Durable corrosion-resistant coating based in graphene oxide for cost-effective fuel cells components
Abstract
The current imperative transition to environmentally friendly technologies for power generation requires the reduction of their production costs. In the case of proton exchange membrane fuel cells, current collectors, which are usually integrated as flow field plates in the cells, constitute a critical component due to its weight and cost. In this paper, a cost-effective alternative is proposed, which is based in copper as conductive substrate. The protection of this metal in the aggressive media resulting from the operation conditions is the principal challenge. A continuous reduced graphene oxide coating has been developed to avoid corrosion under operation. The results of the protection behavior of this coating under accelerated stress tests performed in a real fuel cell reveal that the cost-effective procedure for copper coating is able to compete with gold-plated nickel collectors and constitute a real alternative to reduce the production costs and the weight of these systems.
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iScience, Volume 26 Supplemental information Durable corrosion-resistant coating based in graphene oxide for cost-effective fuel cells components Alba Fernández-Sotillo and Paloma Ferreira-Aparicio
Figure S1. Polarization and power density curves obtained for the air-breathing PEMFC assembled with gold-coated nickel (a) and rGO-coated copper current collectors (b), related to Figure 7. Figure S2. Operation parameters (voltage, current intensity, and temperature) of the air breathing PEMFC assembled with gold-coated nickel (a) and rGO-coated copper current collectors (b), related to Figure 7. 0.0 0.1 0.2 0.3 0.4 0.5 0.0 0.2 0.4 0.6 0.8 1.0 V / V i / A·cm-2 0.00 0.03 0.06 0.09 0.12 P / W·cm-2 0.0 0.1 0.2 0.3 0.4 0.5 0.0 0.2 0.4 0.6 0.8 1.0 V/ V i /A·cm-2 0.00 0.03 0.06 0.09 0.12 P/W·cm-2 Ni-Au//Ni-Au Cu-rGO//Cu-rGOa) b) 0 5 10 15 20 20 40 60 Tcell / oC t / h 0.0 1.5 3.0 I / A 0.0 0.5 1.0 V / V Ni-Au//Ni-Au 0 5 10 15 20 20 40 60 Tcell / oC t / h 0.0 1.5 3.0 I / A 0.0 0.5 1.0 V / V Cu-rGO//Cu-rGO Ni-Au//Ni-Au Cu-rGO//Cu-rGO a) b)
Figure S3. XPS spectra in the C 1s, O 1s and Cu 2p3/2 regions registered for a freshly prepared coated sample with a completely effective corrosion barrier: black-colored line: original spectrum at the pristine surface; red colored line: spectrum after 70 etching cycles with an Ar+ ion gun; related to Figure 1. Figure S4. a) XPS spectra in the C 1s and Cu 2p3/2 regions registered for a sample after the first stage of the coating synthesis during a depth profiling: black line: original spectrum at the pristine surface; red, green and blue lines: spectra after 16, 32 and 50 etching cycles, respectively. It should be noted that this sample has only a first coating layer, and additional rGO layers are required for an effective corrosion barrier. b) Copper content in the film composition at increasing distances from the substrate surface. Reduced graphene oxide film grown for 1 h by self-assembly and reduction of GO on a copper microgrid. GO dispersion concentration: 0.5 mg·mL-1. These results evidence the presence of increasing amounts of copper in inner sheets of the rGO coating. They are transition layers with intermediate properties, which can contribute to buffer the impact of thermo-mechanical stress forces between rGO and the substrate during temperature changes. Related to Figure 1. 540 535 530 525 2000 4000 6000 8000 10000 Intensity / a.u. Binding energy / eV 0 70 O 1s 295 290 285 280 0 5000 10000 15000 20000 Intensity / a.u. Binding energy / eV 0 70 C 1s 930 935 940 945 950 1000 3000 5000 7000 Intensity / a.u. Binding energy / eV 0 70 Cu 2p3/2 545 540 535 530 525 520 0.0 0.5 1.0 1.5 2.0 0 16 32 50 Intensity /104 cps Binding energy / eV 290 285 280 0.0 0.5 1.0 1.5 2.0 0 16 32 50 Intensity /104 cps Binding energy / eV 950 945 940 935 930 0.0 0.5 1.0 1.5 2.0 0 16 32 50 Intensity /105 cps Binding energy / eV C 1s Cu 2p3/2 0.00 0.05 0.10 0.15 0.20 0.25 0 20 40 60 80 100 Cu content in the inner coating / at. % Distance from from the inner rGO layer / m a) b) O 1s
Figure S5. XPS of the C1s core region for self-standings films synthesized by evaporationassembly of a GO solution as prepared (a) and after the reduction treatment applied to the coatings (b), related to Figure 1. Figure S6. Scanning electron microscopy image of the cross-section of the rGO-coated copper microgrid showing a gap between the open substrate and coating film, related to Figure 1. 292 288 284 280 0 5000 10000 15000 C=C sp2 C-O C=O/quinone O-C=O (3.4%) (15.2%) (5.1%) Intensity / cps Binding Energy / eV (72.3%) 292 288 284 280 0 5000 10000 15000 38% (52%) (8%) (2%) C=C sp2 C-O-C /C-OH C=O/quinone O-C=O Intensity / cps Binding Energy / eV a) b)
Figure S7. a) Exploded view of the passive air-breathing single PEM fuel cell based on WO2015025070A1 and WO2020240063A1; b.1) cell assembly without the external cathode pinned plate showing the coated copper current collector at the cathode; b.2) detail of the coated microgrid; related to STAR Methods. b.1) b.2) a) MEA Current collector frame Current collector frame & microgrid Pinned cathode plate Water permselective membrane Anode gas distribution plate External perforated plate for permeable membrane fixation Fixation bolts H2inlet H2purge, normally closed Sealing joint Current collector grid Gaskets