Hematite Hollow-Sphere-Array Photoanodes for Efficient Photoelectrochemical Water Splitting.

Constructing 3D nanophotonic structures is regarded as an effective method to realize efficient solar-to-hydrogen conversion. These photonic structures can enhance the absorbance of photoelectrodes by the light trapping effect, promote the charge separation by designable charge transport pathway and provide a high specific surface area for catalytic reaction. However, most 3D structures reported so far mainly focused on the influence of light absorption and lacked a systematic investigation of the overall water splitting process. Herein, hematite hollow-sphere-array photoanodes are fabricated through a facile hydrothermal method with polystyrene templates. Validating by simulations and experiments, the hollow sphere array is proved to enhance the efficiency of light harvesting, charge separation and surface reaction at the same time. With an additional annealing treatment in oxygen, a photocurrent density of 2.26 mA cm-2 at 1.23 V versus reversible hydrogen electrode can be obtained, which is 3.70 times larger than that with a planar structure in otherwise the same system. This work gains an insight into the photoelectrochemical water splitting process, which is valuable for the further design of advancing solar driven water splitting devices.

Monolithic Microparticles Facilitated Flower-Like TiO2 Nanowires for High Areal Capacity Flexible Li-Ion Batteries.

Flexible lithium-ion batteries (FLIBs) are intensively studied using free-standing transition metal oxides (TMOs)-based anode materials. However, achieving high areal capacity TMO-based anode materials is yet to be effectively elucidated owing to the poor adhesion of the active materials to the flexible substrate resulting in low active mass loading, and hence low areal capacity is realized. Herein, a novel monolithic rutile TiO2 microparticles on carbon cloth (ATO/CC) that facilitate the flower-like arrangement of TiO2 nanowires (denoted ATO/CC/OTO) is demonstrated as high areal capacity anode for FLIBs. The optimized ATO/CC/OTO anode exhibits high areal capacity (5.02 mAh cm-2 @0.4 mA cm-2 ) excellent rate capability (1.17 mAh cm-2 @5.0 mA cm-2 ) and remarkable cyclic stability (over 500 cycles). A series of morphological, kinetic, electrochemical, in situ Raman, and theoretical analyses reveal that the rational phase boundaries between the microparticles and nanowires contribute to promoting the Li storage activity. Furthermore, a 16.0 cm2 all-FLIB pouch cell assembled based on the ATO/CC/OTO anode and LiNiCoMnO2 cathode coated on ATO/CC (ATO/CC/LNCM) exhibits impressive flexibility under different folding conditions, creating opportunity for the development of high areal capacity anodes in future flexible energy storage devices.

Rational Design of Silicon Nanodots/Carbon Anodes by Partial Oxidization Strategy with High-Performance Lithium-Ion Storage.

Silicon (Si) is considered a promising anode material for rechargeable lithium-ion batteries (LIBs) due to its high theoretical capacity, low working potential, and safety features. However, the practical use of Si-based anodes is hampered by their huge volume expansion during the process of lithiation/delithiation, and they have relatively low intrinsic electronic conductivity, therefore seriously restricting their application in energy storage. Here, we propose a facile approach to directly transform siliceous biomass (bamboo leaves) into a porous carbon skeleton-wrapped Si nanodot architecture through a partial oxidization strategy and magnesium thermal reaction to obtain a high Si nanodot component composite (denoted as Si/C-O). With the synergistic effect of the porous carbon skeleton structure and uniformly dispersed Si nanodots, the Si/C-O composite anode with a stable structure that can avoid pulverization and accommodate volume expansion during cycling is fabricated. As expected, the biomass-converted Si/C-O anode not only presents a high Si component (59.7 wt %) by TGA but also exhibits an excellent capacity of 1013 mAh g-1 at 0.5 A g-1 and robust cycling stability with a capacity retention of 526 mAh g-1 after 650 cycles. Moreover, the Si/C-O anode demonstrates considerable performance in practical LIBs when assembled with a commercial LiNi0.8Co0.1Mn0.1O2 cathode. This work provides an effective strategy and long-term insights into the utilization of porous Si-based materials converted by biomass to design and synthesize high-performance LIB materials.

Electrolyte additive strategy enhancing the electrochemical performance of a soft-packed LiCoO2//graphite full cell.

During the development of high-capacity, ultra-stable battery electrode materials, battery performance, and safety issues are proved to be related to the properties of the electrolyte used. The employment of electrolyte additives is to improve the battery electrolyte properties. Representative commercial two-electrode LiCoO2//graphite pouch cells are used to study electrolyte additives represented by fluoroethylene carbonate (FEC) to improve the electrochemical stability of a commercial pouch full cell. The study reveals that a 1.5% FEC electrolyte additive has the best stability in the voltage range of 3.0-4.2 V.

Turning commercial MnO2 (≥85 wt%) into high-crystallized K+-doped LiMn2O4 cathode with superior structural stability by a low-temperature molten salt method.

The obtainment of low-cost, easily prepared and high-powered LiMn2O4 is the key to achieve its wide application in various electronic devices. In this work, a mild and easily scaled molten salt method (KCl@LiCl) is utilized to convert commercial MnO2 to the high-performance LiMn2O4. At the same reaction temperature, the molten salt method leads to the formation of K+-doped LiMn2O4 with higher crystallinity compared to the conventional solid state method, which contributes to the improved inner charge transfer. The Li3PO4 protective layer is coated on the surface of K+-doped LiMn2O4 to elevate the interfacial stability and the Li+ transfer on interface. Thus, the optimized electrode shows a higher specific discharge capacity (103/60 mAh g-1 at 0.02/2 A g-1) and a longer cyclic life (80 mAh g-1 after 500 cycles at 0.5 A g-1) compared to those of LiMn2O4 by solid state method (49/2 mAh g-1 at 0.02/2 A g-1 and 20 mAh g-1 after 500 cycles at 0.5 A g-1).

Molten salt synthesis of KCl-preintercalated C3N4 nanosheets with abundant pyridinic-N as a superior anode with 10 K cycles in lithium ion battery.

The graphitic carbon nitride is considered as the promising anode of lithium ion battery due to its high theoretical capacity (>1000 mAh g-1) and easy synthesis method. But the electrochemical inactivity and the structural collapse during cycles lead to its poor electrochemical performance in practice. Here, an interesting molten salt method is used to obtain the KCl-preintercalated carbon nitride nanosheets with abundant N vacancies and pyridinic-N. The KCl as a prop enhances the interlayer distance and the structural stability. And the N vacancy and the pyridinic-N increase the conductivity, the active sites and the reversibility of Li+ storage. Thus, the optimized electrode shows a higher specific discharge capacity (389 mAh g-1 at 0.1 A g-1) and a longer cyclic life (66% capacity retention after 10 K cycles at 3.0 A g-1) compared to those of bulk g-C3N4.

Phytic Acid-Based FeCo Bimetallic Metal-Organic Gels for Electrocatalytic Oxygen Evolution Reaction.

Electrocatalysts have been developed to improve the efficiency of gas release for oxygen evolution reaction (OER), and finding a simple and efficient method for efficient electrocatalysts has inspired research enthusiasm. Herein, we report bimetallic metal-organic gels derived from phytic acid (PA) and mixed transition metal ions to explore their performance in electrocatalytic oxygen evolution reaction. PA is a natural phosphorus-rich organic compound, which can be obtained from plant seeds and grains. PA reacts with bimetallic ions (Fe3+ and Co2+ ) in a facile one-pot synthesis under mild conditions to form PA-FeCo bimetallic gels, and the corresponding aerogels are further partially reduced with NaBH4 to improve the electrocatalytic activity. Mixed valence states of Fe(II)/Fe(III) and Co(III)/Co(II) are present in the materials. Excellent OER performance in terms of overpotential (257 mV at 20 mA cm-2 ) and Tafel slope (36 mV dec-1 ) is achieved in an alkaline electrolyte. This reduction method is superior to the pyrolysis method by well maintaining the gel morphology structure. This strategy is conducive to the further improvement of the performance of metal-organic electrocatalysts, and provides guidance for the subsequent application of metal-organic gel electrocatalysts.

Novel Fe4-based metal-organic cluster-derived iron oxides/S,N dual-doped carbon hybrids for high-performance lithium storage.

Metal-organic frameworks (MOFs) have been extensively used in the fabrication of new advanced electrode materials for lithium ion batteries (LIBs). However, low-productivity and high-cost are some of the main challenges of MOF-derived electrodes. Herein, we report a simple solvothermal procedure to fabricate novel Fe4-based metal-organic clusters (Fe-MOCs) with their subsequent conversion to an S,N dual-doped carbon framework incorporating iron oxides under a N2 atmosphere (namely Fe2O3@Fe3O4-SNC). The as-prepared Fe2O3@Fe3O4-SNC composite, owing to the strong interaction between the dual-doped carbon and iron oxides, shows excellent lithium storage performance as an anode with high pseudocapacitance. Furthermore, DFT computational analyses confirm that the hybrid shows excellent adsorption ability with a low energy barrier due to strong electronic interactions between the iron oxides and S,N-doped carbon matrix. In addition, Fe2O3@Fe3O4-SNC-based LIB shows high energy and power densities at the full-cell level, confirming this synthesis strategy to be a promising approach towards MOC-derived electrode materials for their application in LIBs and beyond-lithium batteries.

Correction: Super-large dendrites composed of trigonal PbO2 nanoplates with enhanced performances for electrochemical devices.

Correction for 'Super-large dendrites composed of trigonal PbO2 nanoplates with enhanced performances for electrochemical devices' by Liang-Xin Ding et al., Chem. Commun., 2012, 1275-1277, DOI: 10.1039/C2CC15271A.

Defect Engineering Enhances the Charge Separation of CeO2 Nanorods toward Photocatalytic Methyl Blue Oxidation.

Defect-rich photocatalytic materials with excellent charge transfer properties are very popular. Herein, Sm-doped CeO2 nanorods were annealed in a N2 atmosphere to obtain the defective Sm-doped CeO2 photocatalysts (Vo-Sm-CeO2). The morphology and structure of Vo-Sm-CeO2 were systematically characterized. The Vo-Sm-CeO2 nanorods demonstrated an excellent photodegradation performance of methyl blue under visible light irradiation compared to CeO2 nanorods and Sm-CeO2. Reactive oxygen species including OH, ·O2-, and h+ were confirmed to play a pivotal role in the removal of pollutants via electron spin resonance spectroscopy. Doping Sm enhances the conductivity of CeO2 nanorods, benefiting photogenerated electrons being removed from the surface reactive sites, resulting in the superior performance.

Correction: Cu2O template synthesis of high-performance PtCu alloy yolk-shell cube catalysts for direct methanol fuel cells.

Correction for 'Cu2O template synthesis of high-performance PtCu alloy yolk-shell cube catalysts for direct methanol fuel cells' by Sheng-Hua Ye et al., Chem. Commun., 2014, 50, 12337-12340, DOI: 10.1039/C4CC04108A.

Correction to Boosting the Oxygen Evolution Reaction Activity of NiFe2O4 Nanosheets by Phosphate Ion Functionalization.

[This corrects the article DOI: 10.1021/acsomega.8b03081.].

Correction: Efficient photocatalytic hydrogen evolution over hydrogenated ZnO nanorod arrays.

Correction for 'Efficient photocatalytic hydrogen evolution over hydrogenated ZnO nanorod arrays' by Xihong Lu et al., Chem. Commun., 2012, 48, 7717-7719, DOI: .

Large-Scale Electric-Field Confined Silicon with Optimized Charge-Transfer Kinetics and Structural Stability for High-Rate Lithium-Ion Batteries.

The stereospecific design of the interface effects can optimize the electron/Li-ion migration kinetics for energy-storage materials. In this study, an electric field was introduced to silicon-based materials (C-SiOx@Si/rGO) through the rational construction of multi-heterostructures. This was achieved by manipulating the physicochemical properties at the atomic level of advanced Li-ion batteries (LIBs). The experimental and density functional theory calculations showed that the unbalanced charge distribution generated a large potential difference, which in turn induced a large-scale electric-field response with a boosted interfacial charge transfer in the composite. The as-prepared C-SiOx@Si/rGO anode showed advanced rate capability (i.e., 1579.0 and 906.5 mAh g-1 at 1000 and 8000 mA g-1, respectively) when the migration paths of the Li-ion/electrons hierarchically optimized the large electric field. Furthermore, the C-SiOx@Si/rGO composite with a high SiOx@Si mass ratio (73.5 wt %) demonstrated a significantly enhanced structural stability with a 40% volume expansion. Additionally, when coupled with the LiNi0.8Co0.1Mn0.1O2 (NCM) cathode, the NCM//C-SiOx@Si/rGO full cell delivers superior Li-ion storage properties with high reversible capacities of 157.6 and 101.4 mAh g-1 at 500 and 4000 mA g-1, respectively. Therefore, the electric-field introduction using optimized electrochemical reaction kinetics can assist in the construction of other high-performance LIB materials.

Imine Gels Based on Ferrocene and Porphyrin and Their Electrocatalytic Property.

A series of porphyrin-based imine gels have been synthesized via dynamic covalent gelation between 5,10,15,20-tetra(4-aminophenyl)-21H,23H-porphyrin (H2 TAPP) derivatives and various aldehyde compounds. The porphyrin-ferrocene imine gels based on MTAPP (M=H2 , Ni2+ , Co2+ , Pd2+ and Zn2+ ) and ferrocene-1,1'-dicarbaldehyde (NA) display efficient HER, OER and ORR activities in alkaline media. Among the gels, CoTAPP-NA shows an HER current density of 10 mA cm-2 at low overpotential of 470 mV and small Tafel slope of 110 mV decade-1 in alkaline media. CoTAPP-NA also exhibits OER catalytic activity with low overpotential (416 mV for 10 mA cm-2 ). CoTAPP-NA shows ability in overall water splitting in alkaline media. In addition, CoTAPP-NA exhibits onset potential (Ep ) of 0.95 V and half-wave potential (E1/2 ) of 0.84 V in 1.0 mol L-1 KOH solution for oxygen reduction. Moreover, the gel catalyst shows good stability.

Enhancing Catalytic Activity and Selectivity by Plasmon-Induced Hot Carriers.

Plasmon-assisted chemical transformation holds great potential for solar energy conversion. However, simultaneous enhancement of reactivity and selectivity is still challenging and the mechanism remains mysterious. Herein, we elucidate the localized surface plasmon resonance (LSPR)-induced principles underlying the enhanced activity (∼70%) and selectivity of photoelectrocatalytic redox of nitrobenzene (NB) on Au nanoparticles. Hot carriers selectively accelerate the conversion rate from NB to phenylhydroxylamine (PHA) by ∼14% but suppress the transformation rate from PHA to nitrosobenzene (NSB) by ∼13%. By adding an electron accepter, the as-observed suppression ratio is substantially enlarged up to 43%. Our experiments, supported by in situ surface-enhanced Raman spectroscopy and density functional theory simulations, reveal such particular hot-carrier-induced selectivity is conjointly contributed by the accelerated hot electron transfer and the corresponding residual hot holes. This work will help expand the applications of renewable sunlight in the directional production of value-added chemicals under mild conditions.