Fabrication and Characterization of Nanostructured Rock Wool as a Novel Material for Efficient Water-Splitting Application

Fabrication of PES Modified by TiO2/Na2Ti3O7 Nanocomposite Mixed-Matrix Woven Membrane for Enhanced Performance of Forward Osmosis: Influence of Membrane Orientation and Feed Solutions

Water treatment is regarded as one of the essential elements of sustainability. To lower the cost of treatment, the wastewater volume is reduced via the osmotic process. Here, mixed-matrix woven forward osmosis (MMWFO) PES membranes modified by a TiO₂/Na₂Ti₃O₇ (TNT) nanocomposite were fabricated for treating water from different sources. Various techniques were used to characterize the TNT nanocomposite. The crystal structure of TNT is a mix of monoclinic Na₂Ti₃O₇ and anorthic TiO₂ with a preferred orientation of (2-11). The SEM image shows that the surface morphology of the TNT nanocomposite is a forked nano-fur with varying sizes regularly distributed throughout the sample. The impact of TNT wt.% on membrane surface morphologies, functional groups, hydrophilicity, and performance was investigated. Additionally, using distilled water (DW) as the feed solution (FS), the effects of various NaCl concentrations, draw solutions, and membrane orientations on the performance of the mixed-matrix membranes were tested. Different water samples obtained from various sources were treated as the FS using the optimized PES/TNT (0.01 wt.%) MMWFO membrane. Using textile effluent as the FS, the impact of various NaCl DS concentrations on the permeated water volume was investigated. The results show that the MMWFO membrane generated with the TNT nanocomposite at a 0.01 wt.% ratio performed better in FO mode. After 30 min of use with 1 M NaCl and various sources of water as the FS, the optimized MMWFO membrane provided a steady water flow and exhibited antifouling behavior. DW performed better than other water types whenever it was used owing to its greater flow (136 LMH) and volume reduction (52%). Tap water (TW), textile industrial wastewater (TIWW), gray water (GW), and municipal wastewater (MW) showed volume reductions of 41%, 34%, 33%, and 31.9%, respectively. Additionally, when utilizing NaCl as the DS and TIWW as the FS, 1 M NaCl resulted in more permeated water than 0.25 M and 0.5 M, yet a higher volume reduction of 41% was obtained.

Flexible Electrode Based on PES/GO Mixed Matrix Woven Membrane for Efficient Photoelectrochemical Water Splitting Application

We introduced, for the first time, a membrane composed of nanostructured self-polyether sulphone (PES) filled with graphene oxide (GO) applied to photoelectrochemical (PEC) water splitting. This membrane was fabricated through the phase inversion method. A variety of characteristics analysis of GO and its composite with PES including FTIR, XRD, SEM, and optical properties was studied. Its morphology was completely modified from macro voids for bare PES into uniform layers with a random distribution of GO structure which facilitated the movement of electrons between these layers for hydrogen production. The composite membrane photocathode brought a distinct photocurrent generation (5.7 mA/cm² at 1.6 V vs. RHE). The optimized GO ratio in the membrane was investigated to be PG2 (0.008 wt.% GO). The conversion efficiencies of PEC were assessed for this membrane. Its incident photon-to-current efficiency (IPCE) was calculated to be 14.4% at λ = 390 nm beside the applied bias photon-to-current conversion efficiency (ABPE) that was estimated to be 7.1% at -0.4 V vs. RHE. The stability of the PG2 membrane after six cycles was attributed to high thermal and mechanical stability and excellent ionic conductivity. The number of hydrogen moles was calculated quantitively to be 0.7 mmol h^-1 cm^-2. Finally, we designed an effective cost membrane with high performance for hydrogen generation.

The Influence of Electrode Thickness on the Structure and Water Splitting Performance of Iridium Oxide Nanostructured Films

For a safe environment, humanity should be oriented towards renewable energy technology. Water splitting (WS), utilizing a photoelectrode with suitable thickness, morphology, and conductivity, is essential for efficient hydrogen production. In this report, iridium oxide (IrO_x) films of high conductivity were spin-cast on glass substrates. FE-SEM showed that the films are of nanorod morphology and different thicknesses. UV-Vis spectra indicated that the absorption and reflectance of the films depend on their thickness. The optical band gap (E_g) was increased from 2.925 eV to 3.07 eV by varying the spin speed (SS) of the substrates in a range of 1.5 × 10³-4.5 × 10³ rpm. It was clear from the micro-Raman spectra that the films were amorphous. The E_g vibrational mode of Ir-O stretching was red-shifted from 563 cm^-1 (for the rutile IrO₂ single crystal) to 553 cm^-1. The IrO_x films were used to develop photoelectrochemical (PEC) hydrogen production catalysts in 0.5M of sodium sulfite heptahydrate Na₂SO₃·7H₂O (2-electrode system), which exhibits higher hydrogen evaluation (HE) reaction activity, which is proportional to the thickness and absorbance of the used IrO_x photocathode, as it showed an incident photon-to-current efficiency (IPCE%) of 7.069% at 390 nm and -1 V. Photocurrent density (Jph = 2.38 mA/cm² at -1 V vs. platinum) and PEC hydrogen generation rate (83.68 mmol/ h cm² at 1 V) are the best characteristics of the best electrode (the thickest and most absorbent IrO_x photocathode). At -1 V and 500 nm, the absorbed photon-to-current conversion efficiency (APCE%) was 7.84%. Electrode stability, thermodynamic factors, solar-to-hydrogen conversion efficiency (STH), and electrochemical impedance spectroscopies (EISs) were also studied.