Mapping outcomes of liquid marble collisions

© 2019 The Royal Society of Chemistry. Liquid marbles (LMs) have many promising roles in the ongoing development of microfluidics, microreactors, bioreactors, and unconventional computing. In many of these applications, the coalescence of two LMs is either required or actively discouraged, therefore it is important to study liquid marble collisions and establish parameters which enable the desired collision outcome. Recent reports on LM coalescence have focused on either two mobile LMs colliding, or an accelerating LM hitting a sessile LM with a backstop. A further possible scenario is the impact of a mobile LM against a non-supported static LM. This paper investigates such a collision, using high-speed videography for single-frame analysis. Multiple collisions were undertaken whilst varying the modified Weber number (We∗) and offset ratios (X∗). Parameter ranges of 1.0 0.25, and We∗ 1.55 resulted in 100% non-coalescence. Additionally, observations of LMs moving above a threshold velocity of 0.6 m s -1 have revealed a new and unusual deformation. Comparisons of the outcome of collisions whilst varying both the LM volume and the powder grain size have also been made, revealing a strong link. The results of this work provide a deeper understanding of LM coalescence, allowing improved control when designing future collision experiments

Thickness control in electrophoretic deposition of WO3 nanofiber thin films for solar water splitting

Electrophoretic deposition (EPD) of ground electrospun WO3 nanofibers was applied to create photoanodes with controlled morphology for the application of photoelectrochemical (PEC) water splitting. The correlations between deposition parameters and film thicknesses were investigated with theoretical models to precisely control the morphology of the nanostructured porous thin film. The photoconversion efficiency was further optimized as a function of film thickness. A maximum photoconversion efficiency of 0.924% from electrospun WO3 nanofibers that EPD deposited on a substrate was achieved at a film thickness of 18 µm

Marangoni ring-templated vertically aligned ZnO nanotube arrays with enhanced photocatalytic hydrogen production

Here we report on a novel approach for the synthesis of vertically aligned hexagonal ZnO nanotube arrays. Ring-like structures were formed on substrate using the polymer-based seeding solution through the Marangoni mechanism, guiding the growth of ZnO nanotubes with aqueous chemical bath deposition. Photoelectrochemical hydrogen generation by water splitting on a ZnO nanotube anode is about three times as efficient as that on a similar ZnO nanorod anode

Enhanced photoelectrochemical water splitting by a 3D hierarchical sea urchin-like structure: ZnO nanorod arrays on TiO2hollow hemisphere

A hierarchical sea urchin-like hybrid metal oxide nanostructure of ZnO nanorods deposited on TiO2 porous hollow hemisphere with a thin zinc titanate interface layer is specifically designed and synthesized forming a combined type I straddling and type II staggered junctions. The HHSs, synthesized by electrospinning, facilitate light trapping and scattering. The ZnO nanorods offer a large surface area for improved surface oxidation kinetics The interface layer of zinc titanate (ZnTiO3) between the TiO2 HHSs and ZnO nanorods regulates the charge separation in a closely coupled hierarchy structure of ZnO/ZnTiO3/TiO2. The synergistic effects of improved light trapping, charge separation, and fast surface reaction kinetics result in a superior photoconversion efficiency of 1.07% for the photoelectrochemical (PEC) water splitting with an outstanding photocurrent density of 2.8 mA cm-2 at 1.23 V vs. RHE.</p

Light trapping by porous TiO2 hollow hemispheres for high efficiency photoelectrochemical water splitting

Photocatalytic water splitting has recently received increasing attention as a green fuel source. The controlled nano-geometry of the photocatalytic material can improve light harvesting. In this study, as a proof of concept, hollow hemisphere (HHS)-based films of TiO2 material were created by a conventional electrospray method and subsequently applied for photoelectrochemical (PEC) water splitting. To preserve the morphology of the HHS structure, a hydrolysis precipitation phase separation method (HPPS) was developed. As a result, the TiO2 HHS-based thin films presented a maximum PEC water splitting efficiency of ca. 0.31%, almost two times that of the photoanode formed by TiO2 nanoparticle-based films (P25). The unique morphology and porous structure of the TiO2 HHSs with reduced charge recombination and improved light absorption are responsible for the enhanced PEC performance. Light scattering by the HHS was demonstrated with total reflection internal fluorescence microscopy (TRIFM), revealing the unique light trapping phenomenon within the HHS cavity. This work paves the way for the rational design of nanostructures for photocatalysis in fields including energy, environment, and organosynthesis

Enhanced photoelectrochemical water oxidation by ZnxMyO (M = Ni, Co, K, Na) nanorod arrays

The present work reports a facile approach to the one-pot solution growth of vertically aligned, doped ZnO nanorod (NR) arrays by chemical bath deposition (CBD). The effects of dopant ions on the final morphologies, electronic band structures and donor densities of ZnO NRs were examined. With the introduction of dopants, the optical band gap energies of the samples were reduced. The photoelectrochemical (PEC) water splitting performances of the doped ZnO NRs were tested. When compared with pristine ZnO NRs, the doped ZnO NRs demonstrated an improvement of at least 15% in the PEC water splitting activity. Na-doped ZnO NRs was the most efficient photoanode, where its photocurrent density was 2.1 times greater than that of pristine ZnO NRs. The mechanism for improved PEC performance was proposed