Benjamin Vaughan Cunning

Electrolyzers and fuel cells are promising candidates for sustainable conversion of electricity to hydrogen and hydrogen to electricity, offering an energy storage solution with high efficiency and low environmental impact. However, the problem of hydrogen crossover in the polymer electrolyte membrane (PEM) presents a particular challenge, limiting the efficiency and ultimately hindering their widespread adoption. Meanwhile, graphene is a well-known nanomaterial that is reportedly practically impermeable to gases. Here, we present innovative approaches to tackle the issue of hydrogen crossover by using graphene in different forms and different cell architectures. First, we will explore pure graphene oxide (GO) as a new electrolyte material in both acid and alkaline configurations. Then we will look at thin films of GO sandwiched in Aquivion membranes as a gas barrier layer. Finally, we will demonstrate that monolayer graphene is an effective gas barrier layer when sandwiched in Nafion membranes. Similar to the case of graphene, GO also exhibits remarkable materials properties including high strength, excellent hydrogen gas barrier properties, hydrophilicity, and proton conduction assisted by acidic functional groups. These factors potentially make GO an attractive material for electrolyte membranes. We demonstrate the preparation of pure GO membranes via vacuum-filtration, and measure hydrogen permeability (2x10^-2 barrer) three orders of magnitude lower than conventional Nafion membranes (30 barrer). Furthermore, we observe a significant anisotropy in ionic conductivity, attributed to the lamellar structure of GO. The resulting fuel cell power density was relatively low, due to limited conductivity (0.3 mS cm^-1). To compensate for this, extremely thin (3 µm) electrode-supported GO membranes were deposited via spray deposition, resulting in improved fuel cell power density up to 79 mW cm^-2. This showcases the potential of GO-based membranes in enhancing fuel cell performance. Furthermore, we present a novel class of anion exchange membrane (AEM) fabricated from KOH-modified multilayer graphene oxide paper. As with the case of acidic electrolyte membranes, these also display high tensile strength and low gas permeability. A hydroxide ion conductivity of 6 mS cm^-1 was recorded and confirmed using ion blocking layers, and attributed to a water-mediated reverse Grotthuss-like mechanism. An alkaline fuel cell was assembled but a relatively low proton conductivity of 1 mW cm^-2 was obtained, attributed to reaction with CO₂ in the oxidant gas supply. The above studies are promising, but the low ionic conductivity of pure graphene limits the ultimate achievable fuel cell power densities. Therefore, we explored the use of ultrathin GO layers (100 nm) sandwiched in Aquivion PEMs to combine the high ionic conductivity of Aquivion with the gas barrier properties of graphene oxide (as well as CeO₂ as a radical scavenger). These novel multilayer sandwich PEMs were deposited via spray deposition, resulting in just 10 µm total thickness. This method resulted in extremely high-power densities (1.6 W/cm²) and very low hydrogen crossover current density (1 mA/cm²). As such the concept of adding hydrogen blocking interlayers is shown to be highly effective. Finally, we investigate the potential of monolayer graphene as a barrier to hydrogen crossover in PEMs, since graphene reportedly presents minimal resistance to hydrogen ion transport through the basal plane. Graphene grown via chemical vapor deposition on a copper substrate was coated with Nafion via spray deposition. The copper was removed via etching in acid and then a second layer of Nafion was sprayed onto the freshly exposed graphene surface, forming a sandwich PEM. Again, this resulted in significantly reduced hydrogen crossover current, whilst having minimal impact on the power density. In conclusion, graphene is an ideal material for incorporation into PEMs to minimise hydrogen crossover. This has the potential to enhancing the performance and durability of fuel cells and electrolysers. T. Bayer, S. R. Bishop, M. Nishihara, K. Sasaki, S. M. Lyth, Journal of Power Sources 272 (2014) 239-247 T. Bayer, R. Selyanchyn, S. Fujikawa, K. Sasaki, S. M. Lyth, Journal of Membrane Science 541 (2017) 347–357 T. Daio, T. Bayer, T. Ikuta, T. Nishiyama, K. Takahashi, Y. Takata, K. Sasaki, S. M. Lyth, Scientific Reports, 5 (2015) 11807 T. Bayer, S. R. Bishop, N. H. Perry, K. Sasaki, S. M. Lyth, ACS Applied Materials and Interfaces 8, 18 (2016) 11466–11475 T. Bayer, B. V. Cunning, R. Selyanchyn, T. Daio, M. Nishihara, S. Fujikawa, K. Sasaki, S. M. Lyth, Journal of Membrane Science, 508 (2016) 51–61 M. Breitwieser, T. Bayer, A. Büchler, R. Zengerle, S. M. Lyth, S. Thiele, Journal of Power Sources, 351 (2017) 145-150

Anode-free lithium (Li) batteries that function via direct Li plating/stripping on metal current collectors have garnered significant interest in the field of metallic Li as an ideal negative electrode. However, dendritic Li growth creates unoccupied space in the battery, diminishing volumetric energy density. Our research reveals that Li adatoms can reposition on metal substrates via surface migration by interacting with individual grains at the atomic level after electro-adsorption of Li ions. By examining Li morphologies on diverse types of substrates, we find that the near-zero migration barrier of Li adatoms, especially on single crystal Cu(111) foils, is a key parameter that inhibits Li dendrites by initiating horizontal growth in an isotropically faceted nucleation shape, with 80% capacity retention even after 120 cycles (versus 29 cycles for polycrystalline Cu), paired with LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811) cathodes with a high-loading level (5.3 mA h cm⁻²). Based on our findings, we highlight the importance of metal substrates that promote favorable surface dynamics of Li adatoms.

Presenting a versatile method to make soft, deformable, functional metallic “putty” from liquid gallium and nonmetallic fillers.

Non-platinum group metal (non-PGM) catalysts for the oxygen reduction reaction (ORR) are set to reduce the cost of polymer electrolyte membrane fuel cells (PEFCs) by replacing platinum at the cathode. We previously developed unique nitrogen-doped carbon foams by template-free pyrolysis of alkoxide powders synthesized using a high temperature and high pressure solvothermal reaction. These were shown to be effective ORR electrocatalysts in alkaline media. Here, we present a new optimised synthesis protocol which is carried out at ambient temperature and pressure, enabling us to safely increase the batch size to 2 g, increase the yield by 60%, increase the specific surface area to 1866 m ² g ⁻¹ , and control the nitrogen content (between 1.0 and 5.2 at%). These optimized nitrogen-doped carbon foams are then utilized as effective supports for Fe–N–C catalysts for the ORR in acid media, whilst multiphysics modelling is used to gain insight into the electrochemical performance. This work highlights the importance of the properties of the carbon support in the design of Pt-free electrocatalysts.

A macroscopic film (2.5 cm × 2.5 cm) made by layer‐by‐layer assembly of 100 single‐layer polycrystalline graphene films is reported. The graphene layers are transferred and stacked one by one using a wet process that leads to layer defects and interstitial contamination. Heat‐treatment of the sample up to 2800 °C results in the removal of interstitial contaminants and the healing of graphene layer defects. The resulting stacked graphene sample is a freestanding film with near‐perfect in‐plane crystallinity but a mixed stacking order through the thickness, which separates it from all existing carbon materials. Macroscale tensile tests yields maximum values of 62 GPa for the Young's modulus and 0.70 GPa for the fracture strength, significantly higher than has been reported for any other macroscale carbon films; microscale tensile tests yield maximum values of 290 GPa for the Young's modulus and 5.8 GPa for the fracture strength. The measured in‐plane thermal conductivity is exceptionally high, 2292 ± 159 W m⁻¹ K⁻¹ while in‐plane electrical conductivity is 2.2 × 10⁵ S m⁻¹. The high performance of these films is attributed to the combination of the high in‐plane crystalline order and unique stacking configuration through the thickness.

We report the effect of single crystal graphene on carbonization and graphitization of thin film polymers.