ABSTRACT
Graphene, a two-dimensional carbon allotrope with a honeycomb structure, has emerged as a material of immense interest in diverse scientific and technical domains. It is mainly produced from graphite by mechanical, chemical and electrochemical exfoliation. As renewable energy and source utilization increase, including bioenergy from forest and woody residues, processed, among other methods, by pyrolysis treatment, it can be expected that biochar production will increase too. Thus, its useful applications, particularly in obtaining high-added-value products, need to be fully explored. This study aims at presenting a comprehensive analysis derived from experimental data, offering insights into the potential of biomass pyrolysis-derived biochar as a versatile precursor for the controlled synthesis of graphene and its derivatives. This approach comprehended the highest energy output and lowest negative environmental footprint, including the minimization of both toxic gas emissions during processing and heavy metals' presence in the feedstock, toward obtaining biochar suitable to be modified, employing the Hummers and intercalation with persulfate salts methods, aiming at deriving graphene-like materials. Material characterization has revealed that besides morphology and structural features of the original wooden biomass, graphitized structures are present as well, which is proven clearly by Raman and XPS analyses. Electrochemical tests revealed higher conductivity in modified samples, implying their graphene-like nature.
ABSTRACT
Fe2O3/TiO2 nanocomposites were fabricated via a facile impregnation/calcination technique employing different amounts iron (III) nitrate onto commercial TiO2 (P25 Aeroxide). The as-prepared Fe2O3/TiO2 nanocomposites were characterized by X-ray diffraction (XRD), Raman spectroscopy (RS), scanning electron microscopy/energy-dispersive spectroscopy (SEM/EDXS), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller analysis (BET), electron impedance spectroscopy (EIS), photoluminescence spectroscopy (PL), and diffuse reflectance spectroscopy (DRS). As a result, 5% (w/w) Fe2O3/TiO2 achieved the highest photocatalytic activity in the slurry system and was successfully immobilized on glass support. Photocatalytic activity under visible-light irradiation was assessed by treating pharmaceutical amoxicillin (AMX) in the presence and absence of additional oxidants: hydrogen peroxide (H2O2) and persulfate salts (PS). The influence of pH and PS concentration on AMX conversion rate was established by means of statistical planning and response surface modeling. Results revealed optimum conditions of [S2O82-] = 1.873 mM and pH = 4.808; these were also utilized in presence of H2O2 instead of PS in long-term tests. The fastest AMX conversion possessing a zero-order rate constant of 1.51 × 10-7 M·min-1 was achieved with the photocatalysis + PS system. The AMX conversion pathway was established, and the evolution/conversion of formed intermediates was correlated with the changes in toxicity toward Vibrio fischeri. Reactive oxygen species (ROS) scavenging was also utilized to investigate the AMX conversion mechanism, revealing the major contribution of photogenerated h+ in all processes.
ABSTRACT
Sustainable hydrogen production is one of the main challenges today in the transition to a green and sustainable economy. Photocatalytic hydrogen production is one of the most promising technologies, amongst which BiVO4-based processes are highly attractive due to their suitable band gap for solar-driven processes. However, the performance of BiVO4 alone in this role is often unsatisfactory. Herein we report the improvement of BiVO4 performance with reduced graphene oxide (rGO) as a co-catalyst for the photoelectrochemical water splitting (PEC-WS) in the presence of simple functionalized benzene derivatives (SFBDs), i.e., phenol (PH), benzoic acid (BA), salicylic acid (SA), and 5-aminosalicylic acid (5-ASA) as potential photogenerated hole scavengers from contaminated wastewaters. Linear sweep voltammetry and chronoamperometry, along with electrochemical impedance spectroscopy were utilized to elucidate PEC-WS performance under illumination. rGO has remarkably improved the performance of BiVO4 in this role by decreasing photogenerated charge recombination. In addition, 5-ASA greatly improved current densities. After 120 min under LED illumination, 0.53 µmol of H2 was produced. The type and concentration of SFBDs can have significant and at times opposite effects on the PEC-WS performance of both BiVO4 and rGO-BiVO4.
ABSTRACT
Hydrogels have been investigated due to their unique properties. These include high water content and biocompatibility. Here, hydrogels with different ratios of poly(2-(dimethylamino)ethylmethacrylate) (PDMAEMA) were grafted onto cellulose (Cel-g-PDMAEMA) by the free radical polymerization method and gamma-ray radiation was applied in order to increase crosslinking and content of PDMAEMA. Gamma irradiation enabled an increase of PDMAEMA content in hydrogels in case of higher ratio of 2-(dimethylamino)ethyl methacrylate in the initial reaction mixture. The swelling of synthesized hydrogels was monitored in dependence of pH (3, 5.5 and 10) during up to 60 days. The swelling increased from 270% to 900%. Testing of antimicrobial activity of selected hydrogel films showed weak inhibitory activity against Escherichia coli, Pseudomonas aeruginosa, and Bacillus subtilis. The results obtained by the cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) indicate that chemically synthesized hydrogels have good characteristics for the supercapacitor application.
