Catalytic materials for efficient electrochemical production of hydrogen peroxide

Hydrogen peroxide (H2O2), the simplest peroxide consisting of only hydrogen and oxygen, is globally used as a green oxidant. It is also a promising fuel source, and it can be produced on large scales in centralized containers. H2O2 is mainly produced by the anthraquinone process, but it involves energy-consuming reactions and generates organic waste. As the demand for H2O2 continues to grow, alternative technologies that overcome these drawbacks are sought for its generation. The generation of H2O2 through the redox reaction of water and oxygen can be a low-cost, sustainable, and efficient production method. However, this reaction requires active and stable catalysts. In general, H2O2 can be generated by the oxidation of H2O at the anode of an electrochemical cell. Alternatively, H2O2 can also be formed by the reduction of O-2 at the cathode. Despite the progress in the development and advancement of materials that catalyze these reactions, further research is required to increase the electron transport rates and active sites of the catalyst. In this article, we review the available catalytic materials for the electrochemical production of H2O2 and provide a summary and outlook of this field

Nanoporous Films and Nanostructure Arrays Created by Selective Dissolution of Water-Soluble Materials.

Highly porous thin films and nanostructure arrays are created by a simple process of selective dissolution of a water-soluble material, Sr3Al2O6. Heteroepitaxial nanocomposite films with self-separated phases of a target material and Sr3Al2O6 are first prepared by physical vapor deposition. NiO, ZnO, and Ni1- x Mg x O are used as the target materials. Only the Sr3Al2O6 phase in each nanocomposite film is selectively dissolved by dipping the film in water for 30 s at room temperature. This gentle and fast method minimizes damage to the remaining target materials and side reactions that can generate impurity phases. The morphologies and dimensions of the pores and nanostructures are controlled by the relative wettability of the separated phases on the growth substrates. The supercapacitor properties of the porous NiO films are enhanced compared to plain NiO films. The method can also be used to prepare porous films or nanostructure arrays of other oxides, metals, chalcogenides, and nitrides, as well as films or nanostructures with single-crystalline, polycrystalline, or amorphous nature

Selective phase transformation of layered double hydroxides into mixed metal oxides for catalytic CO oxidation

Phase transformation from layered double hydroxides (LDHs) into mixed metal oxides (MMOs) has been widely used in various catalytic applications owing to its numerous advantages over conventional synthesis methods. Herein we report the results of selective phase transformation of LDHs into spinels and delafossites for the preparation of phase-pure MMO catalysts. Pure cuprous delafossites and cupric spinels were selectively obtained through heat treatment of Cu-based LDHs followed by post-treatments. This enabled the study of the crystalline-phase-dependent CO oxidation activity of the MMO catalysts and their physicochemical properties. The spinel catalysts exhibited higher CO oxidation activities, in comparison with those of the delafossites, with greater redox properties and improved active sites for CO adsorption. Although the crystalline phases were derived from the same LDH precursors, the catalytic properties of the end product were greatly influenced by their crystal structures

Homoepitaxial growth of ZnO nanostructures from bulk ZnO

Material formation mechanisms and their selective realization must be well understood for the development of new materials for advanced technologies. Since nanomaterials demonstrate higher specific surface energies compared to their corresponding bulk materials, the homoepitaxial growth of nanomaterials on bulk materials is not thermodynamically favorable. We observed the homoepitaxial growth of nanowires with constant outer diameters on bulk materials in two different, solution-based growth systems. We also suggested potential mechanisms of the spontaneous and homoepitaxial growth of the ZnO nanostructures based on the characterization results. The first key factor for favorable growth was the crystal facet stabilization effect of capping agents during the early stages of growth. The second factor was the change in the dominant growth mode during the reaction in a closed system. The spontaneous, homoepitaxial growth of nanomaterials enables the realization of unprecedented, complex, hierarchical, single-crystalline structures required for future technologies

Molecular engineering of panchromatic unsymmetrical squaraines for dye-sensitized solar cell applications

Three unsymmetrical squaraine dyes JK-64, JK-65, and JK-64Hx, containing a bulky spirobifluorene or hexyloxyphenyl unit are designed and synthesized. These sensitizers, when anchored onto a TiO2 surface, exhibit decreased aggregation as well as enhanced unidirectional flow of electrons. Under standard global AM 1.5 solar conditions, an optimized JK-64Hx sensitized cell gave a short-circuit photocurrent density (J(sc)) of 12.82 mA cm(-2), an open-circuit voltage (V-oc) of 0.54 V and a fill factor (ff) of 0.75, corresponding to an overall conversion efficiency (eta) of 5.20%

Smart gold nanoparticles for photoacoustic imaging: an imaging contrast agent responsive to the cancer microenvironment and signal amplification via pH-induced aggregation

'Smart' gold nanoparticles can respond to mild acidic environments, rapidly form aggregates, and shift the absorption to red and near-infrared. They were used as a photoacoustic imaging agent responsive to the cancer microenvironment, and have demonstrated the cancer-specific accumulation at the cellular level and an amplified signal which is twice higher than the control in vivo.11156sciescopu

pH-Responsive Gold Nanoparticles-in-Liposome Hybrid Nanostructures for Enhanced Systemic Tumor Delivery

We report a pH-responsive gold nanoparticles-in-liposome hybrid nanostructure, which effectively combines the pH-responsive assembly and surface plasmon property changes of 'smart' gold nanoparticles and enhanced systemic circulation and tumor accumulation of the PEG-grafted liposomes.open111717sciescopu