An electrolyte/anode hollow fibre (HF) for micro-tubular solid oxide fuel cells (SOFCs), i.e. a cerium–gadolinium oxide (CGO)/Ni–CGO dual-layer HF, has been developed in this study via a novel single-step co-extrusion and co-sintering technique, and followed by a reduction process. The microstructure of the developed dual-layer HFs, which are co-sintered at 1450–1550°C, can be characterised by an electrolyte outer layer of approximately 80μm supported by an anode inner layer of around 220μm. Benefiting from the advantages of this fabrication technique, great adhesion between the anode layer and the electrolyte layer can be achieved without any crack formation during the co-sintering. Moreover, no elemental inter-diffusion between layers, such as Ni, was observed even at 1550°C. With the increasing co-sintering temperature, mechanical strength of the developed dual-layer HF, gas-tightness of the electrolyte layer and electrical conductivity of the anode layer are increased. However, gas permeability through the anode layer decreases dramatically with the increasing temperature, which may greatly reduce the efficiency of the related micro-tubular SOFC. According to the investigations on the effects of co-sintering temperature on the mechanical, structural and electrical conducting properties of the dual-layer HFs, a co-sintering temperature at 1500°C is recommended for the construction of the electrolyte/anode half-cell for micro-tubular solid oxide fuel cells (SOFCs).
Membrane fouling takes place due to foulant adsorption on the membrane surface, which leads to the reduction of membrane performance and its durability in application. Hollow fibre alumina membrane incorporated with graphene oxide frameworks (GOFs) could avoid this phenomenon by forming GOFs/alumina composite membranes. Field emission scanning electron microscope (FESEM) structure shows that these composite membranes successfully developed GO and GOFs films with a thickness in the range of ∼234 to ∼635 nm. Meanwhile, the atomic force microscope (AFM) images show that their average roughness (Ra) becomes smoother, in the range of 30–46 nm, which would enhance antifouling properties. GOF(BDA)/alumina had highest proteins separation for all proteins, which are 98.40, 98.32, 95.82 and 95.65 % for bovine serum albumin (BSA), egg albumin (EA), trypsin (TR) and lysozyme (LSZ), respectively. Furthermore, this composite membrane had high flux recovery rate (FRR) of 94.86 % and 95.21 % at low total fouling ratio (Rt) of 21.70 % and 30.22 % for long-term filtration of LSZ protein and humic acid (HA) solute, respectively. Thus, this composite membrane showed better antifouling properties in proteins separation and HA removal application due to formation GOFs film.
Micro-tubular solid oxide fuel cells (MT-SPFC) have emerged as a potential alternative for efficient energy generation. This study investigates the impact of cathode extrusion rates (ranging from 3 to 6 mL min−1) on the triple layer anode/electrolyte/cathode MT-SOFC fabricated via a simplified phase inversion-based co-extrusion/co-sintering technique. Higher cathode extrusion rates (6 mL min−1) indirectly thin the electrolyte layer, improving ion hopping efficiency between the cathode and anode. Moreover, increasing the extrusion rate enhances anode thickness, providing ample electrode reaction sites and thereby enhancing the gas diffusion process. The C6 sample attains a peak power density of 1.46 W cm−2 with 1.08 V OCV at an optimum 800 °C operating temperature, which is high for MT-SOFCs in high-temperature applications. There was a 71.8 % increase in power density for C6 when the temperature changed from 750 °C to 800 °C. The composite cathode material fulfilled both the electronic and ionic conductivity requirements. The optimal cathode extrusion rate for this simplified MT-SOFC fabrication was found to be 6 mL min−1.
No abstract is provided for this article.
Oily wastewater is generated from various sources such as oil/gas exploration (produced water), oil refining, pharmaceutical, food industries, and household waste. Toxins in oily wastewater often percolate into drinking water, seawater, and groundwater. This becomes a source of environmental and public health concern. Due to its hazardous nature, the discharge of oily wastewater into the environment is strictly regulated. This work critically reviews progress in photocatalytic membrane reactor (PMR) for oily wastewater treatment, regulations on allowable oil discharge, various factors that affect PMR performance, and its self-cleaning and anti-fouling properties in oily wastewater treatment. Their removal performance for stabilized oil emulsion and trace oil contaminants is highlighted. This work also evaluates trends of integrated techniques, utilization of functional materials, PMR scale-up and the outlook of PMR. It was evident from 226 published articles (1976–2022) that oily waste water contamination has been a source of concern and PMR which integrates both membrane filtration and photodegradation processes, has emerged as a promising technology for oily wastewater treament, simultaneously degrading oil emulsion and undertaking separation. The PMRs attained over 96% oil rejection. Both the UV and visible light aided the degradation of oil using the PMR. High membrane surface area, provides additional sites for the photocatalyst to occupy, contributing to an efficient degradation. Concludingly, PMRs can exhibit a high flux of recovery ratio after several filtration cycles under UV/Vis irradiation, and with proper design and fabrication methods, the membranes can do self-cleaning and be re-used for several cycles of filtration with high efficiency.
No abstract is provided for this article.
Solid oxide fuel cell (SOFC) has been popular as an alternative method for generating electricity from hydrocarbon fuels like methane. This article critically evaluates carbon deposition problem encountered by hydrocarbon fuelled SOFC, carbon detection method and recent progress in the applications of cermet material as anode to mitigate the carbon deposition. Recently researchers have diverged from using conventional Ni-YSZ cermet material to alloying metals such as Ni, Cu, Zn, Fe, Co, Mo, Sn, W and Sb, coupled with ceramic oxygen conductors like doped zirconia, doped ceria, and perovskite-related materials such as doped promethium barium manganite (PBMO). Due to their reforming catalytic ability, Pt group metals gave outstanding carbon deposition tolerance, while Ni, Co and Fe alloys often result in carbon deposition. Single and alloy of metals yield different tolerance level such as those of Ni-ceramic and Ni-M-ceramic (M = metal). Fabrication methods are crucial in producing alloy. For example, despite of being non-reducible by hydrogen, certain metal oxides such as Zn in NiZn is reducible in alloy form, while other like Co are not. For future direction, we recommend both alloying and combining the ceramic component with mixing oxygen carrier that contain perovskite to enhance the carbon deposition tolerance of SOFC.
As a new field of materials development, photocatalytic membranes have been making progress by moving out from laboratory into real applications in water treatment and/or energy storage, making its presence influential in the body of literature. This chapter reviews the progress in semiconductor materials and their applications in water treatment and energy storage to mitigate their impacts on the environment. To bridge the existing research gaps in the body of literature, this chapter critically evaluates challenges in pilot studies of photocatalytic membrane. Challenges and perspectives of photocatalytic membrane are elaborated. It is anticipated that this would contribute to new understanding in the photocatalytic membrane on the relationship between materials’ structures and photoreaction performance that paves the way for a new direction of photocatalysis technology in pilot scales. Subsequently, the development of its next generation allows an efficient collection of the sunlight to catalyze chemical reactions, promoting solar energy utilization.
In this study, the phase inversion-based co-extrusion method was employed to fabricate a structural-improved electrolyte/anode dual-layer hollow fiber (HF) precursor, which was then co-sintered at 1450 °C. The electrolyte structures were thoroughly investigated by varying the loading of electrolyte material (i.e. Yttria-stabilized zirconia, YSZ) with differing particle sizes (i.e. micron, sub-micron, and nano-sized) during suspension preparation. The results showed that the most promising electrolyte layer with thin, dense, gas-tight, and defect-free properties was obtained by mixing 70% submicron-YSZ and 30% nano-YSZ in electrolyte suspension (E-0.7sub0.3nano). This electrolyte formulation co-extruded with a thick nickel-oxide-YSZ (NiO-YSZ) anode layer yielded the highest bending strength of 85 MPa, providing major mechanical strength to the HF. Besides that, the nitrogen permeability value at 2.87 × 10−6 mol m−2 s−1 Pa−1 suggested that the electrolyte was gas-tight, preventing fuel and oxidant transport. The fiber was then reduced to nickel (Ni)-cermet anode. It was developed to be a complete micro-tubular solid oxide fuel cell (MT-SOFC) by depositing the lanthanum strontium cobalt ferrite (LSCF)/YSZ cathode via brush painting on the dual-layer HF. The cell was fed with hydrogen gas and yielded an open-circuit voltage (OCV) as high as 1.06 V with maximum power density of 0.243 W cm−2, at 875 °C. Based on this test, it was found that the electrolyte structural-modified dual-layer hollow fiber-based MT-SOFC using mixed particle sizes may result in a promising OCV. However, the relatively low value for power density may be due to a less porous anode; thus, improvements in the anode's structure are required in future research.
