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Lignocellulosic biomass photoreforming is a promising and alternative strategy for both sustainable H2 production and biomass valorization with infinite solar energy. However, harsh reaction conditions (high alkalinity or toxic organic solvents), with low biomass conversion and selectivity are often reported in literature. In this work, we report glucose photoreforming for coproduction of H2 and arabinose with improved selectivity under neutral condition using carbon quantum dots (CQDs) modified TiO2 composites. We show that the conventional CQDs fabricated by a facile one-step hydrothermal process could be endowed with novel color changing property, due to the particle aggregation under the regulation of incident light. The as-fabricated CQDs/TiO2 composites with certain colored CQDs could greatly improve glucose to arabinose conversion selectivity (~75%) together with efficient hydrogen evolution (up to 2.43 mmolh−1g−1) in water. The arabinose is produced via the direct C1-C2 α-scissions mechanism with reactive oxygen species of O2− and OH, as evidenced by 13C labeled glucose and the electron spin-resonance (ESR) studies, respectively. This work not only sheds new lights on CQDs assisted photobiorefinery for biomass valorization and H2 coproduction, but also opens the door for rationale design of different colored CQDs and their potential applications for solar energy utilization in the noble-metal-free system.

In this work, ZnO hollow spheres (ZnO-HS) with mesoporous shells were successfully synthesized via a facile two-step method. The hollow structure provides sufficient space and active sites for adsorbing gases. The mesoporous shells assembled from nanoparticles facilitate the diffusion of gas molecules into the inner space and ensure full contact with ZnO. Consequently, ZnO-HS-600 gas sensors deliver a satisfactory response to volatile organic compounds (VOCs) and an excellent response-recovery time at the optimal working temperature of 300 °C, i. e., acetone (9 and 5 s), ethanol (10 and 6 s), and methanol (12 and 14 s), respectively. By combining the theoretical calculation and the experimental observation, the relationship between the structure and performance has been established. The results demonstrate that ZnO-HS-600 materials meet the regional depletion condition, i. e., L

Active crystal facets can generate special properties for various applications. Herein, we report a (001) faceted nanosheet-constructed hierarchically porous TiO2/rGO hybrid architecture with unprecedented and highly stable lithium storage performance. Density functional theory calculations show that the (001) faceted TiO2 nanosheets enable enhanced reaction kinetics by reinforcing their contact with the electrolyte and shortening the path length of Li+ diffusion and insertion-extraction. The reduced graphene oxide (rGO) nanosheets in this TiO2/rGO hybrid largely improve charge transport, while the porous hierarchy at different length scales favors continuous electrolyte permeation and accommodates volume change. This hierarchically porous TiO2/rGO hybrid anode material demonstrates an excellent reversible capacity of 250 mAh g–1 at 1 C (1 C = 335 mA g–1) at a voltage window of 1.0–3.0 V. Even after 1000 cycles at 5 C and 500 cycles at 10 C, the anode retains exceptional and stable capacities of 176 and 160 mAh g–1, respectively. Moreover, the formed Li2Ti2O4 nanodots facilitate reversed Li+ insertion-extraction during the cycling process. The above results indicate the best performance of TiO2-based materials as anodes for lithium-ion batteries reported in the literature.

We report the well-designed active {1 1 0} and {1 1 1} faceted Cu2O hollow nanospheres (Cu2O-HNs) for the quick removal of the high concentration pollutants in water. For the first time, these Cu2O-HNs combine the advantages of the active facets, hollow structure and nanostructures. The abundance of dangling Cu atoms in two active facets results in positively charged surface to effectively react with the negatively charged pollutants. The hollow structure provides the opportunity to take full use of these active sites. Consequently, the active faceted Cu2O-HNs demonstrate excellent adsorption and photodegradation capacities for high concentrated anionic dyes. The smallest Cu2O-HNs (~100 nm) can adsorb ~90% of methyl blue (MB) (100 mg L−1) in 10 min and degrade ~92% of MB (100 mg L−1) in 10 min under visible-light. In particular, a film consisting of the smallest Cu2O-HNs can quickly remove high concentrated organic dyes and be reused after solar light irradiation for 10 min in air, showing the promising practical application for the removal of organic pollutants.

Photocatalytic hydrogen (H 2 )production based on semiconductors is important to utilize solar light for clean energy and environment. Herein, we report a visible light responsive heterostructure, designed and constructed by molybdenum disulfide quantum dots (MoS 2 -QDs)in-situ seeds-directing growth and self-assemble of zinc indium sulfide (ZnIn 2 S 4 )nanosheet to ensure their full contact through a simple one-step solvothermal method for highly improved visible light H 2 production. The MoS 2 -QDs in-situ seeds-directing ZnIn 2 S 4 heterostructure not only builds heterojunctions between MoS 2 and ZnIn 2 S 4 to spatially separate the photogenerated electrons and holes, but also serves as the active sites trapping photogenerated electrons to facilitate H 2 evolution. As a result, MoS 2 -QDs/ZnIn 2 S 4 exhibits high photocatalytic activity for H 2 production, and the optimized 2 wt% MoS 2 -QDs/ZnIn 2 S 4 (2MoS 2 -QDs/ZnIn 2 S 4 )heterostructure exhibits the highest H 2 evolution rate of 7152 umol·h −1 ·g −1 under visible light, ∼9 times of pure ZnIn 2 S 4 . Our strategy here could shed some lights on developing noble-metal free heterostructures for highly efficient photocatalytic H 2 production.

The lithium-selenium (Li-Se) battery has attracted growing interest recently due to its high energy density and theoretical capacity. However, the shuttle effect and volume change during cycling severely hinder its further application. In this work, we report a metal-organic framework (MOF)-derived nitrogen-doped core-shell hierarchical porous carbon (N-CSHPC) with interconnected meso/micropores to effectively confine Se for high-performance Li-Se batteries. The micropores were located at the ZIF-8-derived core and the ZIF-67-derived shell, while mesopores appeared at the core-shell interface after the pyrolysis of the core-shell ZIF-8@ZIF-67 precursor. Such a special hierarchical porous structure effectively confined selenium and polyselenides to prevent their dissolution from the pores and also alleviated the volume change. In particular, in situ nitrogen doping, which afforded N-CSHPC, not only improved the electrical conductivity of Se but also provided strong chemical adsorption on Li 2 Se, as confirmed by density functional theory calculations. On the basis of dual-physical confinement and strong chemisorption, Se/N-CSHPC-II (molar ratio of Co source to Zn source of 1.0 in the core-shell ZIF-8@ZIF-67 precursor) exhibited reversible capacities of up to 555 mA h g -1 after 150 cycles at 0.2 C and 462 mA h g -1 after 200 cycles at 0.5 C and even a discharge capacity of 432 mA h g -1 after 200 cycles at 1 C. Our demonstration here suggests that the carefully designed Se/C composite can improve the reversible capacity and cycling stability of Se cathodes for Li-Se batteries.

We report three types of conducting polymers (CPs), polyaniline (PANI), polypyrrole (PPY) and poly (3,4-ethylenedioxythiophene) (PEDOT) to modify the surface of the CdS nanorods to probe their photocorrosion inhibition and photocatalytic hydrogen production. Various characterizations, such as high resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV) and density function theory (DFT) calculations have been conducted to reveal the intrinsic structure of the as-constructed CPs@CdS (@ means CPs at the surface of CdS) core-shell nanorods. The results show that the PANI and PPY shells with abundant N and C atoms can significantly enhance the binding energy of Cd and S atoms on the surface of the CdS nanorods. However, there is no obvious enhancement of binding energy at the interface of the PEDOT shell and the CdS nanorods core. Therefore, PANI@CdS and PPY@CdS possess stronger driving force than PEDOT@CdS to inject the photogenerated holes in conducting polymer shells. As a result, the polyaniline (PANI) modified PANI@CdS core-shell nanorods demonstrate the most effectively enhanced hydrogen production rate of ∼9.7 mmol h−1 g−1 and effective photocorrosion inhibition in 30 h without deactivation under visible-light irradiation. The hydrogen production performance of PPY@CdS is not effectively promoted owing to the weak transmittance of light for the PPY shell. The PEDOT shell cannot improve the hydrogen production and stability property of the CdS nanorods. This work could shed some light on conducting polymers modifying metal sulfides nanostructures that is of inconceivable significance for effective photocorrosion inhibition and highly enhanced photocatalytic activities.

Sodium-selenium (Na-Se) batteries are a promising substitute for traditional Li-ion batteries due to their high theoretical volumetric capacity (∼3260 mA h cm -3 ). However, shuttle effects and large volume changes still limit their practical applications. Herein, we embed Se clusters in nitrogen-doped hierarchically radial-structured microporous carbon (N-HRMC) derived from a zinc-glutamate metal-organic framework (MOF) for advanced sodium storage. In this carbon-based composite, the micropores and the C-Se and C-O-Se bonds in N-HRMC effectively confine the Se clusters and Na 2 Se during the discharge-charge process. The nitrogen doping in N-HRMC strongly enhances the electrical conductivity of Se and chemical adsorption on Na 2 Se. In particular, density functional theory (DFT) calculations demonstrate that pyridinic-N atoms provide much more chemical adsorption of Na 2 Se than graphitic-N and pyrrolic-N atoms. Consequently, the cathode with Se clusters embedded in N-HRMC deliver a capacity of 612 mA h g -1 after 200 cycles at 0.2C, with cycling stability for >500 cycles and a capacity retention of ∼100% from the 20 th cycle at 0.5C, representing one of the best reported results for Na-Se batteries. Our work here suggests that embedding Se clusters in nitrogen-doped hierarchically structured microporous carbon systems presents an attractive strategy to enhance the capacity and rate capability of Na-Se batteries.

To develop high-performance anode materials of lithium ion batteries (LIBs) for practical high energy application, a grain boundaries enriched hierarchically mesoporous MnO/C microsphere composite has been fabricated by an in-situ carbonization process. The mesoporous MnO/C microsphere is constructed by abundant grains and grain boundaries that are uniformly embedded in a carbon matrix. Such unique nanoarchitecture exhibits high tap density and structural stability, and provides 3D continuous transport pathways for electrons and Li-ions, enabling high electrochemical stability and improved lithium storage kinetics. As a consequence, the mesoporous MnO/C electrode delivers ever-increasing specific capacity (1200 mAh g−1 after 100 cycles at 100 mA g−1) and excellent rate capability (588 mAh g−1 at 2 A g−1). Such superior lithium storage performance suggests that the hierarchically mesoporous MnO/C microsphere electrode should be one of the most promising anode materials for electric vehicle and grid energy storage application.

We report the well-designed active {1 1 0} and {1 1 1} faceted Cu

Metal oxides (MOx) represent one of the most investigated chemiresistive gas sensing platforms in spite of the challenges in selectivity to analytes and interference from humidity (RH). While selectivity is traditionally improved by cross-referencing sensor arrays, interferences from humidity (RH) in ambient environment, to which the majority of the MOx materials are susceptible, cannot be inherently quantified. For standalone MOx sensors, it is therefore difficult to discriminate responses from analytes and humidity. We develop a framework which employs temperature modulation (TM) algorithms and machine learning (ML) approaches using principal component analysis (PCA) and cluster analysis of transient features, to quantify NO2 concentrations under specific RH conditions. With a single inkjet-printed MOx/reduced graphene oxide (rGO) complementary metal-oxide-semiconductor (CMOS)-integrated sensor, we achieve an overall discrimination accuracy of 97.3%. Our approach may enable the development of predictive systems for humidity sensitive sensors under ambient moisture conditions, towards the realisation of low-power, miniaturised adaptive air quality monitoring.

Transition metal oxides with exposed highly active facets have become of increasing interest as anode materials for lithium ion batteries, because more dangling atoms exposed at the active surface facilitate the reaction between the transition metal oxides and lithium. In this work, we probed the electrochemical behavior of hollow Cu2O microspheres with {111} and {110} active facets on the polyhedron surface as anodes for lithium storage. Compared to commercial Cu2O nanoparticles, hollow Cu2O microspheres with {111} and {110} active facets show a rising specific capacity at 30 cycles which then decreases after 110 cycles during the cycling process. Via advanced electron microscopy characterization, we reveal that this phenomenon can be attributed to the highly active {111} and {110} facets with dangling "Cu" atoms facilitating the conversion reaction of Cu2O and Li, where part of the Cu2O is oxidized to CuO during the charging process. However, as the reaction proceeds, more and more formed Cu nanoparticles cannot be converted to Cu2O or CuO. This leads to a decrease of the specific capacity. We believe that our study here sheds some light on the progress of the electrochemical behavior of transition metal oxides with respect to their increased specific capacity and the subsequent decrease via a conversion reaction mechanism. These results will be helpful to optimize the design of transition metal oxide micro/nanostructures for high performance lithium storage.