Guoyin Zhu

Self-Templated Formation of Interlaced Carbon Nanotubes Threaded Hollow Co3S4 Nanoboxes for High-Rate and Heat-Resistant Lithium–Sulfur Batteries

Lithium-sulfur batteries (Li-S) have attracted soaring attention due to the particularly high energy density for advanced energy storage system. However, the practical application of Li-S batteries still faces multiple challenges, including the shuttle effect of intermediate polysulfides, the low conductivity of sulfur and the large volume variation of sulfur cathode. To overcome these issues, here we reported a self-templated approach to prepare interconnected carbon nanotubes inserted/wired hollow Co3S4 nanoboxes (CNTs/Co3S4-NBs) as an efficient sulfur host material. Originating from the combination of three-dimensional CNT conductive network and polar Co3S4-NBs, the obtained hybrid nanocomposite of CNTs/Co3S4-NBs can offer ultrahigh charge transfer properties, and efficiently restrain polysulfides in hollow Co3S4-NBs via the synergistic effect of structural confinement and chemical bonding. Benefiting from the above advantages, the S@CNTs/Co3S4-NBs cathode shows a significantly improved electrochemical performance in terms of high reversible capacity, good rate performance, and long-term cyclability. More remarkably, even at an elevated temperature (50 °C), it still exhibits high capacity retention and good rate capacity.

CsPb0.9Sn0.1IBr2 Based All-Inorganic Perovskite Solar Cells with Exceptional Efficiency and Stability

The emergence of perovskite solar cells (PSCs) has generated enormous interest in the photovoltaic research community. Recently, cesium metal halides (CsMX3, M = Pb or Sn; X = I, Br, Cl or mixed halides) as a class of inorganic perovskites showed great promise for PSCs and other optoelectronic devices. However, CsMX3-based PSCs usually exhibit lower power conversion efficiencies (PCEs) than organic-inorganic hybrid PSCs, due to the unfavorable band gaps. Herein, a novel mixed-Pb/Sn mixed-halide inorganic perovskite, CsPb0.9Sn0.1IBr2, with a suitable band gap of 1.79 eV and an appropriate level of valence band maximum, was prepared in ambient atmosphere without a glovebox. After thoroughly eliminating labile organic components and noble metals, the all-inorganic PSCs based on CsPb0.9Sn0.1IBr2 and carbon counter electrodes exhibit a high open-circuit voltage of 1.26 V and a remarkable PCE up to 11.33%, which is record-breaking among the existing CsMX3-based PSCs. Moreover, the all-inorganic PSCs show good long-term stability and improved endurance against heat and moisture. This study indicates a feasible way to design inorganic halide perovskites through energy-band engineering for the construction of high-performance all-inorganic PSCs.

Cerium Oxide Nanocrystal Embedded Bimodal Micromesoporous Nitrogen-Rich Carbon Nanospheres as Effective Sulfur Host for Lithium–Sulfur Batteries

For developing lithium-sulfur (Li-S) batteries, it is critical to design advanced cathode materials with high sulfur loading/utilization ratios and strong binding interactions with sulfur species to prevent the dissolution of intermediate polysulfides. Here we report an effective sulfur host material prepared by implanting cerium oxide (CeO2) nanocrystals homogeneously into well-designed bimodal micromesoporous nitrogen-rich carbon (MMNC) nanospheres. With the high conductivity and abundant hierarchical pore structures, MMNC nanospheres can effectively store and entrap sulfur species. Moreover, the inserted polar and electrocatalytically active CeO2 nanocrystals and high nitrogen content of MMNC can synergistically solve the hurdle of the polysulfide dissolution and furthermore significantly promote stable redox activity. By combining these advantages, CeO2/MMNC-S cathodes with 1.4 mg cm-2 sulfur exhibit high reversible capacities (1066 mAh g-1 at 0.2 C after 200 cycles and 836 mAh g-1 at 1.0 C after 500 cycles), good rate capability (737 mAh g-1 at 2.0 C), and high cycle stability (721 mAh g-1 at 2.0 C after 1000 cycles with a low capacity decay of 0.024% per cycle). Furthermore, a high and stable reversible capacity of 611 mAh g-1 is achieved after cycling for 200 cycles with higher sulfur loading of 3.4 mg cm-2.

Porous-Shell Vanadium Nitride Nanobubbles with Ultrahigh Areal Sulfur Loading for High-Capacity and Long-Life Lithium–Sulfur Batteries

Lithium-sulfur (Li-S) batteries hold great promise for the applications of high energy density storage. However, the performances of Li-S batteries are restricted by the low electrical conductivity of sulfur and shuttle effect of intermediate polysulfides. Moreover, the areal loading weights of sulfur in previous studies are usually low (around 1-3 mg cm-2) and thus cannot fulfill the requirement for practical deployment. Herein, we report that porous-shell vanadium nitride nanobubbles (VN-NBs) can serve as an efficient sulfur host in Li-S batteries, exhibiting remarkable electrochemical performances even with ultrahigh areal sulfur loading weights (5.4-6.8 mg cm-2). The large inner space of VN-NBs can afford a high sulfur content and accommodate the volume expansion, and the high electrical conductivity of VN-NBs ensures the effective utilization and fast redox kinetics of polysulfides. Moreover, VN-NBs present strong chemical affinity/adsorption with polysulfides and thus can efficiently suppress the shuttle effect via both capillary confinement and chemical binding, and promote the fast conversion of polysulfides. Benefiting from the above merits, the Li-S batteries based on sulfur-filled VN-NBs cathodes with 5.4 mg cm-2 sulfur exhibit impressively high areal/specific capacity (5.81 mAh cm-2), superior rate capability (632 mAh g-1 at 5.0 C), and long cycling stability.

Progress and Perspective of Electrocatalytic CO2 Reduction for Renewable Carbonaceous Fuels and Chemicals

Abstract The worldwide unrestrained emission of carbon dioxide (CO2) has caused serious environmental pollution and climate change issues. For the sustainable development of human civilization, it is very desirable to convert CO2 to renewable fuels through clean and economical chemical processes. Recently, electrocatalytic CO2 conversion is regarded as a prospective pathway for the recycling of carbon resource and the generation of sustainable fuels. In this review, recent research advances in electrocatalytic CO2 reduction are summarized from both experimental and theoretical aspects. The referred electrocatalysts are divided into different classes, including metal–organic complexes, metals, metal alloys, inorganic metal compounds and carbon‐based metal‐free nanomaterials. Moreover, the selective formation processes of different reductive products, such as formic acid/formate (HCOOH/HCOO−), monoxide carbon (CO), formaldehyde (HCHO), methane (CH4), ethylene (C2H4), methanol (CH3OH), ethanol (CH3CH2OH), etc. are introduced in detail, respectively. Owing to the limited energy efficiency, unmanageable selectivity, low stability, and indeterminate mechanisms of electrocatalytic CO2 reduction, there are still many tough challenges need to be addressed. In view of this, the current research trends to overcome these obstacles in CO2 electroreduction field are summarized. We expect that this review will provide new insights into the further technique development and practical applications of CO2 electroreduction.

Hierarchical porous nitrogen-rich carbon nanospheres with high and durable capabilities for lithium and sodium storage

To improve the energy storage performance of carbon-based materials, considerable attention has been paid to the design and fabrication of novel carbon architectures with structural and chemical modifications. Herein, we report that hierarchical porous nitrogen-rich carbon (HPNC) nanospheres originating from acidic etching of metal carbide/carbon hybrid nanoarchitectures can be employed as high-performance anode materials for both lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs). The structural advantages of HPNC nanospheres are that the exceptionally-high content of nitrogen (17.4 wt%) can provide abundant electroactive sites and enlarge the interlayer distance (∼3.5 Å) to improve the capacity, and the large amount of micropores and mesopores can serve as reservoirs for storing lithium/sodium ions. In LIBs, HPNC based anodes deliver a high reversible capacity of 1187 mA h g-1 after 100 cycles at 100 mA g-1, a great rate performance of 470 mA h g-1 at 5000 mA g-1, and outstanding cycling stabilities with a capacity of 788 mA h g-1 after 500 cycles at 1000 mA g-1. In SIBs, HPNC based anodes exhibit a remarkable reversible capacity of 357 mA h g-1 at 100 mA g-1 and high long-term stability with a capacity of 136 mA h g-1 after 500 cycles at 1000 mA g-1.

Engineering tin phosphides@carbon yolk–shell nanocube structures as a highly stable anode material for sodium-ion batteries

Sodium-ion batteries (SIBs) are considered as promising alternatives to lithium-ion batteries because of the natural abundance and low cost of sodium resources. Unfortunately, SIBs usually suffer from the serious volume change of active materials and the sluggish kinetics of sodiation of the structure. To combat the above issues, herein we rationally design an integrated anode material of tin phosphides@carbon (Sn4P3@C) with a yolk–shell nanocube structure for SIBs. The voids and spaces between the Sn4P3 and carbon nanocubes can effective buffer the volume expansion of active materials during sodiation/desodiation processes, and the highly electrically conductive carbon material can promote the fast electron transfer, thus accelerating the kinetics of sodiation/desodiation. In SIBs, the Sn4P3@C yolk–shell nanocube electrode exhibits excellent sodium storage performance with a high discharge capacity of 701 mA h g−1 at 0.1 A g−1 after 50 cycles, remarkable rate capability (508 mA h g−1 even at 2.0 A g−1), and highly stable cycling performance (516 and 368 mA h g−1 after 500 cycles at 1.0 and 2.0 A g−1, respectively).

Controlled growth and photoconductive properties of hexagonal SnS2 nanoflakes with mesa-shaped atomic steps

We demonstrated the controlled growth of two-dimensional (2D) hexagonal tin disulfide (SnS2) nanoflakes with stacked monolayer atomic steps. The morphology was similar to flat-topped and step-sided mesa plateaus or step pyramids. The SnS2 nanoflakes were grown on mica substrates via an atmospheric-pressure chemical vapor deposition process using tin monosulfide and sulfur powder as precursors. Atomic force microscopy (AFM), electron microscopy, and Raman characterizations were performed to investigate the structural features, and a sequential layer-wise epitaxial growth mechanism was revealed. In addition, systematic Raman characterizations were performed on individual SnS2 nanoflakes with a wide range of thicknesses (1–100 nm), indicating that the A1g peak intensity and Raman shifts were closely related to the thickness of the SnS2 nanoflakes. Moreover, photoconductive AFM was performed on the monolayer-stepped SnS2 nanoflakes, revealing that the flat surface and the edges of the SnS2 atomic steps had different electrical conductive properties and photoconductive behaviors. This is ascribed to the dangling bonds and defects at the atomic step edges, which caused a height difference of the Schottky barriers formed at the interfaces between the PtIr-coated AFM tip and the step edges or the flat surface of the SnS2 nanoflakes. The 2D SnS2 crystals with regular monolayer atomic steps and fast photoresponsivity are promising for novel applications in photodetectors and integrated optoelectronic circuits.

Correction to “All-Inorganic Perovskite Solar Cells”

Figure 3. (a) J−V plot of CsPbBr3/carbon-based all-inorganic PSCs. The inset shows the corresponding photovoltaic parameters. (b) Statistical histogram of the PCEs of 40 individual CsPbBr3/ carbon-based all-inorganic PSCs. (c) Normalized PCEs of CsPbBr3/ carbon-based all-inorganic PSCs and MAPbI3/carbon-based and MAPbI3/spiro-MeOTAD-based hybrid PSCs as a function of storage time in humid air (90−95% RH, 25 °C) without encapsulation. (d) Normalized PCEs of CsPbBr3/carbon-based all-inorganic PSCs and MAPbI3/carbon-based hybrid PSCs as a function of time heated at high temperature (100 °C) in a high-humidity ambient environment (90−95% RH, 25 °C) without encapsulation. (e) Normalized PCEs of CsPbBr3/carbon-based all-inorganic PSCs vs storage time during temperature cycles (between −22 and 100 °C) in a high-humidity ambient environment (90−95% RH, 25 °C) without encapsulation. Figure 4. (a) J−V plots of an all-inorganic PSC with a large active area of 1.0 cm measured in the forward and reverse scanning modes. (b) IPCE spectrum and integrated current density of the PSC in (a). Addition/Correction

Interface Engineering of Anchored Ultrathin TiO2/MoS2 Heterolayers for Highly-Efficient Electrochemical Hydrogen Production

An efficient self-standing hydrogen evolution electrode was prepared by in situ growth of stacked ultrathin TiO2/MoS2 heterolayers on carbon paper (CP@TiO2@MoS2). Owing to the high overall conductivity, large electrochemical surface area and abundant active sites, this novel electrode exhibits an excellent performance for hydrogen evolution reaction (HER). Remarkably, the composite electrode shows a low Tafel slope of 41.7 mV/dec, and an ultrahigh cathodic current density of 550 mA/cm2 at a very low overpotential of 0.25 V. This work presents a new universal strategy for the construction of effective, durable, scalable, and inexpensive electrodes that can be extended to other electrocatalytic systems.