Chong Qu

High-Performance Energy Storage and Conversion Materials Derived from a Single Metal–Organic Framework/Graphene Aerogel Composite

Metal oxides and carbon-based materials are the most promising electrode materials for a wide range of low-cost and highly efficient energy storage and conversion devices. Creating unique nanostructures of metal oxides and carbon materials is imperative to the development of a new generation of electrodes with high energy and power density. Here we report our findings in the development of a novel graphene aerogel assisted method for preparation of metal oxide nanoparticles (NPs) derived from bulk MOFs (Co-based MOF, Co(mIM)2 (mIM = 2-methylimidazole). The presence of cobalt oxide (CoOx) hollow NPs with a uniform size of 35 nm monodispersed in N-doped graphene aerogels (NG-A) was confirmed by microscopic analyses. The evolved structure (denoted as CoOx/NG-A) served as a robust Pt-free electrocatalyst with excellent activity for the oxygen reduction reaction (ORR) in an alkaline electrolyte solution. In addition, when Co was removed, the resulting nitrogen-rich porous carbon-graphene composite electrode (denoted as C/NG-A) displayed exceptional capacitance and rate capability in a supercapacitor. Further, this method is readily applicable to creation of functional metal oxide hollow nanoparticles on the surface of other carbon materials such as graphene and carbon nanotubes, providing a good opportunity to tune their physical or chemical activities.

Physical and sexual abuse of women before, during, and after pregnancy

Objectives: To examine patterns of physical and sexual abuse before, during, and after pregnancy. Methods: A community‐based interview survey of a representative group of women with children aged 6–18 months was carried out between November 1, 2001, and February 28, 2002, in 32 communities of the Tianjing, Liaoning, Henan, and Shannxi provinces. Results: The overall prevalence of physical and sexual abuse (occurring before, during, and after pregnancy) was 11.7%. The prevalence of physical and sexual abuse before pregnancy was 8.5%, compared with 3.6% during pregnancy and 7.4% during an average postpartum period of 11 months. Abuse before pregnancy was a strong indicator of abuse during pregnancy and after delivery, and abuse during a previous period was a strong indicator of subsequent abuse. Most abuse was recurrent and not severe. Conclusion: Routine screening for abuse in the maternity services setting is advocated to decrease the effect of abuse on women and their children.

Pristine Metal–Organic Frameworks and their Composites for Energy Storage and Conversion

Metal-organic frameworks (MOFs), a new class of crystalline porous organic-inorganic hybrid materials, have recently attracted increasing interest in the field of energy storage and conversion. Herein, recent progress of MOFs and MOF composites for energy storage and conversion applications, including photochemical and electrochemical fuel production (hydrogen production and CO2 reduction), water oxidation, supercapacitors, and Li-based batteries (Li-ion, Li-S, and Li-O2 batteries), is summarized. Typical development strategies (e.g., incorporation of active components, design of smart morphologies, and judicious selection of organic linkers and metal nodes) of MOFs and MOF composites for particular energy storage and conversion applications are highlighted. A broad overview of recent progress is provided, which will hopefully promote the future development of MOFs and MOF composites for advanced energy storage and conversion applications.

A Universal Strategy for Hollow Metal Oxide Nanoparticles Encapsulated into B/N Co‐Doped Graphitic Nanotubes as High‐Performance Lithium‐Ion Battery Anodes

Yolk-shell nanostructures have received great attention for boosting the performance of lithium-ion batteries because of their obvious advantages in solving the problems associated with large volume change, low conductivity, and short diffusion path for Li+ ion transport. A universal strategy for making hollow transition metal oxide (TMO) nanoparticles (NPs) encapsulated into B, N co-doped graphitic nanotubes (TMO@BNG (TMO = CoO, Ni2 O3 , Mn3 O4 ) through combining pyrolysis with an oxidation method is reported herein. The as-made TMO@BNG exhibits the TMO-dependent lithium-ion storage ability, in which CoO@BNG nanotubes exhibit highest lithium-ion storage capacity of 1554 mA h g-1 at the current density of 96 mA g-1 , good rate ability (410 mA h g-1 at 1.75 A g-1 ), and high stability (almost 96% storage capacity retention after 480 cycles). The present work highlights the importance of introducing hollow TMO NPs with thin wall into BNG with large surface area for boosting LIBs in the terms of storage capacity, rate capability, and cycling stability.

MOF-derived α-NiS nanorods on graphene as an electrode for high-energy-density supercapacitors

Hierarchically porous electrodes made of electrochemically active materials and conductive additives may display synergistic effects originating from the interactions between the constituent phases, and this approach has been adopted for optimizing the performances of many electrode materials. Here we report our findings in design, fabrication, and characterization of a hierarchically porous hybrid electrode composed of α-NiS nanorods decorated on reduced graphene oxide (rGO) (denoted as R-NiS/rGO), derived from water-refluxed metal–organic frameworks/rGO (Ni-MOF-74/rGO) templates. Microanalyses reveal that the as-synthesized α-NiS nanorods have abundant (101) and (110) surfaces on the edges, which exhibit a strong affinity for OH− in KOH electrolyte, as confirmed by density functional theory-based calculations. The results suggest that the MOF-derived α-NiS nanorods with highly exposed active surfaces are favorable for fast redox reactions in a basic electrolyte. Besides, the presence of rGO in the hybrid electrode greatly enhances the electronic conductivity, providing efficient current collection for fast energy storage. Indeed, when tested in a supercapacitor with a three-electrode configuration in 2 M KOH electrolyte, the R-NiS/rGO hybrid electrode exhibits a capacity of 744 C g−1 at 1 A g−1 and 600 C g−1 at 50 A g−1, indicating remarkable rate performance, while maintaining more than 89% of the initial capacity after 20 000 cycles. Moreover, when coupled with a nitrogen-doped graphene aerogel (C/NG-A) negative electrode, the hybrid supercapacitor (R-NiS/rGO/electrolyte/C/NG-A) achieved an ultra-high energy density of 93 W h kg−1 at a power density of 962 W kg−1, while still retaining an energy density of 54 W h kg−1 at an elevated working power of 46 034 W kg−1.

Kinetic-Controlled Formation of Bimetallic Metal–Organic Framework Hybrid Structures

Heterometallic metal-organic frameworks (MOFs) are constructed from two or more kinds of metal ions, while still remaining their original topologies. Due to distinct reaction kinetics during MOF formation, partial distribution of different metals within a single MOF crystal can lead to sophisticated heterogeneous nanostructures. Here, this study reports an investigation of reaction kinetics for different metal ions in a bimetallic MOF system, the ZIF-8/67 (M(2-mIM)2 , M = Zn for ZIF-8, and Co for ZIF-67, 2-mIM = 2-methylimidazole), by in situ optical method. Distinct kinetics of the two metals forming single-component MOFs are revealed, and when both Co and Zn ions are present in the starting solution, homogeneous distributions of the two metals are only achieved at high Co/Zn ratio, while at low Co/Zn ratio concentration gradient from Co-rich cores to Zn-rich shells is observed. Further, by adding the two metals in sequence, more sophisticated structures are achieved. Specifically, when Co2+ is added first, ZIF-67@ZIF-8/67 core-shell nanocrystals are achieved with tunable core/shell thickness ratio depending on the time intervals; while when Zn2+ is added first, only agglomerates of irregular shape form due to the weak nucleation ability of Zn2+ .

Tailoring biomass-derived carbon for high-performance supercapacitors from controllably cultivated algae microspheres

A high-performance “green” carbon-based supercapacitor electrode material is synthesized from selected algae microspheres, which are grown under controlled cultivation conditions. The best-performing sample possesses a high specific surface area of 1337.9 m2 g−1 with a hierarchically porous structure and naturally intrinsic nitrogen dopant. This leads to an excellent specific capacitance of 353 F g−1 at 1 A g−1 and 92% capacitance retention even after 10 000 charge–discharge cycles at 20 A g−1, which makes it superior to many recently reported biomass- and synthetically derived carbon electrode materials. It is found that residual nitrogen and metal contents in algae-derived carbon are highly influenced by biomass components, such as proteins. The content of these components can be controlled by adjusting the concentrations of nutrients in cultivation media. However, nitrogen in algae proteins is not pyrolytically stable, and studies indicate that excessive residual metal content plays the role of “dead mass” and results in a less-developed porous structure. Therefore, this suggests that both biomass selection and cultivation should aim for proteins with a more stable nitrogen content and minimized content of electrochemically inactive metals such as Mg and Ca. Hence, this study does not just demonstrate a green candidate electrode material for high-performance supercapacitors, but also provides an innovative selection and cultivation strategy to improve the capacitive performance of biomass-derived carbon.

Atomically Dispersed Metal Sites in MOF‐Based Materials for Electrocatalytic and Photocatalytic Energy Conversion

Metal sites play an essential role in both electrocatalytic and photocatalytic energy conversion. The highly ordered arrangements of the organic linkers and metal nodes as well as the well-defined pore structures of metal-organic frameworks (MOFs) make them ideal substrates to support atomically dispersed metal sites (ADMSs) located in their metal nodes, linkers, and pores. Porous carbon materials doped with ADMSs can be derived from these ADMS-incorporating MOF precursors through controlled treatments. These ADMSs incorporated in pristine MOFs and MOF-derived carbon materials possess unique advantages over molecular or bulk metal-based catalysts and bridge the gap between homogeneous and heterogeneous catalysts for energy-conversion applications. This Review presents recent progress in the design and incorporation of ADMSs in MOFs and MOF-derived materials for energy-conversion applications.

Ultralow Loading Ruthenium Nanoparticles on Nitrogen‐Doped Graphene Aerogel for Trifunctional Electrocatalysis

A three‐dimensional (3 D) nitrogen‐doped graphene aerogel (NGA) with confined ultrasmall ruthenium nanoparticles (2–4 nm) was prepared through a hydrothermal reaction of graphene oxide (GO), ammonia solution, and ruthenium trichloride hydrate, followed by high‐temperature annealing and oxidation. The reactants self‐assemble into a 3 D porous structure with Ru nanoparticles embedded inside. With ultralow N and Ru contents of 2.40 and 1.21 at %, the introduction of Ru and N in the 3 D graphene aerogel gives rise to multifunctional catalytic performance in oxygen‐ and hydrogen‐involved reactions. Particularly, its performance in the oxygen evolution reaction (OER) surpassed those of commercial Pt/C and RuO2 in terms of both smaller potential (1.62 V vs. RHE) to reach 10 mA cm−2 and larger current densities across the applied potential range of 1 to 2 V (vs. RHE). Structural and chemical characterization revealed that the nanoparticle size and Ru/RuO2 ratio played decisive roles in determining the aerogels electrocatalytic performance. Hence, this study demonstrates that the synergistic effect of nanosized Ru and a porous NGA can be applied to achieve effective multifunctional electrocatalysis, for which the Ru nanoparticles can be tailored to achieve optimized performance with the lowest‐necessary doping concentration.

Large-scale fabrication of BCN nanotube architecture entangled on a three-dimensional carbon skeleton for energy storage

Boron and nitrogen co-doped graphene (BCN) nanotubes have tremendous properties for energy storage devices. Herein, we first report a BCN nanotubes architecture entangled on a three dimensional (3D) melamine foam derived carbon skeleton with high surface area, hierarchical porosity and heteroatoms (B, C, N) extant. Having such efficacious properties, 3D-BCN-950 (calcinated under 950 °C) exhibited excellent capacitance of 344 F g−1 at a current density of 1 A g−1. Furthermore, 3D-BCN-950 nanotubes are utilized as electrodes in a symmetric and negative electrode in asymmetric hybrid supercapacitors. The symmetric supercapacitor presented a high energy density of 19.8 W h kg−1 and elevated power density of 5074 W kg−1, the asymmetric supercapacitor also demonstrated a high energy density of 72 W h kg−1 and power density of 22 732 W kg−1. These results indicate the as-synthesized heteroatoms doped graphene nanotubes architecture could be a potential negative electrode materials for the fabrication of future high energy density hybrid supercapacitors.