Fuel cells are a promising technology to use as a source of electricity and heat for buildings, and as an electrical power source for electric motors propelling vehicles. They consume hydrogen as ...fuel and oxygen to produce electricity, heat and water. Conventional fuels, such as natural gas, methanol, or even gasoline are reformed to produce the hydrogen required by the fuel cells. During the reforming process, impurities are inevitably obtained in the hydrogen flow. One of them is ammonia (NH3) that can result in serious damage to the fuel cell operation. In this paper, the effects produced by different concentrations of NH3 present in the hydrogen flow on the membrane electrode assembly (MEA) performance are studied, differentiating between irreversible and recoverable damages. Strictly experimental, the study includes both low and high temperature polymer electrolyte fuel cells (PEFC). The NH3 poisoning effect is analyzed and quantified by comparing the polarization curves. After the poisoning stage, the cells are subjected to a regeneration process (feeding the cell with neat H2) with the aim of knowing the membrane's recovery capacity. The experimental results demonstrate that in low temperature (LT)‐PEFCs, the cell recovers its performance almost completely with a new exposure to neat H2, in spite of the damage previously caused by the presence of traces of NH3 in the anode feed stream. In contrast, in high temperature (HT)‐PEFCs, the cell suffers irreversible damage, even with short time exposure to NH3. The paper concludes with discussing the possible chemical interactions by which NH3 affects the cell performance.
The impact of forest certification standards on firm management and market performance is analysed in this paper, so as to isolate the influence of internal (moral and learning) and external (market ...and signalling) sources of motivation. To do so, three propositions are formulated and then empirically tested on a sample of Spanish companies certified by the Programme for the Endorsement of Forest Certification (PEFC). In the structural model, the association of the external motivations with management performance was not confirmed, although the one of internal motivations was significant and companies certified due to internal reasons yielded greater benefits. Our results suggested that the implementation of forest certification per se will not improve overall performance. Moreover, when the standard is internally driven, it is reasonable to expect the implementation of the necessary measures to improve management performance, using the guidelines prescribed by such standard. The findings may be used to characterize certified firms and to anticipate the benefits of both the implementation and the certification of the standard, shedding light on the associations between the motivational factors and the benefits of forest certification standards, a field which has yet to be addressed.
•This study aims to analyse the link of drivers and outcomes of forest certification.•The size and activity of companies influence internal motivations and performance.•Internal drivers are positively associated with the management and market benefits.•Management benefits are positively associated with market results.•Firms need time to consider drivers and potential benefits to maximize results.
Despite being the European Union country with the second largest wooded area and the fourth in terms of forest occupation with respect to its territory, only 9.47% of the forest area in Spain is ...certified by one of the two most important forest certification systems (PEFC and FSC). The literature review has shown that forest certification drivers may be divided into five main mechanisms. The first three are external: Market, Signalling and Legal mechanisms, and the last two internal: Moral and Learning mechanisms. 124 completed questionnaires out of 1194 certified companies in Spain were received to carry out a descriptive and a cluster analysis of the main motivations that encourage the adoption and certification of the PEFC standard and how these motivations vary depending on the characteristics of the companies. Findings reveal that the most valued motivations by this order are related to attracting customer attention, the improvement of companies’ corporate image, the sensitivity to environmental problems and the increase of the competitiveness of the company. Some of the motivations are significantly influenced by the characteristics of the companies, but only the export level has a significative influence (negative) on all the characteristics of the moral mechanism. The implications of the findings can help to identify and characterize the different clusters that exist among certified companies in the Spanish forestry sector. This information can be useful for managers and policy makers to better understand the specific reasons for each conglomerate of companies when opting for certification.
•Forest certification drivers may be divided into five main mechanisms.•The main external drivers are “access new markets” and “improve corporate image”.•The main internal drivers are related to ethical or moral aspects.•These motivations vary according to the characteristics of the companies.
This work deals with the theoretical and experimental analysis of fuel-cell-based auxiliary power units operated with reformate from diesel and kerosene reforming for trucks and aircraft. In the ...theoretical part, a PEFC and an HT-PEFC system were analyzed using process simulation software. In the experimental part, a fuel processor consisting of an autothermal reformer, a water-gas shift reactor and a catalytic burner with 28 kW thermal power was characterized using different diesel and kerosene fuels. These fuels included desulfurized Jet A-1 and Aral Ultimate diesel as petroleum-based fuels and GTL kerosene, GTL diesel (winter and summer grades) and BTL diesel as non-petroleum-based synthetic fuels.
The PEFC system showed a calculated electrical net efficiency of 28.5%, whereas 22.3% was calculated for the HT-PEFC system. A high-quality reformate was produced using various diesel and kerosene fuel qualities in the reformer with a relevant technical power class for the APU application. Although a performance loss of the shift reactor was observed, it was kept at an acceptable level at the end of experiments.
•Fuel-cell-based auxiliary power units for trucks and aircraft.•Analysis of PEFC and HT-PEFC systems with diesel using process simulation software.•Fuel processor system tests using different diesel and kerosene fuels.•Production of high-quality reformate at 28 kW power class.
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•This review describes metal complexes of N4-macrocycles as electrocatalysts.•The catalysts are used in anode and cathode of fuel cells and water electrolyzers.•Strategies of the ...development of cathode catalysts are discussed.•The recent development of such cathode catalysts in fuel cells is described.•Some metallomacrocycles catalysts catalyze the electro-oxidation of fuels.
Metal complexes of N4-macrocycles such as porphyrins and phthalocyanines have been studied for several decades asalternatives to Pt catalysts in polymer electrolyte fuel cells (PEFCs) and polymer electrolyte membrane (PEM) water electrolyzers. This review mainly describes the recent development of these catalysts for use in anode and cathode of PEFCs and PEM water electrolyzers. Performance of the developed catalysts and strategies of the development are summarized. This review aimed to discuss the advantages and disadvantages of the metallomacrocycle-based catalysts compared to conventional Pt electrocatalysts, and to emphasize their functions that the Pt catalyst does not have.
Amine functionalized carbon nanotube (ANCT) is applied as an inorganic potential proton conducting material embedded in a sulfonated poly(ether ether ketone) (SPEEK) matrix. The morphological, ...structural, thermomechanical, physiochemical and electrochemical properties of SPEEK/ACNT composite were investigated and compared to obtained results from bare SPEEK. The synthesized ACNT-incorporated SPEEK membrane have uniform and dense morphology and exhibit improved properties as proton exchange membrane (PEM); for example, SPEEK/ACNT possessed higher thermal stability and tensile strength than SPEEK alone. The amine functionalized structure of ACNT is assumed to be one of critical factors resulting in higher performance of SPEEK/ACNT membrane, since it can induce acid-base conducting networks between ACNT and SPEEK matrix, which would improve water uptake and proton conductivity while lowering ion exchange capacity of membrane. When used in 20% relative humidity, a polymer electrolyte fuel cell (PEFC) with SPEEK/ACNT membrane is found to exhibit much higher performance than a PEFC with bare SPEEK, suggesting the potential use of SPEEK/ACNT membrane as PEM.
Proton hopping mechanism between acid-base networks in SPEEK/ACNT composite. Display omitted
•ACNT was employed as inorganic potential filler to prepare SPEEK/ACNT composite.•Addition of ACNT to SPEEK resulted in improved physiochemical and thermomechanical properties.•Optimized SPEEK/ACNT (1.5 wt%) exhibited improved PEFC performance under 20% RH while holding excellent durability compared to bare SPEEK.
Increasing Polymer Electrolyte Fuel Cells’ (PEFCs) operating temperature has benefits on the performance and the ease of utilisation of the heat generated; however, efforts for high temperature PEFCs ...have resulted in high degradation and reduced life time. In the literature, conventional low temperature (T < 80 °C) and high temperature (140–200 °C) regimes have been extensively studied, while the gap of operating at intermediate temperature (IT) (100–120 °C) has been scarcely explored.
The main bottleneck for operating at IT conditions is the development of a suitable proton exchange membrane with comparable performance and lifetime to the commercially used Nafion operating at conventional conditions. In this work, composite membranes of Graphene Oxide (GO) and Nafion of varied thickness were fabricated, characterised and assessed for in-situ single cell performance under automotive operating conditions at conventional and intermediate temperatures.
The material characterisation confirmed that a composite GO-Nafion structure was achieved. The composite membrane demonstrated higher mechanical strength, enhanced water uptake, and higher performance. It was demonstrated that by utilising GO-Nafion composite membranes, an up to 20% increase in the maximum power density at all operating temperatures can be achieved, with the optimum performance is obtained at 100 °C. Moreover, the GO-Nafion membrane was able to maintain its open circuit voltage values at increased temperature and reduced thickness, indicating better durability and potentially higher lifetime.
•GO-Nafion composite membranes were fabricated and characterised successfully.•GO-Nafion membranes showed up to 20% increase in the maximum power density at elevated temperatures.•Reducing GO-Nafion membrane thickness resulted in significant increase in performance.•GO-Nafion had higher water uptake and better mechanical strength than Nafion.
According to the H2 and fuel cell road map in Japan, the target operating temperature of polymer electrolyte fuel cell (PEFC) should be 90 °C from 2020 to 2025. In this study, the impact of polymer ...electrolyte membrane (PEM) and gas diffusion layer (GDL)'s thickness on heat and mass transfer characteristics as well as power generation performance of PEFC is investigated at operating temperature of 90 °C. The in-plane temperature distributions on anode and cathode separator are also measured using thermograph. As a result, it is observed that the increase in power from 1 W to 5 W at the current density of 0.80 A/cm2 as well as even temperature distribution within 1 °C can be obtained at operating temperature of 90 °C by decrease in GDL's thickness from 190 μm to 110 μm. In addition, the power is increased from 3 W to 4 W at the current density of 0.80 A/cm2 operated at 90 °C by decrease in the PEM's thickness from 127 μm to 25 μm.
•The power generation performance is promoted by decreasing GDL's thickness.•The temperature distribution is flat at both anode and cathode side for thinner GDL.•The power generation performance is promoted by decreasing PEM's thickness.•The impact of GDL's thickness is larger than that of PEM's thickness.•The combination of thinner PEM and GDL is effective for higher temperature operation.
Fibrous carbon has attracted attention for use as a carbon support of polymer electrolyte fuel cells (PEFC). In this study, Marimo carbon (MC), a fibrous carbon, was used as the carbon support. The ...MC has a higher order structure in which many carbon nanofilaments (CNFs) are grown on the surface of diamond particles (dia.). The MC was synthesized by the contact reaction between a Ni supported oxidized diamond (Ni/O-dia.) and CH4 gas, the carbon source of the CNFs. The flow rate of the CH4 gas during the MC synthesis altered the structure of the CNFs. A thick CNFs was observed in the MC with a low CH4 gas flow rate, which was not observed in the MC with a high CH4 gas flow rate. The MC with the thicker CNFs had wider interspaces between the CNFs and higher Pt supporting amounts. Electrochemical measurements of the Pt support MC (Pt/MC) were evaluated by cyclic voltammetry (CV), linear sweep voltammetry (LSV) and current–voltage (I–V) measurements. The lower CH4 gas flow rate of the MC indicated faster charge transfer. The MC structural and charge transfer changed with the flow rate of the CH4 gas altered the electrochemical active surface area (ECSA), the oxygen reduction reaction (ORR) catalytic activity and the I–V performance of the Pt/MC.
•Highly ordered structure of fibers (MC) was used as a catalyst support for PEFC.•Flow rate of the CH4 gas during MC synthesis altered interspaces between CNFs.•Flow rate of the CH4 gas during MC synthesis altered charge transfer of Pt/MC.•I–V performance of Pt/MC1000 was high in high current density region.•Maximum power density of Pt/MC1000 was 1.4 times higher than that of Pt/CB.
•A fuel cell system for application as auxiliary power unit was developed.•Key components were a high-temperature PEFC stack and an autothermal reformer.•The system was tested with GTL kerosene, BTL ...diesel and premium diesel fuel.•The target electrical power of 5kW was achieved with all fuels used.•Self-sustaining system operation was demonstrated with the integrated system design.
A high-temperature PEFC system, developed with the aim of delivering 5kW electrical power from the chemical energy stored in diesel and kerosene fuels for application as an auxiliary power unit, was simulated and tested. The key components of the system were an autothermal reformer, a water–gas shift reactor, a catalytic burner, and the HT-PEFC stack. The targeted power level of 5kW was achieved using different fuels, namely GTL kerosene, BTL diesel and premium diesel. Using an integrated system approach, operation without external heat input was demonstrated. The overall analysis showed slight but non-continuous performance loss for 250h operation time.
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