Ni/Graphene Coating for Enhanced Corrosion Resistance of Metal Foam Flow Field in Simulated PEMFC Cathode Environment

Zhou Y., Chen B., Meng K., Zhou H., Chen W., Zhang N., Deng Q., Yang G., Tu Z.

Flow field design plays a key role in enhancing the performance of proton exchange membrane fuel cell (PEMFC). In this work, the cathode flow field is optimized to enhance the performance of PEMFC by improving the capacity of mass transfer and water removal, and a three-dimensional, two-phase, isothermal numerical model is established to evaluate its performance. Additionally, visualization experiment is carried out to verify the simulation results. It shows that the opposite sinusoidal wave flow fields (OSWFFs) with single-inlet, dual-inlet and the block provide 6.86%, 1.26%, and 2.31% performance enhancement, respectively, compared with the parallel flow fields (PFFs), which positively affects the mass transfer capacity and water removal performance. Among them, the dual-inlet OSWFF with block is the most helpful for performance enhancement, with an enhancement of 9.30% at 2.2 A cm−2 compared to the PFF. Moreover, Pearson correlation coefficient (PCC) is proposed for the first time to evaluate the correlation between each index and PEMFC performance. The comparison of stoichiometric ratios shows that the more significantly correlated indexes contribute to the dual-inlet OSWFF outperforming the single-inlet OSWFF at high inlet velocities, verifying the applicability of PCC in PEMFC.

Bian H., Du Y., Ren Y., Wu H., Ma Y., Yang B., Tang S., Bin D., Lu H., Meng X.

Polypyrrole (PPY) coating is promising for the anticorrosion of stainless steel (SS) bipolar plates (BPs) in virtue of its good conductivity and corrosion resistance. However, the poor adhesion and pore defects of pure PPY coating limit its application. In this work, a PPY/Ti3C2Tx MXene composite coating was synthesized on 304SS BPs by one-step electrodeposition, which is a facile method to realize the polymerization of PPY and the doping of MXene at the same time. The PPY/MXene coating exhibits better long-term immersion stability in simulated proton exchange membrane fuel cell (PEMFC) environment than pure PPY. The enhanced corrosion resistance is mainly benefited from the enhanced barrier effect, anodic protection effect and adhesion by the introduction of MXene. Meanwhile, the introduction of MXene significantly improves the conductivity of the coating and decreases the interfacial contact resistance at 1.4 MPa from 108.16 mΩ·cm2 to 55.24 mΩ·cm2.

Bian H., Zhang G., Zhai Q., Du Y., Ma Y., Yang B., Tang S., Bin D., Meng X., Lu H.

Stainless steel (SS) is a promising material for designing bipolar plates (BPs), but their further application is limited by serious corrosion problems in the acidic environment containing chloride ions. Ti3C2Tx is expected to be used for SS BPs coatings, while galvanic corrosion will occur after the damage of Ti3C2Tx coating. Herein, a PPY/Ti3C2Tx-AE double-layer coating (DC) is well-designed and prepared on 304SS BP, which is composed of an inner electropolymerized PPY layer and an outer Ti3C2Tx-acrylic epoxy layer. When tested in 0.2 M HCl solution, the corrosion potential and corrosion current density of the DC are 38 mV and 0.00927 μA cm-2 respectively, which are superior to those of the PPY coating and the Ti3C2Tx coating. Moreover, the DC presents the best long-term stability among the three coatings. The excellent corrosion resistance is attributed to the barrier and anodic protection effects as well as the solution of galvanic corrosion. The new coating system provides a new insight into the design of DC coatings of SS BPs.

Abdel-Basset M., Mohamed R., Abouhawwash M.

The proton exchange membrane fuel cell (PEMFC) is a potential source of renewable energy that offers a dual benefit of reducing environmental pollution and enabling easy electricity savings. The mathematical model of PEMFC involves several unknown parameters that need to be precisely estimated for developing an accurate model. This process of estimating parameters is known as the parameter estimation of PEMFC and is considered an optimization problem. Although the problem of parameter estimation for PEMFC belongs to the category of optimization problems, it cannot be solved by all optimization techniques as it is a complex and nonlinear problem. Therefore, this paper presents a new parameter estimation technique based on adopting a recently published metaheuristic algorithm known as the artificial hummingbird algorithm (AHA). AHA is simple and easy to implement as its main advantages encourage us to adopt it for tackling this problem. However, unfortunately, AHA suffers from slow convergence speed and hence will consume a huge number of function evaluations even reaching the desired outcomes. Therefore, two improvements have been applied to the classical AHA for proposing a new variant , namely IAHA, for overcoming the parameter estimation of PEMFC stacks. IAHA was applied to estimate the unknown parameters of six different PEMFC stacks and compared with 11 well-known competing optimizers in terms of accuracy of outcomes, convergence speed, stability, and CPU time. Based on the experimental results, IAHA outperforms all other algorithms across all performance parameters except for CPU time, which is on par with the other methods.

Suranshe S.S., Patil A., Deshmukh T., Chavhan J.

The electrochemical and supercapacitive properties of an electrochemically deposited graphene oxide-polypyrrole composite are investigated. Graphene oxide (GO) for this study is synthesized by electrochemical exfoliation of graphite rod in 0.1M H2SO4 solution, with graphite rod for exfoliation is recycled from waste C-type primary battery. One step deposition of graphene oxide-polypyrrole (GO-PPy) composite using electrochemical technique by Cyclic voltammetry (CV) was successful. FEG-SEM, XRD, Raman, and FTIR technique were used to examine the physical properties of the deposited film. The deposited composite's surface morphology demonstrates a uniform and evenly distributed composite film. Electrochemical properties and supercapacitive behavior of composite are investigated using cyclic voltammetry (CV), galvanostatic charge discharge (GCD), electrochemical impedance spectroscopy (EIS), and stability in 0.5M NaCl solution. The influence of GO proportion in composite on total capacitance is assessed, and the number of CV cycles is optimized to investigate the effect of mass loading on total capacitance. It is found that the capacitance of the composite increases with increasing GO proportion, with a maximum at 20% GO, whereas the mass loading effect shows decrease in capacitance with increasing number of CV cycles during coating. The 20% GO-PPy composite has maximum capacitance of 111.11 Cg−1 for 2 cycles at 5 mVs−1. This increase in capacitance with increase in GO proportion is attributed to improved synergetic effect of between EDLC type GO and the pseudocapacitive type PPy.

Bai H., Maxwell T.L., Kordesch M.E., Balk T.J.

Nanoscale tungsten particles have attracted an increasing level of interest recently. In the current study, tungsten nanoparticles were fabricated utilizing physical vapor deposition and deposited on sapphire (α-Al2O3) substrates. The particles generated using this procedure were found to form a network with a continuous nanoporous structure. To study the influence of temperature and pressure on the stability and morphology of tungsten nanoparticles, a multitude of varying pre-heating steps were applied to these nanoscale tungsten particles in a vacuum chamber. The morphology and structure of the annealed tungsten particles were investigated by a series of materials characterization techniques including scanning electron microscopy, X-ray energy dispersive spectroscopy and X-ray photoelectron spectroscopy. The tungsten nanoparticles grew into nonuniform islands when annealed directly at 1100 °C, under a pressure of 10−7 Torr. Conversely, the deposited tungsten network transformed into individual, highly faceted nanoparticles when first pre-heated at an intermediate temperature, followed by annealing at 1100 °C, under a pressure of 10−7 Torr. Wulff analysis indicated that these well-developed tungsten particles exhibit {110} crystallographic facets.

Dehghani Z., Ostovari F., Sharifi S.

Optical properties of graphene transform in presence of amine or amide groups. So, the comparison of the linear and nonlinear optical (NLO) properties of reduced graphene oxide (RGO) nanosheets and aminated graphene (AMG) nanosheets will significantly accelerate the development of a flexible optoelectronic device based on this material in the future. In this paper, the structural and optical properties of RGO and AMG are investigated by TEM, XRD, Raman, and UV-Vis analysis. TEM images show the formation of the very thin layer of RGO and AMG nanosheets. The peak of XRD spectra (26.6◦) for both indicate the good quality of crystallization of RGO and AMG. Raman spectra result in ID/IG of about 0.9 and 1.1 for RGO and AMG, respectively. Also, different functional groups for RGO and AMG nanosheets are shown in FTIR spectra. Then, Kramers-Kronig (KK) method was employed to determine the dielectric function, ε̃(λ), extinction coefficient, k(λ) and refractive index, n(λ). Third-order optical nonlinearities of nanosheets dispersed in DMF are investigated with the Z-scan method. The nanosheets achieve an appropriate figure of merit (FOM) due to their high nonlinear refractive (NLR) index, n2 (10−8cm2/W) and low nonlinear absorption (NLA) coefficient, β (10−4cm/W).

Ren Y., Wu H., Du J., Liu B., Wang X., Jiao Z., Tian Y., Baker I.

The effect of different laser scanning speeds on the microstructural evolution and associated tribological and corrosion behavior of Ti-23Nb alloys produced by laser metal deposition (LMD) was systematically investigated. The microstructures of all specimens were composed of equiaxed β grains, acicular α″ phases, and unmelted Nb particles. With the increase of scanning speed, the volume fractions of the α″ phase and unmelted Nb particle increased, while the volume fraction and grain size of the β phase decreased. This results in a high hardness (∼ 304 HV) for the specimen with a high scanning speed (2.6 mm/s). Although the hardness of the specimen produced at 2.0 mm/s is slightly lower (∼ 296 HV), it possesses less unmelted Nb particles (soft phases, low hardness of ∼ 107 HV), resulting in a lower wear rate (∼ 4.9 × 10−4 mm3N−1 m−1). Compared to fully alloyed areas, unmelted Nb particles corrode preferentially. The specimen produced at 2.6 mm/s possesses a lower corrosion potential (Ecorr) value owing to the presence of more α″ phase and unmelted Nb particles. Grain size is a critical factor in determining the corrosion current density (icorr). The high scanning speed specimen (2.6 mm/s) with small grain sizes has high resistance and low icorr.

Lu J., Xia Y., Hu Y., Wang Z., Lei H., Hu G.

Zhang G., Qu Z., Tao W., Wang X., Wu L., Wu S., Xie X., Tongsh C., Huo W., Bao Z., Jiao K., Wang Y.

Porous flow fields distribute fuel and oxygen for the electrochemical reactions of proton exchange membrane (PEM) fuel cells through their pore network instead of conventional flow channels. This type of flow fields has showed great promises in enhancing reactant supply, heat removal, and electrical conduction, reducing the concentration performance loss and improving operational stability for fuel cells. This review presents the research and development progress of porous flow fields with insights for next-generation PEM fuel cells of high power density (e.g., ∼9.0 kW L-1). Materials, fabrication methods, fundamentals, and fuel cell performance associated with porous flow fields are discussed in depth. Major challenges are described and explained, along with several future directions, including separated gas/liquid flow configurations, integrated porous structure, full morphology modeling, data-driven methods, and artificial intelligence-assisted design/optimization.

Li T., Zhang H., Wang Y., Wu C., Yan Y., Chen Y.

High chemical stability under the harsh acidic working condition of proton exchange membrane fuel cell (PEMFC) is of great importance for bipolar plates. In present study, a series of TiCr alloys from amorphous to nanocrystalline state are designed as transition layers to promote the growth of smooth and dense TiCrN surface layer as coating material for Ti bipolar plate. Under the accelerated corrosion environment of PEMFC (0.5 M H 2 SO 4 + 2 ppm HF, 80 °C with air, 0.2 V vs. Hg/Hg 2 SO 4 ), the double-layer TiCr/TiCrN coating exhibits excellent long-term stability. A low current density of 0.25 μA/cm 2 and a small interfacial contact resistance ( ICR ) of 6.5 mΩ cm 2 are observed after 100 h corrosion test for the double-layer TiCr/TiCrN, which are much lower than the values of 1.35 μA/cm 2 and 13.5 mΩ cm 2 for single-layer TiCrN after 70 h corrosion test. These results indicate the high potential of double-layer TiCr/TiCrN as the coating material for Ti bipolar plate. TiCr transition layers promote the formation of smooth, dense and compact TiCrN surface layer. The double-layer TiCr/TiCrN coatings show both low corrosion current density of 0.154–0.099 μA/cm 2 (0.5 M H 2 SO 4 + 2 ppm HF, 80 °C with air) and small interface contact resistance of 1.3–3.2 mΩ cm 2 . The optimized TiCr/TiCrN-6 shows high stability with a low current density of 0.25 μA/cm 2 after 100 h corrosion test at 0.2 V vs. Hg/Hg 2 SO 4 , which is much lower than that (1.35 μA/cm 2 ) on single-layer TiCrN tested for 70 h. • TiCr transition layer promotes the growth of smooth, dense and compact TiCrN. • Low I corr of 0.099 μA/cm 2 is achieved at 0.5 M H 2 SO 4 + 2 ppm HF, 80 °C, with air. • Low ICR values of 1.3–3.2 mΩ cm 2 at 140 N/cm 2 are obtained. • Current density reaches 0.25 μA/cm 2 after 100 h test at 0.2 V vs. Hg/Hg 2 SO 4 .

Wang Z., Xia Y., Lei H., Hu G.

Metal foam, with large specific surface area, suffers serious corrosion problems, as flow field in proton exchange membrane fuel cell (PEMFC). Ni/Sn nanoparticles are deposited onto the surface at galvanostatic and gradient current, respectively. The morphology of coated foams is examined by scanning electron microscopy (SEM), coupled with x-ray diffraction (XRD) and energy dispersive spectroscopy (EDS). The effect of deposited current on its corrosion resistance in simulated PEMFC cathode environment is evaluated by Tafel polarization test, constant potential test and electrochemical impedance spectra. The results show that the coating effectively improved the stability of metal foam in acid environment. A uniform and dense protective film is formed by Ni/Sn electrodeposition at a gradient current density from 0 to 40 mA cm −2 . Its corrosion current at 25, 50 and 80 °C, accounts around 38.0%, 47.3% and 46.7%, respectively, of the value of uncoated metal foam. The most positive corrosion current is obtained, −0.12 mA, which is explained to higher coating resistance (R coat ). No obvious pitting is depicted in the surface morphology after 8 h, which further proves its high corrosion resistance. • Ni/Sn are electrodeposited onto metal foam for PEM fuel cell application. • Ni/Sn coated Ni foam performs higher corrosion resistance than uncoated Ni foam. • The galvanostatic and gradient current modes result different surface morphologies. • A dense and compact Ni/Sn film obtained at gradient current shows better stability.

Gou Y., Jiang G., Hao J., Shao Z., Wei Z.

A series of NbC/α-C:H films were prepared through arc ion plating for the protection of metallic bipolar plates in proton exchange membrane fuel cells (PEMFCs). Phase characterizations show that NbC grains were randomly embedded into the α-C:H matrix and their size and content increased with the decreasing of C 2 H 2 flow rate. Results from the kelvin probe force microscope (KPFM) and conductive atomic force microscope (CAFM) presented a uniform surface potential distribution but significant local conductivity differences. DFT calculations and potentiostatic polarization tests indicated that dissolution of NbC grains were preferred in PEMFC cathode environment due to preferential adsorption of corrosive media. On the basis of theoretical calculations and experimental results, a corrosion mechanism was presented based on percolation model to better understand the corrosion process of NbC/α-C:H films in PEMFC cathode. • NbC content and size increase with the decrease of C 2 H 2 flow rate. • NbC grains are preferred to be corroded than а-C:H. • Corrosion mechanism of NbC/а-C:H films conforms to percolation model.

Khalid N.B., Sarwar M., Rakha A., Khalid A.M., Munawar A., Riaz A., Rehman R.A., Akhtar S.

Here we are reporting the usage of Cassia Angustifolia leaves’ extract as a reducing agent in the synthesis of ceria nanoparticles. The structural composition of nanomaterials thus prepared was investigated using UV–Vis Spectroscopy, FT-IR, XRD, SEM and EDX techniques. The SEM images revealed that the structure of these particles was like honeycomb, circular and cubic with smooth surfaces ranging from 50 to 100 nm in size. Further, the morphology and size analysis was endorsed by X-ray Diffraction Analysis. X-ray Diffraction analysis corresponds to cubic phase centered with lattice parameters of a = b = c = 0.5412 nm while the average size of ceria nanoparticles calculated by using the Debye-Sherrer equation presents 58.23 nm. The most important function of these nanoparticles is the determination of them in vitro antibacterial usage against Gram-Positive and -Negative microbe. It was found that these nanoparticles exhibited some antibacterial activity against all these microorganisms. For that, Cerium oxide nanoparticles were prepared and found to possess significant antibacterial activities when tested against the pathogenic bacteria viz. clinically isolated Gram-negative Escherichia coli and Gram-Positive Bacillus subtilis. With the increase in the concentration of nanoparticles, the inhibition zone also increased. The greatest value recorded for the zone of inhibition of Escherichia coli is 9 cm, of Pseudomonas aeuroginosa is 19 cm and of Staphylococcus aureus is 18 cm. The significance of the present study is that Cassia Angustifolia leaf extract was used for the synthesis of Cerium Oxide nanoparticles and confirmed their antimicrobial activity.

Tan Q., Wang Y.

Focusing on the special electrical conductivity and corrosion resistance of Ti 4 O 7 , this work proposes for the first time to reduce TiO 2 film grown in situ on Ti substrate in a high-temperature tube furnace by using Ti/TiO 2 mixed powder as reducing agent to obtain Ti 4 O 7 surface coating. By characterization, the surface of the coated sample is identified as a Ti 4 O 7 coating, with a partially unconverted TiO 2 present at the interface between the Ti substrate and the Ti 4 O 7 surface coating. The electrochemical, water contact angle and surface contact resistance tests show that the Ti 4 O 7 surface coating provides superior protection to the Ti bipolar plate in the simulated proton exchange membrane fuel cell cathode environment, and simultaneously improving the electrical conductivity and water contact angle of the sample. • A novel preparation method of Ti 4 O 7 coating is proposed. • Uniform and dense Ti 4 O 7 coating on Ti substrate is obtained in a short time. • Ti 4 O 7 coating maintains excellent corrosion resistance in simulate PEMFC cathode environment . • The Ti 4 O 7 coating exhibits high conductivity and hydrophobicity.

Sun C., Zuo Q., Hu G., Xia Y.

Collins G., Barwa T.N., Glennon L., Kasturi P.R., Breslin C.B.

Xia Y., Zuo Q., Sun C., Hu G., Fang B.

Metal foams are promising materials for the flow fields of proton exchange membrane fuel cells (PEMFCs) because of excellent mass transport characteristics and high electronic conductivity. To resolve the corrosion problem in the acidic environment under high temperature, nickel/graphene (Ni/G) composite coatings with hierarchical structures were electrodeposited on the surface of Ni foam. The effect of grain size and the distribution in the double layer was discussed. It was found that Ni/G5-10, with larger inner size and middle outer size, exhibited the best corrosion performance. Meanwhile, the corrosion current in the Tafel plots and the steady current density in constant potential analysis was lower than that obtained under steady and gradient currents. Combined with the results of XRD, XPS, and SEM, it was proven that a uniform and dense protective film was produced during the two-step electrodeposition. Moreover, the ICR value was 8.820 mΩ·cm2, which met the requirement of 2025 DOE.

Safina L.R., Krylova K.A., Murzaev R.T., Shcherbinin S.A., Baimova J.A.