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Proton exchange membrane fuel cell (PEMFC) with dead-ended anode is of outstanding advantages of high hydrogen utilization and simple hydrogen system. Because of its unique operation mode, the effect of gravity on water and gas transportation in PEMFC with dead-ended anode cannot be ignored. A two-phase model of PEMFC with dead-ended anode was developed, and the effects of placement orientation and cross section sizes of flow channel on water transport characteristics were analyzed. The results show that the flow channel with smaller cross section (0.5mm × 0.5 mm) showed better initial performance, but its voltage drop rate was faster due to liquid water was easier to be accumulated in the channel. Conversely, the liquid water volume fraction was smaller with a larger flow channel size. Moreover, the volume fraction of liquid water at the end of the channel was significantly greater than that in other areas when it was placed vertically. According to the results, the flow channel placed vertically combined with a larger cross section size (2mm × 2 mm) could effectively transferred liquid water to the end of the flow channel. Thus, it can effectively reduce the damage to PEMFC caused by water accumulation. • Water Transport Characteristics of PEMFC with dead-ended anode were simulated. • The flow channel placed vertically facilitates the removal of liquid water. • Flow channel size needs to balance PEMFC performance and water flooding. [ABSTRACT FROM AUTHOR]

During the proton exchange membrane fuel cell (PEMFC) operation, liquid water accumulates in the PEMFC, causing water flooding and performance degradation, especially at high current densities. Moisture dehumidification has been used to remove excess water in PEMFCs by forming a high water vapor concentration gradient between the inside and outlet of PEMFCs. In this study, the cathode outlet gas was condensed by adding thermoelectric refrigeration equipment to the cathode outlet of a single cell, and the influence of gas condensation on PEMFC performance under different working conditions was studied. The results showed that the effect of moisture dehumidification on PEMFC performance depended on the water content in the PEMFC, and the positive effect was more evident under high current density, high relative humidity, and high pressure. Moreover, moisture dehumidification is beneficial to alleviate the degradation of the catalyst layer. When there was no exhaust gas condensation, large-area fractures and loss occurred in the catalyst layer after 100 h of operation, and the electrochemically active area (ECSA) was reduced by 22.28%. There was only a slight reduction in the thickness of the catalyst layer with moisture dehumidification, and the ECSA was only reduced by 1.82%. Therefore, the degree of moisture dehumidification should be adjusted according to the water content inside the PEMFC in actual operation. • The effects of moisture dehumidification on the PEMFC performance is studied. • The effect of moisture dehumidification depended on the water content. • Moisture dehumidification can effectively alleviate water flooding. • The more water content in the PEMFC, the more obvious the positive effect. • The degree of moisture dehumidification should be adjusted according to the water content. [ABSTRACT FROM AUTHOR]

• A residential cogeneration system combining fuel cell and adsorption chiller is constructed. • A flexible load regulation method for a residential cogeneration system is established. • The proposed regulation method is compared with the traditional control strategy. • The cogeneration system with regulation method is evaluated using 4E analysis. To increase the use of renewable energy sources and reduce the consumption of energy and environmental pollution, a flexible load regulation method is proposed for a hybrid residential combined cooling, heating, and power system based on fuel cells and adsorption chillers. The combined cooling, heating, and power system consisted of a proton exchange membrane fuel cell stack, an adsorption refrigerator, a thermal storage tank, a wall-hanging boiler, and related accessories. A system model was established for a typical Shanghai household and a 4E (energy, exergy, environment and economy) analysis evaluation method was used to evaluate the performance of the system during winter and summer. The energy savings and CO 2 emission reduction rates of the system with and without regulation were compared. The results indicated that energy and exergy efficiencies can be improved by using flexible load regulation. The energy efficiencies of the combined cooling, heating, and power system with regulation in winter and summer were 89.21% and 73.26%, respectively, and the exergy efficiencies were 58.04% and 55.47%, respectively. When compared with the traditional system, the CO 2 emission reductions in the combined cooling, heating, and power system with flexible load regulation in winter and summer reached as high as 67.26% and 67.43%, respectively. Therefore, the environmental benefits of the proposed system can be significant. If the hydrogen price can drop below 1.557 $/kg and the costs of the proton exchange membrane fuel cell and adsorption chiller can be reduced, the application of the combined cooling, heating, and power system will become economically viable. [ABSTRACT FROM AUTHOR]

Proton exchange membrane fuel cell (PEMFC) vehicles (PEMFCV) have drawn tremendous attention owing to the advantages of low or zero emissions. Effective integrated thermal management systems (ITMS) considering thermal loops coupling and interaction and with a rational strategy are crucial for the efficient and secure operation of PEMFCV. Therefore, ITMS in PEMFCV are worthy to be reviewed comprehensively. This paper aims to provide the general and current ideas of ITMS design in PEMFCV from part-level to system-level, along with control strategies. The factors that affect the thermal performance of heat-generating components and systems are deeply analysed, and the key findings, challenges, and future work are presented. It is found that liquid cooling is more appropriate for ITMS because of the high specific heat and the convenience of integrating other thermal systems, and that heat pumps tend to be a more suitable choice for air conditioning systems. The future work mainly includes the improvement of cooling and cold start of PEMFC, perfection and verification of waste heat recovery system, exploration of new air conditioning systems, integration of systems, coupling of ITMS and energy management systems, and enhancement of model accuracy. The provided information is useful to guide the system layout and control strategies for ITMS at the early design stage. [Display omitted] • The state of art for thermal management of the main components and systems in PEMFCV was reviewed. • ITMS in HEV were summarized for comparison with those in PEMFCV. • The current progress, challenges and future work of ITMS in PEMFCV were presented. [ABSTRACT FROM AUTHOR]

Hydrogen-oxygen proton exchange membrane fuel cell with good application prospect in the special occasions of space exploration and underwater navigation, its durability is still a key problem to be solved. In this research, current cyclic loading durability experiment of a hydrogen-oxygen proton exchange membrane fuel cell with an active area of 50 cm2 was carried out. The performance degradation was characterized by polarization curves, Cyclic Voltammetry and Electrochemical Impedance Spectroscopy. Finally, the decay of catalyst and membrane was evaluated by Scanning Electron Microscopy, Energy Dispersive X-ray Spectroscopy and Transmission Electron Microscope. After 2500 loading cycles, it with a total performance degradation of 31.05% at 1200 mA cm−2. The electrochemical active surface Area decreased by 61.6% and electrochemical Impedance increased by 33.04%. What' more, the catalyst layer in outlet area had been partially damaged, and its Pt particles have agglomerated and grown. More seriously, Pt particles had migrated and lost. The decay phenomenon was also found in the proton exchange membrane, in which element F, S and C were partially lost, especially element F. The findings reported here are expected to provide more insights into the effect of current loading on the decay of membrane electrode assembly. ∙ Gas starvation accompanied by cyclic loading leaded to MEA damage. ∙ Pt particles at PEMFC outlet have obviously agglomerated, grown and lost. ∙ PEM structure is damaged and elements F, C, S were lost seriously. [ABSTRACT FROM AUTHOR]

• A PEMFC-based CCHP system integrated with methanol reforming and dehumidification. • Realize the cooling and dehumidification of the data center simultaneously. • The dynamic performance under the cooling-led strategy is studied. • The temperature and humidity of the data center are controlled at 25 °C and 55–63%. For data centers with strict requirements on temperature and humidity, this study proposes a combined cooling, heating and power (CCHP) system integrated with methanol-reforming and dehumidification based on proton exchange membrane fuel cells (PEMFCs). The system consists of a methanol-reformer, preferential oxidation (PROX) reactor, PEMFC stack, adsorption chiller, desiccant air conditioning (DAC), and phase change material (PCM) heat storage tank. Taking a data center in Harbin as the research object, the dynamic response characteristics of the system are studied, and the system has good dynamic response characteristics. The CO concentration in the reformed gas is controlled by controlling the O 2 /CO ratio in the PROX. The CO concentration in the transformation gas can be controlled below 4 ppm. The cooling and dehumidification requirements of the data center are met by controlling the cooling power of the system and the air intake conditions of the data center. The results show that the cooling power of the system rises for 400 s at the beginning of the operation, and stabilizes after about 2 h, and the temperature and relative humidity of the data center can be controlled at 25 °C and 55–63%. The novel system develops an efficient way to recover low-grade waste heat of PEMFC stacks for cooling and dehumidification in data centers. [ABSTRACT FROM AUTHOR]

• PEMFC is stable when compression ratio of nickel metal foam on cathode is beyond 0.69. • The performance of PEMFC increases with the rise of compression ratio on cathode. • There is optimal compression ratio of nickel metal foam on anode, namely 0.38. • There is optimal PPI of nickel metal foam on cathode, namely 75. • Compared with the CMF, maximum power density of the OMF increases by 9.8%. In order to tackle the water flooding issue in proton exchange membrane fuel cell (PEMFC), the effects of structure parameters of nickel metal foam on water management and the performance of PEMFC were experimentally investigated. Experimental results indicated that when compression ratio of nickel metal foam on cathode is beyond 0.69, the voltage of PEMFC is completely stable in a 3-hour constant current density test. Furthermore, the performance of PEMFC enhances with the rise of compression ratio on cathode. However, there is an optimal compression ratio of nickel metal foam on anode, namely 0.38. Regarding PPI (pores per inch) of nickel metal foam, it has been found that there is an optimal PPI on cathode, namely 75, due to the synergic effect between the distribution of reactant gas and water management in nickel metal foam flow fields with different PPIs. In contrast with cathode, a higher PPI of nickel metal foam results in better performance on anode. Compared with the case that uncompressed nickel metal foam with 110 PPI for anode and cathode, the maximum power density and energy conversion efficiency of the optimized metal foam fuel cell, namely 110 PPI and compression ratio of 0.38 for anode and 75 PPI and compression ratio of 0.75 for cathode, increase by 9.8% and 4.6%, respectively. In order to further intensify the performance of PEMFC, the effect of assembly force was considered. Since nickel metal foam could protect the MEA, a higher assembly force can be tolerated to obtain better performance. [ABSTRACT FROM AUTHOR]

• A PEMFC-driven CCP system with heat pipe for data center applications is proposed. • New operation strategies for power and cooling supplies in a CCP system are proposed. • Performances of two PEMFC-driven CCP systems with multiple cooling are compared. • Effect of heat pipe on the power and cooling supplies in the CCP system was studied. With the dramatic development of data centers, the energy management system in data center applications has become significantly important in recent years. A proton exchange membrane fuel cell (PEMFC)-driven combined cooling and power (CCP) system with multiple cooling devices was proposed in this paper to fully utilize a natural cold source. Another CCP system without natural cold source utilization was also proposed for comparison. Power and cooling were supplied to these systems with new operational strategies. Based on the proposed model, the operational performance of the two CCP systems was analyzed for a sample data center. The seasonal and annual power supplied, cooling supplies, matching degrees, energy consumption for removing cooling loads, and system efficiencies in the two proposed CCP systems are discussed and analyzed in detail. Results indicate that by using the designed operational strategies, the power and cooling supplies almost matched perfectly with the requirements of the sample data center. The annual energy efficiencies can reach 86.53% and 85.02% for the two proposed CCP systems. [ABSTRACT FROM AUTHOR]

This paper proposes a novel PEMFC-based combined cooling, heating and power (CCHP) system with independent control of refrigeration and dehumidification, which is used in data centers with strict requirements on temperature and humidity. The effects of operating parameters of PEMFC (current density, hydrogen and oxygen pressure) and refrigeration system (hot water distribution ratio, mass flow of cooling water and chilled water) on the 4E (energy, exergy, economy and environment) are investigated. Meanwhile, multiobjective optimization of the above parameters is carried out. The results show that a high inlet pressure is beneficial to improve system efficiency and reduce annual greenhouse gas (GHG) emissions. An increase in the chilled water mass flow increases system efficiency and reduces annual GHG emissions, while an increase in the cooling water mass flow yields the opposite results. Moreover, an increase in the proportion of hot water entering the adsorption chiller causes system efficiency and the annual GHG reduction to initially decrease and then increase. Compared with the unoptimized system, the energy efficiency, exergy efficiency, system cost, GHG emission reduction, electric power, cooling power, heating power and dehumidification rate of the system increase by 5.5%, 0.77%, 10%, 21.27%, 12.87%, 5.37%, 45.73% and 1.53%, respectively. [ABSTRACT FROM AUTHOR]

The durability and reliability of H 2 /O 2 proton exchange membrane fuel cell (PEMFC) is a key factor that prevents its wide application in the civil field. PEMFC inevitably experience different dynamic loading cycles according to different power switching requirements during practical operation. To explore the degradation behavior under different dynamic cycles, a single H 2 /O 2 PEMFC with 50 cm2 active area was operated under the circulating current density from 100 mAcm−2 to 600 mAcm−2, 100 mAcm−2 to 800 mAcm−2, and 100 mAcm−2 to 1000 mAcm−2, respectively. The change of polarization curve, performance degradation at different current density, Cyclic Voltammetry (CV), Electrochemical Impedance Spectroscopy (EIS) were characterized to investigate the performance degradation over dynamic current cycles. Besides, the Scanning Electron Microscopy (SEM) was used to evaluate the degradation of catalyst layer. The results indicated that the degradation rate of the fuel cell performance increased corresponding to the cycle number, at 1200 mA/cm2, it with a total performance degradation rate of 11.83% after 2000 dynamic loading cycles with the circulating current density from 100 mAcm−2 to 600 mAcm−2. The degradation of electrochemical performance such as CV and EIS was consistent with that of fuel cell performance. The degradation rate is accelerated with the increase of loading cycle number and load step amplitude. What' more, EIS provides additional sensitivity to differentiate catalyst layer degradation within PEMFC. Moreover, the degradation of the catalyst layer became much more severe under a larger load step amplitude. • Degradation behavior of H 2 /O 2 PEMFC under dynamic loading cycles was studied. • The current loading process can cause gas starvation in both anode and cathode. • Hydrogen starvation induced carbon corrosion in the anode. • Catalyst layer degradation became much more severe with a larger loading rate. [ABSTRACT FROM AUTHOR]

The field of predictive chemistry relates to the development of models able to describe how molecules interact and react. It encompasses the long-standing task of computer-aided retrosynthesis, but is far more reaching and ambitious in its goals. In this review, we summarize several areas where predictive chemistry models hold the potential to accelerate the deployment, development, and discovery of organic reactions and advance synthetic chemistry., Competing Interests: Authors declare no competing interests., (This journal is © The Royal Society of Chemistry.)