Ru@N/S/TiO2/rGO: a high performance HER electrocatalyst prepared by dye-sensitization.

Hydrogen production from water-splitting is one of the most promising hydrogen production methods, and the preparation of the hydrogen evolution reaction (HER) catalyst is very important. Although Pt-based materials have the best catalytic activity for HER, their high price and scarcity greatly limit their large-scale industrial application prospects. Herein, a new method to prepare HER catalyst is described, where dyes used in dye-sensitized solar cells (DSSCs) were used as precursors. A high performance HER catalyst (Ru@N/S/TiO2/rGO, Ru nanoparticles (NPs) supported on N/S-doped TiO2/rGO hybrids) was prepared, and the stereoscopic molecular structure of the porphyrin dye, JR1, not only provides a prerequisite for the preparation of the hyperdispersed Ru NPs, but also successfully realizes N/S co-doping. The Ru@N/S/TiO2/rGO shows an excellent catalytic performance for the HER, which is almost the same as that with Pt/C. In 0.5 M H2SO4, the overpotential is 60 mV at 10 mA cm-2, and the Tafel slope is only 51 mV dec-1. In 1 M KOH, the overpotential is only 5 mV at 10 mA cm-2, and the Tafel slope is only 45 mV dec-1, and this performance is much better than most of the HER catalysts that have been reported. When Ru@N/S/TiO2/rGO is utilized as a catalyst in an alkaline water electrolyzer, a bias of only 1.52 V is able to complement overall water-splitting at 10 mA cm-2 (1.78 V, 100 mA cm-2). The molecular structure and coordination metal species of the dyes are easy to adjust, and the the stereoscopic structure is very helpful for inhibiting the aggregation of the metal NPs, and the strong anchoring effect with TiO2 or other carbon materials is also very helpful to achieve heteroatom doping. In addition, the process of dye-sensitization is simple and repeatable, and is a novel and efficient method to prepare the electrocatalyst.

Self-Assembly by Coordination with Organic Antenna Chromophores for Dye-Sensitized Solar Cells.

The development of new sensitizers and new sensitization methods is one of the important means to enhance the conversion efficiency of dye-sensitized solar cells (DSSCs); the ultimate goal is to broaden the spectral response of dyes, reduce electron recombination, and suppress dye aggregation. In this study, we have developed a series of new self-assembled dyes and applied them in DSSCs. We prepared two organic antenna chromophores S1 and S2 and coordinated them with two acceptors A1 and A2 via zinc to construct A-Zn-S series self-assembled dyes. This method is very simple and feasible and can avoid the complex synthesis steps of traditional dyes; the results show that the light-harvesting ability of devices can be improved and charge recombination can be reduced by adjusting the structures of the antenna chromophores and acceptors. The device with A2-Zn-S1 gave a power conversion efficiency of 4.25%, which was higher than those with A1-Zn-S1 (3.88%), A1-Zn-S2 (3.21%), and A2-Zn-S2 (3.52%); the main reason for this is that the different coordination combinations between the antenna chromophore and the acceptor show great differences in Voc and Jsc. The device based on A2-Zn-S1 showed a high Voc of 632 mV and a high Jsc of 9.54 mA cm-2; one reason for this is that S1 has better spectral responsiveness and another reason is that A2 has better steric resistance that effectively reduces charge recombination. Besides, IR spectra indicate that these self-assembled dyes anchored on a TiO2 surface by bicarboxyl anchoring groups are also very beneficial for improving the performance of dyes.

A supramolecular assembly of metal-free organic dye with zinc porphyrin chromophore for dye-sensitized solar cells.

Two porphyrin chromophores, P1 and P2, were prepared and used as antenna units to coordinate with a metal-free organic dye, JH1, containing pyridine groups. This supramolecular self-assembly strategy can not only effectively improve the light-harvesting ability of the devices but also effectively reduces electron recombination by preventing I3- of the electrolyte from penetrating into the TiO2 surface. The DSSC based on JH1 showed a PCE of 2.46%, with a Voc of 615 mV, Jsc of 6.54 mA cm-2, and FF of 61.18%. After supramolecular self-assembly, the Jsc and Voc of the device were greatly improved. Specifically for the device based on JH1 + P2, the PCE reached 4.39%, which is about 78% greater than the PCE of the device based on JH1; this is mainly due to the Jsc increase of 2.85 mA cm-2 and the Voc increase of 93 mV. Compared to co-sensitization, supramolecular self-assembly does not require tedious optimization steps; thus, this may be a promising and convenient way to improve the overall performance of DSSCs.

An ultrafast rechargeable aluminium-ion battery.

The development of new rechargeable battery systems could fuel various energy applications, from personal electronics to grid storage. Rechargeable aluminium-based batteries offer the possibilities of low cost and low flammability, together with three-electron-redox properties leading to high capacity. However, research efforts over the past 30 years have encountered numerous problems, such as cathode material disintegration, low cell discharge voltage (about 0.55 volts; ref. 5), capacitive behaviour without discharge voltage plateaus (1.1-0.2 volts or 1.8-0.8 volts) and insufficient cycle life (less than 100 cycles) with rapid capacity decay (by 26-85 per cent over 100 cycles). Here we present a rechargeable aluminium battery with high-rate capability that uses an aluminium metal anode and a three-dimensional graphitic-foam cathode. The battery operates through the electrochemical deposition and dissolution of aluminium at the anode, and intercalation/de-intercalation of chloroaluminate anions in the graphite, using a non-flammable ionic liquid electrolyte. The cell exhibits well-defined discharge voltage plateaus near 2 volts, a specific capacity of about 70 mA h g(-1) and a Coulombic efficiency of approximately 98 per cent. The cathode was found to enable fast anion diffusion and intercalation, affording charging times of around one minute with a current density of ~4,000 mA g(-1) (equivalent to ~3,000 W kg(-1)), and to withstand more than 7,500 cycles without capacity decay.

Highly active and stable hybrid catalyst of cobalt-doped FeS2 nanosheets-carbon nanotubes for hydrogen evolution reaction.

Hydrogen evolution reaction (HER) from water through electrocatalysis using cost-effective materials to replace precious Pt catalysts holds great promise for clean energy technologies. In this work we developed a highly active and stable catalyst containing Co doped earth abundant iron pyrite FeS(2) nanosheets hybridized with carbon nanotubes (Fe(1-x)CoxS(2)/CNT hybrid catalysts) for HER in acidic solutions. The pyrite phase of Fe(1-x)CoxS(2)/CNT was characterized by powder X-ray diffraction and absorption spectroscopy. Electrochemical measurements showed a low overpotential of ∼0.12 V at 20 mA/cm(2), small Tafel slope of ∼46 mV/decade, and long-term durability over 40 h of HER operation using bulk quantities of Fe(0.9)Co(0.1)S(2)/CNT hybrid catalysts at high loadings (∼7 mg/cm(2)). Density functional theory calculation revealed that the origin of high catalytic activity stemmed from a large reduction of the kinetic energy barrier of H atom adsorption on FeS(2) surface upon Co doping in the iron pyrite structure. It is also found that the high HER catalytic activity of Fe(0.9)Co(0.1)S(2) hinges on the hybridization with CNTs to impart strong heteroatomic interactions between CNT and Fe(0.9)Co(0.1)S(2). This work produces the most active HER catalyst based on iron pyrite, suggesting a scalable, low cost, and highly efficient catalyst for hydrogen generation.

Nanoscale nickel oxide/nickel heterostructures for active hydrogen evolution electrocatalysis.

Active, stable and cost-effective electrocatalysts are a key to water splitting for hydrogen production through electrolysis or photoelectrochemistry. Here we report nanoscale nickel oxide/nickel heterostructures formed on carbon nanotube sidewalls as highly effective electrocatalysts for hydrogen evolution reaction with activity similar to platinum. Partially reduced nickel interfaced with nickel oxide results from thermal decomposition of nickel hydroxide precursors bonded to carbon nanotube sidewalls. The metal ion-carbon nanotube interactions impede complete reduction and Ostwald ripening of nickel species into the less hydrogen evolution reaction active pure nickel phase. A water electrolyzer that achieves ~20 mA cm(-2) at a voltage of 1.5 V, and which may be operated by a single-cell alkaline battery, is fabricated using cheap, non-precious metal-based electrocatalysts.

Facile preparation method for rare earth phosphate hollow spheres and their photoluminescence properties.

We have developed a template-free hydrothermal method of constructing rare earth phosphate hollow spheres using H(6)P(4)O(13) as the PO(4) (3-) source. The mechanism of hollow spheres formation was proposed on the basis of Ostwald ripening. The resulting hollow spheres, especially with the aid of doping of other lanthanide cations, exhibit emission spanning the whole UV-visible wavelength range.

[Chemical modification on the surface of nano-particles of ZnO and its characterization].

After nano-particles (ZnO) had been encapsulated by a kind of water-soluble cellulose Hydoxyl-Propyl-Methyl Cellulose (HPMC), then methyl methacrylate was grafted onto the surface of them. Thus the surface of nano-ZnO had been successfully modified. FTIR, DTA and TEM were utilized to confirm the results. FTIR shows that HPMC was adsorbed onto the surface of ZnO, and PMMA was also grafted onto its surface, DTA says that the heat stability of HPMC, HPMC-g-PMMA and ZnO/HPMC-g-PMMA increased greatly, TEM photo demonstrates that polymer adhered onto the surface of nano-ZnO which was encapsulated by a layer of film-like polymer.