Proton Exchange Research Articles

Ultrafine PtFeMo intermetallic compound nanowires for efficient oxygen reduction reaction in proton exchange membrane fuel cells

To advance the application of proton exchange membrane fuel cells (PEMFCs), it is crucial to develop high-performance oxygen reduction reaction (ORR) catalyst. Pt-based alloy nanowires exhibit excellent ORR activity due to their unique one-dimensional structure, but transition metals undergo spontaneous leaching under the harsh operating condition, often leading to decreased activity. Herein, ultrafine PtFeMo intermetallic compound nanowires were successfully synthesized as a high-performance ORR catalyst for PEMFC. The average diameter of the nanowires was 2.1 nm and the incorporation of inexpensive and high melting point metal Mo improved both catalytic performance and structural stability. The as-prepared ultrafine PtFeMo intermetallic compound nanowires exhibited mass activity of 2.56 A mgPt−1 for ORR, which is higher than that of disordered PtFeMo alloy nanowires (1.36 A mgPt−1) and commercial Pt/C (0.24 A mgPt−1) in rotating disk electrode test. And it exhibited peak power density of 2716 mW cm−2 under 250 kPa H2-O2 single-cell and mass activity of 0.62 A mgPt−1 under 100 kPa H2-O2 single-cell test in PEMFC. After long-time durability test, the intermetallic compound nanowires maintained their original structure, composition and electrocatalytic performance well, highlighting the importance of Mo incorporation and ordered phase structure generation.

Activating CoP via spontaneous atomic palladium doping for efficient hydrogen evolution

Electrocatalytic hydrogen evolution is an efficient and clean hydrogen production technology with simple process and high product purity. Searching for inexpensive alternatives to platinum will help popularize proton exchange membrane water electrolysis (PEMWE) technology. However, the alternative catalytic materials are essentially limited by low catalytic efficiency. Herein, we address this challenge through chemically activating cobalt phosphide (CoP) by doping a small amount of atomic palladium. Palladium substitution occurs at the cobalt site of CoP. Theoretical calculations manifest that the phosphorus atoms near the palladium sites exhibit almost zero hydrogen adsorption free energy. The final cobalt phosphide doped with only 2 wt% of palladium shows wonderful HER performance. Specifically, its overpotential at a current density of 10 mA cm−2 is only 37.5 mV in an acidic medium, and the corresponding Tafel slope is 56 mV dec−1. This work provides a reference for preparing high performance non-platinum catalysts.

Multi-objective optimization of comprehensive performance enhancement for proton exchange membrane fuel cell based on machine learning

The comprehensive performance of proton exchange membrane fuel cells depends on operating conditions. This paper innovatively uses the Pearson correlation coefficient to screen the optimization objectives (uniformity index of oxygen, standard deviation of temperature, net power density), and obtains the optimal operating conditions of the proton exchange membrane fuel cell through a multi-objective optimization method. The optimized dataset comes from the simulation results of the three-dimensional numerical model, and the regression model is established through the response surface method. Moreover, the non-dominated sorting genetic algorithm-II is used for processing to obtain the Pareto front solution set, and the optimal operating conditions are obtained from it through the Technique for order preference by similarity to an ideal solution. The analysis of variance result shows that the influence of cathode operating conditions on the comprehensive performance is greater than that of anode, especially the influence of cathode stoichiometry ratio is the most significant. The optimal solution obtained 1.0981 %, 10.5845 %, and 1.0376 % enhancement compared to the optimal values in the simulation results. The differences between the three optimization objectives are only 0.8190 %, 1.0315 %, and 0.8789 % as verified by numerical simulation, thus the machine learning results are reliable and accurate.

The effect of wind environment on temperature and performance of an open-cathode proton exchange membrane fuel cell stack

The effect of wind environment on temperature and performance of an open-cathode proton exchange membrane fuel cell stack

Optimizing wind-solar hydrogen production through collaborative strategy with ALK/PEM multi-electrolyzer arrays

This paper presents an innovative sustainable hydrogen production system integrating solar and wind energy to provide power to alkaline (ALK) and proton exchange membrane (PEM) electrolyzers. On this basis, a novel source and load collaborative optimization strategy is proposed to optimize the hydrogen production system, aiming to address the challenges of the intermittent and variable nature of renewable energy sources. The proposed strategy consists of a classification prediction module using the XGBoost algorithm, which analyzes historical energy generation data to predict optimal electrolyzer operation. Furthermore, the proposed collaborative optimization strategy is able to balance the loads between the electrolyzer arrays, aiming to minimize cold-start situations, prolong steady-state hydrogen production time, and reduce operational variations due to maintenance. The proposed strategy is proved to significantly reduce the standard deviation of the electrolyzer runtime, enhancing the overall system stability, and contributing to the reduction of maintenance frequency. Theoretical analyzes and extensive simulation results validate the effectiveness of the proposed strategy in improving hydrogen production efficiency and sustainability. This work contributes to the integration of renewable energy sources for clean energy production, and provides a practical and effective solution for the urgently needed green hydrogen production.

Effect of TiC grain size on corrosion behaviors of Ti-Si-C nanocomposite coatings fabricated by heterogeneous targets high-power impulse magnetron sputtering

Ti-Si-C coatings with different carbon contents were prepared on SS316L substrates by heterogeneous targets high-power impulse magnetron sputtering with a repetitive C and TiSi deposition. Various tests were employed to analyze the microstructure, anti-corrosion properties in a simulated proton exchange membrane fuel cells (PEMFC) environment and interfacial conductivity of the coatings. Results indicated that the Ti-Si-C coating possessed a typical nanocomposite structure of TiC nanocrystals embedded in amorphous carbon matrix. With the increase of the carbon content, the grain size of TiC nanocrystals was reduced gradually. Electrochemical measurements revealed that a proper decrease of TiC grain size led to an enhanced corrosion resistance of the as-deposited coating. The smallest interfacial contact resistance and corrosion rate of the Ti-Si-C coating in the simulated PEMFC solution reached 5.07 mΩ cm2 and 5.93E-07 A/cm2, respectively. This improvement could be attributed to the formation of a dense and continuous passivation layer composed of Ti2O3 and SiO2 on the top surface of the coating.

Fabrication of self‐supported catalysts via electrodeposition for proton exchange membrane water electrolysis: Emphasizing on the porous transport layers

Fabrication of self‐supported catalysts via electrodeposition for proton exchange membrane water electrolysis: Emphasizing on the porous transport layers

Toward highly ionic polyelectrolyte membrane: Synthesis, characterization, membrane performance and theoretical studies of PVDF-g-PAN/PAMPS hybrid membranes

Novel highly ionic polyvinylidene fluoride (PVDF) membranes grafted with an acrylonitrile monomer to yield the target (PVDF-g-PAN) via radical polymerization and then blended with the amphiphilic copolymer poly (2-acrylamido-2-methyl-1-Propane sulfonic acid (PAMPS) via physical interactions (PVDF-g-PAN)/(PAMPS), were designed and constructed. The new functional groups obtained (fluoride, nitrile, and sulfonic functions) were confirmed via FTIR analysis, and the prepared membranes were characterized using SEM, TGA, tensile strength, water contact angle, and mechanical stability instruments. The essential characteristics of the polyelectrolyte membranes, including the IEC, ionic conductivity, methanol permeability, thermal stability, and high mechanical qualities, were examined. It was discovered that, the oxidative stability of the modified membrane (P3) with a high concentration of conductive PAMPS affected the percentage of weight loss (5.25 %) at the end of 24 h. In addition, the water absorption capacity increased with increasing in the concentration of PAMPS. Similarly, the highly concentrated PAMPS modified membranes (P3) have an ionic exchange capacity and proton conductivity equal to IEC= 1.93 meq/g, which is greater than that of the Nafion membrane by 0.91 meq/g. Furthermore, appropriate DFT theoretical studies such as EHOMO, ELUMO, energy band gap and dipole moment (µ) were thoroughly examined and employed to validate the highly ionic system. It was found that, the energy band gap of PVDF-g-PAN/PAMPS was 5.19 eV, which is lower than that of the grafted polymer value (7.17 eV), confirming that the electrons are transferred readily from the HOMO level to the LUMO level. In addition, the dipole moment of the PVDF-g-PAN/PAMPS was 7.10 Debye, which is greater than the dipole moment value of the grafted polymer (2.07 Debye), indicating the highly ionic character of the hybrid polymer. Finally, the promising results obtained demonstrated favorable film-forming and structural properties, making it a promising option for polyelectrolyte membranes. It also has the added advantage of being cost-effective and can be applied in many electrochemical applications.

Sulfonamide-Sulfonimide Copolymers as Novel, Fluorine-Lean Type of Proton Exchange Membranes for Fuel Cell Application.

In this work, a novel type of fluorine-lean proton exchange membranes is presented, using sulfonamide-sulfonimide functional groups for ion conduction. These groups are constructed on a polystyrene backbone for simple and cost-efficient usage as well as rapid scalability. The polymer is further tailored by adjusting the sulfonamide functionality with various end-groups, namely pentafluorophenyl, 4-fluorophenyl, butyl and octyl groups. These groups affect the pKa, leading to pKa values of 5.7 for the pentafluorophenyl substitution and pKa 10.5 for the alkyl chain. The glass transition temperature of the sulfonamide homopolymers can be reduced from Tg = 151°C (Pentafluorophenyl) to 49°C (Octyl), making the ionomer more flexible at room temperature. The combination of the non-swelling sulfonamide further mitigates the high water uptake of the sulfonimide while maintaining the nominal ion exchange capacity. This combination leads to extremely high proton conductivities with up to σ = 283 mS cm-1 at room temperature, which is clearly outperforming Nafion and approaches values for acid doped systems. This approach can pave the way to a novel type of ion conducting class in proton exchange membrane fuel cells.

Degradation Analysis for Platinum Group Metal-Free Fuel Cell Cathodes

Recent advancements in platinum-group metal-free (PGM-free) catalysts have overwhelmingly prioritized improving initial electrocatalytic activity rather than focusing on catalyst stability. Unfortunately, this emphasis has led to less significant progress in addressing catalyst degradation, ultimately falling well below the level required for commercialization. Shifting the focus towards understanding and mitigating degradation unlocks the true potential of PGM-free catalysts and paves the way for their successful implementation in commercial applications. This work explores methods to mitigate degradation and expand models to predict PGM-free cathode fuel cell degradation due to voltage cycling, specifically current density loss over time. The tested PGM-free cathode fuel cells, using iron (Fe)-based catalyst, were electrochemically characterized before and after the accelerated stress tests (AST) using H2/N2 electrochemical impedance spectroscopy, cyclic voltammetry, and air polarization curves. This study reports the functions of each acceleration factor due to changes in temperature, cycling upper potential limits, and relative humidity are reported. The data indicates that degradation rates increase as temperature, upper potential limit, and relative humidity increase in Fe-based cathode proton exchange membrane fuel cells (PEMFCs). This finding is essential to more accurately quantify losses in active site density with respect to temperature, varying upper potential cycling limit, and relative humidity. More generally, these results can aid in predicting Fe-based cathode fuel cell degradation due to changes in operational conditions.

Cathode fine-scale flow channel optimization enhancing the performance of proton exchange membrane fuel cells

High performance and long durability have been the continuous pursuit of proton exchange membrane fuel cells (PEMFCs). Performance and durability are related to the PEMFC distributional uniformity of internal state, which are deeply influenced by the flow channel structures and operating conditions. Therefore, this study proposes a fine-scale flow channel (FSFC) with gradually decreasing flow channel widths (wch) based on parallel flow field. Following, fixing wch at 0.3 mm, the effects of different rib width (wrib), cathode humidity (RHc), stoichiometric ratio (ξc) and coolant mass flow rate (mcool) are studied. Simulation results indicate that FSFC can significantly enhance the various properties of fuel cells, especially the performance and uniformity. Reducing the wrib can enhance performance, reduce pressure drop. The appropriate RH and ξc can improve the performance and uniformity while avoiding flooding and purging effects. Similarly, mcool should be kept in the right range to avoid unnecessary power loss. This study aims to develop the flow fields in a more fined direction, offering solutions that strike a balance between durability and power density for PEMFC optimization.

A manganese doping deficient cerium base metal organic framework as radical scavenger for highly-durable proton exchange membrane water electrolysis

Eliminating hydrogen peroxide and free radicals from electrochemical reactions is crucial for mitigating chemical degradation and improving the durability of proton exchange membranes (PEMs). Herein, we prepare a metal–organic framework containing manganese and cerium ions that possesses oxygen vacancy defects and amino functional groups. The prepared Ce4MnBDC-NH2 acts as a catalyst for H2O2 decomposition and as a free radical scavenger, and it is incorporated into a perfluorosulfonic acid (PFSA) ionomer matrix. Featuring large pore volume, high porosity, and abundant amino groups, the Ce4MnBDC-NH2 is locked in a PEM. The obtained Ce4Mn-NH2BDC@PFSA composite membrane exhibits high dimensional stability, excellent proton conductivity and low high-frequency impedance, yielding a proton conductivity of up to 137 mS cm–1 and superior water electrolysis performance of up to 1.83 V at 3.0 A cm–2. Moreover, the obtained Ce4Mn-NH2BDC@PFSA membrane experiences lower weight loss during the Fenton reaction, a low fluoride-ion release rate, and excellent stability in high current density durability testing: its decay rate is only 5.2 μV h–1, which is lower than that of CeO2@PFSA and Nafion 117 membranes. This work provides a promising method to prepare efficient free radical scavengers for steady-state PEM water electrolysis.

Nanostructure-transportation relation to PEMFCs activity and durability degradation

The Proton exchange membrane (PEM) is a crucial component in the membrane electrode assembly (MEA), playing a vital role in providing a channel for water transport and acting as a bridge for proton conduction. However, during the long-term operation of fuel cells, PEM is susceptible to attack from metal ions such as Cr3+ originating from the corrosion of metallic bipolar plates, leading to changes in its transport properties. Here, we report on the impact of Cr3+ on the microstructure and mechanical properties of PEM and then correlate it with changes in water uptake and proton conductivity, studying the effect of Cr3+ contamination on fuel cell performance and durability. The study reveals that Cr3+ forms a dense cross-linking structure with sulfonic acid groups inside the ionomer, resulting in an increase in storage modulus due to the larger ion radius and higher valence state, leading to a decrease in water uptake and proton conductivity. The membrane transport properties are primarily dependent on its water content. It is observed that Cr3+ contamination reduced the fuel cell voltage and maximum power density by 47.6% and 57.1%, respectively, with a voltage attenuation rate up to 2.9 mV/h, nearly 14 times that of the uncontaminated condition (0.21 mV/h). These findings provide valuable insights for developing high-transmission PEMs and aid in predicting the degradation and lifespan of fuel cells under actual operating conditions.

Pulsed dynamic electrolysis enhanced PEMWE hydrogen production: Revealing the effects of pulsed electric fields on protons mass transport and hydrogen bubble escape

The transition of hydrogen sourcing from carbon-intensive to water-based methodologies is underway, with renewable energy-powered proton exchange membrane water electrolysis (PEMWE) emerging as the preeminent pathway for hydrogen production. Despite remarkable advancements in this field, confronting the sluggish electrochemical kinetics and inherent high-energy consumption arising from deteriorated mass transport within PEMWE systems remains a formidable obstacle. This impediment stems primarily from the hindered protons mass transfer and the untimely hydrogen bubbles detachment. To address these challenges, we harness the inherent variability of electrical energy and introduce an innovative pulsed dynamic water electrolysis system. Compared to constant voltage electrolysis (hydrogen production rate: 51.6 mL h−1, energy consumption: 5.37 kWh Nm−3 H2), this strategy (hydrogen production rate: 66 mL h−1, energy consumption: 3.83 kWh Nm−3 H2) increases the hydrogen production rate by approximately 27% and reduces the energy consumption by about 28%. Furthermore, we demonstrate the practicality of this system by integrating it with an off-grid photovoltaic (PV) system designed for outdoor operation, successfully driving a hydrogen production current of up to 500 mA under an average voltage of approximately 2 V. The combined results of in-situ characterization and finite element analysis reveal the performance enhancement mechanism: pulsed dynamic electrolysis (PDE) dramatically accelerates the enrichment of protons at the electrode/solution interface and facilitates the release of bubbles on the electrode surface. As such, PDE-enhanced PEMWE represents a synergistic advancement, concurrently enhancing both the hydrogen generation reaction and associated transport processes. This promising technology not only redefines the landscape of electrolysis-based hydrogen production but also holds immense potential for broadening its application across a diverse spectrum of electrocatalytic endeavors.

Influences of reformate on the performance of high temperature proton exchange membrane fuel cell and its optimization strategy

Due to the challenges of hydrogen production, storage and transport, hydrocarbon reformate-based high temperature proton exchange membrane fuel cell (HT-PEMFC) has wide application opportunities. However, the inevitable water vapor and CO in reformate significantly determines the fuel cell performance and durability. In this work, a three-dimensional, non-isothermal and multiphase model based on agglomerate sub-model is developed to investigate the effects of reformate components and operating conditions, in which multiphase transport, dissolution, diffusion, adsorption, desorption and reaction of H2 and CO are considered. The results show that the fuel cell performance increases with the rising of water vapor content as CO content higher than 2 % (dry basis, the same below) and water vapor content lower 20 % (wet basis). The alleviation effect of water vapor on CO poisoning is discovered due to reduced CO coverage rather than enhanced CO electrochemical oxidation. An elevated temperature leads to improved performance and the effect of CO poisoning (CO<3%) is weak at 180°C.

Energy management strategy for accurate thermal scheduling of the combined hydrogen, heating, and power system based on PV power supply

To solve the negative impact of renewable energy volatility on the power system, a combined hydrogen, heating and power system integrating alkaline water electrolysis, metal hydride hydrogen storage, and proton exchange membrane fuel cells (PEMFCs) is proposed. However, water electrolysis, hydrogen adsorption and PEMFC all generate heat, and how to use this heat is the key to improving the system efficiency. Therefore, four energy scheduling schemes are proposed in this study, aiming at making full use of waste heat to improve its energy utilization efficiency. The results show that the system heat is almost entirely utilized under the proposed four strategies. Meanwhile, the peak-valley strategy is more suitable for on-grid operation, and heat priority, peak clipping and load reduction strategy are more suitable for off-grid operation. Under the heat priority strategy, residual electricity and heat are the lowest. Under the peak clipping strategy, the current density of the PEMFC fluctuates the least and is maintained at 0.59 A·cm-2 during the heat-led period. Under the load reduction strategy, during the heat-led period (5:00 pm ∼ 6:00 am), the system electric power is lower than the power load for the shortest time, accounting for 23.93% of this operating duration.

Laser driven generation of single atom Fe-N-C catalysts for the oxygen reduction reaction

Single-Atom Catalysts (SACs) have emerged as the ultimate solutions bridging the gap between homogeneous and heterogeneous catalysts. However, feasible synthesis methods are necessary to stabilize single metal atoms, increase catalyst loadings and scale up the synthesis. Due to the sluggish kinetics, the oxygen reduction reaction (ORR) is the main source of irreversibility in proton exchange membrane fuel cells (PEMFC). The most promising candidates to replace Pt-based catalysts for the ORR in fuel cells are the so-called Fe-N/C catalysts. These catalysts display high ORR activity in acidic and alkaline electrolytes. In this work, we propose a laser-driven pyrolysis approach to generate Fe-N/C SACs that involves decomposition of aerosolized iron-phthlocyanines. The resulting catalyst displays ORR activity in acidic and alkaline electrolytes, with competitive half-potential and kinetic current density values in comparison with state-of-the-art electrocatalysts.

Exploiting the waste heat in a proton exchange membrane fuel cell with a capacitive salinity/heat engine

For fully utilizing the low-grade waste heat (LGWH) of the proton exchange membrane fuel cell (PEMFC), a novel coupled system primarily involving a PEMFC and a capacitive salinity/heat engine (CSHE) is proposed. Based on thermodynamic and electrochemical theories, mathematical formulas of the power output, efficiency, and exergy efficiency are deduced accounting for the significant irreversible losses within the coupled system. The superiority is expounded by contrasting the generic performance characteristics of the sub-systems and the coupled system. In addition, numerical results demonstrate that the maximal power output density and its corresponding efficiency and exergy efficiency of the coupled system enhanced by 11.43%, 12.75%, and 9.96%, respectively, over the PEMFC alone under the same operating conditions. Furthermore, the impacts of some parameters, for instance, proton exchange membrane (PEM) thickness, the PEMFC working temperature and working pressure, electric charge density ratio, charging cut-off voltage, and Stern layer distance, on the coupled system performance are meticulously discussed. The results of the study may supply a reference for the design and operation of such a salinity gradient energy recovery system and create a new pathway for recycling LGWH from PEMFC.

Imidazole and triazine framed porous aromatic framework with rich proton transport sites for high performance high-temperature proton exchange membranes

Phosphoric acid-doped polybenzimidazole (PA-PBI) membranes for high-temperature proton exchange membranes (HT-PEMs) exhibit low proton conductivity under low phosphoric acid loading and poor mechanical properties under high phosphoric acid loading. In order to overcome these disadvantages, a novel kind of porous aromatic framework framed with imidazole and triazine groups (PAF-227) was designed and synthesized, phosphoric acid (PA) was incorporated into PAF-227 by utilizing vacuum-assisted infusion to yield the product PAF-227-PA. Subsequently, this dopant was combined with polybenzimidazole (OPBI) to create the PAF-227-PA/OPBI composite high-temperature proton exchange membranes (HT-PEMs). The PAF-227-PA/OPBI exhibited high proton conductivity (0.24 S cm-1) at 200 °C, as well as a favorable mechanical property (6.73 MPa) and a high PA absorption rate (250.2%), and the peak power density of the fabricated fuel cells was significantly increased to 678.21 mW cm-2 at 200 °C with the Pt loading of 0.3 mg cm-2. The basic sites of PAF-227 framed with rigid imidazole and triazine groups can anchoring the PA to achieve a high PA retention rate through the acid-basic interaction with PA, and provide sufficient proton conduction sites by forming hydrogen bonds with PA, and synergized with OPBI membranes to form a multiple hydrogen bond and proton transfer network for enhanced mechanical properties and dimensional thermal stability. Thus, this work provided a novel approach to the preparation of HT-PEMs, which exhibited excellent overall performance for HT-PEMs fuel cells.

Low-cost porous transport layers for water electrolysis cells with polymer electrolyte membranes

Proton exchange membrane (PEM) water electrolysis has advantages over other methods of producing green hydrogen such as its excellent response to power input fluctuations; wide operating range of current density; ease of production of high-pressure, high-purity hydrogen; and high durability. However, the conventional precious metal coatings used on the bipolar plates (BPPs) and porous transport layers (PTLs) of the PEM water electrolysis cell to prevent their oxidation are problematic because of their high cost; indeed, the BPPs and PTLs combined are the largest contributor (50%–70%) to the total cost of PEM water electrolysis stacks. Here, the Pt-coated PTL on the oxygen electrode side of a PEM water electrolysis cell was replaced with one with an alternative low-cost material coating (Ti4O7 or NiTiP), and the water electrolysis characteristics of the system were evaluated. We found that Ti4O7, but not NiTiP, functioned as a conductive, corrosion-resistant PTL coating in the PEM water electrolysis cell.