Eco-friendly mixed metal (Mg-Ni) ferrite nanosheets for efficient electrocatalytic water splitting.

Eco-friendly and cost-effective catalysts with multiple active sites, large surface area, high stability and catalytic activity are highly desired for efficient water splitting as a sustainable green energy source. Within this line, a facile synthetic approach based on solventless thermolysis was employed for the simple and tunable synthesis of Ni1-xMgxFe2O4 (0 ≤ x ≤ 1) nanosheets. The characterization of nanosheets (via p-XRD, EDX, SEM, TEM, HRTEM, and SAED) revealed that the pristine ferrites (NiFe2O4 and MgFe2O4), and their solid solutions maintain the same cubic symmetry throughout the composition regulation. Elucidation of the electrochemical performance of the nanoferrite solid solutions showed that by tuning the local chemical environment of Ni in NiFe2O4 via Mg substitution, the intrinsic catalytic activity was enhanced. Evidently, the optimized Ni0.4Mg0.6Fe2O4 catalyst showed drastically enhanced HER activity with a much lower overpotential of 121 mV compared to the pristine NiFe2O4 catalyst. Moreover, Ni0.2Mg0.8Fe2O4 catalyst exhibited the best OER performance with a low overpotential of 284 mV at 10 mA/cm2 in 1 M KOH. This enhanced electrocatalytic activity could be due to improved electronic conductivity caused by the partial substitution of Ni2+ by Mg2+ in the NiFe2O4 matrix as well as the synergistic effect in the Mg-substituted NiFe2O4. Our results suggest a feasible route for developing earth-abundant metal oxide-based electrocatalysts for future water electrolysis applications.

Optimum iron-pyrophosphate electronic coupling to improve electrochemical water splitting and charge storage.

Tuning the electronic properties of transition metals using pyrophosphate (P2O7) ligand moieties can be a promising approach to improving the electrochemical performance of water electrolyzers and supercapacitors, although such a material's configuration is rarely exposed. Herein, we grow NiP2O7, CoP2O7, and FeP2O7 nanoparticles on conductive Ni-foam using a hydrothermal procedure. The results indicated that, among all the prepared samples, FeP2O7 exhibited outstanding oxygen evolution reaction and hydrogen evolution reaction with the least overpotential of 220 and 241 mV to draw a current density of 10 mA/cm2. Theoretical studies indicate that the optimal electronic coupling of the Fe site with pyrophosphate enhances the overall electronic properties of FeP2O7, thereby enhancing its electrochemical performance in water splitting. Further investigation of these materials found that NiP2O7 had the highest specific capacitance and remarkable cycle stability due to its high crystallinity as compared to FeP2O7, having a higher percentage composition of Ni on the Ni-foam, which allows more Ni to convert into its oxidation states and come back to its original oxidation state during supercapacitor testing. This work shows how to use pyrophosphate moieties to fabricate non-noble metal-based electrode materials to achieve good performance in electrocatalytic splitting water and supercapacitors.

Sunflower Oil as a Renewable Resource for Polyurethane Foams: Effects of Flame-Retardants.

Currently, polyurethane (PU) manufacturers seek green alternatives for sustainable production. In this work, sunflower oil is studied as a replacement and converted to a reactive form through epoxidation and oxirane opening to produce rigid PU foams. Confirmatory tests such as Fourier-transform infrared spectroscopy (FT-IR), gel permeation chromatography (GPC), and hydroxyl value among others were performed to characterize the synthesized polyol. Despite the versatility of rigid PU foams, they are highly flammable, which makes eco-friendly flame retardants (FRs) desired. Herein, expandable graphite (EG) and dimethyl methyl phosphonate (DMMP), both non-halogenated FR, were incorporated under different concentrations to prepare rigid PU foams. Their effects on the physio-mechanical and fire-quenching properties of the sunflower oil-based PU foams were elucidated. Thermogravimetric and compression analysis showed that these foams presented appreciable compressive strength along with good thermal stability. The closed-cell contents (CCC) were around 90% for the EG-containing foams and suffered a decrease at higher concentrations of DMMP to 72%. The burning test showed a decrease in the foam's flammability as the neat foam had a burning time of 80 s whereas after the addition of 13.6 wt.% of EG and DMMP, separately, there was a decrease to 6 and 2 s, respectively. Hence, our research suggested that EG and DMMP could be a more viable alternative to halogen-based FR for PU foams. Additionally, the adoption of sunflower polyol yielded foams with results comparable to commercial ones.

Effect of Graphene Oxide and Reduced Graphene Oxide on the Properties of Sunflower Oil-Based Polyurethane Films.

Sunflower oil was used for the synthesis of a polyol via an epoxidation reaction followed by a ring-opening reaction. The successful synthesis of the sunflower oil-based polyol (SFO polyol) was demonstrated through structural characterizations and wet-chemistry analysis. Bio-based polyurethane (BPU) films were fabricated using synthesized polyol and diisocyanate. Various amounts of graphene oxide (GO) and reduced graphene oxide (rGO) were added separately to see their effect on the physicomechanical and thermal properties of BPU films. Several tests, such as thermogravimetric analysis, tensile strength, dynamic mechanical analysis, hardness, flexural strength, and the water contact angle, were performed to evaluate the effect of GO and rGO on the properties of the BPU films. Some of the analyses of the BPU films demonstrated an improvement in the mechanical properties, for example, the tensile strength increased from 22.5 to 26 MPa with the addition of only 0.05 wt.% GO. The storage modulus improved from 900 to 1000 and 1700 MPa after the addition of 0.02 and 0.05 wt.% GO, respectively. This study shows that a small amount of GO and rGO could improve the properties of BPU films, making them suitable for use in coating industries.

Decontamination of wastewater containing contaminants of emerging concern by electrooxidation and Fenton-based processes - A review on the relevance of materials and methods.

In recent years, there has been an increasingly growing interest regarding the use of electrochemical advanced oxidation processes (EAOPs) which are considered highly promising alternative treatment techniques for addressing environmental issues related to pollutants of emerging concern. In EAOPs, electrogenerated oxidizing agents, such as hydroxyl radical (HO•), can react non-selectively with a wide range of organic compounds, degrading and mineralizing their structures to unharmful molecules like CO2, H2O, and inorganic ions. To this date, a broad spectrum of advanced electrocatalysts have been developed and applied for the treatment of compounds of interest in different matrices, specifically aiming at enhancing the degradation performance. New combined methods have also been employed as alternative treatment techniques targeted at circumventing the major obstacles encountered in Fenton-based processes, such as high costs and energy consumption, which still contribute significantly toward inhibiting the large-scale application of these processes. First, some fundamental aspects of EAOPs will be presented. Further, we will provide an overview of electrode materials which have been recently developed and reported in the literature, highlighting different anode and cathode structures employed in EAOPs, their main advantages and disadvantages, as well as their contribution to the performance of the treatment processes. The influence of operating parameters, such as initial concentrations, pH effect, temperature, supporting electrolyte, and radiation source, on the treatment processes were also studied. Finally, hybrid techniques which have been reported in the literature and critically assess the most recent techniques used for evaluating the degradation efficiency of the treatment processes.