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•Carbon paper as anode PTLs in PEMWE cells is investigated and characterized.•Carbon FC hardware & materials can be used in initial PEMWE performance testing.•Contact between membrane ...and graphite must be avoided.
The research and development of proton exchange membrane water electrolysis (PEMWE) is an upcoming and growing area due to a rising interest in hydrogen as an energy carrier. Operating conditions are harsher than in a fuel cell system, particularly because the potentials required for the oxygen evolution reaction are significantly higher. In commercial water electrolysis systems, this is compensated by typically using titanium material sets that are often protected against oxidation through coating processes. Such material choices make small scale research hardware and porous transport layers expensive and difficult to source. In this work, we show that the stability of traditional, carbon-based fuel cell materials such as porous transport layers and graphite flow fields can be sufficient for electrolyzer initial performance characterization procedures such as cell conditioning, a limited number of polarization curve measurements, and electrochemical impedance spectroscopy. We identify and quantify the onset of carbon degradation in porous transport layers with regards to operating length and define a strategy that enables the utilization of standard fuel cell hardware for short-term PEMWE experiments. With the knowledge that existing fuel cell material sets can be applied to conduct electrolyzer research when adhering to such limitations, fuel cell research hardware and experience can be more readily transferred to the younger and rapidly growing electrolysis research field.
Hydrogen storage is a promising technology for storage of renewable energy resources. Despite its high energy density potential, the development of hydrogen storage has been impeded, mainly due to ...its significant cost. Although its cost is governed mainly by electrical energy expense, especially for hydrogen produced with alkaline water electrolysis, it is also driven by the value of the cell tension. The most common means of electrolyzer improvement is the use of an electrocatalyst, which reduces the energy required for electrochemical reaction to take place. Another efficient means of electrolyzer improvement is to use the Computational Fluid Dynamics (CFD)-assisted design that allows the comprehension of the phenomena occurring in the electrolyzer and also the improvement in the electrolyzer’s efficiency. The designed two-phase hydrodynamics model of this study has been compared with the experimental results of velocity profiles measured using Laser Doppler Velocimetry (LDV) method. The simulated results were in good agreement with the experimental data in the literature. Under the good fit with experimental values, it is efficient to introduce a new physical bubble transfer phenomenon description called “bubble diffusion”.
Owing to the progressive abandoning of the fossil fuels and the increase of atmospheric CO2 concentration, the use of renewable energies is strongly encouraged. The hydrogen economy provides a very ...interesting scenario. In fact, hydrogen is a valuable energy carrier and can act as a storage medium as well to balance the discontinuity of the renewable sources. In order to exploit the potential of hydrogen it must be made available in adequate quantities and at an affordable price. Both goals can be potentially achieved through the electrochemical water splitting, which is an environmentally friendly process as well as the electrons and water are the only reagents. However, these devices still require a lot of research to reduce costs and increase efficiency. An approach to improve their performance is based on nanostructured electrodes characterized by high electrocatalytic activity. In this work, we show that by using template electrosynthesis it is possible to fabricate Ni nanowires featuring a very high surface area. In particular, we found that water-alkaline electrolyzers with Ni nanowires electrodes covered by different electrocatalyst have good and stable performance at room temperature as well. Besides, the results concern nickel-cobalt nanowires electrodes for both hydrogen and oxygen evolution reaction will be presented and discussed. Finally, preliminary tests concerning the use of Ni foam differently functionalized will be shown. For each electrode, electrochemical and electrocatalytic tests aimed to establishing the performance of the electrolyzers were carried out. Long term amperostatic test carried out in aqueous solution of KOH will be reported as well.
To realize the benefits of a hydrogen economy, hydrogen must be produced cleanly, efficiently and affordably from renewable resources and, preferentially, close to the end-users. The goal is a ...sustainable cycle of hydrogen production and use: in the first stage of the cycle, hydrogen is produced from renewable resources and then used to feed a fuel cell. This cycle produces no pollution and no greenhouse gases. In this context, the development of electrolyzers producing high-purity hydrogen with a high efficiency and low cost is of great importance. Electrode materials play a fundamental role in influencing electrolyzer performances; consequently, in recent years considerable efforts have been made to obtain highly efficient and inexpensive catalyst materials. To reach both goals, we have developed electrodes based on Pd-Co alloys to be potentially used in the PEMEL electrolyzer. In fact, the Pd-Co alloy is a valid alternative to Pt for hydrogen evolution. The alloys were electrodeposited using two different types of support: carbon paper, to fabricate a porous structure, and anodic alumina membrane, to obtain regular arrays of nanowires. The goal was to obtain electrodes with very large active surface areas and a small amount of material. The research demonstrates that the electrochemical method is an ideal technique to obtain materials with good performances for the hydrogen evolution reaction. The Pd-Co alloy composition can be controlled by adjusting electrodeposition parameters (bath composition, current density and deposition time). The main results concerning the fabrication process and the characterization are presented and the performance in acid conditions is discussed.
Nanostructured Pb electrodes consisting of nanowire arrays were obtained by electrodeposition, to be used as negative electrodes for lead–acid batteries. Reduced graphene oxide was added to improve ...their performances. This was achieved via the electrochemical reduction of graphene oxide directly on the surface of nanowire arrays. The electrodes with and without reduced graphene oxide were tested in a 5 M sulfuric acid solution using a commercial pasted positive plate and an absorbed glass mat separator in a zero-gap configuration. The electrodes were tested in deep cycling conditions with a very low cut-off potential. Charge–discharge tests were performed at 5C. The electrode with reduced graphene oxide outperformed the electrode without reduced graphene oxide, as it was able to work with a very high utilization of active mass and efficiency. A specific capacity of 258 mAhg−1–very close to the theoretical one–was achieved, and the electrode lasted for more than 1000 cycles. On the other hand, the electrode without reduced graphene oxide achieved a capacity close to 230 mAhg−1, which corresponds to a 90% of utilization of active mass.
Hydrogen is an excellent energy source for long-term storage and free of greenhouse gases. However, its high production cost remains an obstacle to its advancement. The two main parameters ...contributing to the high cost include the cost of electricity and the cost of initial financial investment. It is possible to reduce the latter by the optimization of system design and operation conditions, allowing the reduction of the cell voltage. Because the CAPEX (initial cost divided by total hydrogen production of the electrolyzer) decreases according to current density but the OPEX (operating cost depending on the cell voltage) increases depending on the current density, there exists an optimal current density. In this paper, a genetic algorithm has been developed to find the optimal evolution parameters and to determine an optimum electrolyzer design. The optimal current density has been increased by 10% and the hydrogen cost has been decreased by 1%.
Ni–Co alloy nanostructured electrodes with high surface area were investigated both as a cathode and anode for an alkaline electrolyzer. Electrodes were obtained by template electrosynthesis at room ...temperature. The electrolyte composition was tuned in order to obtain different NiCo alloys. The chemical and morphological features of nanostructured electrodes were evaluated by EDS, XRD and SEM analyses. Results show that electrodes with different composition of Ni and Co, made of nanowires well anchored to the substrate, were obtained. For both hydrogen and oxygen evolution reactions, electrochemical and electrocatalytic tests, performed in 30% w/w KOH aqueous solution, were carried out to establishing the best alloy composition. Mid-term tests conducted at a constant current density were also reported. Nanostructured electrodes with a Co atomic composition of 94.73% have the best performances for both hydrogen and oxygen evolution reactions. In particular, with this alloy, a potential of −0.43 V (RHE) and of 1.615 V (RHE) was measured for hydrogen and oxygen evolution reaction at −50 mA cm−2 and at 50 mA cm−2, respectively, after 6 h of electrolysis. The calculated Tafel's slopes for HER and OER were −0.105 and 0.088 V/dec, respectively. Furthermore, HER and OER η10 potential values were measured founding −0.231 V (RHE) and 1.494 V (RHE) respectively.
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•Ni-Co alloy electrodes were studied as electrodes for alkaline electrolyzer.•Template electrosynthesis was used as fabrication method due its simplicity.•Nanowires of Ni-Co alloys well anchored to the substrate were obtained.•Tests in KOH solution were performed to found the best alloy composition.•Electrodes with 94.73% of Co are the best for both H2 and O2 evolution.
Ever-widespread employment of renewable energy sources, such as wind and sun, request the simultaneous use of effective energy storage systems owing to the intermittent and unpredictable energy ...generation by these sources. The most reliable storage systems currently under investigation are batteries and electrochemical cells for hydrogen production from water splitting. Both systems store chemical energy which can be converted on demand. The low power density is the weakness of the batteries while the high production cost limits currently the wide use of hydrogen from electrochemical water splitting. In this work, attention was focused on the use of nanostructured Ni as a cathode for electrochemical production of hydrogen from alkaline solution. The work is aimed at analysing the energy dissipation at 0.5 Acm−2, which is a value of applicative interest, for detecting one of the cause determining the high production cost. The development of electrochemical cells employing alkaline solution is currently the most promising approach in comparison with electrolysers using acidic solution which are expensive, because require precious metals as electrodes and high cost cation-selective membrane for efficiently conducting water splitting. Nanostructured Ni electrodes were fabricated through a cheap and easily scalable process, based on the Ni electrodeposition inside the pores of a commercial polycarbonate membrane acting as a template. On the contrary, a galvanic connection driving a spontaneous displacement reaction was employed for synthesising Pd nanostructured electrode which was tested for comparison purposes. Once the membrane is dissolved in an organic solution, the electrodes were initially characterized by SEM, EDS and XRD analysis. Then, electrochemical tests were performed to evaluate electrocatalytic properties of the electrodes. The tests were conducted through either cyclic or linear sweep voltammetry in 30% w/w KOH aqueous solution. Then, the nanostructured electrodes were tested under constant current density of 0.5 Acm−2. In comparison with nanostructured Pd, Ni electrodes with the same morphology and in otherwise identical conditions show a better response in terms of electrocatalytic activity. In addition, these electrodes showed satisfying stability over time through tests longer than 60 h. The analysis of energy dissipation revealed that the prevalent contribution was due to the ohmic drop)which can be reduced through a properly cell design) based on the accurate control of the parameters determining ohmic drop inside the cell.
•Nanostructured Ni cathodes for hydrogen production from alkaline solutions.•Comparison between Ni and Pd nanostructured cathodes.•On short and long time nanostructured Ni cathode stability.•Contribution of reaction overvoltage and ohmic drop on cell voltage.•Role of the cell architecture and electrocatalytic features.
1Ni-Fe alloy nanowire were studied as cathode and anode for alkaline electrolyzer.2Nanostructured arrays were obtained by template electrosynthesis method.3Alloy composition was controlled tuning the ...composition of deposition bat.4Electrochemical tests in KOH solution were performed at room temperature..5Electrodes with a Fe of 78.95% have the best performances.
In this work, nickel-iron alloy nanostructured electrodes obtained by template electrosynthesis method are investigated for both hydrogen and oxygen evolution reactions. Electrodes consist of nanowire arrays with high surface area that are able to ensures a high electrolytic activity. To obtain different alloy compositions, the concentration of the elements in the deposition baths is appropriately tuned. Results show that the composition of nanowires does not change linearly with the composition of deposition bath but are richer in Fe. Nanostructured electrodes are tested as both cathodes and anodes in 30 wt% KOH aqueous solution, at room temperature to determine the best alloy composition. In all electrochemical tests, the electrodes that performed best are those with iron content of 78.95 at%. Particularly, the results are very promising for the oxygen evolution reaction, with a Tafel's slope of 40 mV and a potential of 1.532 V vs. RHE after 6 h at constant current of 50 mA cm−2. Besides, preliminary tests in 0.5 M NaCl alkaline aqueous solution are also reported showing very promising results.
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The fabrication and characterization of nickel-alloy electrodes for alkaline electrolysers is reported. Three different alloys (Ni–Co, Ni–Zn and Ni–W) at different composition were studied in order ...to determine the optimum condition. Nanostructured electrodes were obtained by template electrodeposition into a nanoporous membrane, starting from aqueous solution containing the two elements of the alloy at different concentrations. Composition of alloys can be tuned by electrolyte composition and also depends on the difference of the redox potential of elements and on the presence of complexing agents in deposition bath. Electrochemical and electrocatalytic tests, aimed at establishing the best alloy composition, were carried out for hydrogen evolution reaction. Then, test conducted at a constant current density in potassium hydroxide (30% w/w) aqueous solution were also performed. For all investigated alloys, very encouraging results were obtained and in particular Ni–Co alloys richer in Co showed the best performance.
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•Nanostructured Ni-alloy was used for hydrogen production in alkaline solution.•Nanostructures were grown by template electrosynthesis that is simple and scalable.•Arrays of NiZn, NiCo and NiW alloys with different composition were obtained.•Electrochemical characterization was performed in KOH solution at room temperature.•Electrodes made of NiCo alloys have the best performances for the H2 evolution.
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