Nailiang Yang

Two-dimensional graphene bridges enhanced photoinduced charge transport in dye-sensitized solar cells.

As a novel two-dimensional (2D) material, graphene shows great benefits in electric and material science. Compared to 1D nanomaterials, it may show more excellent properties. Here, we introduced graphene as 2D bridges into the nanocrystalline electrodes of dye-sensitized solar cells, which brought a faster electron transport and a lower recombination, together with a higher light scattering. On the basis of these advantages, the short-circuit current density was increased by 45% without sacrificing the open-circuit voltage, and the total conversion efficiency was 6.97%, which was increased by 39%, comparing with the nanocrystalline titanium dioxide photoanode, and it was also much better than the 1D nanomaterial composite electrode.

Hierarchically Ordered Macro−Mesoporous TiO2−Graphene Composite Films: Improved Mass Transfer, Reduced Charge Recombination, and Their Enhanced Photocatalytic Activities

Hierarchically ordered macro-mesoporous titania films have been produced through a confinement self-assembly method within the regular voids of a colloidal crystal with three-dimensional periodicity. Furthermore, graphene as an excellent electron-accepting and electron-transporting material has been incorporated into the hierarchically ordered macro-mesoporous titania frameworks by in situ reduction of graphene oxide added in the self-assembly system. Incorporation of interconnected macropores in mesoporous films improves the mass transport through the film, reduces the length of the mesopore channel, and increases the accessible surface area of the thin film, whereas the introduction of graphene effectively suppresses the charge recombination. Therefore, the significant enhancement of photocatalytic activity for degrading the methyl blue has been achieved. The apparent rate constants for macro-mesoporous titania films without and with graphene are up to 0.045 and 0.071 min(-1), respectively, almost 11 and 17 times higher than that for pure mesoporous titania films (0.0041 min(-1)).

Accurate Control of Multishelled Co3O4 Hollow Microspheres as High-Performance Anode Materials in Lithium-Ion Batteries

More than just an empty shell: Multishelled Co3O4 microspheres were synthesized as anode materials for lithium-ion batteries in high yield and purity. As their porous hollow multishell structure guarantees a shorter Li+ diffusion length and sufficient void space to buffer the volume expansion, their rate capacity, cycling performance, and specific capacity were excellent (1615.8 mA?h?g-1 in the 30th cycle for triple-shelled Co3O4; see graph).

Accurate Control of Multishelled ZnO Hollow Microspheres for Dye-Sensitized Solar Cells with High Efficiency

A series of multishelled ZnO hollow microspheres with controlled shell number and inter-shell spacing have been successfully prepared by a simple carbonaceous microsphere templating method, whose large surface area and complex multishelled hollow structure enable them load sufficient dyes and multi-reflect the light for enhancing light harvesting and realize a high conversion efficiency of up to 5.6% when used in dye-sensitized solar cells.

Photocatalytic Properties of Graphdiyne and Graphene Modified TiO2: From Theory to Experiment

The chemical structure and electronic properties of two-dimensional (2D) carbon-supported TiO₂, TiO₂-graphdiyne, and TiO₂-graphene composites have been studied by first-principles density functional theory. Calculation results show that TiO₂(001)-graphdiyne composites possess superior charge separation and oxidation properties, having the longest lifetimes of photoexcited carriers among all of the 2D composites containing TiO₂ of different facets. Our experimental results further proved that TiO₂(001)-graphdiyne composites could be a promising photocatalyst. For photocatalytic degradation of methylene blue, the rate constant of the TiO₂(001)-graphdiyne composite is 1.63 ± 0.15 times that of the pure TiO₂(001) and 1.27 ± 0.12 times that of the TiO₂(001)-graphene composite.

Molecular Architecture of Cobalt Porphyrin Multilayers on Reduced Graphene Oxide Sheets for High-Performance Oxygen Reduction Reaction†

Thanks to their lightweight, highly efficient, modular and scalable properties, polymer electrolyte membrane fuel cells (PEMFCs) have long been thought to be a promising candidate for applications in transportation and in both stationary and portable electronics. [1] Unfortunately, despite the above advantages, until now the fuel-cell technologies have failed to reach mass commercialization, and the main problems include short operational time and high cost of the materials used. [1b–d] For example, platinum-based materials are generally believed to be ideal catalysts for the oxygen reduction reaction (ORR) at the cathodes of PEMFCs; however, their disadvantages, for example, low tolerance to methanol fuel, high price and scarcity, limit the practical application of platinum-based catalysts. [2] Therefore, replacement of platinum-based materials with non-precious-metal catalysts, which are of low cost, high catalytic activity, and robust, has become one of the key issues for the realization of mass applications of PEMFCs. [3a,b]

One Dimensional CuInS2-ZnS Heterostructured Nanomaterials as Low-Cost and High-Performance Counter Electrodes of Dye-Sensitized Solar Cells

Wurtzite CuInS2-ZnS heterostructured nanorods are synthesized via a seed-assisted synthetic route. Cu1.94S-ZnS heterostructured nanorods are transformed into CuInS2-ZnS by reacting with indium ions to convert copper sulfide to wurtzite CuInS2. The shapes of the CuInS2-ZnS heterostructured nanorods can be tuned from burning torch-like to longer rod-like by varying the concentration of added indium. Dye-sensitized solar cells (DSSCs) using these heterostructured nanocrystals as counter electrodes had a power conversion efficiency (7.5%) superior to DSSCs made with conventional platinum electrode (7.1%) under the same device configuration.

Granum‐Like Stacking Structures with TiO2–Graphene Nanosheets for Improving Photo‐electric Conversion

Solar energy is commonly considered to be one of the most important forms of future energy production. This is due to its ability to generate essentially free power, after installation, with low environmental impact. Green plants, meanwhile, exhibit a process for light-to-charge conversion that provides a useful model for using solar radiation efficiently. Granum, the core organ in photosynthesis consists of a stack of ~10-100 thylakoids containing pigments and electrons acceptors. Imitating the structure and function of granum, stacked structures are fabricated with TiO(2) /graphene nanosheets as the thylakoids unit, and their photo-electric effect is studied by varying the number of layers present in the film. The photo-electric response of the graphene composites are found to be 20 times higher than that of pure TiO(2) in films with 25 units stacked. Importantly, the cathodic photocurrent changes to anodic photocurrent as the thickness increases, an important feature of efficient solar cells which is often ignored. Here graphene is proposed to perform similarly to the b6f complex in granum, by separating charges and transporting electrons through the stacked film. Using this innovation, stacked TiO(2) /graphene structures are now able to significantly increase photoanode thickness in solar cells without losing the ability to conduct electrons.

Enhanced light harvesting in plasmonic dye-sensitized solar cells by using a topologically ordered gold light-trapping layer.

Dye-sensitized solar cells (DSSCs) are promising low-cost, high-efficiency devices with low environmental impact. One of the important methods to improve their efficiencies involves increasing the light-harvesting efficiency. Earlier work has focused on varying the morphology of the photoanode. With such a hierarchical structured photoanode in hand, we modify herein the structure of the counter electrode to enhance the optical path length through the plasmonic and reflecttion effects. With the introduced topological gold layer, the photocurrent and efficiency are increased by 16 % and 18 %, respectively, due to the increased light collection. Besides, this effect is effective at both high and low levels of solar irradiation.

Photoelectric conversion behavior based on direct interfacial charge-transfer from porphyrin derivative to silicon nanowires

A porphyrin derivative was prepared, and the photoelectric conversion behaviors of porphyrin derivative sensitized silicon nanowires had been studied that showed the maximum photocurrent generation that occurred at the near infrared region, which can be attributed to the direct interfacial charge-transfer from the highest occupied molecular orbital of porphyrin derivative to the conduction band of silicon nanowires. These properties open up the possibility of constructing photovoltaic devices and light-harvesting systems using various dyes and semiconductors.