Power electronics and fuel cell technologies play an important role in the field of renewable energy. The demand for fuel cells will increase as fuel cells become the main power source for portable applications. In this application, a high-efficiency converter is an essential requirement and a key parameter of the overall system. This is because the size, cost, efficiency, and reliability of the overall system for portable applications primarily depend on the converter. Therefore, the selection of an appropriate converter topology is an important and fundamental aspect of designing a fuel cell system for portable applications as the converter alone plays a major role in determining the overall performance of the system. This paper presents a review of power electronics applications in fuel cell systems, which include various topology combinations of DC converters and AC inverters and which are primarily used in fuel cell systems for portable or stand-alone applications. This paper also reviews the switching techniques used in power conditioning for fuel cell systems. Finally, this paper addresses the current problem encountered with DC converters and AC inverter.
The high methanol crossover and high cost of Nafion® membrane are the major challenges for direct methanol fuel cell application. With the aim of solving these problems, a non-Nafion polymer electrolyte membrane with low methanol permeability and high proton conductivity based on the sodium alginate (SA) polymer as the matrix and sulfonated graphene oxide (SGO) as an inorganic filler (0.02-0.2 wt%) was prepared by a simple solution casting technique. The strong electrostatic attraction between -SO3H of SGO and the sodium alginate polymer increased the mechanical stability, optimized the water absorption and thus inhibited the methanol crossover in the membrane. The optimum properties and performances were presented by the SA/SGO membrane with a loading of 0.2 wt% SGO, which gave a proton conductivity of 13.2 × 10-3 Scm-1, and the methanol permeability was 1.535 × 10-7 cm2 s-1at 25 °C, far below that of Nafion (25.1 × 10-7 cm2 s-1) at 25 °C. The mechanical properties of the sodium alginate polymer in terms of tensile strength and elongation at break were improved by the addition of SGO.
This study presents a novel anodic PdAu/VGCNF catalyst for electro-oxidation in a glycerol fuel cell. The reaction conditions are critical issues affecting the glycerol electro-oxidation performance. This study presents the effects of catalyst loading, temperature, and electrolyte concentration. The glycerol oxidation performance of the PdAu/VGCNF catalyst on the anode side is tested via cyclic voltammetry with a 3 mm2 active area. The morphology and physical properties of the catalyst are examined using X-ray diffraction (XRD), field emission scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectroscopy. Then, optimization is carried out using the response surface method with central composite experimental design. The current density is experimentally obtained as a response variable from a set of experimental laboratory tests. The catalyst loading, temperature, and NaOH concentration are taken as independent parameters, which were evaluated previously in the screening experiments. The highest current density of 158.34 mAcm-2 is obtained under the optimal conditions of 3.0 M NaOH concentration, 60 °C temperature and 12 wt.% catalyst loading. These results prove that PdAu-VGCNF is a potential anodic catalyst for glycerol fuel cells.
Adsorption technology has led to the development of promising techniques to purify biogas, i.e., biomethane or biohydrogen. Such techniques mainly depend on the adsorbent ability and operating parameters. This research focused on adsorption technology for upgrading biogas technique by developing a novel adsorbent. The commercial coconut shell activated carbon (CAC) and two types of gases (H2S/N2 and H2S/N2/CO2) were used. CAC was modified by copper sulfate (CuSO4), zinc acetate (ZnAc2), potassium hydroxide (KOH), potassium iodide (KI), and sodium carbonate (Na2CO3) on their surface to increase the selectivity of H2S removal. Commercial H2S adsorbents were soaked in 7 wt.% of impregnated solution for 30 min before drying at 120°C for 24 h. The synthesized adsorbent's physical and chemical properties, including surface morphology, porosity, and structures, were characterized by SEM-EDX, FTIR, XRD, TGA, and BET analyses. For real applications, the modified adsorbents were used in a real-time 0.85 L single-column adsorber unit. The operating parameters for the H2S adsorption in the adsorber unit varied in L/D ratio (0.5-2.5) and feed flow rate (1.5-5.5 L/min) where, also equivalent with a gas hourly space velocity, GHSV (212.4-780.0 hour-1) used. The performances of H2S adsorption were then compared with those of the best adsorbent that can be used for further investigation. Characterization results revealed that the impregnated solution homogeneously covered the adsorbent surface, morphology, and properties (i.e., crystallinity and surface area). BET analysis further shows that the modified adsorbents surface area decreased by up to 96%. Hence, ZnAc2-CAC clarify as the best adsorption capacity ranging within 1.3-1.7 mg H2S/g, whereby the studied extended to adsorption-desorption cycle.
This study focuses on the synthesis, characterization, and evaluation of the performance of core shell nanostructure adsorbent for hydrogen sulfide (H2S) capture. Commercial coconut shell activated carbon (CAC) and commercial mixed gas of 5000 ppm H2S balanced N2 were used. With different preparation techniques, the CAC was modified by core shell impregnation with zinc oxide (ZnO), titanium oxide (TiO2), potassium hydroxide (KOH), and zinc acetate (ZnAC2). The core structure was prepared with CAC impregnated by single chemical and double chemical labelled with ZnAC2-CAC (single chemical), ZnAC2/KOH-CAC, ZnAC2/ZnO-CAC, and ZnAC2/TiO2-CAC. Then, the prepared core was layered either with KOH, TiO2, NH3, or TEOS for the shell. The synthesized adsorbents were characterized in physical and chemical characterization through scanning electron microscopy (SEM), thermal gravimetric analysis (TGA), and Brunauer-Emmett-Teller (BET) analyzers. Operation of the adsorber column takes place at ambient temperature, with absolute pressure at 1.5 bar. The H2S gas was fed into the column at 5.5 L/min and the loaded adsorbents were 150 g. The performance of synthesized adsorbent was analyzed through the adsorbent's capability in capturing H2S gas. Based on the results, ZnAc2/ZnO/CAC_WOS shows a better adsorption capacity with 1.17 mg H2S/g and a 53% increment compared to raw CAC. However, the degradation of the adsorbents was higher compared to ZnAc2/ZnO/CAC_OS and to ZnAc2/ZnO/CAC_WS ZnAc2/ZnO/CAC_OS. The presence of silica as a shell has potentially increased the adsorbent's stability in several cycles of adsorption-desorption.
The biocathode in a microbial fuel cell (MFC) system is a promising and a cheap alternative method to improve cathode reaction performance. This study aims to identify the effect of the electrode combination between non-chemical modified stainless steel (SS) and graphite fibre brush (GFB) for constructing bio-electrodes in an MFC. In this study, the MFC had two chambers, separated by a cation exchange membrane, and underwent a total of four different treatments with different electrode arrangements (anodeǁcathode)-SSǁSS (control), GFBǁSS, GFBǁGFB and SSǁGFB. Both electrodes were heat-treated to improve surface oxidation. On the 20th day of the operation, the GFBǁGFB arrangement generated the highest power density, up to 3.03 W/m3 (177 A/m3), followed by the SSǁGFB (0.0106 W/m3, 0.412 A/m3), the GFBǁSS (0.0283 W/m3, 17.1 A/m3), and the SSǁSS arrangements (0.0069 W/m-3, 1.64 A/m3). The GFBǁGFB had the lowest internal resistance (0.2 kΩ), corresponding to the highest power output. The other electrode arrangements, SSǁGFB, GFBǁSS, and SSǁSS, showed very high internal resistance (82 kΩ, 2.1 kΩ and 18 kΩ, respectively) due to the low proton and electron movement activity in the MFC systems. The results show that GFB materials can be used as anode and cathode in a fully biotic MFC system.
Metal-based adsorbents with varying active phase loadings were synthesized to capture hydrogen sulfide (H2S) from a biogas mimic system. The adsorption-desorption cycles were implemented to ascertain the H2S captured. All prepared adsorbents were evaluated by nitrogen adsorption, Brunauer-Emmett-Teller surface area analysis, scanning electron microscopy-energy-dispersive X-ray spectroscopy, and Fourier transform infrared spectroscopy. From the results, modified adsorbents, dual chemical mixture (DCM) and a core-shell (CS) had the highest H2S adsorption performance with a range of 0.92-1.80 mg H2S/g. After several cycles of heat/N2 regeneration, the total H2S adsorption capacity of the DCM adsorbent decreased by 62.1%, whereas the CS adsorbent decreased by only 25%. Meanwhile, the proposed behavioral model for H2S adsorption-desorption was validated effectively using various analyses throughout the three cycles of adsorption-desorption samples. Moreover, as in this case, the ZnAc2/ZnO/CAC_OS adsorbents show outstanding performances with 30 cycles of adsorption-desorption compared to only 12 cycles of ZnAc2/ZnO/CAC_DCM. Thus, this research paper will provide fresh insights into adsorption-desorption behavior through the best adsorbents' development and the adsorbents' capability at the highest number of adsorption-desorption cycles.
This study reports on the synthesis of bi-metal compound (BMC) adsorbents based on commercial coconut activated carbon (CAC), surface-modified with metal acetate (ZnAc2), metal oxide (ZnO), and the basic compounds potassium hydroxide (KOH) and sodium hydroxide (NaOH). The adsorbents were then characterized by scanning electron microscopy and elemental analysis, microporosity analysis through Brunauer-Emmett-Teller (BET) analysis, and thermal stability via thermogravimetric analysis. Adsorption-desorption test was conducted to determine the adsorption capacity of H2S via 1 L adsorber and 1000 ppm H2S balanced 49.95% for N2 and CO2. Characterization results revealed that the impregnated solution homogeneously covered the adsorbent surface, morphology, and properties. The adsorption test result reveals that the ZnAc2/ZnO/CAC_B had a higher H2S breakthrough adsorption capacity and performed at larger than 90% capability compared with a single modified adsorbent (ZnAc2/CAC). Therefore, the synthesized BMC adsorbents have a high H2S loading, and the abundance and low cost of CAC may lead to favorable adsorbents in H2S captured.
In this work, the performance of anion exchange membrane (AEM) electrolysis is evaluated. A parametric study is conducted, focusing on the effects of various operating parameters on the AEM efficiency. The following parameters-potassium hydroxide (KOH electrolyte concentration (0.5-2.0 M), electrolyte flow rate (1-9 mL/min), and operating temperature (30-60 °C)-were varied to understand their relationship to AEM performance. The performance of the electrolysis unit is measured by its hydrogen production and energy efficiency using the AEM electrolysis unit. Based on the findings, the operating parameters greatly influence the performance of AEM electrolysis. The highest hydrogen production was achieved with the operational parameters of 2.0 M electrolyte concentration, 60 °C operating temperature, and 9 mL/min electrolyte flow at 2.38 V applied voltage. Hydrogen production of 61.13 mL/min was achieved with an energy consumption of 48.25 kW·h/kg and an energy efficiency of 69.64%.
An investigation was conducted to determine the effects of operating parameters for various electrode types on hydrogen gas production through electrolysis, as well as to evaluate the efficiency of the polymer electrolyte membrane (PEM) electrolyzer. Deionized (DI) water was fed to a single-cell PEM electrolyzer with an active area of 36 cm2. Parameters such as power supply (50-500 mA/cm2), feed water flow rate (0.5-5 mL/min), water temperature (25-80 °C), and type of anode electrocatalyst (0.5 mg/cm2 PtC [60%], 1.5 mg/cm2 IrRuOx with 1.5 mg/cm2 PtB, 3.0 mg/cm2 IrRuOx, and 3.0 mg/cm2 PtB) were varied. The effects of these parameter changes were then analyzed in terms of the polarization curve, hydrogen flowrate, power consumption, voltaic efficiency, and energy efficiency. The best electrolysis performance was observed at a DI water feed flowrate of 2 mL/min and a cell temperature of 70 °C, using a membrane electrode assembly that has a 3.0 mg/cm2 IrRuOx catalyst at the anode side. This improved performance of the PEM electrolyzer is due to the reduction in activation as well as ohmic losses. Furthermore, the energy consumption was optimal when the current density was about 200 mA/cm2, with voltaic and energy efficiencies of 85% and 67.5%, respectively. This result indicates low electrical energy consumption, which can lower the operating cost and increase the performance of PEM electrolyzers. Therefore, the optimal operating parameters are crucial to ensure the ideal performance and durability of the PEM electrolyzer as well as lower its operating costs.