Juhana Jaafar

Physicochemical properties of “green” nanocrystalline cellulose isolated from recycled newspaper

“Green” nanocrystalline cellulose (NCC) was isolated through an acid hydrolysis process from recycled newspapers and prepared via treatment with NaOH and NaClO2. Morphological characterization and physicochemical property measurements were executed using scanning electron microscopy (SEM), atomic force microscopy (AFM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and thermogravimetric analysis (TGA). FTIR and chemical composition analysis demonstrated that lignin and hemicellulose structures were removed using different pretreatment steps with NaOH and NaClO2. From the SEM results, it was discovered that the size of purified cellulose fibrils reduced to a great extent, and the structure of cellulose microfibers became smoother and cleaner due to the removal of lignin with other extracts. The XRD analysis results revealed that NCC exhibits the highest crystallinity index after acid hydrolysis of bleached cellulose microfibers. TEM and AFM analysis revealed that the rod-like structure of NCC was obtained with size 5.78 ± 2.14 nm wide and 121.42 ± 32.51 nm long. The TGA results suggested that the thermal stability of the NCC was affected mainly by the dehydration reaction caused by sulphate groups. The isolated nanocrystalline cellulose attracts great interest as an inexpensive bio-based filler in polymer nanocomposites.

Incorporation of N-doped TiO2 nanorods in regenerated cellulose thin films fabricated from recycled newspaper as a green portable photocatalyst

In this work, an environmental friendly RC/N-TiO2 nanocomposite thin film was designed as a green portable photocatalyst by utilizing recycled newspaper as sustainable cellulose resource. Investigations on the influence of N-doped TiO2 nanorods incorporation on the structural and morphological properties of RC/N-TiO2 nanocomposite thin film are presented. The resulting nanocomposite thin film was characterized by FESEM, AFM, FTIR, UV-vis-NIR spectroscopy, and XPS analysis. The results suggested that there was a remarkable compatibility between cellulose and N-doped TiO2 nanorods anchored onto the surface of the RC/N-TiO2 nanocomposite thin film. Under UV and visible irradiation, the RC/N-TiO2 nanocomposite thin film showed remarkable photocatalytic activity for the degradation of methylene blue solution with degradation percentage of 96% and 78.8%, respectively. It is crucial to note that the resulting portable photocatalyst produced via an environmental and green technique in its fabrication process has good potential in the field of water and wastewater treatment application.

Regenerated cellulose membrane as bio-template for in-situ growth of visible-light driven C-modified mesoporous titania.

Visible light driven C-doped mesoporous TiO2 (C-MTiO2) nanorods have been successfully synthesized through green, low cost, and facile approach by sol-gel bio-templating method using regenerated cellulose membrane (RCM) as nanoreactor. In this study, RCM was also responsible to provide in-situ carbon sources for resultant C-MTiO2 nanorods in acidified sol at low temperatures. The composition, crystallinity, surface area, morphological structure, and optical properties of C-MTiO2 nanorods, respectively, had been characterized using FTIR, XRD, N2 adsorption/desorption, TEM, UV-vis-NIR, and XPS spectroscopy. The results suggested that the growth of C-MTiO2 nanorods was promoted by the strong interaction between the hydroxyl groups of RCMs and titanium ion. Optical and XPS analysis confirmed that carbon presence in TiO2 nanorods were responsible for band-gap narrowing, which improved the visible light absorption capability. Photocatalytic activity measurements exhibited the capability of C-MTiO2 nanorods in degradation of methyl orange in aqueous solution, with 96.6% degradation percentage under visible light irradiation.

Biopolymer-based electrolyte membranes from chitosan incorporated with montmorillonite-crosslinked GPTMS for direct methanol fuel cells

A composite membrane was fabricated from biopolymer chitosan and montmorillonite (MMT) filler as an alternative membrane electrolyte for direct methanol fuel cell (DMFC) application. To first improve the organic–inorganic interfacial morphology, the pristine MMT was pre-treated using 3-glicidoxy propyltrimethoxysilane (GPTMS) surface modifier to produce organophilic MMT (O-MMT). The GPTMS modified MMT was mixed with chitosan in acetic acid solution and cast into membranes. SEM images and FTIR analysis showed that the O-MMT was successfully incorporated into the chitosan polymer matrix. Water and methanol uptake of the Ch/O-MMT composite membranes decreased with increasing O-MMT loadings, but the ion exchange capacity (IEC) value increased. The Ch/O-MMT with 5 wt% O-MMT loading exhibited the best methanol permeability and proton conductivity characteristics among the other Ch/O-MMT membranes, which were 3.03 × 10−7 cm2 s−1 and 4.66 mS cm−1, respectively. All the results obtained from this study can be used to conclude that the chitosan membrane with O-MMT filler is a promising high performance PEM candidate for DMFC application.

Physicochemical characterization of cellulose nanocrystal and nanoporous self-assembled CNC membrane derived from Ceiba pentandra

This research involves the rare utilisation of the kapok fibre (Ceiba pentandra) as a raw material for the fabrication of cellulose nanocrystal (CNC) and self-assembled CNC membranes. The isolation of CNC from Ceiba pentandra began with the extraction of cellulose via the chemical alkali extraction by using 5wt% NaOH, followed by the typical acidified bleaching method and, finally, the CNC production through acid hydrolysis with 60wt% H2SO4 at the optimum time of 60min. The prepared CNC was then employed for the preparation of self-assembled membrane through the water suspension casting evaporation technique. The obtained CNC membrane was characterised in terms of its composition, crystallinity, thermal stability, as well as, structural and morphological features with the use of several techniques including FTIR, XRD, AFM, TEM, FESEM, and TGA. The FESEM and AFM analyses had illustrated the achievement of a self-assembled CNC membrane with a smooth surface and a well-distributed nano-porous structure, with the porosity of 52.82±7.79%. In addition, the findings proved that the self-assembled CNC membrane displayed good adsorption capability indicated by the recorded efficiency of 79% and 85% for 10mg/L and 5mg/L of methylene blue in an aqueous solution, respectively.

A review on the fabrication of electrospun polymer electrolyte membrane for direct methanol fuel cell

Proton exchange membrane (PEM) is an electrolyte which behaves as important indicator for fuel cells performance. Research and development (R&;D) on fabrication of desirable PEM have burgeoned year by year, especially for direct methanol fuel cell (DMFC). However, most of the R&;Ds only focus on the parent polymer electrolyte rather than polymer inorganic composites. This might be due to the difficulties faced in producing good dispersion of inorganic filler within the polymer matrix, which would consequently reduce the DMFCs performance. Electrospinning is a promising technique to cater for this arising problem owing to its more widespread dispersion of inorganic filler within the polymer matrix, which can reduce the size of the filler up to nanoscale. There has been a huge development on fabricating electrolyte nanocomposite membrane, regardless of the effect of electrospun nanocomposite membrane on the fuel cells performance. In this present paper, issues regarding the R&;D on electrospun sulfonated poly (ether ether ketone) (SPEEK)/inorganic nanocomposite fiber are addressed.

Role of lithium oxide as a sintering aid for a CGO electrolyte fabricated via a phase inversion technique

The incorporation of lithium oxide (Li2O) as a sintering additive has specific advantages for electrolyte membrane fabrication. However, the viability of the sintering additive to be implemented in a phase inversion technique is still ambiguous. In this first attempt, lithium was doped into a gadolinium-doped ceria (CGO) crystal structure using the metal nitrate doping method and calcined at four different temperatures, i.e. 140, 300, 500 and 700 °C. The prepared Li-doped CGO (Li–CGO) powders were analyzed by thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray diffraction (XRD), N2 adsorption/desorption, and Fourier-transform infrared (FTIR). Primary results demonstrate that the calcination temperature of the Li–CGO influences the condition of the electrolyte suspension. Li–CGO calcined at 700 °C (D-700), as compared with other Li–CGO, possessed a strong interaction between the Li and CGO. The D-700 was then incorporated into the electrolyte flat sheet membrane which was prepared by a phase inversion technique. The membrane was then sintered at different sintering temperatures from 1350 °C to 1450 °C. In comparison with the unmodified CGO, the morphological results suggest that the Li2O can remarkably promote the densification of CGO at a lower sintering temperature (1400 °C). These findings help to promote the use of sintering additives in a ceria-based electrolyte suspension specifically for the phase inversion technique.

The influence of PEEK as a pore former on the microstructure of brush-painted LSCF cathodes

At lower operation temperature of intermediate temperature solid oxide fuel cells (IT-SOFC), polarization resistance was recognized as a limiting step because polarization at cathode is dependent on the rate of oxygen reduction reaction. The enhancement of cathode microstructure is one of the effective ways to improve the reaction rate. Pore former addition method is proven to be able to tailor the microstructure of cathode. The addition of polyether ether ketone (PEEK) as pore former was evaluated and compared with common pore formers (corn starch and graphite) for the microstructure cathode layer. Brush painting technique was used to deposit cathode layer on anode/electrolyte dual layer support hollow fiber. X-ray diffraction (XRD) analysis had proven that the resulting layer was free from impurities after the sintering treatment. Corn starch was able to induced cathode layer with coarse and large interconnected pores for efficient gas diffusion, as was proven by the SEM analysis. Additionally, SEM analysis also showed the formation of fine micropores throughout the layer when graphite was used as the pore former that can provide the increase in triple phase boundary region (TPB) in the layer. PEEK was able to generate both high porosity for oxygen diffusion to the reactive sites and increased number of TPB by the formation of fine microstructure pores in the cathode layer.

Efficient reduction of graphene oxide nanosheets using Na2C2O4 as a reducing agent

The efficient synthesis of reduced graphene oxide (RGO) nanosheets via chemical reduction process of exfoliated graphene oxide (GO) nanosheets was performed by introducing sodium oxalate (Na2C2O4) as a reducing agent. To study the effects of the reduction time on the synthesized RGO, the GO was reduced within -1/2, 1 and 2 h for RGO-1, RGO-2 and RGO-3, respectively. The C/O atomic ratio of the synthesized RGO-3 has increased from 2.16 to 6.32 after reduction as determined by X-ray photoelectron spectroscopy (XPS). The morphology analysis of the RGO-3 was determined by high-resolution transmission electron microscopy (HRTEM) almost revealed the formation of single layer. The number of RGO layers decreases as the time of the reduction increases. Based on these analysis results, sodium oxalate plays an important role in the efficient removal of the oxygen containing groups in the GO to produce high quality of RGO.

Enhancement in photocatalytic degradation of methylene blue by LaFeO3-GO integrated photocatalyst-adsorbents under visible light irradiation

Perovskite LaFeO3 photocatalyst prepared by using sol-gel glucose method was assembled on graphene oxide sheets to produce integrated photocatalyst-adsorbents (IPCA) and investigated as photocatalyst for the degradation of methylene blue under visible light irradiation. The prepared photocatalyst was characterized by FTIR, XRD, FESEM, BET specific surface area measurement, TEM/HRTEM and UV-Vis spectroscopy analysis. The FTIR, FESEM and TEM analysis has suggested that the photocatalyst LaFeO3 has been successfully embedded at the surface of the graphene oxide (GO) sheets due to a strong interaction between the photocatalyst and the adsorbents matrix. Methylene blue degradation shows that IPCA possesses higher photodegradation kinetics compared to bare LaFeO3 photocatalyst. The resultant photocatalyst also possesses magnetic properties which can overcome the difficulty in recollecting and removal of photocatalyst suspension in water after photocatalytic treatment.