Evaluation of mechanical and thermal properties of carrageenan/hydroxypropyl methyl cellulose hard capsule

The inherent source of gelatin used for commercial hard capsules causes a surging demand for vegetarian capsules. In this work, carrageenan is utilized in preparing hard capsules to meet consumer preferences. Hydroxypropyl methylcellulose (HPMC) was incorporated as a reinforcing agent to improve the low mechanical properties of hard capsules made of carrageenan. The HPMC concentration was manipulated from 0.2 to 1.0 w/v% in the carrageenan matrix. The increasing concentration of HPMC exerts significant effects on the tensile strength and elongation at break, with an improvement of 59.1% and 46.9%, respectively, at the optimized HPMC concentration of 0.8 w/v%. The loop strength of the capsule is also increased by 56.4% with decreasing moisture content. The downfield movement from around 3.20 ppm of the carrageenan proton to 3.33 ppm in the proton nuclear magnetic resonanance ( ¹H-NMR) spectrum suggests the formation of intermolecular hydrogen bonding between carrageenan and HPMC, which correlates to the results of Fourier-transform infrared spectroscopy (FTIR) and zeta potential. The glass transition temperature of the film was increased from 37.8 to 65.3°C, showing an upgrade in thermal stability. The film possesses a major mass loss with an activation energy of 64.7 kJ/mol with an increment of 43.4% compared to the control carrageenan. These findings support the conclusion that HPMC enhanced the mechanical properties and thermal stability of the carrageenan film, and the comprehensive analysis of the molecular interaction and decomposition kinetics subsequently may expand the application fields of the carrageenan-HPMC hard capsule as an alternative to gelatin in the future.     

Synthesis and characterization of cobalt-free Ba0.5Sr0.5Fe0.8Cu0.2O3−δ perovskite oxide cathode nanofibers

The cobalt-free perovskite-oxide, Ba_0.5Sr_0.5Fe_0.8Cu_0.2O_3−δ (BSFC) is a very important cathode material for intermediate-temperature proton-conducting solid oxide fuel cells. Ba_0.5Sr_0.5Fe_0.8Cu_0.2O_3−δ nanofibers were synthesized for the first time by a sol-gel electrospinning. Process wherein a combination of polyvinylpyrrolidone and acetic acid was used as the spinning aid and barium, strontium, iron and copper nitrates were used as precursors for the synthesis of BSFC nanofibers. X-ray diffraction studies on products prepared at different calcination temperatures revealed a cubic perovskite structure at 900 °C. The temperature of calcination has a direct effect on the crystallization and surface morphology of the nanofibers. High porosity, and surface area, in addition to an electrical conductivity of 69.54 S cm⁻¹ at 600 °C demonstrate the capability of BSFC nanofibers to serve as effective cathode materials for intermediate-temperature solid oxide fuel cells.     

An overview of photocells and photoreactors for photoelectrochemical water splitting

Solar hydrogen production from direct photoelectrochemical (PEC) water splitting is the ultimate goal for a sustainable, renewable and clean hydrogen economy. While there are numerous studies on solving the two main photoelectrode (PE) material issues i.e. efficiency and stability, there is no standard photocell or photoreactor used in the study. The main requirement for the photocell or photoreactor is to allow maximum light to reach the PE. This paper presents an overview of the PE configurations and the possible photocell and photoreactor design for hydrogen production by PEC water splitting.     

Activated carbon nanofibers as an alternative cathode catalyst to platinum in a two-chamber microbial fuel cell

This paper evaluated the oxygen reduction reaction (ORR) in a microbial fuel cell (MFC) system by using chemically and physically activated electrospun carbon nanofibers (ACNFs) in an MFC and comparing their performance with that of plain carbon paper. The chemical and physical activation was carried out by KOH reagents and CO₂ gas to increase the electrode surface area and the catalytic activity. As a result, it was found that the MFC with the chemically activated carbon nanofibers (ACNFs) exhibited better catalytic activity than that of the physically activated ACNFs. Chemically ACNFs with 8 M KOH were found to be one of the most promising candidates for the ORR and could generate up to 3.17 times more power than that of the carbon paper. The ACNFs with 8 M KOH exhibited 78% more power generation than that of the physically activated ACNFs and exhibited 16% more power generation than the chemically activated ACNFs with 4 M KOH. The power per cost of ACNFs with 8 M KOH is 2.65 times greater than that of the traditionally used platinum cathode. Thus, ACNFs are a good alternative catalyst to Pt for MFCs.     

Development and application of vanadium oxide/polyaniline composite as a novel cathode catalyst in microbial fuel cell

Polyaniline (Pani), vanadium oxide (V₂O₅), and Pani/V₂O₅ nanocomposite were fabricated and applied as a cathode catalyst in Microbial Fuel Cell (MFC) as an alternative to Pt (Platinum), which is a commonly used expensive cathode catalyst. The cathode catalysts were characterized using Cyclic Voltammetry and Linear Sweep Voltammetry to determine their oxygen reduction activity; furthermore, their structures were observed by X‐ray Diffraction, X‐ray Photoelectron Spectroscopy, Brunauer–Emmett–Teller, and Field‐Emission Scanning Electron Microscopy. The results showed that Pani/V₂O₅ produced a power density of 79.26 mW/m², which is higher than V₂O₅ by 65.31 mW/m² and Pani by 42.4 mW/m². Furthermore, the Coulombic Efficiency of the system using Pani/V₂O₅ (16%) was higher than V₂O₅ and Pani by 9.2 and 5.5%, respectively. Pani–V₂O₅ also produced approximately 10% more power than Pt, the best and most common cathode catalyst. It declares that Pani–V₂O₅ can be a suitable alternative for application in a MFC system. Copyright © 2013 John Wiley & Sons, Ltd.     

Ni/Pd-promoted Al2O3–La2O3 catalyst for hydrogen production from polyethylene terephthalate waste via steam reforming

Ni/Pd-co-promoted Al₂O₃–La₂O₃ catalysts for selective hydrogen production from polyethylene terephthalate (PET) plastic waste via steam reforming process has been investigated. The catalysts were prepared by impregnation method and were characterized using XRD, BET, TPD-CO₂, TPR-H₂, SEM, TGA and DTA. The results showed that Ni-Pd-co-impregnated Al₂O₃–La₂O₃ catalyst has excellent activity for the production of hydrogen with a prolong stability. The feed conversion of 87% was achieved over 10% Ni/Al₂O₃ catalyst which increased to 93.87% in the case of 10% Ni-1% Pd/Al₂O₃–La₂O₃ catalysts with an H₂ fraction of 0.60. The catalyst performance in term of H₂ selectivity and feed conversion was further investigated under various operating parameters, e.g., temperatures, feed flow rates, feed ratios and PET concentrations. It was found that the temperature has positive effects on H₂ selectivity and conversion, yet feed flow rate has the adverse effects. In addition, PET concentrations showed improved in H₂ selectivity in comparison to when only phenol as a solvent was involved. The Ni particles, which are the noble-based active species are more effective, thus offered good hydrogen production in the PET steam reforming process. Incorporation of La₂O₃ as support and Pd as a promoter to the Ni/Al₂O₃ catalyst significantly increased catalyst stability. The Ni–Pd/Al₂O₃–Al₂O₃ catalyst showed remarkable activity even after 36 h along with the production of carbon nanotubes, while H₂ selectivity and feed conversion was only slightly decreased.     

Effect of pre-treatment and biofouling of proton exchange membrane on microbial fuel cell performance

Nafion^® 117, as the most popular proton exchange membrane, has been studied with regards to the effect of pre-treatment and biofouling for bioelectricity production and wastewater treatment, in dual chamber microbial fuel cells. The obtained results showed that maximum generated power was obtained using pre-treated Nafion^® 117, at approximately 100 mW/m². However, maximum generated power for untreated Nafion^® 117 and biofouled Nafion^® 117 were 52.8 mW/m² and 20.9 mW/m², respectively. Furthermore, the columbic efficiency of pre-treated Nafion^® 117 was 2.32 and 4.15 times higher than untreated and biofouled Nafion^® 117, respectively. Obtained results demonstrated that the pre-treatment of the proton exchange membrane is necessary to reach higher powers, and biofouling is a major obstacle for proton exchange membranes in dual chamber MFCs.     

Copper-phthalocyanine and nickel nanoparticles as novel cathode catalysts in microbial fuel cells

In this study, four different catalysts (i.e., carbon black, nickel nanoparticle (Ni)/C, Phthalocyanine/C and copper-phthalocyanine/C), were tested in a two-chamber Microbial Fuel Cell (MFC) and their performances were compared with Pt as the common cathode catalyst in MFC. The characterization of catalysts was done by TEM, XPS and EDX and their electrochemical characteristics were compared by cyclic voltammetry (CV) and Linear Sweep Voltammetry (LSV). The results proved that copper phthalocyanine and nickel nanoparticles are potential alternatives catalyst for Pt. Even copper-phthalocyanine generated power is almost the same as Pt. The CV and LSV results reported high electrochemical activity of these catalysts. The maximum power density and coulombic efficiency was achieved by copper-phthalocyanine/C as 118.2 mW/m² and 29.3%.     

Optimization of purity and yield of amorphous bio-silica nanoparticles synthesized from bamboo leaves

The fallen yellowish bamboo leaves around bamboo crops are always overlooked even though they contain high silica in their ash. Bamboo leaf valorization consequently has the potential to be a green process for synthesizing amorphous silica. Unfortunately, the optimum process parameters have not been widely disclosed. Hence, this study intends to optimize the synthesis of amorphous bio-silica nanoparticles from bamboo leaves using Box–Behnken design (BBD). Bamboo leaves were initially washed with HCl, followed by combustion at 700°C, and then ash washing, extraction of silica with NaOH (sol–gel method), gelation, and drying. According to the results, optimum conditions occur under no acid washing of leaves, solvent-to-feed ratio = 5 mL/g, and extraction duration = 1.5 h. The optimum conditions give the highest purity (94.1 wt.%) and yield (42.33%) as well as the highest surface area (328.61 m²/g), smallest pore diameter (8.69 nm), and largest pore volume (0.71 cc/g) of bio-silica nanoparticles. Furthermore, bio-silica nanoparticles are amorphous, spherical-shaped aggregates, and have a white powdered colour.