Non-Conventional Hybrid Microporous Layers for Enhanced Performance and Durability of PEM Fuel Cells

In this work, novel microporous layers (MPLs) were developed based on fluorinated ethylene propylene (FEP), as a hydrophobic agent, and carboxymethylcellulose (CMC), as a wettability modulator and rheology controller for the inks, which were deposited onto pre-hydrophobized macroporous gas diffusion layers (GDLs). Higher CMC amounts led to higher dynamic viscosities of the inks, which induced the formation of a more compact and less cracked MPL surface. Different concentrations of CMC were tested and the experimental measurements showed a threshold limit pointing out an optimal composition that positively affected the electrochemical performances at medium-low relative humidity (RH), which is important to mitigate the need of saturating inlet gases. Durability of the best performing samples was assessed by means of an ad hoc developed accelerated stress test (AST) and compared to one of the conventional FEP-based GDMs. It was found that a lower decrement of both the output power density and the overall cell efficiency can be obtained upon the ASTs with the novel samples

A novel approach to water softening based on graphene oxide-activated open cell foams

This work focuses on exploring a new configuration for the reduction of water hardness based on the surface modification of polyurethane (PU) open cell foams by the deposition of thin graphene oxide (GO) washcoat layers. GO was deposited by the dip–squeeze coating procedure and consolidated by thermal treatment. The final washcoat load was controlled by performing consecutive depositions, after three of which, a GO inventory up to 27 wt% was obtained onto PU foams of 60 pores per inch (PPI). The GO-coated PU foams were assembled into a filter, and the performance of the system was tested by continuously feeding water with hardness in the 190–270 mgCa2+,eq·L−1 range. Remarkable results were demonstrated in terms of total adsorbing capacity, which was evaluated by measuring the outlet total hardness by titration and exhibited values up to 63 mgCa2+,eq·gGO−1 at a specific filtered water volume of 650 mLH2O·gGO−1, outperforming the actual state-of-the-art adsorbing capacity of similar GO-based materials

Study of Innovative GO/PBI Composites as Possible Proton Conducting Membranes for Electrochemical Devices

The appeal of combining polybenzimidazole (PBI) and graphene oxide (GO) for the manufacturing of membranes is increasingly growing, due to their versatility. Nevertheless, GO has always been used only as a filler in the PBI matrix. In such context, this work proposes the design of a simple, safe, and reproducible procedure to prepare self-assembling GO/PBI composite membranes characterized by GO-to-PBI (X:Y) mass ratios of 1:3, 1:2, 1:1, 2:1, and 3:1. SEM and XRD suggested a homogenous reciprocal dispersion of GO and PBI, which established an alternated stacked structure by mutual π-π interactions among the benzimidazole rings of PBI and the aromatic domains of GO. TGA indicated a remarkable thermal stability of the composites. From mechanical tests, improved tensile strengths but worsened maximum strains were observed with respect to pure PBI. The preliminary evaluation of the suitability of the GO/PBI X:Y composites as proton exchange membranes was executed via IEC determination and EIS. GO/PBI 2:1 (IEC: 0.42 meq g−1; proton conductivity at 100 °C: 0.0464 S cm−1) and GO/PBI 3:1 (IEC: 0.80 meq g−1; proton conductivity at 100 °C: 0.0451 S cm−1) provided equivalent or superior performances with respect to similar PBI-based state-of-the-art materials

LCA of a Proton Exchange Membrane Fuel Cell Electric Vehicle Considering Different Power System Architectures

Fuel cell electric vehicles are a promising solution for reducing the environmental impacts of the automotive sector; however, there are still some key points to address in finding the most efficient and less impactful implementation of this technology. In this work, three electrical architectures of fuel cell electric vehicles were modeled and compared in terms of the environmental impacts of their manufacturing and use phases. The three architectures differ in terms of the number and position of the DC/DC converters connecting the battery and the fuel cell to the electric motor. The life cycle assessment methodology was employed to compute and compare the impacts of the three vehicles. A model of the production of the main components of vehicles and fuel cell stacks, as well as of the production of hydrogen fuel, was constructed, and the impacts were calculated using the program SimaPro. Eleven impact categories were considered when adopting the ReCiPe 2016 midpoint method, and the EF (adapted) method was exploited for a final comparison. The results highlighted the importance of the converters and their influence on fuel consumption, which was identified as the main factor in the comparison of the environmental impacts of the vehicle

Preliminary Study On The Development Of Sulfonated Graphene Oxide Membranes As Potential Novel Electrolytes For PEM Fuel Cells

Innovative graphene oxide (GO)-based self-assembling membranes have been prepared in order to study their possible application in PEMFCs as a solid proton-conducting electrolyte alternative to Nafion®. Firstly, a pure GO membrane has been produced as a benchmark, then it has been sulfonated with different quantities of sulfuric acid and characterized by using several techniques: Fourier transformed infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), optical microscopy (OM), water uptake (WU) and ion exchange capacity (IEC). On the basis of IEC measurements, the corresponding degree of sulfonation was calculated. Preliminary impedance spectroscopy measurements have been also performed in order to obtain conductivity of the membranes and compare it to the one of a commercial Nafion membrane. A relation between IEC, degree of sulfonation and conductivity was found and the sulfonated membrane prepared with an acid/GO molar ratio of 20 showed the best results

Reduced Graphene Oxide/Waste-Derived TiO2 Composite Membranes: Preliminary Study of a New Material for Hybrid Wastewater Treatment

This work reports the preliminary results of the development of composite self-assembling membranes obtained by the combination of reduced graphene oxide (rGO) with commercial Degussa P25 titanium dioxide (TiO2). The purpose is to demonstrate the possibility of combining, in the same self-standing material, the capability to treat wastewater containing both inorganic and organic pollutants by exploiting the established ability of rGO to capture metal ions together with that of TiO2 to degrade organic substances. Moreover, this study also investigates the potential photocatalytic properties of tionite (TIO), to demonstrate the feasibility of replacing commercial TiO2 with such waste-derived TiO2-containing material, fulfilling a circular economy approach. Thus, rGO–TiO2 and rGO–TIO composite membranes, 1:1 by weight, were prepared and characterized by SEM-EDX, XRD, thermogravimetry, as well as by Raman and UV-Vis spectroscopies to verify the effective and homogeneous integration of the two components. Then, they were tested towards 3-mg L−1 aqueous synthetic solutions of Fe3+ and Cu2+ ions to evaluate their metal adsorption ability, with values of the order of 0.1–0.2 mmol gmembrane−1, comparable or even slightly higher than those of pristine rGO. Finally, the ability of the composites to degrade a common organic pesticide, i.e., Imidacloprid®, was assessed in preliminary photocatalysis experiments, in which maximum degradation efficiencies of 25% (after 3 h) for rGO–TiO2 and of 21% (after 1 h) for rGO–TIO were found. The result of tionite-containing membranes is particularly promising and worthy of further investigation, given that the anatase content of tionite is roughly 1/6 of the one in commercial TiO2

Investigation of Sulfonated Graphene Oxide as the Base Material for Novel Proton Exchange Membranes

This work deals with the development of graphene oxide (GO)-based self-assembling membranes as possible innovative proton conductors to be used in polymer electrolyte membrane fuel cells (PEMFCs). Nowadays, the most adopted electrolyte is Chemours’ Nafion; however, it reveals significant deficiencies such as strong dehydration at high temperature and low humidity, which drastically reduces its proton conductivity. The presence of oxygenated moieties in the GO framework makes it suitable for functionalization, which is required to enhance the promising, but insufficient, proton-carrying features of GO. In this study, sulfonic acid groups (–SO3H) that should favor proton transport were introduced in the membrane structure via a reaction between GO and concentrated sulfuric acid. Six acid-to-GO molar ratios were adopted in the synthesis procedure, giving rise to final products with different sulfonation degrees. All the prepared samples were characterized by means of TGA, ATR-FTIR and Raman spectroscopy, temperature-dependent XRD, SEM and EDX, which pointed out morphological and microstructural changes resulting from the functionalization stage, confirming its effectiveness. Regarding functional features, electrochemical impedance spectroscopy (EIS) as well as measurements of ion exchange capacity (IEC) were carried out to describe the behavior of the various samples, with pristine GO and commercial Nafion® 212 used as reference. EIS tests were performed at five different temperatures (20, 40, 60, 80 and 100 °C) under high (95%) and medium (42%) relative humidity conditions. Compared to both GO and Nafion® 212, the sulfonated specimens demonstrate an increase in the number of ion-carrying groups, as proved by both IEC and EIS tests, which reveal the enhanced proton conductivity of these novel membranes. Specifically, an acid-to-GO molar ratio of 10 produces a six-fold improvement of IEC (4.23 meq g−1) with respect to pure GO (0.76 meq g−1), while a maximum eight-fold improvement (5.72 meq g−1) is achieved in SGO-15

Development of Self-Assembling Sulfonated Graphene Oxide Membranes as a Potential Proton Conductor

A simple method is reported for the preparation of self-assembling sulfonated graphene oxide membranes (SGOX) to be studied as a potential proton conductor for proton exchange membrane fuel cells (PEMFCs). The effect of three different sulfuric acid-to-GO molar ratios is investigated, the main aim being the identification of an optimal sulfonation interval ensuring a successful trade-off among composition, structural stability and functional properties. ATR-FTIR and EDX spectroscopies, SEM, thermogravimetry and static contact angle measurements allow to analyze the efficacy of the functionalization of graphene oxide (GO) with sulfonic acid groups (–SO3H) and the uniformity of the component’s structure. A preliminary examination of the proton conductivity is performed on the most promising samples (SGO-1, SGO-20) by means of electrochemical impedance spectroscopy (EIS), together with the evaluation of water uptake, ion exchange capacity and degree of sulfonation. This introductory work demonstrates that the proposed SGO-X membranes exhibit notable water-retaining and proton-exchanging properties at elevated temperatures and reduced humidity, compared to pristine GO and Nafion® 212 benchmark specimens. Therefore, these innovative self-standing materials are proved to be worthy of additional studies for the optimization of their features, foreseeing the assessment of their behavior as a possible electrolyte in a PEM fuel cell

Greenhouse gas implications of extending the service life of PEM fuel fells for automotive applications: a life cycle assessment

A larger adoption of hydrogen fuel-cell electric vehicles (FCEVs) is typically included in the strategies to decarbonize the transportation sector. This inclusion is supported by life-cycle assessments (LCAs), which show the potential greenhouse gas (GHG) emission benefit of replacing internal combustion engine vehicles with their fuel cell counterpart. However, the literature review performed in this study shows that the effects of durability and performance losses of fuel cells on the life-cycle environmental impact of the vehicle have rarely been assessed. Most of the LCAs assume a constant fuel consumption (ranging from 0.58 to 1.15 kgH2/100 km) for the vehicles throughout their service life, which ranges in the assessments from 120,000 to 225,000 km. In this study, the effect of performance losses on the life-cycle GHG emissions of the vehicles was assessed based on laboratory experiments. Losses have the effect of increasing the life-cycle GHG emissions of the vehicle up to 13%. Moreover, this study attempted for the first time to investigate via laboratory analyses the GHG implications of replacing the hydrophobic polymer for the gas diffusion medium (GDM) of fuel cells to increase their durability. LCA showed that when the service life of the vehicle was fixed at 150,000 km, the GHG emission savings of using an FC with lower performance losses (i.e., FC coated with fluorinated ethylene propylene (FEP) instead of polytetrafluoroethylene (PTFE)) are negligible compared to the overall life-cycle impact of the vehicle. Both the GDM coating and the amount of hydrogen saved account for less than 2% of the GHG emissions arising during vehicle operation. On the other hand, when the service life of the vehicle depends on the operability of the fuel cell, the global warming potential per driven km of the FEP-based FCEV reduces by 7 to 32%. The range of results depends on several variables, such as the GHG emissions from hydrogen production and the initial fuel consumption of the vehicle. Higher GHG savings are expected from an FC vehicle with high consumption of hydrogen produced with fossil fuels. Based on the results, we recommend the inclusion of fuel-cell durability in future LCAs of FCEVs. We also advocate for more research on the real-life performance of fuel cells employing alternative materials

Sulfonated graphene oxide as innovative self-assembling electrolyte for PEM fuel cells

Sulfonated graphene oxide (SGO) membranes have been developed and evaluated as a viable alternative to Nafion® in polymer electrolyte membrane fuel cells (PEMFCs). Even though Nafion® is currently the most widely used electrolyte in PEMFC systems, some crippling drawbacks induce the need of finding feasible replacements. In particular, Nafion® suffers a severe conductivity drop upon dehydration, which limits the possibility of operation in conditions of high temperature and low relative humidity [1]. As shown in previous works, graphene oxide (GO) appears to be an excellent candidate for making both freestanding [2] and polymer-based hybrid membranes [3], thanks to its good mechanical properties and to the presence of oxygen-containing functionalities that are likely to improve water retention. However, we verified in a preliminary study [4] that, at high temperatures, GO suffers a partial loss of the chemical groups which foster protons transport and a lowering of the structural integrity of the carbon network. Hence, its properties may be enhanced by functionalization with some acid groups more tightly bound to its skeleton, e.g. sulfonic acid groups (–SO3H) analogous to those of Nafion®. In this work, we present an effective method for the sulfonation of graphene oxide, based on the reaction between sulfuric acid and a commercial aqueous dispersion of GO. Different samples have been prepared by varying the quantity of sulfuric acid employed in the sulfonation reaction, and an optimal acid-to-GO molar ratio has been identified, taking into account an empirical formula of GO. Such formula has been derived, as a first approximation, from the elemental analysis of the commercial solution and confirmed by the results of SEM and EDX analysis. The sulfonated membranes have been widely characterized by ATR-FTIR, XRD, SEM and EDX spectroscopies, thermogravimetric (TG-DTG) analysis, optical microscopy and static contact angle (OCA) measurements. These techniques confirmed the effective functionalization of GO and the stability of sulfonic acid groups even after water uptake (WU) experiments, which have been carried out at different temperatures and relative humidity. The ion exchange capacity (IEC) of the different samples has been evaluated as well, and a correlation among WU, IEC and degree of sulfonation (DS) can be established. Test results showed that sulfonated membranes have an improved WU behaviour with respect to both Nafion and unfunctionalized GO, especially at low temperature and humidity (Fig. 1); they also show an IEC value higher than 1 meq/g, which is even better than IEC determinations reported for Nafion® [5]. The increase of the amount of sulfuric acid seems to be beneficial for both properties. Then, one sulfonated membrane has been selected and subjected to a preliminary test in a lab-scale hydrogen-fed fuel cell. Promising results have been found from the point of view of mechanical resistance, even though a low open circuit voltage (OCV) has been measured (0.63 V) at 40 °C, which might be ascribed to hydrogen crossover issues. These issues should be addressed in future developments of such components. However, after testing, the active area showed absence of carbon residues left by the gas diffusion electrode (GDE), which are a typical problem in the case of Nafion®. [1] Q. Li, R. He, J. O. Jensen, N. J. Bjerrum. Chem. Mater., 2003, 15, 4896. [2] T. Bayer, S. R. Nishihara, K. Sasaki, S. M. Lyth. J. Power Sources, 2014, 272, 239. [3] M. Vinothkannan, A. R. Kim, G. G. Kumar, D. J. Yoo. Rsc Adv., 2018, 8, 7494. [4] S. Latorrata, A. Basso Peressut, P. Gallo Stampino, C. Cristiani, G. Dotelli. ECS Trans., 2018, 86, 347. [5] H. Dai, H. Zhang, Q. Luo, Y. Zhang, C. Bi. J. Power Sources, 2008, 185, 19