Effects Of H2O2 Concentrations Research Articles

Effects of Hydrogen Peroxide Concentration on Properties of Black Silicon Fabricated by Two-Step Silver-Assisted Wet Chemical Etching for Photovoltaics

Crystalline silicon (c-Si) has low optical absorption due to its high surface reflection of incident light. Nanotexturing of c-Si which produces black silicon (b-Si) offers a promising solution. In this work, effect of H2O2 concentrations towards surface morphological and optical properties of b-Si fabricated by two-step silver-assisted wet chemical etching (Ag-based two-step MACE) for potential photovoltaic (PV) applications is presented. The method involves a 30 s deposition of silver nanoparticles (Ag NPs) in an aqueous solution of AgNO3:HF (5:6) and an optimized etching in HF:H2O2:DI H2O solution under 0.62 M, 1.85 M, 2.47 M, and 3.7 M concentrations of H2O2 at 5 M HF. On the b-Si, nanowires with 250-950 nm heights and an average diameter of 150-280 nm are obtained. Low concentrations of H2O2 result in denser nanowires with an average length of 900-950 nm and diameters of about 150-190 nm. The b-Si exhibit outstanding broadband antireflection due to the refractive index grading effect represented as WAR within the 300-1100 nm wavelength region. B-Si obtained after etching in a solution with 0.62 M concentration of H2O2, demonstrate WAR of 7.5%. WAR of 7.5% results in an absorption of up to 95.5 % at a wavelength of 600 nm. The enhanced broadband light absorption yields maximum potential short-circuit current density (Jsc(max)) of up to 38.2 mA/cm2, or 45.2% enhancement compared to the planar c-Si reference.

Effect of hydrogen peroxide concentration on the nanostructure of hydroxyapatite coatings via ultrasonic-assisted electrodeposition

Hydroxyapatite (HA) coating is prepared by ultrasonic-assisted electrodeposition from the electrolytes containing hydrogen peroxide (H2O2). Effects of H2O2 concentrations (0, 0.5, 2.0, 4.0 mL/L) on the morphology, chemical bonds, crystallinity and roughness of the HA coatings are investigated. The results show that the HA coating via ultrasonic-assisted electrodeposition is spindle-like in the absence of H2O2, but becomes flake-like and wrinkle-like morphology after adding different concentrations of H2O2 into the electrolyte. The SEM image of HA coating at half of the deposition time (i.e. 30 min) reveals the transition from spindle-like to wrinkle-like. TEM image shows that wrinkle-like HA coating electrodeposited at 4.0 mL/L H2O2 is also found with spindle-like HA crystal nanostructure. The influencing mechanism of H2O2 on the HA coating nanostructure is also proposed. This study provides a new idea for the preparation of hydroxyapatite electrodeposited coatings.

An Alkaline Al–H2O2 Semi‐Fuel Cell Based on a Nickel Foam Supported Co3O4 Nanowire Arrays Cathode

AbstractThe electrode of Co3O4 nanowire arrays directly grown on nickel foam is prepared via a facile one‐step method. The electrode is characterised by scanning and transmission electron microscopy and tested as the cathode of an Al–H2O2 semi‐fuel cell. We found that Co3O4 forms clusters of nanowires with length up to around 15 μm and diameter around 250 nm. The nanowire is composed of interconnected nanoparticles. Effects of H2O2 concentrations, catholyte KOH concentration, catholyte flow rate and operation temperature on the cell performance are investigated. The cell exhibited an open circuit voltage of 1.4 V, and peak power densities of 85 and 137 mW cm–2 at 25 and 65 °C, respectively, while running on 0.4 mol L–1 H2O2 at a flow rate of 80 mL min–1.

Autothermal Gelation Synthesis of Uniform Titania Nanoparticles

Titania nanoparticles were successfully synthesized through an easily controlled and simple autothermal gelation process. Effects of H2O2 concentrations, solvent quantity and dissolving temperature were investigated in detail. DSC–TGA and XRD analysis showed that the synthesized TiO2 nanoparticles were in anatase phase at 400°C and in rutile phase at 650°C. TEM image indicated that the titania nanoparticles were uniform and approximately spherical, the average grain size of the product was about 20 nm.

Synthesis of CoOOH Hierarchically Hollow Spheres by Nanorod Self-Assembly through Bubble Templating

CoOOH hierarchically hollow spheres consisting of nanorods by self-assembly coupled with bubble templating through a facile one-step hydrothermal route have been demonstrated. An energy-minimizing-driven self-assembly of CoOOH nanorods on the base of O2 bubbles induced by CTAC is responsible for the formation of hierarchically hollow structure. The effects of H2O2 concentrations and CTAC during the crystallization and self-assembly process of CoOOH nanorods have been studied. It is found that H2O2 concentration is a key factor that affects not only the crystallinity, shape, and size but also the further self-assembly process of CoOOH nanorods, determining the final formations of hollow spheres or solid aggregates of nanorod self-assemblies, while CTAC can probably induce the CoOOH nanorods to get more ordered self-assembly. This is the first synthesis of complex hollow structure of CoOOH crystals with hierarchy.