Introduction
Because the supply of batteries as an energy source cannot follow up compared to the increased demand for portable/mobile electric machinery, the price of batteries and their components has soared dramatically.[1,2] Direct liquid fuel cells (DLFCs), one of the new types of energy supply systems, are a well-respected field, compensating for the batteries’ disadvantages: weight, booming price, and charging time.[3–6] Among various DLFCs, hydrazine fuel cells (HzFCs) applying for an anion exchange membrane (AEM) show as much high power density (1.0–1.2 W cm−2) as hydrogen proton exchange membrane fuel cells (PEMFCs). In addition, HzFCs do not emit carbon dioxide unlike typical direct methanol fuel cells (DMFCs).[7–11] Therefore, HzFCs could be an ecofriendly energy source suitable for small and midterm electronic devices such as scooters, drones, golf carts, and emergency robots.
Many studies are still focusing on the development of hydrazine oxidation electrocatalysts and are limited to the small single-cell application of the developed catalysts.[12–17] Only a couple of studies on operational conditions for HzFCs have been conducted, and even that does not provide sufficient information.[18,19] Even though several fuel cell/stack types of research using a cation exchange membrane (CEM) have been reported, it is difficult to apply them to HzFC/stack using the AEM.[20–26] The difference in the membrane means that the pH condition being operated is different and induces a change in the oxygen reduction reaction (ORR) mechanism. In other words, the ORR mechanism in a cathode part produces water (Equation (1) in acidic media) or consumes water (Equation (2) in alkaline media).
Therefore, appropriate cathode humidification could be a critical factor in the HzFC operation. At the same time, since HzFC uses a hydrated hydrazine fuel, water diffusion from the anode part to the cathode part should be considered.
The cell temperature should be controlled carefully between the fuel cell performance and the thermal stability. As AEM has less thermal stability than CEM, it is sensitive to cell temperature which directly affects the fuel cell performance.[27–30] In general, the fuel cell using AEM operates at ≈60 °C, and the fuel cell using CEM operates at around 80–90 °C.
For the energy source of portable devices, fuel cell components are also important.[20] The size of the gas-supplying component varies depending on what kind of gas is injected into the fuel cell among compressed air, pure O2, and the general atmosphere. A liquid pump as one of the components is also needed to control the fuel flow rate. Under the practical operation, two-phase contents of N2H4 as a liquid fuel and N2 as a generated gas exist on the anode side, and thus fuel flow rate should be controlled with the consideration of fast removal of the N2 gas and securement of the reaction time between fuel and catalysts.[31]
In this study, we try to investigate the effect of various operational factors on HzFC performance, including cathode relative humidity, back pressure on the cathode side, cell temperature, fuel concentration of the anodic side, and stoichiometric factor of both sides (λfuel/λair). Each feature is not independent but rather interdependent on the fuel cell performance. A comprehensive analysis of the HzFC stack, which has a complicated internal structure and large surface area, is accompanied by the reason for the difference in performance with the single cell.
Results and Discussion
Standard operation condition is designated for accurate comparison of the fuel cell performance (Table 1).
Table 1 The standard operation condition of alkaline liquid fuel cell
| Featuresa) | Value | Features | Value |
| Fuel concentration | 4 m | Relative humidity | 100% |
| Stoichiometric factor (λfuel) | 9 | Cell temperature | 60 °C |
| Stoichiometric factor (λgas) | 9 | Back pressure | 0 bar |
As we mentioned earlier, since alkaline liquid fuel cells consume water on the cathode side and hydrated N2H4 fuel on the anode side is supplied, anode water could be already sufficiently supplied to the cathode side through the AEM. In other words, air humidification may not be an essential need at the cathode side. Therefore, we assessed fuel cell performance in terms of air relative humidity adjusting the gas bottle temperature (TBT) and gas preheater temperature (TPT). Another concern is that when humidified air is injected, the gas flow rate just before being supplied to the cell increases because of steam. In addition, the actual reaction process becomes extremely complicated because air, not pure oxygen, is supplied. For example, assuming the dry air condition of 60 °C, 1 atm, and 5000 sccm, 100% humidified air at 60 °C has 0.1524 kg water kg−1 dry air from the psychrometric chart. So, the flow rate of N2, O2, and H2O is 3950, 1050, and 1221 sccm, respectively, showing that the total flow rate is increased to 6221 sccm before the gas inlet. That is, it can be confirmed through the simple calculation that when humidifying, not only the partial pressure of oxygen decreases from 0.21 (O2/(O2 + N2)) to 0.17 (O2/(O2 + N2 + H2O)), but also increases to the flow rate (5000 → 6221 sccm). Therefore, elements that require humidification and elements that do not require humidification are combined to form the optimal humidification point. Because of these considered elements, we expected that the fuel cell performance is maximized under the particular humidification condition.
Figure 1 shows single-cell performances between 100% humidified air and full dry air. Maximum power densities at a relative humidity of 0, 20, 40, 60, 80, and 100% are 487, 530, 524, 571, 610, and 673 mW cm−2, respectively. We confirmed that relative humidity affected not only the performance of the fuel cell but also the open-circuit voltage (OCV) because of the different overpotentials of ORR. Interestingly, the performance and even OCV are the highest at 100% humidified air. It can be elucidated by a similar CO2 reduction system using AEM.[32] If there is no moisture in the supplied gas, a diffusion gradient is formed in the gas diffusion layer (GDL) region, which adversely affects performance. On the other hand, the effect of the consumed water on the cathode side could be negligible in sufficient humidification conditions.
[IMAGE OMITTED. SEE PDF]
This means that the mentioned elements of consideration may not have a greater impact than expected, and water consumption is actively progressing in the cathode part.
The application of the back pressure pushes air in the perpendicular direction of the GDL, resulting in more contact with the ORR catalyst. However, at the same time, pressurization increases the pressure inside the fuel cell and may cause problems in which fuel or gas leaks through the gasket. To compose the portable liquid fuel cell, the injected gas type should be selected from pure O2, compressed air, and the general atmosphere, and if proper performance of the fuel cell is exhibited only in compressed air, an increase in weight and volume due to the compressor construction should also be considered. Figure 2 shows the different polarization curves of a single fuel cell by increasing the back pressure up to 2.0 bar. OCV in all experiments is ≈0.99 V, indicating that OCV is not affected by back pressure at all, since the potential of the fuel cell is irrelevant to the number of reactants. Peak power densities gradually increase as the back pressure increases, from 673 (0 bar) to 929 mW cm−2 (2.0 bar). From the absence of back pressure, it is increased by 7–12% each time the back pressure increases by 0.5 bar, and the maximum performance of 929 mW cm−2 seems to converge at 2.0 bar, which is presumed to be due to the approach of oxygen density by the limit of the reaction catalyst. Therefore, a portable fuel cell system should be designed in both considerations of a performance increase due to the back pressure and an efficiency decrease due to the weight of the compressor construction.
[IMAGE OMITTED. SEE PDF]
Controlling both fuel concentration and fuel flow rate could be considered in terms of multiple perspectives. The higher the fuel concentration, the smaller the size of the fuel tank of the portable liquid fuel cell, and concentration loss could be observed in a higher current density region when oxygen is sufficient. To control the fuel concentration, we kept the stoichiometric factor of fuel as 9 in all experiments. In addition, to analyze the effect of fuel concentration on the cell performance precisely, the fuel cell operation is conducted from the low concentration to the high concentration. Figure 3 shows different power performances as a function of the fuel concentration, showing the highest peak power density of 673 mW cm−2 at 4.0 m N2H4. Because a very high stoichiometric value of 9 is maintained, the performance applying 1.0 m N2H4 was relatively low at 238 mW cm−2. It might be due to insufficient contacting fuel reactivity of the catalyst. On the other hand, the reason for the low performance of 483 mW cm−2 at 8.0 m might be the slow flow rate and incomplete emission of nitrogen gas. The design of a flow channel for emitting the generated gas will be covered in our future work.
[IMAGE OMITTED. SEE PDF]
Increasing cell temperature is the simplest way to improve fuel cell performance, but it should be thoroughly considered because the AEM is vulnerable to heat. Figure 4 shows that cell temperature influences power performance. In this study, at a cell temperature of 80 °C, the maximum peak power density of 773 mW cm−2 was observed, whereas the minimum peak power density of 287 mW cm−2 was obtained at 100 °C. The increase in fuel cell performance at 70 → 80 °C is relatively lowered compared to that at 60 → 70 °C, and the performance is decreased at 80 °C or more, it being estimated that the thermal resistance of AEM we used is around 80 °C. That's why the fuel cell performance is severely decreased at 100 °C.
[IMAGE OMITTED. SEE PDF]
The stoichiometric factor is one of the important operational factors of the fuel cell in the efficiency of the fuel cell and the device size. In the case of liquid fuel cells that emphasize portability, which gas is used among oxygen, compressed air, or the general atmosphere is an essential consideration for constituting the equipment of the initial fuel cell system. The lower λair, the fewer additional devices required, so the compact fuel cell system could be achieved. Figure 5a shows the polarization curve of the alkaline liquid fuel cell maintaining λair. As λfuel decreases, initial performance (≈1 A cm−2) minutely increases. However when λfuel is 1.5, the N2 product gas at the anode side could not be properly emitted, so the peak power density is not observed. Meanwhile, we also conducted the performance test maintaining λfuel (Figure 5b). Because the generated gas was properly discharged, the peak power density was observed, but it was confirmed that the fuel cell performance decreased as a function of λair. Figure 5c shows the fuel cell performance when both stoichiometric factors are reduced, keeping the ratio of λfuel/λair. The same power density is shown under all conditions in the low-current region (≈0.5 A cm−2), but the difference in the peak power density was observed in the high-current-density region due to problems such as lack of reactants and slowing down of product emission. The peak power density of all conditions is enumerated in Figure 5d.
[IMAGE OMITTED. SEE PDF]
Fuel cell efficiency is composed of the product of voltage efficiency (εvoltage), thermodynamic efficiency (εthermo), and fuel efficiency (εfuel) (Equation (3)).[33] Especially, HzFC has the advantage because εthermo of HzFC is even higher than 1, compared to εthermo of PEMFC (Equation (4)).[34]
As shown in Figure 5a, under sufficient air supply conditions, the lower λfuel (the higher εfuel), the better the fuel cell performance in the low-current region (≈1 A). However, λfuel should not be just reduced, because N2H4 fuel should be injected excessively to react from the beginning to the end of the flow channel. In addition, the phase transition of fuel inside the fuel cell (N2H4, (l) → N2, (g)) interferes with the catalyst contact of the fuel and makes the flow rate unstable. Therefore, although higher fuel cell efficiency could be achieved, λfuel cannot be easily reduced.
By referring to the above single-cell measurements, the operational condition of the five-stack HzFC (HzFC-5S) is designed. The preparation of catalysts and membrane electrode assembly (MEA) is the same as those in the single-cell condition except for the size of MEA (25 → 31.5 cm2). Because the stack does not have heating bars, 100% humidified N2 gas and DI water heated to 60 °C were supplied for 1 h during the hydration process to increase the initial stack temperature. Besides, the commonly used λair was fixed as 1.5 (4778 sccm, Equation (5)).[35,36] And λfuel was fixed as 3.0 based on the highest peak current density at λair of 1.5 (Figure 5d).
Figure 6 shows the polarization curve of the HzFC-5S as a function of fuel concentration. Unlike the highest power performance in the fuel concentration of 4 m in the single cell, the HzFC-5S rather showed the highest power performance applying the lower fuel concentration of 2 m. This result shows when a low concentration of N2H4 fuel is supplied at a high flow rate, the generated N2 gas can be easily emitted out. So the generated gas emission in the stack operation is much more important than in the single-cell operation.
[IMAGE OMITTED. SEE PDF]
The OCV of the HzFC-5S in the series circuit is ≈4.8 V, so the effect on the fuel crossover seems to be weak. However, the peak power density of the HzFC-5S in 2 m is around 200 mW cm−2 (at the stack power of 31 W), which is even 50% lower than the single-cell performance of 436 mW cm−2 in 2 m under the same condition (λfuel/λair = 3/1.5).
To confirm the inherent full power of HzFC-5S, we changed the stack test condition to O2 atmosphere and observed the maximum stack power of around 100 W (Figure 7a). The result shows that if sufficient fuel and oxidant are supplied to the stack, the overall performance could be improved. However, there is a cell temperature issue in the stack that was not observed in single cell. When the cell temperature is high, the reaction rate and ion diffusivity increase, thereby positively increasing the fuel cell performance and negatively damaging the AEM. In the case of the single cell, which maintains the cell temperature of 80 °C via heating bars, the maximum variation of temperature is 3 °C during the operation (Figure 7b), whereas in the case of the stack, which heats as the exothermic reaction is easily accumulated, the temperature rises almost 20 °C from the lowest 77 °C to the highest 97 °C even if there are air-cooling fans (Figure 7c). It should be noted that heat management is possible through fuel concentration. A fast flow rate of a low concentration of fuel is effective to remove the accumulated heat inside the stack, but a slow flow rate of a high concentration of fuel is relatively vulnerable to controlling the cell temperature.
[IMAGE OMITTED. SEE PDF]
Conclusion
The gap between a half-cell measurement of each component and a single-cell operation considering various experimental conditions should be intensively analyzed to develop the stack for emerging delivering devices/systems. We showed that the performance change of the single cell could be constructed by various operational parameters such as relative humidity, back pressure, cell temperature, fuel concentration, and stoichiometric factors. It is quite encouraging to show around 100 W power of the short-stack HzFC. There are still a couple of hurdles that should be overcome for fuel application; we discussed various operational perspectives of alkaline liquid fuel cells. To jump from the laboratory research stage to the empirical research stage, other operational components such as the compressor, the liquid pump, the gas blower, the fuel/water tank, and the flow channel design should also be considered for the practical fuel cell/stack.
Experimental Section
6.6 g of nickel chloride (NiCl2, 98%, Sigma-Aldrich) and 3.0 g of polyvinylpyrrolidone (PVP, 10 000 g mol−1, Sigma-Aldrich) were dissolved in 1.0L of ethylene glycol (EG, Sigma-Aldrich). 1.0 g of carbon support (Vulcan XC-72) was added to a green solution after stirring. 1.0 m NaOH was added into the mixed solution until pH 10. Reflux and distillation in processing the conventional polyol reduction method were applied at 160 °C for 4 h. Centrifugation was carried out three times with deionized (DI) water to remove the unreacted materials. Then, the catalyst slurry was filtered with DI water. Synthesized catalyst slurry was dried in an oven at 60 °C for 24 h. At last, the dried sample was annealed at 300 °C for under the 4% hydrogen contained in Ar. Ni/C catalyst of anode catalyst for HzFC contained 45–50 wt% of Ni metal on the carbon support. The cathode catalyst was the commercial Pt/C (46.7%, Tanaka).
Catalyst ink was prepared with each catalyst powder, nPA, and 10% Nafion ionomer solution. Nafion ionomer was used at 5% versus the catalyst weight.[7,8] The ink mixture was ultrasonicated in an ice bath for 1.0 h. The sonicated ink was air sprayed on AvCarb MGL 190 for the anode electrode and Sigracet 29 BC for the cathode electrode, respectively. The loading amounts of the catalyst at the anode and cathode were 1.6 mgCat cm−2 and 1.0 mgPt cm−2, respectively. The MEA was fabricated by pressing at 60 °C with both sprayed electrodes and a lab-made AEM.[7] The size of MEA was 25.0 cm2 for a single cell and 31.5 cm2 for a bipolar plate of the stack, respectively.
Before the single-cell test, DI water and 100% humidified N2 were injected into the anode line and the cathode line, respectively, for the hydration of MEA. Operation conditions such as cell temperature, the concentration of hydrazine fuel, back pressure, stoichiometric factors (λfuel/λgas), and relative humidity were differently applied in the single-cell test. The stoichiometric factor and relative humidity were calculated by Equation (6) and (7), respectively.[37]
Both the HzFC single cell and stack consisted of graphite bipolar plates, 0.3 mm PTFE gaskets, gold-coated copper current collectors, and aluminum endplates (see Figure S1a,b, Supporting Information). The flow field pattern of bipolar plates was four-channel serpentine and the active electrode area was 25 cm2 (single-cell)/31.5 cm2 (stack). The feed flow through the single cell/stack was U shaped, where the inlet downside for liquid fuel and outlet upside for gas products with the unreacted liquid fuel were located on the same side, considering the phase transition of reactants and gravity effect. After stacking the prepared MEAs and bipolar plates in layers, the HzFC single cell/stack was completely assembled with a force of 60 kgf·m.
All performances of the HzFC single cell/stack were obtained through the polarization curve. The single cell was tested with heating bars to control the cell temperature, whereas the stack was operated with air-cooling fans due to an excessive exothermic reaction. After the hydration process with DI water and 100% humidified N2 for 1.0 h, the test was conducted after the circulation of fuel/oxygen until the resistance of each MEA reached 10 mΩ or less. The turn voltage of single cell and stack was 0.3 and 1.5 V, respectively. Figure S1c, Supporting Information, shows a photograph of the HzFC stack during the operation.
Acknowledgements
This research was supported by the National R&D Program through the National Research Foundation of Korea (NRF), funded by the Ministry of Science and ICT (NRF-2021K1A4A8A01079455) and this research was supported by the Korea Institute of Energy Technology Evaluation and Planning (KETEP) granted financial resources from the Ministry of Trade, Industry & Energy, Republic of Korea (No. 20213030040590).
Conflict of Interest
The authors declare no conflict of interest.
Data Availability Statement
The data that support the findings of this study are available from the corresponding author upon reasonable request.
C. Grosjean, P. H. Miranda, M. Perrin, P. Poggi, Renewable Sustainable Energy Rev. 2012, 16, 1735.
G. Martin, L. Rentsch, M. Höck, M. Bertau, Energy Storage Mater. 2017, 6, 171.
K. Scott, P. Argyropoulos, K. Sundmacher, J. Electroanal. Chem. 1999, 477, 97.
B. C. Ong, S. K. Kamarudin, S. Basri, Int. J. Hydrogen Energy 2017, 42, 10142.
W. Qian, D. P. Wilkinson, J. Shen, H. Wang, J. Zhang, J. Power Sources 2006, 154, 202.
K. Tran, T. Q. Nguyen, A. M. Bartrom, A. Sadiki, J. L. Haan, Fuel Cells 2014, 14, 834.
S. Bae, J. Park, Y. Hwang, J.-S. Park, J. Lee, B. Jeong, J. Energy Chem. 2022, 64, 276.
J. Park, S. Bae, J.-S. Park, S. Bong, J. Lee, ACS Appl. Nano Mater. 2021, 4, 8145.
D. Khalafallah, M. Zhi, Z. Hong, ChemCatChem 2021, 13, 81.
Z. Lu, M. Sun, T. Xu, Y. Li, W. Xu, Z. Chang, Y. Ding, X. Sun, L. Jiang, Adv. Mater. 2015, 27, 2361.
Y. Yan, J.-Y. Zhang, X.-R. Shi, Y. Zhu, C. Xia, S. Zaman, X. Hu, X. Wang, B. Y. Xia, ACS Nano 2021, 15, 10286.
T. Wang, Q. Wang, Y. Wang, Y. Da, W. Zhou, Y. Shao, D. Li, S. Zhan, J. Yuan, H. Wang, Angew. Chem. 2019, 131, 13600.
G. Wang, J. Chen, P. Cai, J. Jia, Z. Wen, J. Mater. Chem. A 2018, 6, 17763.
J. Ding, P. Kannan, P. Wang, S. Ji, H. Wang, Q. Liu, H. Gai, F. Liu, R. Wang, J. Power Sources 2019, 413, 209.
T. Zhang, T. Asefa, Adv. Mater. 2019, 31, 1804394.
Q. Qian, J. Zhang, J. Li, Y. Li, X. Jin, Y. Zhu, Y. Liu, Z. Li, A. El-Harairy, C. Xiao, G. Zhang, Y. Xie, Angew. Chem. 2021, 133, 6049.
K. Ojha, E. M. Farber, T. Y. Burshtein, D. Eisenberg, Angew. Chem. Int. Ed. 2018, 57, 17168.
K. Asazawa, T. Sakamoto, S. Yamaguchi, K. Yamada, H. Fujikawa, H. Tanaka, K. Oguro, J. Electrochem. Soc. 2009, 156, B509.
H. Hwang, S. Hong, D.-H. Kim, M.-S. Kang, J.-S. Park, S. Uhm, J. Lee, J. Energy Chem. 2020, 51, 175.
D. Kim, J. Lee, T.-H. Lim, I.-H. Oh, H. Y. Ha, J. Power Sources 2006, 155, 203.
M. R. Andrew, W. J. Gressler, J. K. Johnson, R. T. Short, K. R. Williams, J. Appl. Electrochem. 1972, 2, 327.
J.-Y. Park, Y. Seo, S. Kang, D. You, H. Cho, Y. Na, Int. J. Hydrogen Energy 2012, 37, 5946.
D. Buttin, M. Dupont, M. Straumann, R. Gille, J.-C. Dubois, R. Ornelas, G. P. Fleba, E. Ramunni, V. Antonucci, A. S. Aricoá, P. Cretiá, E. Modica, M. Pham-Thi, J.-P. Ganne, J. Appl. Electrochem. 2001, 31, 275.
Y. Liu, X. Xie, Y. Shang, R. Li, L. Qi, J. Guo, V. K. Mathur, J. Power Sources 2007, 164, 322.
H. Joh, S. Hwang, J. Cho, T. Ha, S. Kim, S. Moon, H. Ha, Int. J. Hydrogen Energy 2008, 33, 7153.
K. Scott, W. M. Taama, P. Argyropoulos, J. Power Sources 1999, 79, 43.
Z. Pan, H. Zhuang, Y. Bi, L. An, J. Power Sources 1999, 79, 43.
A. M. Bartrom, J. L. Haan, J. Power Sources 2012, 214, 68.
S. Hong, S. Chung, J. Park, J. P. Hwang, C. H. Lee, S. Uhm, S. Bong, J. Lee, ACS Catal. 2021, 11, 4722.
R. C. Raimundo, J. V. C. Vargas, J. C. Ordonez, W. Balmant, P. T. B. Polla, A. B. Mariano, C. E. B. Marino, Int. J. Hydrogen Energy 2020, 45, 5723.
Y.-C. Park, D.-H. Peck, S.-K. Dong, S.-K. Kim, S. Lim, D.-H. Jung, J.-H. Jang, D.-Y. Lee, Int. J. Hydrogen Energy 2011, 36, 1853.
W. Choi, S. Park, W. Jung, D. H. Won, J. Na, Y. J. Hwang, ACS Energy Lett. 2022, 7, 939.
R. O’Hayre, S.-W. Cha, W. Colella, F. B. Prinz, Fuel Cell Fundamentals, John Wiley & Sons, Hoboken NJ 2016.
P. Vanysek, CRC Handbook of Chemistry and Physics (Ed: W. M. Haynes), 97th ed., Vol. 8, CRC Press 2016, p. 1, [DOI: https://dx.doi.org/10.1201/9781315380476].
D. Candusso, F. Harel, A. De Bernardinis, X. François, M. C. Péra, D. Hissel, P. Schott, G. Coquery, J.-M. Kauffmann, Int. J. Hydrogen Energy 2006, 31, 1019.
N. Dyantyi, A. Parsons, C. Sita, S. Pasupathi, Open Eng. 2017, 7, 287.
O. A. Alduchov, R. E. Eskridge, J. Appl. Meteorol. Climatol. 1996, 35, 601.
You have requested "on-the-fly" machine translation of selected content from our databases. This functionality is provided solely for your convenience and is in no way intended to replace human translation. Show full disclaimer
Neither ProQuest nor its licensors make any representations or warranties with respect to the translations. The translations are automatically generated "AS IS" and "AS AVAILABLE" and are not retained in our systems. PROQUEST AND ITS LICENSORS SPECIFICALLY DISCLAIM ANY AND ALL EXPRESS OR IMPLIED WARRANTIES, INCLUDING WITHOUT LIMITATION, ANY WARRANTIES FOR AVAILABILITY, ACCURACY, TIMELINESS, COMPLETENESS, NON-INFRINGMENT, MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Your use of the translations is subject to all use restrictions contained in your Electronic Products License Agreement and by using the translation functionality you agree to forgo any and all claims against ProQuest or its licensors for your use of the translation functionality and any output derived there from. Hide full disclaimer
Copyright John Wiley & Sons, Inc. 2023
Abstract
Although hydrazine fuel cells (HzFCs) have various advantages such as a high theoretical potential, low operating temperature, and no carbon dioxide emission, only a couple of studies on HzFC stack have been reported due to the peculiarity of using an anion exchange membrane and the toxic issue of highly concentrated hydrazine fuel. Herein, how the power output performance in a single‐cell system is affected by various operational factors of cell temperature, humidification level, pressurization, fuel concentration, and stoichiometric value is investigated and then a home‐made short stack consisting of five single cells (HzFC‐5S) to evaluate the difference between the single cell and the stack is built up. Confirmation that the optimization point in the single‐cell does not apply to the short stack can be meaningful in accessing its possible commercialization process for portable and mobile devices.
You have requested "on-the-fly" machine translation of selected content from our databases. This functionality is provided solely for your convenience and is in no way intended to replace human translation. Show full disclaimer
Neither ProQuest nor its licensors make any representations or warranties with respect to the translations. The translations are automatically generated "AS IS" and "AS AVAILABLE" and are not retained in our systems. PROQUEST AND ITS LICENSORS SPECIFICALLY DISCLAIM ANY AND ALL EXPRESS OR IMPLIED WARRANTIES, INCLUDING WITHOUT LIMITATION, ANY WARRANTIES FOR AVAILABILITY, ACCURACY, TIMELINESS, COMPLETENESS, NON-INFRINGMENT, MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Your use of the translations is subject to all use restrictions contained in your Electronic Products License Agreement and by using the translation functionality you agree to forgo any and all claims against ProQuest or its licensors for your use of the translation functionality and any output derived there from. Hide full disclaimer
Details
1 Ertl Center for Electrochemistry and Catalysis, Gwangju Institute of Science and Technology, Gwangju, South Korea
2 International Future Research Center of Chemical Energy Storage and Conversion Processes, Gwangju Institute of Science and Technology, Gwangju, South Korea