Dr. Valdes-Morales, Hector

A facile, fluorine-free and non-toxic one-pot solvothermal technique was adopted to synthesis TiO2 nanoflowers with anatase phase having 98% highly exposed {001} facets (TiO2 {001} NFs). The morphology, grain size and crystallinity of pure TiO2 {001} NFs and reduced graphene oxide (RGO) sheets modified TiO2 {001} NFs (RGOTiO2 {001} NFs) were inspected by diffuse reflectance spectroscopy (DRS), X-ray diffractometry (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). TEM images showed the development of anatase TiO2 {001} NFs with high crystallinity and uniform shape. The influence of RGO on the performance of the TiO2 {001} NFs as a photoanode material in dye-sensitized solar cell (DSSC) was examined. High energy conversion efficiency (ɳ) was observed for the DSSC based on a photoanode made of RGO-TiO2 {001} NFs when compared to DSSCs based on photoanodes fabricated using pure TiO2 {001} NFs and commercial Degussa P25 TiO2, which exhibited η of 6.78, 4.59 and 2.71%, respectively. The improved performance of the DSSC based on a photoanode composed of RGOTiO2 {001} NFs was due to its good crystallinity, high dye intake and enhanced light-harvesting properties. Moreover, the presence of RGO greatly hindered the recombination of photogenerated electrons and increased their lifespan. This work discloses a novel efficient photoanode design for improving performance of the DSSCs.

Nowadays, there is a great demand for low-cost and highly active electrocatalyst for the production of clean renewable energy. However, most of the electrocatalysts are noble metal-based which are very costly and unstable. To counter this, electrochemical water splitting in energy storage systems is been widely applied, using non-noble metal-based nanostructured electrocatalysts. In this work, a novel noble metal-free MoSe2eNi(OH)2 nanocomposite electrocatalyst is synthesized using a multi-step hydrothermal technique for efficient hydrogen evolution reaction (HER). The morphology, structural, chemical composition, and functional features of the synthesized nanomaterials were characterized using different techniques that include scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction analysis (XRD), X-ray photoelectron spectroscopy (XPS), and Raman analysis. The new developed MoSe2eNi(OH)2 nanocomposite combines a high active surface area with a high chemical stability, generating a novel material with a synergistic effect that enhances water splitting process performance. Thus, an outstanding low Tafel slope of 54 mV dec1 is accomplished in the hydrogen evolution reaction.

Low frequency (40 kHz) ultrasound-assisted technique was utilized in the synthesis of CoFe2O4, GaOOH and α-Ga2O3 nanorods. CoFe2O4 was tethered successfully at the crystal matrices of GaOOH and α-Ga2O3 nanorods to form heterojunction nanocatalysts (CoFe2O4/GaOOH; CoFe2O4/Ga2O3). The heterojunction nanocatalysts were characterized using various analytical tools to confirm the expected modifications. The band gap of GaOOH (Eg = 4.50 eV) and α-Ga2O3 (Eg = 4.46 eV) are reduced in the formed heterojunction nanocatalysts CoFe2O4/GaOOH (Eg =2.56 eV) and CoFe2O4/Ga2O3 (Eg = 2.51 eV), respectively. Moreover, the XRD and HR-TEM analyses demonstrate the formation of heterojunction nanocatalysts composed of the lattice diffusion of Co and Fe of CoFe2O4 into the matrix of α-Ga2O3 nanorods with good crystallinity. The photocatalytic efficiency was assessed during solar light-driven photocatalyic oxidation of norflurazon in single treatments and also assisted by peroxymonosulfate addition. The experimental results indicate that ~ 98% of the norflurazon (NRF) is oxidized within 40 min of solar light irradiation in the presence of CoFe2O4/α-Ga2O3 heterojunction nanophotocatalyst, having higher photocatalytic efficiency than benchmarked TiO2 nanoparticles (Degussa P25). Moreover, the results also show that the addition of peroxymonosulfate (PMS) boosts the photocatalytic oxidation and achieving 99% NRF oxidation within 10 min of solar light irradiation by the generation of SO4 •− and • OH radicals. The novel synthesized heterojunction nanophotocatalyst (CoFe2O4/α-Ga2O3) results to be highly stable after six consecutive operating cycles.

In this study, 250 nm sized porous anatase TiO2 nanospheres (TiO2 NSPs) composed of 10 nm sized anatase TiO2 nanoparticles are obtained through a green synthetic route and their surfaces have been decorated with 3–4 nm sized plasmonic silver nanoparticles (AgNPs). Photoluminescence studies confirm that the AgNPs presence on TiO2 NSPs surface effectively inhibits the radiative charge recombination and thus facilitates charge separation process at the Ag-TiO2 NSPs interface, causing an enhanced photocatalytic activity. About 92% of the ceftiofur sodium (CFS) antibiotic taken initially is oxidized by Ag-TiO2 NSPs upon 90 min white light irradiation, while Ag loaded Degussa P25 TiO2 nanoparticles effects only 71% CFS oxidation. The synergistic effect given by plasmonic AgNPs and the continuous framework of anatase TiO2 NPs contributes to inhibit the electron-hole recombination in the Ag-TiO2 NSPs. Oxidation products of CFS in different water sources and their eco-toxicity effects identified through LC-MS and microtoxbioassays, respectively, indicate that the obtained oxidation products are non-toxic compared to pure CFS. Therefore, porous Ag-TiO2 NSPs could be successfully applied in photocatalytic oxidation technologies, exploiting sunlight for the effective removal of pharmaceutical pollutants from wastewater.