The photocatalytic activity of titanium dioxide (TiO₂) nanoparticles toward hydrogen generation can be significantly improved via the loading of various metals e.g., Ru, Co, Ni as co-catalysts. The metal co-catalysts are loaded into TiO₂ nanoparticles via different deposition methods; incipient wet impregnation (Imp), hydrothermal (HT), or photocatalytic deposition (PCD). Among all of the tested materials, 0.1 wt% Ru–TiO₂ (Imp) provided the highest initial hydrogen catalytic rate of 23.9 mmol h⁻¹ g⁻¹, compared to 10.82 and 16.55 mmol h⁻¹ g⁻¹ for 0.3 wt% Ni–TiO₂ (Imp) and 0.3 wt% Co–TiO₂ (Imp), respectively. The loading procedures, co-catalyst metals type, and their loading play a significant role in elevating the photocatalytic activity of pristine TiO₂ semiconductors toward hydrogen generation. Redox transition metals e.g., Co and Ni exhibit comparable photocatalytic performance to expensive elements such as Ru.

Cadmium ion Cd²⁺ contamination is a major environmental issue caused by industry. Polyarylidene N-hexane pyrrole (PAP_h) and crosslinked polyarylidene N-phenyl pyrrole (PAP_D) were prepared from the previously synthesized polymer (polyarylidene ketone (PAK)) by using the advantage of repeating carbonyl groups at the 1,4 position and reacting it with hexylamine and P-phenylenediamine via the Paal–Knorr reaction. Various methods were used to characterize polymers, such as FT-IR spectroscopy, X-ray diffraction (XRD), thermogravimetry analysis (TGA), UV–visible spectroscopy, scanning electron microscope (SEM), zeta potential, and surface area measurements (BET), revealing successful fabrication, good thermostability, and well-defined microporous structures useful for Cd²⁺ adsorption. Optimal adsorption capacities of 55.8 mg g⁻¹ for PAP_h and 86.95 mg g⁻¹ for PAP_D indicate a significant enhancement in Cd²⁺ adsorption via their microporous structures, Cd²⁺ adsorption was also investigated in terms of contact time, initial concentration, and pH. A total input concentration of 30 ppm Cd ions, may yield an 84.3% removal rate for PAP_h and an 89.2% removal rate for PAP_D. The experimental results were well-fit by many models, including pseudo-second-order kinetics (PSO), Freundlich isotherms, intraparticle diffusion, and Langmuir. The varying adsorption performances of the two polymers studied, (PAP_h) and (PAP_D), were found to be derived from their respective chemical structures, which include various functional groups, according to studies conducted on Cd²⁺ in an aqueous solution. Cd²⁺ adsorption on polymers was considered physisorption; π–cation interactions and surface complexation played significant roles in adsorption. The PAP polymers may be considered promising substitutes and innovative adsorbents to remove Cd²⁺ ions from a water solution.

Background

Hydrogen is a promising source of alternative energy. Fermentative production is more feasible because of its high hydrogen generation rate, simple operating conditions, and utilization of various organic wastes as substrates. The most significant constraint for biohydrogen production is supplying it at a low cost with fewer impurities.

Results

Leaf biomass of Calotropis procera was used as a feedstock for a dark fermentative production of hydrogen by Bacillus coagulans AH1 (MN923076). The optimum operation conditions for biohydrogen production were 5.0% substrate concentrationand pH 9.0, at 35 °C. In which the biohydrogen yield was 3.231 mmol H₂/g dry biomass without any pretreatments of the biomass. A freshwater microalga Oscillatroia sp was used for upgrading of the produced biohydrogen. It sequestrated 97 and 99% % of CO₂ from the gas mixture when it was cultivated in BG11 and BG11-N media, respectively After upgrading process, the residual microalgal cells exhibited 0.21mg/mL of biomass yield,high content of chlorophyll-a (4.8 µg/mL) and carotenoid (11.1 µg/mL). In addition to Oscillatroia sp residual biomass showed a lipid yield (7.5–8.7%) on the tested media.

Conclusion

Bacillus coagulans AH1 is a promising tool for biohydrogen production avoiding the drawbacks of biomass pretreatment. Oscillatroia sp is encouraged as a potent tool for upgrading and purification of biohydrogen. These findings led to the development of a multiproduct biorefinery with zero waste that is more economically sustainable.

Herein, we report the modification of TiO₂ nanostructures with two different metal chalcogenides (CuS or MoS₂). The effect of the preparation scheme (hydrothermal and coprecipitation methods) and the mass ratio of metal chalcogenides were investigated. The as-synthesized photocatalyst nanocomposites were fully characterized by various techniques. Moreover, the photo/electrochemical analysis were performed to investigate the photoelectric properties and photocatalytic mechanism. The photocatalytic performance was evaluated using two test reactions. In the case of H₂ generation via water splitting, it was found that 0.5 wt% CuS-TiO₂ synthesized via the coprecipitation method exhibited an initial hydrogen evolution rate (HER) of 2.95 mmol h⁻¹ g⁻¹. While, the optimized 3 wt% MoS₂-TiO₂ synthesized by the hydrothermal method, showed an HER of 1.7 mmol h⁻¹ g⁻¹. Moreover, the degradation efficiency of methylene blue dye was 98% under UV–Vis light irradiation within 2 h over 0.5 CT_PP and 3MT_HT. Under visible irradiation, the degradation efficiency was 100% and 96% for 3MT_PP and 0.5CT_HT in the presence of H₂O₂, respectively. This study has proven that metal chalcogenides can act as effective, stable, and low-cost bifunctional co-catalysts to enhance the overall photocatalytic performance.

4-Nitrophenol (4-NP) is reported to originate disadvantageous effects on the human body collected from industrial pollutants; therefore, the detoxification of 4-NP in aqueous contamination is strongly recommended. In this study, the heterojunction mesoporous α-Fe₂O₃/TiO₂ modulated with diverse Ag percentages has been constructed via a sol–gel route in the occurrence of a soft template P123. The formation of biphasic crystalline TiO₂ anatase and brookite phases has been successfully achieved with the average 10 nm particle sizes. The photo/-catalytic reduction of 4-NP has been performed utilizing NaBH₄ as a reducing agent with and without visible illumination. All Ag/Fe₂O₃/TiO₂ nanocomposites exhibited significantly higher photo/-catalytic reduction efficiency than pure Fe₂O₃, TiO₂ NPs, and Fe₂O₃/TiO₂ nanocomposite. 2.5% Ag/Fe₂O₃/TiO₂ nanocomposite was considered the highest and superior photocatalytic reduction efficiency, and it almost achieved 98% after 9 min. Interestingly, the photocatalytic reduction of 4-NP was accelerated 9 times higher than the catalytic reduction over 2.5% Ag/Fe₂O₃/TiO₂; its rate constant value was 709 and 706 times larger than pure TiO₂ and Fe₂O₃ NPs, respectively. The enhanced photocatalytic reduction ability of Ag/Fe₂O₃/TiO₂ nanocomposite might be referred to as significantly providing visible light absorption and a large surface area, and it can upgrade the effective separation and mobility of electron holes. The stability of the synthesized catalysts exhibited that the obtained catalysts can undergo a slight decrease in reduction efficiency after five successive cycles. This approach highlights a novel route for constructing ternary nanocomposite systems with high photo/-catalytic ability.

Because of its sustainability and cleanliness, hydrogen has recently been a research focus as a potential fuel. One promising way to produce hydrogen is water electrolysis in an alkaline solution. However, this process requires much energy to split the H–OH bond and transfer multiple electrons/protons. To overcome this challenge, catalytic electrodes have been developed to reduce the energy needed and maintain sustainable water electrolysis. This study explores the potential of utilizing a two-dimensional nickel-based cyanide coordination polymer (2D Ni-CP) precursor to synthesize effective Ni-based inorganic nanostructured electrodes. Various types of electrodes, including Ni-O, Ni-S, Ni-Se, and Ni-P, are synthesized through direct thermal treatment of the coordination polymer. The performance of the as-prepared materials in the hydrogen evolution process (HER) in an alkaline medium is examined. Ni-P demonstrates the most promising HER performance with an overpotential of 266 mV at 10 mA cm⁻² and a Tafel slope of 186 mV dec⁻¹. These results are compared to those of the benchmark expensive and scarce Pt/C-40% catalyst (38 mV and 48 mV dec⁻¹) examined under identical conditions. Additionally, Ni-P shows outstanding HER durability over four days, as reflected by chronopotentiometry measurements.

A wet‐incipient impregnation method was reported to synthesize hierarchical porous bimetallic (Co, Zn)‐zeolitic imidazolate frameworks (ZIF‐8)/TiO₂ (Co@ZIF‐8/TiO₂) for green hydrogen generation via photocatalytic water splitting. Co@ZIF‐8/TiO₂ showed higher photocatalytic efficiency than TiO₂, with a hydrogen generation rate (HGR) of 13 mmol·h⁻¹·g⁻¹ with a 151‐fold increase in the catalytic performance of TiO₂. The photocatalytic HGR of Co@ZIF‐8/TiO₂ was superior to that of the ZIF‐8/TiO₂ heterostructure. Co@ZIF‐8 showed a hierarchical porous structure containing micropores and mesopores regimes, providing a proficient transport channel for charge transfer. This study presents new prospects for using hierarchical porous metal–organic frameworks (MOFs) as support and promoter in photocatalytic applications of semiconductor such as TiO₂.

Abstract
Our present study provides expedient methods for the synthesis of novel substituted indanes, pyrido[3,2,1-
jk]carbazoles and pyrido[3,2,1-kl]phenothiazines utilizing intramolecular Friedel-Crafts cyclialkylations of
synthesized heteroaryl alcohols. This methodology is realized by a three-step protocol involving first
esterification of starting carboxylic acids to the corresponding esters, addition of Grignard reagents to give
carbinol precursors and followed by Friedel-Crafts cyclizations of alcohols mediated by AlCl3/CH3NO2, PPA or
P2O5-catalysts to furnish the desired polycycles in good to excellent yields of 65-85%. The designed protocol
offers easy access to the pharmaceutically promising templates in good yields. The molecular structural
elucidations of all newly obtained compounds have been proved by spectral and elemental analysis.

Background: Cobalt oxide nanocubes have garnered significant attention as potential supercapacitor electrodes due to their unique structural and electrochemical properties. The spent lithium-ion batteries (LiBs) are considered as zero-cost source for cobalt oxide production.

Objectives: The aim of this work is to recover cobalt oxide from spent LiBs and study its electrochemical performance as a supercapacitor electrode material.

Methods: This study uses an electrodeposition method to obtain cobalt oxide honeycomb-like anodes coated on Ni foam substrates from spent Li-ion batteries for supercapacitors applications. The effect of annealing temperature on the cobalt oxide anode has been carefully investigated; 450ºC annealing temperature results in nanocubes on the surface of the cobalt oxide electrode. X-ray diffraction confirmed the formation of the Co_-3O_-4-NiO electrode.

Results: The Co₃O₄-NiO nanocubes electrode has shown a high specific capacitance of 1400 F g^-1 at 1 A g^-1 and high capacitance retention of ~96 % after 2250 cycles at a constant current density of 10 A g^-1 compared to 900 F g^-1 at 1 A g^-1 as for prepared Co3O4 honeycomb.

Conclusion: This strategy proves that the paramount importance of Co₃O₄-NiO nanocubes, meticulously synthesized at elevated temperatures, as a supremely effective active material upon deposition onto transition metal foam current collectors, establishing their indispensability for supercapacitor applications.