2S. Such a core–shell configuration has great potential for real applications of Ce2S3 as an odorless and non-toxic inorganic pigment.

Melamine cyanurate (MCA) – a kind of hydrogen-bonded self-assembly supramolecular structure material – is readily synthesized by a hydrothermal method. Noble metal nanoparticles (NPs) (Pd, Au bimetallic and monometallic NPs) with an ultrasmall size below 5 nm are homogeneously distributed in the as-prepared MCA via a simple procedure at room temperature without any additional reductant and stabilizer. The as-prepared bimetallic noble metal NPs exhibit good catalytic activities toward the reduction of 4-nitrophenol to 4-aminophenol, and the resulting catalytic activities are even much better than those of monometallic counterparts. This unusual catalytic property should be relevant to the small size of noble nanoparticles and the electronic interaction between the support, Pd and Au nanoparticles.

Uniform AlPO4 nanoshells are successfully achieved on different core materials by controlling their formation kinetics in solution. The application of this coating protocol to LiCoO2 shows an obvious improvement in its battery performance.

Pd nanoparticles were successfully introduced into the channels of mesoporous silica MCM-41 with their dispersion well-tuned. We identified the dual role played by CTAB, which was critical for both the micelle template and Pd grafting, leading to the formation of a highly active Pd–MCM-41 nanocomposite for catalysing the Suzuki reaction.

Yolk–shell structured nanomaterials have shown interesting potential in different areas due to their unique structural configurations. A successful construction of such a hybrid structure relies not only on the preparation of the core materials, but also on the capability to manipulate the outside wall. Typically, for Al2O3, it has been a tough issue in preparing it into a uniform nanoshell, making the use of Al2O3-based yolk–shell structures a challenging but long-awaited task. Here, in benefit of our success in the controlled formation of Al2O3 nanoshell, we demonstrated that yolk–shell structures with metal confined inside a hollow Al2O3 nanosphere could be successfully achieved. Different metals including Au, Pt, Pd have been demonstrated, forming a typical core@void@shell structure. We showed that the key parameters of the yolk–shell structure such as the shell thickness and the cavity size could be readily tuned. Due to the protection of a surrounding Al2O3 shell, the thermal stability of the interior metal nanoparticles could be substantially improved, resulting in promising performance for the catalytic CO oxidation as revealed by our preliminary test on Au@Al2O3.Keywords: Al2O3 coating; catalysis; CO oxidation; thermal stability; yolk−shell structure

Manganese-based mixed polyanion cathodes known as LiMn1−xFexPO4 can show much higher energy density as compared to the well-commercialized product of lithium iron phosphate. However, their much lower electronic conductivity has long plagued their further application. Here, by means of a facile solution-based synthesis route, we are able to introduce a uniform and conformal carbon coating layer onto LiMn1−xFexPO4 nanoparticles. The versatility in the synthesis control endows us with the capability of controlling the shell thickness with one nanometer accuracy, offering an effective way to optimize the battery performance through a systematic shell control. Detailed investigation reveals that the carbon nanoshells not only act as good electronic conducting media, but also contribute to the inhibition of the metal (Mn and Fe) dissolution and reduce the exothermic heat released during cycling. The core–shell structured cathode materials show promising potential for their application in lithium ion batteries as revealed by their high charge–discharge capacity, remarkable thermal stability, and excellent cyclability.

A facile protocol is developed for the direct observation and characterization of a single particle electrode during the lithium ion battery operation by using in situ AFM. The SEI formation on the LiNi0.5Mn1.5O4 particle cathode surface is found to be highly related to the exposed planes.

Polyanion-type cathode materials are well-known for their low electronic conductivity; accordingly, the addition of conductive carbon in the cathode materials becomes an indispensable step for their application in lithium ion batteries. To maximize the contribution of carbon, a core–shell structure with a full coverage of carbon should be favorable due to an improved electronic contact between different particles. Here, we report the formation of a uniform carbon nanoshell on a typical cathode material, LiFePO4, with the shell thickness precisely defined via the 3-aminophenol–formaldehyde polymerization process. In addition to the higher discharge capacity and the improved rate capability as expected from the carbon nanoshell, we identified that the core–shell configuration could lead to a much safer cathode material as revealed by the obviously reduced iron dissolution, much less heat released during the cycling, and better cyclability at high temperature.Keywords: carbon coating; cathode materials; core−shell structure; iron dissolution; lithium ion batteries

Core–shell structures as LiFePO4@carbon with a continuous and uniform carbon coating were achieved by means of the in situ polymerization of dopamine. Systematic control of the coating layer identified that a 5 nm carbon coating produces the best battery performance. Our results provide conclusive evidence for an optimal carbon coating for polyanion-type cathode materials.

We report a simple and environmentally-benign method for the synthesis of Pd nanoclusters through a continuous etching process. With the help of L-methionine, newly-formed Pd nanoparticles (larger than 50 nm) will gradually reduce their size, finally resulting in the formation of tiny nanoclusters with a diameter around 1.4 nm. A following sol–gel process can encapsulate these highly-active nanoclusters into a silica matrix. In this way, Pd nanoclusters can be stabilized and can sustain a high temperature treatment up to 600 °C. Moreover, these Pd nanoclusters are proved to be promising for a catalytic Suzuki reaction. Due to the composite structure of nanoclusters and silica, the Pd@SiO2 catalysts show integrated merits including good catalytic activity, high stability and notable cyclability.

P2-type sodium layered oxides NaxMO2 (M = transition metal) are considered as one kind of promising cathode material for sodium-ion batteries because of their known structures, superior electrochemical properties, and their ease of synthesis. The Ni2+/Ni3+ and Ni3+/Ni4+ redox reactions endow the P2–Na2/3Ni1/3Mn2/3O2 electrode with a relatively high operating voltage and high specific capacity. However, the phase transition from P2 to O2 and Na+/vacancy ordering make P2–Na2/3Ni1/3Mn2/3O2 susceptible to severe voltage and capacity decay. Herein, we propose to employ the electrochemically active copper(II) as a unique substituent to stabilize the P2 phase, forming Na0.67Ni0.3−xCuxMn0.7O2 (x = 0, 0.1, 0.2 and 0.3). Our work highlights the importance of Cu(II) in the structural engineering of high performance cathode materials, whose existence can not only stabilize the P2 phase against the notorious phase transition, but also contribute to the rechargeable capacity due to the high potential Cu2+/Cu3+ redox. We identified that the cathode formulated as P2-type Na0.67Ni0.1Cu0.2Mn0.7O2 shows favorable battery performance with much-alleviated structural degradation.

Uniform nanoshells of manganese oxides have been successfully prepared by controlling their growth kinetics in solution. The prepared manganese oxides show promising electrochemical performance when used as an anode material in lithium ion batteries.

Uniform CeO2 nanoshells were successfully prepared by using buffer solution as a unique growth medium. The application of this methodology to construct a yolk–shell structured Au@CeO2 nanocatalyst shows improved performance for the catalytic CO oxidation.

By using phthalic acid as a soft template, we showed that it was possible to prepare a microporous aluminum-based material when the precipitation of Al3+ was properly controlled. We also identified that this microporous aluminum-based material could be promising for the removal of fluoride ions in water treatment.

This communication reports that the TiO2@polydopamine nanocomposite with a core–shell structure could be a highly active photocatalyst working under visible light. A very thin layer of polydopamine at around 1 nm was found to be critical for the degradation of Rhodamine B.

Uniform AlPO4 nanoshells are successfully achieved on different core materials by controlling their formation kinetics in solution. The application of this coating protocol to LiCoO2 shows an obvious improvement in its battery performance.

Pd nanoparticles were successfully introduced into the channels of mesoporous silica MCM-41 with their dispersion well-tuned. We identified the dual role played by CTAB, which was critical for both the micelle template and Pd grafting, leading to the formation of a highly active Pd–MCM-41 nanocomposite for catalysing the Suzuki reaction.

A facile protocol is developed for the direct observation and characterization of a single particle electrode during the lithium ion battery operation by using in situ AFM. The SEI formation on the LiNi0.5Mn1.5O4 particle cathode surface is found to be highly related to the exposed planes.

The potential use of cerium selenide (Ce2S3) as a non-toxic pigment has long been plagued by its release of hydrogen sulfide (H2S). Here, it is shown that a uniform nanoshell of zinc oxide (ZnO) can effectively eliminate the released H2S and also improve the thermal stability of Ce2S3. Through a series of investigations, a 40 nm thick ZnO surface coating layer was found to provide full protection for the Ce2S3 core, and this thickness is best for eliminating the release of H2S. Such a core–shell configuration has great potential for real applications of Ce2S3 as an odorless and non-toxic inorganic pigment.

Melamine cyanurate (MCA) – a kind of hydrogen-bonded self-assembly supramolecular structure material – is readily synthesized by a hydrothermal method. Noble metal nanoparticles (NPs) (Pd, Au bimetallic and monometallic NPs) with an ultrasmall size below 5 nm are homogeneously distributed in the as-prepared MCA via a simple procedure at room temperature without any additional reductant and stabilizer. The as-prepared bimetallic noble metal NPs exhibit good catalytic activities toward the reduction of 4-nitrophenol to 4-aminophenol, and the resulting catalytic activities are even much better than those of monometallic counterparts. This unusual catalytic property should be relevant to the small size of noble nanoparticles and the electronic interaction between the support, Pd and Au nanoparticles.

Manganese-based mixed polyanion cathodes known as LiMn1−xFexPO4 can show much higher energy density as compared to the well-commercialized product of lithium iron phosphate. However, their much lower electronic conductivity has long plagued their further application. Here, by means of a facile solution-based synthesis route, we are able to introduce a uniform and conformal carbon coating layer onto LiMn1−xFexPO4 nanoparticles. The versatility in the synthesis control endows us with the capability of controlling the shell thickness with one nanometer accuracy, offering an effective way to optimize the battery performance through a systematic shell control. Detailed investigation reveals that the carbon nanoshells not only act as good electronic conducting media, but also contribute to the inhibition of the metal (Mn and Fe) dissolution and reduce the exothermic heat released during cycling. The core–shell structured cathode materials show promising potential for their application in lithium ion batteries as revealed by their high charge–discharge capacity, remarkable thermal stability, and excellent cyclability.