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Microbial electrolysis cells (MECs) have rapidly evolved as a promising technology to produce hydrogen from organic sources through anodic and cathodic electrochemical reactions. The MEC cathode has a rate-limiting effect on the hydrogen evolution reaction (HER) that necessitated the usage of expensive metal catalysts. Biocathode defined as microorganisms attached to the cathode is a promising alternative to abiotic catalysts for hydrogen production. Sulphate-reducing bacteria (SRB) are a potential source for biocathode enrichment. This study unlike previous literature mainly focused on the detailed characterization of autotrophic SRB-based biocathode MEC which produces hydrogen from a mixed culture source. The HER of MEC was optimized prior to the characterization step by adjusting sodium sulphate concentration, hydrogen feeding step during enrichment and adjusting pH of the media. Hydrogen production rate drastically increased from 0.15 m3/(m3 d) in the mixed culture-catalysed cathode to 1.53 m3/(m3 d) after three months of enrichment, while the cathodic charge transfer resistance decreased substantially from 463 to 1.8 Ω over the same enrichment period. DNA of the microbial communities attached to the biocathodes was then extracted at different enrichment times, and the dominant communities were identified using metagenomic amplicon sequencing. Moreover, Desulfovibrio was detected as the dominant genus in the enriched biocathodes through the enrichment stages. The findings of this study enable development of less-complex system for biocathode-based hydrogen production from any mixed culture sources. This in turn facilitates future commercial-scale implementation of MEC technology.

Catalyst-coated membranes (CCMs) have gained popularity among membrane electrode assembly (MEA) fabricators for their abilities and advantages compared with those of other methods, such as catalyst-coated substrates (CCSs). CCMs show a profound new analysis for reducing platinum (Pt) catalyst loading. In addition, they increase the total number of reactions that occur on the MEA because of their active area amplification, which leads to an improved catalyst-utilization efficiency rate. Moreover, several characteristics are involved in the MEA fabrication methods. Material-manufacturing effects with regard to catalyst inks and analysis of the overall performance of MEAs prepared by the CCM and CCS methods are deliberated. This deliberation emphasizes the practical approaches in minimizing performance deterioration during the fabrication of MEAs using the CCM method and converses the commercialization of the CCM fabrication method toward developing an end product. Novel research is required for MEA fabrication using the CCM methods to ensure that the fuel cell performance is improved. Therefore, this review is focusing on the pros and cons of both distinguished methods, that is, CCM and CCS fabrication, for better comparison.

A biophotovoltaic cell (BPV) is an electrobiochemical system that utilises a photosynthetic microorganism for instance is algae to trap sunlight energy and convert it into electricity. In this study, a local algae strain, UKM2 Chlorella sp. was grown in a BPV under different trophic conditions and light wavelengths. Once the acclimatisation phase succeeded, and biofilm formed, power generation by UKM2 algae at the autotrophic mode in synthetic Bold’s Basal media (BBM) under white, blue and red lights were tested. Polarisation and power curves were generated at these different conditions to study the bioelectrochemical performance of the system. Later, the condition switched to algal mixotrophic nutritional mode, with palm oil mill effluent (POME) as substrate. Maximum power generation obtained when using UKM2 in BBM under red light where a power density of 1.19 ± 0.16 W/m3 was obtained at 25.74 ± 3.89 A/m3 current density, while the open circuit voltage OCV reached 226.08 ± 8.71 mV. UKM2 in POME under blue light recorded maximum power density of 0.85 ± 0.18 W/m3 at current density of 16.75 ± 3.54 A/m3, while the OCV reached 214.05 ± 23.82 mV. Chemical oxygen demand (COD) removal reached an efficiency of 35.93%, indicating the ability of wastewater treatment and electricity generation in BPV at the same time.

A commercial perfluorinated sulfonic acid (PFSA) membrane, Nafion, shows outstanding conductivity under conditions of a fully humidified surrounding. Nevertheless, the use of Nafion membranes that operate only at low temperature (

A conventional reactor in microbial electrochemical technology (MET) consists of anode and cathode compartments divided by a separator, which is usually a proton exchange membrane (PEM), such as Nafion 117. In this study, a novel porous clay earthenware (NCE) was fabricated as the separator to replace the highly cost PEM. The fabrication of NCEs is with raw clay powder and starch powder that acts as a pore-forming agent at different starch powder contents (10 vol%, 20 vol%, and 30 vol%), ball-milled before hydraulically pressed to form green ceramic pellets and sintered up to 1200 °C. The highest power density of 2250 ± 21 mW/m2 (6.0 A/m2), the internal resistance of 75 ± 24 Ω and coulombic efficiency (CE) of 44 ± 21% were produced for MFC–NCE from 30 vol% starch powder content under batch mode operation. The MFC–PEM combination produced the lowest power density, CE and the highest internal resistance up to 1350 ± 17 mW/m2 (3.0 A/m2), 23 ± 15% and 326 ± 13 Ω, respectively.

Microbial electrodialysis cells (MEDCs) offer simultaneous wastewater treatment, water desalination, and hydrogen production. In a conventional design of MEDCs, the overall performance is retarded by the accumulation of protons on the anode due to the integration of an anion exchange membrane (AEM). The accumulation of protons reduces the anolyte pH to become acidic, affecting the microbial viability and thus limiting the charge carrier needed for the cathodic reaction. This study has modified the conventional MEDC with an internal proton migration pathway, known as the internal proton migration pathway-MEDC (IP-MEDC). Simulation tests under abiotic conditions demonstrated that the pH changes in the anolyte and catholyte of IP-MEDC were smaller than the pH changes in the anolyte and catholyte without the proton pathways. Under biotic conditions, the performance of the IP-MEDC agreed well with the simulation test, showing a significantly higher chemical oxygen demand (COD) removal rate, desalination rate, and hydrogen production than without the migration pathway. This result is supported by the lowest charge transfer resistance shown by EIS analysis and the abundance of microbes on the bioanode through field emission scanning electron microscopy (FESEM) observation. However, hydrogen production was diminished in the second-fed batch cycle, presumably due to the active diffusion of high Cl¯ concentrations from desalination to the anode chamber, which was detrimental to microbial growth. Enlarging the anode volume by threefold improved the COD removal rate and hydrogen production rate by 1.7- and 3.4-fold, respectively, owing to the dilution effect of Cl¯ in the anode. This implied that the dilution effect satisfies both the microbial viability and conductivity. This study also suggests that the anolyte and catholyte replacement frequencies can be reduced, typically at a prolonged hydraulic retention time, thus minimizing the operating cost (e.g., solution pumping). The use of a high concentration of NaCl (35 g L

An integrated model between surface and sub-surface is typically done by interconnecting many process modelling platforms. PROSPER and GAP are the common steady state modelling platforms for sub-surface while VMGSim and HYSYS are typical steady state surface modelling platforms. A major issue of using multiple simulation platforms is the compatibility of thermodynamic physical properties calculations among the platforms. This situation makes the simulations difficult to converge to a consistent thermo physical properties values. This is due to different interaction parameters applied in each platform that impact flashing and the physical property values even though the same property package such as Peng Robinson is used. To overcome this convergence problem, a single simulation platform within iCON (PETRONAS’s standard process simulation software, co-developed with VMG-Schlumberger) has been developed. This allows the use of one thermodynamic package across the integrated model. PROSPER sub-surface pressure-flow relationship results were automatically correlated and connected to surface models within the iCON environment. This integrated model was validated with data from operations and yielded about 1.23% average error tolerance. Based on this validated model, an optimization envelope can be developed with all possible well lineup configurations. This envelope covers set points for the operations where CAPEX free optimization can readily be applied.

The effect of the operating voltage on the performance of a microbial electrolysis cell (MEC) equipped with both a bioanode and a biocathode for hydrogen production is reported. Chronoamperometry tests ranged between 0.3 and 2.0 V were carried out after both bioelectrodes were developed. A maximum current density up to 1.6 A m−2 was recorded at 1.0 V with hydrogen production rate of nearly 6.0 ± 1.5 L m−2 cathode day−1. Trace amounts of methane, acetone and formate were detected in cathode's headspace and catholyte which followed the same trend as hydrogen production rate. Meanwhile substrate consumption in anolyte also followed the trend of hydrogen production and current density changes. The bioanode could utilise up to 95% of acetate in the tested voltage ranges, however, at a cell voltage of 2.0 V the bioanode's activity stopped due to oxygen evolution from water hydrolysis. Cyclic voltammograms revealed that the bioanode activity was vital to maintain the functionality of the whole system. The biocathode relied on the bioanode to maintain its potential during the hydrogen evolution. The overall energy efficiency recovered from both bioanode and external power in terms of hydrogen production at the cathode was determined as 29.4 ± 9.0%, within which substrate oxidation contributed up to nearly 1/3 of the total energy marking the importance of bioanode recovering energy from wastewater to reduce the external power supply.

Stainless steel (SS) has been reported as a suitable electrode material for the growth of electrochemically active biofilm whether it is for a microbial fuel cell (MFC) or microbial electrolysis cell (MEC) in the bioelectrochemical system. Although the flame oxidation technique could improve SS property as electrodes, it comes with an increased risk of corrosion. The undesirable corrosion may cause the release of a toxic element such as chromium. At present, mitigation actions have been identified such as connecting iron to a sacrificial metal in a mechanism known as galvanic corrosion protection (GCP). An external power source could be used as an alternative to supply current similar to the sacrificial metal, which technique applied in MEC. In this review, the electron flow mechanisms between microbiologically influenced corrosion (MIC) and MEC biocathode will be addressed. Thus, it proposes a hypothesis of SS protection from corrosion in a similar way as in the GCP.

A cell network consists of a combination of fuel cells to achieve the targeted power consumption for a specific application. The main objective of this study is to design and optimise direct methanol fuel cell (DMFC) via cell integrated network model targeted for small portable application, such as cell phones and tablets. The target current and voltage was 1400 mA and 3.7 V, respectively, for a 5.18 W of cell network power. The optimisation was performed using 16 cells that were arranged in series with a voltage output of 3.781 V and a current of 1400 mA. The overall active area for the cell network was 128 cm2, and the cost of 1 set of cell networks is USD 1400.

A proper system must be applied in order to have reliable power production and higher levels of durability. The functions of this system are to fully utilize the benefits of the fuel cell components and to deliver the required power. This paper presents the design for an HT-PEMFC single-cell test cell with the development of a test station to operate the cell. The single-cell test cell and the real-time monitoring test station were designed using LabVIEW software, and were implemented using NI's cFP hardware devices, the details of which are provided. The architecture of the test station was aimed at measuring and controlling the mass flow rate, pressure and temperature of the reactant gases, and the stack temperature and current. An electronic load, with a quick dynamic response, was used to test the fuel cell reaction. The start-up, shutdown and monitoring functions were managed by the test station, which monitored the critical parameters of the fuel cell, namely, the voltage, current loading, generated power, hydrogen/air inlet and outlet and stack temperature. The results showed that the designed and developed single-cell HT-PEMFC and test station were able to generate power. An in-depth research needs to be conducted into the innovative design and development of HT-PEMFC systems since these are the key factors for optimum performance.

The recent interest in microbial electrolysis cell (MEC) technology has led the research platform to develop full biological MECs (bioanode-biocathode, FB-MEC). This study focused on biohydrogen production from a biologically catalyzed MEC. A bioanode and a biocathode were initially enriched in a half biological MFC (bioanode-abiocathode, HB-MFC) and a half biological MEC (abioanode-biocathode, HB-MEC), respectively. The FB-MEC was established by transferring the biocathode of the HB-MEC and the bioanode of the HB-MFC to a two-chamber MEC. The FB-MEC was operated under batch (FB-MEC-B) and recirculation batch (FB-MEC-RB) modes of operation in the anodic chamber. The FB-MEC-B reached a maximum current density of 1.5 A/m2 and the FB-MEC-RB reached a maximum current density of 2.5 A/m2 at a similar applied voltage while the abiotic control system showed the maximum of 0.2 A/m2. Hydrogen production rate decreased in the FB-MEC compared to that of the HB-MEC. However, the cathodic hydrogen recovery increased from 42% obtained in the HB-MEC to 56% in the FB-MEC-B and 65% in the FB-MEC-RB, suggesting the efficient oxidation and reduction rates in the FB-MEC compared to the HB-MEC. The onset potential for hydrogen evolution reaction detected by linear sweep voltammetry analysis were −0.780 and −0.860 V vs Ag/AgCl for the FB-MEC-RB and the FB-MEC-B (−1.26 for the abiotic control MEC), respectively. Moreover, the results suggested that the FB-MEC worked more efficiently when the biocathode and the bioanode were enriched initially in half biological systems before transferring to the FB-MEC compared to that of the simultaneously enriched in one system.

Poly(vinyl alcohol) (PVA) is a biodegradable, water-soluble membrane that has low methanol permeation and reactive chemical functionalities. Modification of these features makes PVA an attractive p...

Optimizations of oil productions in current practices have been done separately in both subsurface and surface facilities. This approach might not lead to an optimum state when the whole system is interconnected. In this work, a superstructure model of an existing integrated subsurface and surface facilities was developed and evaluated to maximize the oil productions. In subsurface facilities, well performance data were taken from PROSPER well simulations. Operating variables such as downstream pressures of choke valves and gas lift flowrates, which influence the flow of oil, gas, and water from reservoirs, were considered. Based on these variables, performance correlations of the wells were then developed. On the evaluated surface facility, three pressure levels of vessels on the platform (high-, medium-, and low-pressure vessels) and their current designs were also considered. The optimization result shows that to reach optimum oil production, one well should be connected to the high-pressure vessel, four wells to the medium-pressure vessel, and the rest goes to the low-pressure vessel. Several choke valves and gas lift flowrates also need to be adjusted accordingly.

Gasification of coconut shell (CS) and palm kernel shell (PKS) is conducted in a batch type downdraft fixed-bed reactor to evaluate the effect of particle size (1–3 mm, 4–7 mm, and 8–11 mm) and temperature (700, 800, and 900 °C) on gas composition and gasification performance. The response surface methodology integrated variance-optimal design is used to identify the optimum condition for gasification. Gas composition, which is measured using the biomass particle size of 1–11 mm at 700–900 °C, are 8.20–14.6 vol% (H2), 13.0–17.4 vol% (CO), 14.7–16.7 vol% (CO2), and 2.82–4.23 vol% (CH4) for CS and 7.01–13.3 vol% (H2), 13.3–17.8 vol% (CO), 14.9–17.1 vol% (CO2), and 2.39–3.90 vol% (CH4) for PKS. At similar conditions, the syngas higher heating value, dry gas yield, carbon conversion efficiency, and cold gas efficiency are 4.01–5.39 MJ/Nm3, 1.50–1.95 Nm3/kg, 52.2–75.9%, and 30.9–56.4% for CS, respectively, and 3.82–5.09 MJ/Nm3, 1.48–1.92 Nm3/kg, 59.0–81.5%, and 33.0–57.1% for PKS, respectively. Results reveal that temperature has a greater role than particle size in influencing the gasification reaction rate.

Management of the water in the stack is a major problem in achieving optimal performance of a Proton Exchange Membrane (PEM) fuel cell. One of the problems caused by water imbalance in the PEM system is the formation of liquid water on the side of the cathode. High water content in the PEM fuel cell stack causes liquid water and flooding, and decreases its performance. The presence of liquid water on the cathode side of the fuel cell leads to a decrease in the amount of oxygen reacting in the catalyst layer. The results of this study indicate that a general increase in water content results in a decrease in the performance of PEM fuel cell systems. The highest water content occurs at a current density of 0.9, with Rha and RHc of 90%. In this condition, system performance is relatively stable at 0.67 volts, with 0.00016 gr/cm2 of liquid water content produced. Above this water content, system performance decreases significantly.

Polymer electrolyte membranes, also known as proton exchange membranes (PEMs), are a type of semipermeable membrane that exhibits the property of conducting ions while impeding the mixing of reactant materials across the membrane. Due to the large potential and substantial number of applications of these materials, the development of proton exchange membranes (PEMs) has been in progress for the last few decades to successfully replace the commercial Nafion® membranes. In the course of this research, an alternate perspective of PEMs has been initiated with a desire to attain successful operations at higher working temperatures (120–200 °C) while retaining the physical properties, stability and high proton conductivity. Both low- and high-temperature PEMs have been fabricated by various processes, such as grafting, cross-linking, or combining polymer electrolytes with nanoparticles, additives and acid-base complexes by electrostatic interactions, or by employing layer-by-layer technologies. The current review suggests that the incorporation of additives such as plasticisers and fillers has proven potential to modify the physical and chemical properties of pristine and/or composite membranes. In many studies, additives have demonstrated a substantial role in ameliorating both the mechanical and electrical properties of PEMs to make them effective for fuel cell applications. It is notable that plasticiser additives are less desirable for the development of high-temperature PEMs, as their inherent highly hydrophilic properties may stiffen the membrane. Conversely, filler additives form an inorganic-organic composite with increased surface area to retain more bound water within the polymer matrices to overcome the drawbacks of ohmic losses at high operating temperatures.

The ever increasing energy consumption, rising public awareness for environmental protection, and higher prices of fossil fuels have motivated many to look for alternative and renewable energy sources [...]

Plat dwikutub adalah salah satu komponen utama sel fuel membran pertukaran proton (PEMFC). Aloi aluminium (Al5052) merupakan salah satu logam yang digunakan sebagai plat dwikutub kerana mempunyai kekonduksian yang tinggi dan ringan. Namun, sistem PEMFC yang berasid (pH3-6) adalah mudah untuk bahan Al5052 mengalami kakisan sehingga dapat mengurangkan prestasi PEMFC. Oleh itu, bagi mengurangkan halaju kakisan yang berlaku, kajian ini menggunakan perencat hijau gam Arab dengan kaedah pemendapan elektroforesis (EPD). Kesan kakisan plat Al5052 bersalut 0.5 gL-1 gam Arab di dalam larutan sulfurik asid diuji menggunakan kaedah elektrokimia dan ujian morfologi. Hasil ujian morfologi permukaan Al5052 yang bersalut gam Arab terlihat lebih halus dan homogen berbanding permukaan yang tidak disalut serta hasil keratan rentas ketebalan salutan adalah antara 7.5 μm sehingga 8.8 μm. Kesan peningkatan suhu (30oC sehingga 90oC) terhadap nilai rintangan hubungan antara muka (ICR) pada Al5052 yang tidak bersalut akan menurun daripada 11.8552 sehinggs 9.9042 mΩ cm2 manakala yang bersalutkan gam Arab mempunyai nilai daripada 13.3497sehingga 11.812 mΩ cm2. Keputusan menunjukkan bahawa gam Arab dapat memberikan perlindungan terhadap permukaan logam yang apabila pengujian menggunakan kaedah polarisasi linear tafel dalam larutan 0.5 M H2SO4 (pH4) menunjukkan nilai ketumpatan arus kakisan (Icorr) semakin menurun daripada 0.00264 kepada 0.00012 μA cm-2. Selain itu, halaju kakisan turut menurun daripada 3.06 × 10-5 mpy kepada 1.61 × 10-6 mpy setelah disalut gam Arab. Kesimpulannya, gam Arab dan kaedah salutan EPD boleh digunakan bagi mengurangkan halaju kakisan pada plat Al5052, supaya jangka hayat bahan ini lebih panjang dan boleh mencapai piawai yang ditetapkan oleh DOE untuk plat dwikutub.

The distribution of reactant in the proton exchange membrane fuel cell (PEMFC) is crucial because the performance of the fuel cell is determined by the lowest performance cell. The reactant is distributed from the manifold to the cells in the stack and further distributed into the flow field channels (depending on the flow field design). The three-dimensional PEMFC is comparatively studied as a dual-cell, a quad-cell and a hexa-cell stack. The previously investigated modified parallel flow field is used as the anode flow field. The dual-, quad- and hexa-cell stacks are connected in series to study the effect of PEMFC performance when the number of cells increases in a PEMFC stack. Computational fluid dynamics (CFD) is used to study the current density generation of a PEMFC stack. The results demonstrate that when the quantity of cells rises in a stack, the current density decreases. Six equations are formed at different cell potentials to predict the PEMFC performance as the quantity of cells increases.

The long-term performance of non-ion selective separators, zirconia ceramic filter (ZCF) with a various pore size such as 0.14 μm ZCF1, 150 kDa ZCF2 and 5 kDa ZCF3 were compared to commercial cation exchange membrane (CEM), Nafion 117 in microbial fuel cells. The ZCF3 generated the highest performance of 2800 ± 14.5 mWm−2 (5.9 Am−2) compared to CEM: 1800 ± 17.8 mWm−2, 4.0 Am−2. Meanwhile, the CEM exhibited maximum power decline during the reverse sweep (61.7%) when analyzed using the bi-directional polarization method. The non-ion selective membranes displayed reduced in maximum power decline during the reverse sweep (ZCF1 50%, ZCF2 40% and ZCF3 42.8%). In addition, the ZCF3 showed the highest proton conductivity and water uptake, 0.863 × 10−1 Scm−1 and 93.7% respectively, followed by ZCF2 (0.729 × 10−1 Scm−1, 80.98%), ZCF1 (0.624 × 10−1 Scm−1, 73.99%) and Nafion 117 (0.367 × 10−2 Scm−1, 57.07%). The ZCF3 appeared as an efficient material for electrochemical active bacteria, maintaining the high power of 1600 mWm−2, compared to CEM: 600 mWm−2 after eight months’ operation under batch mode. The long-term operation of MFCs was affected by the reduction of power output, caused by the increase in the thickness of the biofilm.

Microbial desalination cells (MDCs) have been experimentally proven as a versatile bioelectrochemical system (BES). They have the potential to alleviate environmental pollution, reduce water scarcity and save energy and operational costs. However, MDCs alone are inadequate to realise a complete wastewater and desalination treatment at a high-efficiency performance. The assembly of identical MDC units that hydraulically and electrically connected can improve the performance better than standalone MDCs. In the same manner, the coupling of MDCs with other BES or conventional water reclamation technology has also exhibits a promising performance. However, the scaling-up effort has been slowly progressing, leading to a lack of knowledge for guiding MDC technology into practicality. Many challenges remain unsolved and should be mitigated before MDCs can be fully implemented in real applications. Here, we aim to provide a comprehensive chronological-based review that covers technological limitations and mitigation strategies, which have been developed for standalone MDCs. We extend our discussion on how assembled, coupled and scaled-up MDCs have improved in comparison with standalone and lab-scale MDC systems. This review also outlines the prevailing challenges and potential mitigation strategies for scaling-up based on large-scale specifications and evaluates the prospects of selected MDC systems to be integrated with conventional anaerobic digestion (AD) and reverse osmosis (RO). This review offers several recommendations to promote up-scaling studies guided by the pilot scale BES and existing water reclamation technologies.

Microbial fuel cells (MFCs) have a high potential application for simultaneous wastewater treatment and electricity generation. However, the choice of the electrode material and its design is critical and directly affect their performance. As an electrode of MFCs, the anode material with surface modifications is an attractive strategy to improve the power output. In this study, stainless steel (SS) and carbon steel (CS) was chosen as a metal anode, while graphite felt (GF) was used as a common anode. Heat treatment was performed to convert SS, CS and GF into efficient anodes for MFCs. The maximum current density and power density of the MFC-SS were achieved up till 762.14 mA/m2 and 827.25 mW/m2, respectively, which were higher than MFC-CS (641.95 mA/m2 and 260.14 mW/m2) and MFC-GF (728.30 mA/m2 and 307.89 mW/m2). Electrochemical impedance spectroscopy of MFC-SS showed better catalytic activity compared to MFC-CS and MFC-GF anode, also supported by cyclic voltammetry test.

Microbial desalination cells (MDCs) are known among the bioelectrochemical systems for their green and cost-effective application in salt removal. However, the low efficiency of desalination compared to other chemical and membrane-based methods still holding this technology in laboratory and requiring further research and development (R&D) to establish actual plants. This study focused on integrating different applicable functions in one setup to promote applying MDCs in actual scale. In this research, the behavior of the MDC upon applying different salt concentrations in the desalination chamber was studied. Moreover, salt, sulphate and organic matter removal in acetate and sulphate-fed MDCs (A.MDC and S.MDC) were investigated. 10, 20 and 35 g/l of salt were successfully removed by using MDC technology. Sulphate removal of 72% was achieved within the S.MDC setup while similar current productions were observed in both A.MDC and S.MDC. Higher COD removal (88%) was recorded in S.MDC compared to 65% in A.MDC. Furthermore, the microbial communities were characterized and Rubrivivax was identified as the dominant genus in A.MDC while Desulfobulbus, Geobacter and Desulfovibrio were the most abundant genera in S.MDC setup.

A solid polymer electrolyte of poly(2-hydroxyethyl methacrylate) PHEMA and lithium hexafluorophosphate (LiPF6) and 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide [Bmim][TFSI] was successfully prepared via the solution casting method. X-ray diffractometer, Fourier transformation infrared spectroscopy, scanning electron microscopy and electrochemical impedance spectroscopy were used to study the structural, optical, morphological and electrochemical properties of the prepared solid polymer electrolytes. From the results, with the addition of ionic liquid in the polymer electrolytes system improved the properties of the polymer electrolytes such as lower the crystallinity and become smooth in surface morphology, hence helps increase in ionic conductivity. High ionic conductivity exhibited at 30 wt% of 1.0 M LiPF6 (EC/DEC) (1:1) in the PHEMA with the value of 2.13 × 10−6 S cm−1. This value was increased up to one magnitude order with the addition of ionic liquid where the value is 8.01 × 10−5 S cm−1 at room temperature. This implies that these polymer electrolytes are possibly suitable for further application in low-power electrochemical devices.

Hybrid electric vehicle technologies emerge mainly because of the instability in fossil fuel prices, resources and the terrible impact of global warming. As most transport systems use fossil fuel and emit greenhouse gases, many researchers have studied the potential of fuel-cell hybrid electric vehicles (FCHEVs). FCHEVs are vehicles with zero greenhouse gas emission because they only depend on hydrogen. Numerous studies have proven that fuel cells with energy storage elements can provide sufficient energy required by FCHEVs. However, end users demand FCHEVs that are not only efficient in delivering the energy required but can also optimize hydrogen consumption and prolong battery lifetime to compete with current internal combustion engine vehicles. Therefore, advanced optimization algorithms for an FCHEV energy management system (EMS) must be developed to improve the performance efficiency of FCHEVs. This paper presents a critical review of the different types of FCHEV EMSs and their optimization algorithms to solve existing limitations and enhance the performance of future FCHEVs. Consequently, a comprehensive review on the major categories of FCHEV EMSs, such as proportional–integral–derivative controller, operational or state mode, rule-based or fuzzy logic, and equivalent consumption minimization strategies, are explained. This paper also describes optimization techniques such as linear programming, dynamic programming, Pontryagin’s minimum principle, genetic algorithm, particle swarm optimization and rule-based logic optimization for the EMSs of FCHEVs. Furthermore, it focuses on the various factors and challenges of existing optimization algorithms, hydrogen fuel source, environment and safety, and economical and societal concerns, as well as provides recommendations for designing capable and efficient EMSs for FCHEVs. All the highlighted insights of this review will hopefully lead to increasing efforts toward the development of an advanced optimization algorithm for future FCHEV EMSs.

In this work, a preliminary study was conducted to study the effects of different types and concentrations of cosolvents based on the total yield and antioxidants capacity prior to supercritical fluid extraction (SFE) of Orthosiphon stamineus (locally referred as misai kucing). Initially, a comparison was made by cold maceration technique with nine types of different cosolvents, namely water, pure ethanol, 25% (v/v) of ethanol in water, 50% (v/v) of ethanol in water, 75% (v/v) of ethanol in water, pure methanol, 25% (v/v) of methanol in water, 50% (v/v) of methanol in water and 75% (v/v) of methanol in water. The antioxidant capacity was analysed by free radical scavenging activity of 2,2-diphenyl-1-picrylhydrazyl (DPPH), total phenolic content (TPC) and total flavonoid content (TFC). Aqueous ethanolic solvent of 50% (v/v) ethanol in water showed the highest total yield of extract of 4.64 ± 0.02%. All antioxidant assays of TPC and TFC showed the highest value of 3.42 ± 0.08 mg GAE g−1 extract, 4.7 ± 0.14 mg CAE g−1 extract, respectively and IC50 value for DPPH was 0.625 μg/mL for 50% (v/v) ethanol in water extract. Based on the overall result, ethanolic solvents gave a better result for all antioxidant assays compared to those of methanolic solvents. Using the selected cosolvent, the identification of target compounds, which were rosmarinic acid, eupatorin and sinensetin from supercritical fluid extraction was determined by using HPLC. In conclusion, ethanol-water solvent was efficient in extracting bioactive compounds in O. stamineus and also improved the total yield, thus the usage of ethanolic solvent in different concentrations should be considered for further optimisation of SFE with cosolvent studies.