Hierarchical Hollow Zinc Oxide Nanocomposites Derived from Morphology-Tunable Coordination Polymers for Enhanced Solar Hydrogen Production.

Infinite coordination‐polymer particles (CPPs) are promising materials for solar energy conversion with high efficiency. However, the range of organic ligands that may be used to create CPPs is limited, as are strategies for modification, thereby hindering the applications of such material. In this paper, competitive evolution–morphological and structural change from Zn‐based crystallites to amorphous particles is described. Controlled contribution of organic linkers selectively derived six Zn‐CPPs with multivariate characters. Based on the diversity of these substructures, hollow zinc oxide particles were initially formed by self‐pyrolysis of CPPs and effectively modified by ultrathin doped nanosheets. The obtained double‐sided heterojunctions offer fully‐covered active sites, bringing together efficient light‐excited charge‐transfer nanochannels, which exhibit an excellent solar H2‐releasing activity (e.g., 4512.5 μmol h−1 g−1) and stable cyclability.

Ultrathin nanosheets of molecular sieve SAPO-5: A new photocatalyst for efficient photocatalytic reduction of CO2 with H2O to methane

Nanostructures have been the focus of considerable interest for solar energy conversion in the areas of renewable green energy sources as well as environmental remediation due to their unique physicochemical properties. Here we highlight the recent efforts on developing new materials for solar energy conversion with a focus on one-dimensional homogeneous and heterogeneous nanowires. We first outline challenges and strategies to develop highly efficient and stable semiconductor materials for solar energy conversion, and then discuss the potential advantages and recent progress in exploring one-dimensional homogeneous and heterogeneous structures. We will particularly focus our discussion on the photovoltaic performance of various one-dimensional nanowire materials. Lastly, the perspectives for further improving the efficiency and stability of the solar energy conversion system using one-dimensional homogeneous and heterogeneous nanowires and their potential applications will be discussed.

The invention of the laser in 1960 gave us the ruby laser, which generally produced chaotic pulses of light. Six years later, in 1966, a concept called passive mode-locking applied to neodymium-glass lasers produced reasonably well-behaving picosecond pulses. This triggered an intense activity, with respect to developing improved laser pulse sources, measurement techniques, and application to chemistry, physics, and biology. Initially, only ∼10 –ps-long pulses at a few wavelengths were available. Nevertheless, insight into the function of complex biological systems, like photosynthetic proteins, and molecules of chemical interest was gained in very early studies. Today, both duration and color of ultrashort pulses can be tuned to almost any value. This has of course opened up possibilities to study almost any atomic, molecular, or solid-state system and any dynamic process. This review focuses on the use of laser spectroscopy to investigate light energy conversion mechanisms in both natural photosynthesis and a topical selection of novel materials for solar energy conversion. More specifically, in photosynthesis we will review light harvesting and primary electron transfer; materials for solar energy conversion that we discuss include sensitized semiconductors (dye sensitized solar cells), polymer:fullerene and polymer:polymer bulk heterojunctions (organic solar cells), organometal halide perovskites, as well as molecular and hybrid systems for production of solar fuel and valuable chemicals. All these scientific areas, and in particular photosynthesis and the solar cell materials, have been extensively studied with ultrafast spectroscopy, resulting in a vast literature; a comprehensive review of the individual materials is, therefore, not feasible, and we will limit our discussion to work that we think has been of particular importance for understanding the function of the respective systems.

Nowadays, the serious resource shortage and environmental polluting issues have attracted tremendous attention worldwide. Renewable energy such as hydroenergy, wind energy and solar energy, has been in high demanded and emerged as promising substitutions of fossil fuel. Among them, solar irradiation is the most valuable energy source in the near future, which is abundant and naturally unlimited. Researchers have devoted to seek methods to efficiently utilize solar energy and practically applied in various areas. Solar evaporation is an attractive strategy to utilize solar energy for distillation without consuming fossil fuels. Recently, different solar absorbers based on diverse materials have been extensively studied to transfer solar energy into heat for vapor generation, such as gold nanoparticles and carbon-based bilayer structures.[1], [2] However, most of the absorbers are fabricated complexly with extra cost, which limits their large-scale application. In this work, the black polyurethane (PU) sponge with three dimensional porous structures was demonstrated as the solar light absorber for heat localization. The black PU sponge can be recycled from the used packaging materials, which are usually abandoned after utilization and difficult to decompose naturally. Every year, the production of black PU sponge as the packaging materials is numerous. Recycling and reusing the PU sponge contributes to sustainable development. Here, the PU sponge provides porous channels for fluent water supply, low thermal conductivity for heat localization and low intensity to create surface evaporation. A simple hydrophilic treatment of this PU sponge was applied to improve the wettability by being stirred in dopamine solution. An evaporation efficient of 52.2%, which is more than 3 times higher than natural evaporation process, was achieved by this modified sponge in a relatively simple and low cost method. Furthermore, it provides a new idea to reutilize the waste materials for solar energy conversion.   Acknowledgements This work is financially supported by the Research Grants Council of Hong Kong, China (Project Number: GRF 152109/16E PolyU B-Q52T).   Reference [1] Neumann, Oara, et al. "Solar vapor generation enabled by nanoparticles." Acs Nano 7.1 (2012): 42-49. [2] Jiang, Qisheng, et al. "Bilayered Biofoam for Highly Efficient Solar Steam Generation." Advanced Materials 28.42 (2016): 9400-9407.  

Colloidal quantum-confined semiconductor nanoheterostructures (SNHs) that are composed of multiple component materials in rationally designed spatial arrangements are promising light harvesting and charge separation materials for solar energy conversion. SNHs can be engineered to exhibit type I, quasi-type II and type II carrier localization, affecting their photophysical properties and photochemical performances. Unlike bulk semiconductor heterostructures, the electron and hole energy levels and spatial distributions in SNHs can be continuously tuned by adjusting the material dimension through the quantum confinement effect, providing additional control of their properties through wavefunction engineering. In this article, we review recent progress in using wavefunction engineering to control the absorption and emission spectra, single and multiple exciton dynamics and charge transfer properties of SNHs (core/shell QDs and dot-in-rod nanorods) as well as to improve their performance as light harvesting and charge separation materials for solar energy conversion.

Polarized light emission from grain boundaries in photovoltaic silicon

Enhanced solar-driven hydrogen evolution over ultrathin g-C3N4/ReSe2 heterojunction-like nanosheets with surface selenium vacancies

Understanding the effect of multiple configurations in polymeric carbon nitride for efficient solar-driven hydrogen peroxide photosynthesis

In this study, for the first time, {111} facet exposed anatase TiO2 single crystals are prepared via both F– and ammonia as the capping reagents. In comparison with the most investigated {001}, {010}, and {101} facets for anatase TiO2, the density functional theory (DFT) calculations predict that {111} facet owns a much higher surface energy of 1.61 J/m2, which is partially attributed to the large percentage of undercoordinated Ti atoms and O atoms existed on the {111} surface. These undercoordinated atoms can act as active sites in the photoreaction. Experimentally, it is revealed that this material exhibits the superior electronic band structure which can produce more reductive electrons in the photocatalytic reaction than those of the TiO2 samples exposed with majority {010}, {101}, and {001} facets. More importantly, we demonstrate that this material is an excellent photocatalyst with much higher photocatalytic activity (405.2 μmol h–1), about 5, 9, and 13 times that of the TiO2 sample exposed with dominant {010}, {101}, and {001} facets, respectively. Both the superior surface atomic structure and electronic band structure significantly contribute to the enhanced photocatalytic activity. This work exemplifies that the surface engineering of semiconductors is one of the most effective strategies to achieve advanced and excellent performance over photofunctional materials for solar energy conversion.

Alternative lead-free mixed-valence double perovskites for high-efficiency photovoltaic applications

Building a direct Z-scheme heterojunction photocatalyst by ZnIn2S4 nanosheets and TiO2 hollowspheres for highly-efficient artificial photosynthesis

CIGS are very promising semiconducting materials for solar energy conversion due to their high efficiency. However, when analyzing the full life cycle assessment the toxicity and shortage of the involved elements along with the EROEI (Energy Return Over Energy Investment) needed to assemble the devices are considered unfavorable for the large scale exploitation of the CIGS. To overcome this issues, scientific community is focusing attention on new compounds based on economic and low-environmental impact elements such as Cu, Sn, Fe and Zn. In particular, quaternary semiconducting materials based on the kesterite (Cu2ZnSnS4) mineral structure are the most promising candidates to overtake the current generation of light-absorbing materials for thin-film solar cells. Electrodeposition is known as a low-cost semiconductor technique for the growth of semiconducting materials in electronic devices. Surface limited electrodeposition of atomic layers, can be performed by means of Electrochemical Atomic Layer Deposition (E-ALD) technique to obtain ultra-thin films of copper sulphides on a Ag(111) single crystal. Although its band gap it is not optimal for solar energy conversion, this materials can have interesting electronic proprieties, for instance Cu2S is a superionic conductor. However, from the E-ALD scheme one would expect a CuS hexagonal structure (covellite) with no any important electronic proprieties. Still, recently reported operando SXRD on this material allowed to assign a crystallographic cell corresponding to a cell directly derived from chalcocite’s (Cu2S). These unexpected results are confirmed by the analysis of the growth mechanism performed by means of operando SXRD and XRR. In this communication we reports a morphological and compositional study, confirming the composition and morphology expected from the results of the SXRD operando measurements pointing to the growth of Cu2S by means of E-ALD.

We succeed in preparation of anatase TiO₂ single crystals with marked photocatalytic activity via a facile and effective method. This TiO₂ is composed of TiO₂ ultrathin nanosheets (2 nm in thickness) with 95% of exposed {100} facet, which is considered to be the active facet for photocatalytic reaction. This percentage (95%) is the highest among previously reported {100} facet exposed anatase TiO₂. More importantly, due to this high ratio, our developed TiO₂ nanosheets showed marked photocatalytic activity, about 5 times higher activity in both H₂ evolution and CO₂ reduction than the reference sample, TiO₂ cuboids with 53% of exposed {100} facet. For the TiO₂ nanosheets, both the higher percentage of exposed {100} facets and larger surface area can offer more surface active sites in the photocatalytic reaction. On the other hand, the superior electronic band structure which results from the higher percentage of {100} facet is also beneficial for the higher activity. This study exemplifies that the facet engineering of semiconductors is one of the most effective strategies to achieve advanced properties over photofunctional materials for solar energy conversion.

Adenine-functionalized graphene oxide as a charge transfer layer to enhance activity and stability of Cu2O photocathode for CO2 reduction reaction