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The spinel Co3O4 has emerged as a promising alternative to noble-metal-based electrocatalysts for electrochemical water electrolysis in alkaline medium. However, pure Co3O4, despite having high activity in anodic water oxidation, remains inactive toward the hydrogen evolution reaction (HER). Here, a Ni-doped Co3O4 (Co3-xNixO4) prepared by a simple method exhibits favorable HER activity and stability (>300 h, whether in 1 M KOH or the realistic 30 wt % KOH solution) after in situ electrochemical activation, outperforming almost all of the oxide-based electrocatalysts. More importantly, using the combination of in situ Raman spectroscopy and multiple high-resolution electron microscopy techniques, it is identified that the surface of Co3-xNixO4 crystals is reduced into intertwined CoyNi1-yO nanoparticles with highly exposed {110} reactive planes. Density functional theory calculations further prove that the Ni- doped CoO component in CoyNi1-yO plays a major role during the alkaline HER, because the introduction of Ni atoms into Co-O octahedra can optimize the electrical conductivity and tailor the adsorption/desorption free energies of H-ad and OHad intermediates.

Metal organic frameworks (MOFs) have emerged as a novel template to develop porous photocatalytic materials for solar fuel conversion. In this work, we report the synthesis, charge separation dynamics, and photocatalytic performance of the TiO2/CuO heterostructure derived from mixed-phase MOFs based on Ti and Cu metal nodes, which demonstrates significantly enhanced catalytic activity for the hydrogen evolution reaction (HER) compared to metal oxides derived from single node MOFs. More importantly, using transient absorption spectroscopy, we identified the specific role each component in the heterostructure plays and unravelled the key intermediate species that is responsible for the exceptional photocatalytic activity of the heterostructure. We found that the HER is initiated with ultrafast electron transfer (

Metal-organic frameworks (MOFs) represent an emerging class of platforms to assemble single site photocatalysts for artificial photosynthesis. In this work, we report a new CO2 reduction photocatalyst (UiO-68-Fe-bpy) based on a robust Zr(iv)-MOF platform with incorporated Fe(bpy)Cl3 (bpy refers to the 4'-methyl-[2,2'-bipyridine] moiety) via amine-aldehyde condensation. We show that this hybrid catalyst can reduce CO2 to form CO under visible light illumination with excellent selectivity and enhanced activity with respect to its parent MOF and corresponding homogeneous counterpart. Using steady state and transient absorption (TA) spectroscopy, we show that the enhanced photocatalytic activity of UiO-68-Fe-bpy is attributed to the elongated excited state lifetime of Fe(bpy)Cl3 after being incorporated to the UiO-68-NH2 platform. This work demonstrates the great potential of MOFs as a next generation platform for solar fuel conversion.

The intrinsic activity and durability of oxygen evolution reaction (OER) electrocatalysts are mainly dominated by the surface and interface properties of active materials. Herein, a core-shell heterogeneous structure (NF/[email protected]2O3) is fabricated via two-step hydrothermal method, which exhibits a low overpotential of 220 mV (or 282 mV) at 10 mA/cm2 (or 200 mA/cm2), a small Tafel slope of 36.9 mV/dec, and long-term stability (~230 h) in 1 mol/L KOH for OER. X-ray photoelectron spectroscopy and X-ray absorption spectroscopy reveal the (oxy)hydroxide-rich surface and strong coupling interface between NiSe and Fe2O3 via the Fe-Se bond. Density functional theory calculation suggests that the d-band center and electronic state of [email protected]2O3 heterojunction are well optimized due to the formation of Fe-Se bond, which is favorable for the enhanced OER activity because of the easy adsorption of oxygen-containing intermediates and desorption of O2 in the OER process. In addition, the unique core-shell structure and robust bonding interface are responsible for the good stability for OER. This work provides fundamental insights on the bonding effect that determine the performance of OER electrocatalyst.

Nanostructured hollow materials have emerged as a promising class of materials for energy conversion and storage. In this work, we report a Co3O4 hollow sphere nanostructure that can serve as a CO2...

A gas-phase approach to form Zn coordination sites on metal-organic frameworks (MOFs) by vapor-phase infiltration (VPI) was developed. Compared to Zn sites synthesized by the solution-phase method, VPI samples revealed approximately 2.8 % internal strain. Faradaic efficiency towards conversion of CO2 to CO was enhanced by up to a factor of four, and the initial potential was positively shifted by 200-300 mV. Using element-specific X-ray absorption spectroscopy, the local coordination environment of the Zn center was determined to have square-pyramidal geometry with four Zn-N bonds in the equatorial plane and one Zn-OH2 bond in the axial plane. The fine-tuned internal strain was further supported by monitoring changes in XRD and UV/Visible absorption spectra across a range of infiltration cycles. The ability to use internal strain to increase catalytic activity of MOFs suggests that applying this strategy will enhance intrinsic catalytic capabilities of a variety of porous materials.

Zeolitic imidazolate frameworks (ZIFs) represent a novel class of porous crystalline materials that have demonstrated potential as light harvesting materials for solar energy conversion. In order to facilitate their application in solar energy conversion, it is necessary to expand their absorption further into the realm of the solar spectrum. In this work, we report the incorporation of semiconductor cadmium sulfide nanowires (CdS NWs) into ZIF-67 (CdS@ZIF-67), where a broader region of the solar spectrum can be absorbed by CdS NWs and relayed to ZIF-67 through an energy transfer (EnT) process. Using steady-state emission and time resolved emission and absorption spectroscopy, we show that efficient EnT can occur from CdS NWs to ZIF-67 by selective excitation of CdS NWs. The EnT time is ∼729.9 ps, which corresponds to 71.2% EnT efficiency.

Zeolitic Imidazolate frameworks (ZIFs) have been demonstrated as promising light harvesting and photocatalytic materials for solar energy conversion. To facilitate their application in photocatalysis, it is essential to develop a fundamental understanding of their light absorption properties and energy transfer dynamics. In this work, we report distance-dependent energy transfer dynamics from a molecular photosensitizer (RuN3) to ZIF-67, where the distance between RuN3 and ZIF-67 is finely tuned by depositing an ultrathin Al2O3 layer on the ZIF-67 surface using an atomic layer deposition (ALD) method. We show that energy transfer time decreases with increasing distance between RuN3 and ZIF-67 and the Förster radius is estimated to be 14.4 nm.

Metal organic frameworks (MOFs) have emerged as a novel platform offering new promise for photocatalytic applications. In this work, we report a mixed-node MOF (MOF-74) based on earth-abundant meta...

In this work, ruthenium (Ru) catalysts supported on CeO2 nanorods (NR), nanocubes (NC), and nanoctahedra (NO) were comparatively investigated to correlate the shape and exposed surface planes ({100...

Particle size-tuned photocatalytic activity has been recognized for noble metals such as platinum; however, it is not established for metal–organic frameworks (MOFs). In this work, nanoscaled MOF M...

In this work, we report the design and photophysical properties of a unique class of Ni porphyrins, in which the tert-butyl benzene substituents at the meso positions of the macrocycle were tethered by ethers with alkyl linkers. This not only results in the permanently locked ruf distortion of the macrocycle but also enables the engineering of the degree of distortion through varying the length of alkyl linkers, which addressed the complication of uncertainty in the specific structural distortions that has long plagued the porphyrin photophysical community. Using advanced time-resolved optical and X-ray absorption spectroscopy, we observed tunability in the excited-state relaxation pathway depending on the degree of distortion and characterized the associated transient intermediate structure. These findings provide a new avenue to afford accessibility to a wide range of excited-state properties in nonplanar porphyrins.

Conductive metal organic frameworks (MOFs) are a promising class of porous crystalline materials for photocatalytic applications. We report direct evidence of a charge transport (CT) mechanism in 2D Cu-THQ MOFs using a combination of terahertz (THz) and transient absorption spectroscopies. Zn2+ ions were added to this MOF in order to understand their impact on CT, ultimately causing a decrease in conductivity. This work provides insight into the rational design of 2D MOFs for photoelectronic and photocatalytic applications.

Metal organic frameworks (MOFs) have emerged as promising photocatalytic materials for solar energy conversion. However, a fundamental understanding of light harvesting and charge separation (CS) dynamics in MOFs remains underexplored, yet they are key factors that determine the efficiency of photocatalysis. Herein, we report the design and CS dynamics of the Ce–TCPP MOF using ultrafast spectroscopic methods.

We report a facile synthesis of carbon quantum dot (CQD)-sensitized TiO2/Pt nanocomposites as efficient and robust photocatalysts for light-driven proton reduction from water. We show that this met...

Metal organic frameworks (MOFs), an emerging class of nanoporous crystalline materials, have become increasingly attractive for solar energy applications. In this work, we report a newly designed mixed-node MOF catalyst, CoxFe1–x-MOF-74 (0 < x ≤ 1), which acts as a highly efficient electrocatalyst for oxygen evolution reaction (OER) in alkaline solution with remarkably low overpotential (280 mV at a current density of 10 mA/cm2), small Tafel slope (56 mV/dec), and high faradic efficiency (91%) and can deliver a current density of 20 mA/cm2 at 1.58 V for overall water splitting. Moreover, using the combination of multiple spectroscopic methods, including X-ray absorption, electron spin resonance, and X-ray photoelectron spectroscopy, etc., we unraveled the mechanistic origin of the enhanced catalytic performance of CoxFe1–x-MOF-74 compared to its single-metal counterparts. We show the mixed-node MOF can provide more open metal sites and an enhanced electron-rich environment, which facilitates efficient cha...

In this work, we report a new single-site photocatalyst (Co-Ru-UIO-67(bpy)) based on a metal–organic framework platform with incorporated molecular photosensitizer and catalyst. We show that this catalyst not only demonstrates exceptional activity for light-driven H2 production but also can be recycled without loss of activity. Using the combination of optical transient absorption spectroscopy and in situ X-ray absorption spectroscopy, we not only captured the key CoI intermediate species formed after ultrafast charge transfer from the incorporated photosensitizer but also identified the rate-limiting step in the catalytic cycle, providing insight into the catalysis mechanism of these single-site metal–organic framework photocatalysts.

Metal–organic frameworks (MOFs) have emerged as novel scaffolds for artificial photosynthesis due to their unique capability in incorporating homogeneous photosensitizer and catalyst to their robust heterogeneous matrix. In this work, we report the charge separation dynamics between molecular Ru-photosensitizer and Pt-catalyst, both of which were successfully incorporated into a Zr-MOF that demonstrates excellent activity and stability for light-driven H2 generation from water. Using optical transient absorption (OTA) spectroscopy, we show that charge separation in this hybrid MOF occurs via electron transfer (ET) from Ru-photosensitizer to Pt-catalyst. Using Pt L3-edge X-ray transient absorption (XTA) spectroscopy, we observed the intermediate reduced Pt site, directly confirming the formation of charge separated state due to ET from Ru-photosensitizer and unraveling their key roles in photocatalysis.

Owing to their porous structure and tunable framework, zeolitic imidazolate frameworks (ZIFs) have garnered considerable attention as promising photocatalytic materials. However, little is known regarding their photophysical properties. In this work, we report the photoinduced charge separation dynamics in a ZIF-67 thin film through interfacial electron transfer (ET) to methylene blue (MB+) via ultrafast transient absorption spectroscopy. We show that the ET process occurs through two distinct pathways, including an ultrafast (

In this work, we report the direct correlation of photoinduced carrier dynamics and electronic structure of CuInS2 (CIS) nanoparticles (NPs) using the combination of multiple spectroscopic techniques including steady-state X-ray absorption spectroscopy (XAS), optical transient absorption (OTA), and X-ray transient (XTA) absorption spectroscopy. XAS results show that CIS NPs contain a large amount of surface Cu atoms with ≪four-coordination, which is more severe in CIS NPs with shorter nucleation times, indicating the presence of more Cu defect states in CIS NPs with smaller size particles. Using the combination of OTA and XTA spectroscopy, we show that electrons are trapped at states with mainly In or S nature while holes are trapped in sites characteristic of Cu. While there is no direct correlation of ultrafast trapping dynamics with NP nucleation time, charge recombination is significantly inhibited in CIS NPs with larger particles. These results suggest the key roles that Cu defect sites play in carri...

In this work, we report water-soluble CuInS2/ZnS nanoparticles (NPs) as intrinsic single-component photocatlaysts for light-driven hydrogen generation. In the presence of ascorbic acid (AA), this catalyst can efficiently generate H2 from water with an exceptionally long lifetime (≫84 h). Mechanistic insight into the catalysis revealed by transient absorption spectroscopy demonstrates that the catalytic cycle initiates by a reductive quenching process through electron transfer from AA to CuInS2/ZnS NPs, which is followed by a rate limiting step, i.e., proton reduction from electrons in the conduction band/defect states of the CuInS2/ZnS NPs.

Zeolitic imidazolate frameworks (ZIFs) are a subclass of metal organic frameworks that have attracted considerable attention in the past years and have found many applications including heterogeneous catalysis due to their highly ordered porous structure, large surface area, and structural flexibility. However, ZIFs are largely utilized as simple hosts or passive media for dispersing other catalytically active species, resembling the roles of zeolites in catalysis. In contrast, our recent findings show that ZIFs not only have broad absorption across the UV-visible and near IR spectral region but also have an exceptionally long-lived excited charge separated state, suggesting that ZIFs may be used as intrinsic light harvesting and photocatalytic materials rather than as inert hosts. This Perspective will focus on the recent progress on the fundamental studies of the intrinsic light absorption, charge separation, and photocatalytic properties of ZIFs and will discuss the outlook for future development.

In this work, we report a new photocatalytic system that links multifunctional semiconductor nanocrystals with emerging water-soluble molecular catalysts made of earth-abundant elements for H2 generation [Ni(P2RN2R′)2(BF4)2]4−, R = Ph, R′ = [PhSO3]− (NiS). This noble metal free hybrid exhibits remarkable catalytic activity with a turnover number of 511 for H2 production and a photon-to-H2 conversion efficiency of 12.5%. The mechanistic insight into such high efficiency in this photocatalytic system was examined using a combination of steady-state emission and time-resolved absorption spectroscopy.

A rational design of highly active and robust catalysts based on earth-abundant elements for hydrogen evolution reaction (HER) is essential for future renewable energy applications. Herein, we report the synthesis of a new class of ultrathin metallic CuFeS2 nanosheets (NSs) with abundant exposed high-index {04} facets. They serve as a robust catalyst for the HER with a lower onset potential of 28.1 mV, an overpotential of only 88.7 mV (at j = 10 mA cm−2) and remarkable long-term stability in 0.5 M H2SO4, which make them the best system among all the reported non-noble metal catalysts. The theoretical calculations reveal that the mechanistic origin for such a high HER activity should be attributed to the excess S2− active sites on the exposed {04} high-index facets of CuFeS2 NSs, which have a rather favorable Gibbs free energy for atomic hydrogen adsorption. The present work highlights the importance of designing ultrathin metallic chalcopyrite nanosheets with high-index facets in order to increase the number of active sites for boosting the HER performance.

Zeolitic imidazolate frameworks (ZIFs) with intrinsic photoactivity represent an excellent scaffold for a single-site photocatalytic center. However, their application in visible-light-driven photocatalysis is hampered by their light-harvesting ability due to limited coverage in the realm of the solar spectrum and relatively low extinction coefficient. In this work, we report the first example of the enhanced light-harvesting property of ZIF-67 via energy transfer from a molecular photosensitizer, that is, the RuN3 complex, sensitized on the surface of ZIF-67. Using transient absorption spectroscopy, we show that energy transfer occurs from the excited RuN3 to ZIF-67 with ∼86.9% efficiency. More importantly, this RuN3/ZIF-67 hybrid system exhibits significantly enhanced photocatalytic activity for H2 production from water, which can be attributed to efficient energy transfer from RuN3.

Engineering catalytic sites at the atomic level provides an opportunity to understand the catalyst’s active sites, which is vital to the development of improved catalysts. Here we show a reliable and tunable polyoxometalate template-based synthetic strategy to atomically engineer metal doping sites onto metallic 1T-MoS2, using Anderson-type polyoxometalates as precursors. Benefiting from engineering nickel and oxygen atoms, the optimized electrocatalyst shows great enhancement in the hydrogen evolution reaction with a positive onset potential of ~ 0 V and a low overpotential of −46 mV in alkaline electrolyte, comparable to platinum-based catalysts. First-principles calculations reveal co-doping nickel and oxygen into 1T-MoS2 assists the process of water dissociation and hydrogen generation from their intermediate states. This research will expand on the ability to improve the activities of various catalysts by precisely engineering atomic activation sites to achieve significant electronic modulations and improve atomic utilization efficiencies., While heterogeneous catalysts can act as tangible, efficient materials for energy conversion, understanding the active catalytic sites is challenging. Here, authors engineer specific catalytic sites into molybdenum sulfide to improve and elucidate hydrogen evolution electrocatalysis.

Doping with electron-rich elements in BiVO4 photoanodes has been demonstrated as a desirable approach for improving their carrier mobility and charge separation efficiency. However, the effect of doping and dopant concentration on the carrier dynamics and photoelectrochemical performance remains unclear. In this work, we examined the effects of Mo doping on the charge separation dynamics and photocurrent performance in BiVO4 photoanodes. We show that the photocurrent of BiVO4 photoanodes increases with increasing concentration of the Mo dopant, which can be attributed to both the improved carrier mobility resulting from increased electron density and charge separation efficiency due to the diminishing of trap states upon Mo doping. The effect of doping on the electronic structure, carrier dynamics and photocurrent performance of BiVO4 photoanodes resulting from W and Mo dopants was also compared and discussed in this study. The knowledge gained from this work will provide important insights into the optimization of the carrier mobility and charge separation efficiency of BiVO4 photoanodes by controlling the dopants and their concentrations.

Deep magnetic field is the key factor to carry out the application of electromagnetic cauterization in thermotherapy of tumor in deep human body. This article proposes a coil design for generating deep magnetic field. The new designated coil is wrapped up by high permeability magnetic material powder so that the generated alternating magnetic field is much more focused, thereby generating higher magnetic flux density. Through the assistance of this magnetic field, a deeper position to cauterize the targeted tumor tissues is thus reached. Experimental results confirm that the magnetic material-wrapped coil has a better heating effect than a naked coil without wrapping any magnetic material. By using this design to heat the positions at the distance of 6 cm and 10 cm, the net temperature generations are measured to be 198.1°C and 34.2°C, while the temperature rise rates are 34.03% and 16.72%, respectively. This magnetic-wrapped coil design takes only a 0.41% inductance more than the naked one, yet the magnetic fields can be highly increased. As a result, the requirement of supplying-power can be reduced, meanwhile exhibiting feasibility and practicality of the method for the application considered.

Water soluble CuInS2/ZnS quantum dots (QDs) represent one of the most promising single component photocatalysts for the hydrogen evolution reaction (HER). In this work, we report the effect of cation composition in CuInS2/ZnS QDs on the carrier relaxation and charge separation dynamics as well as their photocatalytic performance for the HER. With decreasing Cu to In ratio (increasing Cu deficiency), we observed slightly faster electron trapping and carrier recombination but significantly improved photocatalytic activity for the HER. This can be attributed to the enhanced electron transfer (ET) from the sacrificial donor to CuInS2/ZnS QDs resulting from the lower valence band (larger driving force for ET) of QDs with higher Cu deficiency. This work not only provides important insight into the mechanistic origins of the HER but also demonstrated that altering the composition in CuInS2/ZnS QDs is a viable approach to further improve their performance for solar to fuel conversion.

A rapid charge strategy based on the residual energy evaluation is proposed for LiFePO $_{4}$ (LFP) batteries to reduce charging time and improve charging performance. In the approach, the residual energy model was formulated based on the measured terminal voltage with respect to a certain state of charge value. Subsequently, the stored energy of an LFP battery was evaluated by using the obtained voltage characterizations. This is followed by the difference calculated between the fully stored energy and the residual energy such that the suitable time to enact the high-rate charge is determined, thereby ensuring a battery of full capacity in stable, safe, and nonovercharged conditions. Moreover, for the hysteresis effects that may affect the battery voltage evaluation, they are also included in the charge process in this study. In order to validate the method, this proposed strategy has been examined from perspectives of charge time, charge efficiency, and the number of charge cycles. Compared with other charge strategies, both the charge time and the charge efficiency are highly improved, hence confirming the feasibility of the method for energy storage applications.

The cobalt phosphate “CoPi” oxygen evolving catalyst (OEC) was photochemically grown on the surface of TiO2 photoanodes short-circuited to a Pt wire under bandgap illumination in the presence of Co(NO3)2 and sodium phosphate (NaPi) buffer. Extended photodeposition (15 h) using a hand-held UV lamp readily permitted quantitative structural and electrochemical characterization of the photochemically deposited CoPi OEC on titania. The formed catalytic material was characterized by scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectroscopy experiments, illustrating the production of easily visualized micrometer scale clusters throughout the titania surface containing both cobalt and phosphate. X-ray absorption fine structure (XAFS) and X-ray absorption near edge structure (XANES) studies indicated that the newly formed material was structurally consistent with the production of molecular cobaltate clusters composed of a cobalt oxide core that is most likely terminated by phosphate ions. ...

The role of the interface-bound charge-separated pair (IBCSP) in electron transfer at molecule/inorganic semiconductor interface remains poorly understood despite the importance of its counterpart in the solution-phase charge-separation process. To probe their role, we have compared the dynamics of electron transfer from C343 to TiO2, SnO2, and ZnO nanocrystalline thin films. The decay of the C343 excited state and the formation of oxidized C343 are measured by transient visible absorption to follow the rate of charge separation across the interface to form the IBCSPs. The dissociation of IBCSPs to form free electrons in semiconductor is probed by the free-carrier absorption in the mid-IR. For C343 on TiO2 and SnO2, the rate of the overall electron-transfer process is determined by the rate of the initial charge separation across the interface to form the IBCSP, which dissociates with negligible lifetime. The charge-separation rates are instrument-response-function limited (

Interfacial electron transfer (ET) dynamics from excited rhodamine B (RhB) to three semiconductor nanocrystalline thin films (In2O3, SnO2, and ZnO) was investigated to examine their dependence on semiconductors. The injected electrons in the semiconductors were directly measured by their transient absorption in the mid-IR region (∼5 μm), and the evolution of the adsorbate in its ground, excited, and cation states was monitored by its transient absorption in the visible region. The formation of the IR absorption of injected electrons correlates well with the decay of the RhB excited state, allowing an unambiguous determination of electron injection rates from the adsorbate excited state to the semiconductor nanoparticles. The recombination processes were monitored by following the decay of injected electrons and RhB cations and the recovery of the RhB molecules in the ground state. The effects of dye aggregation and excited-state quenching on the injection dynamics were also examined and were shown to be n...

Pd/titanium dioxide nanombes (Pd/TiO(2)-NTs) catalysts were prepared by a simple reduction method using TiO(2)-NTs as support. The structure and morphology of the resulting Pd/TiO(2)-NTs were characterized by transmission electron microscopy and X-ray diffraction. The results showed that Pd nanoparticles with a size range from 6 to 13 nm were well-dispersed on the surface of TiO(2)-NTs. The electrocatalytic properties of Pd/TiO(2)-NTs catalysts for hydrazine oxidation were also investigated by cyclic voltammetry. Compared to that of pure Pd particles and Pd/TiO(2) particles, Pd/TiO(2)-NTs catalyst showed much higher electrochemical activity. This may be attributed to the uniform dispersion of Pd nanoparticles on TiO(2)-NTs, smaller particle size and unique properties of TiO(2)-NTs support. In addition, the mechanism of hydrazine electrochemical oxidation catalyzed by Pd/TiO(2)-NTs are also investigated. The oxidation of hydrazine was an irreversible process, which might be controlled by diffusion process of hydrazine. (C) 2007 Published by Elsevier B.V.

In this work, we investigated photoinduced charge separation dynamics in a CdSe quantum dot/cobaloxime molecular catalyst hybrid using the combination of transient optical (OTA) and X-ray absorption (XTA) spectroscopy. We show that ultrafast charge separation occurs through electron transfer (ET) from CdSe QDs to cobaloxime. In addition to the enhanced 1S exciton bleach recovery in CdSe QDs due to the presence of cobaloxime, the direct evidence for ET process, i.e. the formation of the transient charge separated state, is captured by XTA. These results not only demonstrate the capability of XTA to capture the transient species during the photoinduced reactions in hybrid nanostructures but also enhance our understanding of charge separation dynamics in semiconductor nanocrystal/molecular catalyst hybrid.

Ni(OH)2 have emerged as important functional materials for solar fuel conversion because of their potential as cost-effective bifunctional catalysts for both hydrogen and oxygen evolution reactions. However, their roles as photocatalysts in the photoinduced charge separation (CS) reactions remain unexplored. In this paper, we investigate the CS dynamics of a newly designed hybrid catalyst by integrating a Ru complex with Ni(OH)2 nanoparticles (NPs). Using time resolved X-ray absorption spectroscopy (XTA), we directly observed the formation of the reduced Ni metal site (~60 ps), unambiguously demonstrating CS process in the hybrid through ultrafast electron transfer from Ru complex to Ni(OH)2 NPs. Compared to the ultrafast CS process, the charge recombination in the hybrid is ultraslow (≫50 ns). These results not only suggest the possibility of developing Ni(OH)2 as solar fuel catalysts, but also represent the first time direct observation of efficient CS in a hybrid catalyst using XTA.

Well-coated single-walled carbon nanotube (SWNT) with polyaniline (PANI) composite electrodes with good uniformity for electrochemical capacitors are prepared by the polymerization of aniline containing well-dissolved SWNTs. The capacitance properties are investigated with cyclic voltammetry, charge–discharge tests and ac impedance spectroscopy. The composite electrode shows much higher specific capacitance, better power characteristics and is more promising for application in capacitor than pure PANI electrode. The effect and role of SWNT in the composite electrode are also discussed in detail.

LiMnO2 nanowire arrays were prepared using a porous anodic aluminum oxide (AAO) template from a sol–gel solution containing Li(OAc) and Mn(OAc)2. Electron-microscope results showed that a uniform length and diameter of LiMnO2 nanowires were obtained, and the length and diameter of the LiMnO2 nanowires are dependent on the pore diameter and the thickness of the applied AAO template. X-ray diffraction and electron diffraction pattern investigations demonstrate that LiMnO2 nanowires are a layered structure of LiMnO2 crystal. X-ray photoelectron spectroscopy analysis indicates that a material closely resembling stoichiometric layered LiMnO2 has been obtained.

Single-walled carbon nanotube (SWNT)/polyaniline (PANI) composite films with good uniformity and dispersion were prepared by electrochemical polymerization of aniline containing well-dissolved SWNTs. The results of atomic force microscopy (AFM) and UV–Vis adsorption spectroscopy show that aniline can be used to solubilize SWNTs via formation of donor–acceptor complexes. The electrochemical deposition of SWNT–aniline solutions have been investigated by cyclic voltammetry. The results show that SWNT-based aniline solutions exhibit a drastic increase in peak current within the potential scanning region. The doping effect of SWNTs on PANI films was investigated by electrochemistry and FTIR spectroscopy. The results indicate that the enhanced electroactivity and conductivity of the SWNT/PANI composite films may be due to the strong interaction between SWNTs and PANI, which facilitates the effective degree of electron delocalization.

LiNiO 2 nanowire arrays were prepared with porous anodic aluminum oxide (AAO) templates from sol–gel solution containing Li(OAc) and Ni(OAc) 2 . Electron microscope results showed that uniform length and diameter of LiNiO 2 nanowires were obtained, and the length and diameter of the LiNiO 2 nanowires are dependent on the pore diameter and the thickness of the applied AAO template. X-ray diffraction (XRD) and electron diffraction investigations demonstrate that the LiNiO 2 nanowires have the layered structure of LiNiO 2 . X-ray photoelectron spectroscopy (XPS) analysis indicates that a nearly stoichiometric layered LiNiO 2 material has been obtained.

This paper proposes a contactless energy-transfer system (CETS) for lithium iron phosphate battery-charging circuits. In the study, the design flow of contactless transformers and compensated circuit are investigated through the analysis of their impedance-matching and resonant features, by which the appropriate inductive coils can be optimally determined such that power transmission efficiency can be increased. Moreover, an algorithm of charging strategy is integrated into the microcontroller chip to facilitate the charging process. From theoretical analysis and hardware realization, they help support the proposed approach applied for the performance improvement of lithium iron phosphate battery-charging applications.

We present three methods of measuring the velocity of ultrasound in self-supported thin films (1 μm or thicker). The first method involves time-of-flight measurements of sound pulses excited by a pulsed laser. These pulses are detected with a wide band laser interferometer and we measure the propagation delay time as a function of the path length. In the second method, we continuously excite the film using an interdigital transducer (IDT) while performing narrow band detection using the laser interferometer. The interferometer allows us to determine the position dependence of both the in-phase and the out-of-phase components of the film vibration (relative to the emitted signal). The third method is similar to the second, but both the generation and the detection of the ultrasonic wave are accomplished with IDTs. The receiving IDT is translated across the surface of the film and the ultrasonic continuity is maintained through a liquid bond. All three methods have been tested on the same film and yield similar values (within experimental limits) of the velocity of sound of the various modes excited. From these results, we deduce the shear and flexural moduli of the film and compare them with values quoted in the literature.