Journal: Energy Advances

Abbreviation

Energy Adv.

Publisher

Royal Society of Chemistry

Journal Volumes

ISSN

2753-1457

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2022 - 20233
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Publications 1 - 3 of 3
  • On the water transport mechanism through the microporous layers of operando polymer electrolyte fuel cells probed directly by X-ray tomographic microscopy
    Item type: Journal Article
    Chen, Yen-Chun; Dörenkamp, Tim; Csoklich, Christoph; et al. (2023)
    Energy Advances
    Product water transport via the microporous layer (MPL) and gas diffusion layer (GDL) substrate during polymer electrolyte fuel cell (PEFC) operation was directly and quantitatively observed by X-ray tomographic microscopy (XTM). The liquid water distribution in two types of MPLs with different pore size distributions (PSDs) was characterized as a function of the inlet gas relative humidity (RH) and current density under humid operating conditions at 45(degrees)C. During the first minute of PEFC operation, liquid water mainly accumulated at the catalyst layer (CL)/MPL interface and in the GDL substrate close to the flow fields. Furthermore, under all tested conditions, saturation in the MPL was low (<25%), whereas under the rib, the saturation in the GDL was up to ca. 70%. Based on these XTM results, it is confirmed that in the high porosity MPLs, vapor transport was non-negligible even at high humidity conditions. Therefore, on top of the widely discussed MPL pore size and its distribution, it is proposed that the lower thermal conductivity from the high porosity of MPLs can also be a main cause of promoted vapor transport, reducing water saturation near the CL.
  • Quantifying global costs of reliable green hydrogen
    Item type: Journal Article
    Freire Ordóñez, Diego; Ganzer, Caroline; Halfdanarson, Thorsteinn; et al. (2023)
    Energy Advances
    The current energy crisis has resulted in natural gas prices at an unprecedented level in many parts of the world, with significant consequences for the price of food and fertiliser. In this context, and with the projected reduction in the costs of renewables and electrolysers, green hydrogen is becoming an increasingly attractive option. In this study, we evaluate the current and future costs of green hydrogen, produced on a reliable schedule, so as to be coherent with industrial demand. Here, we take full account of both inter- and intra-annual variability of renewable energy, using 20 years of hourly resolution wind and solar data from 1140 grid points around the world. We observe that simply using average annual capacity factors will result in a significantly under-sized system that will frequently be unable to meet demand. In order to ensure production targets are met, over-capacity of power generation assets and energy storage assets are required to compensate for inter-annual and intra-annual variations in the availability of wind and solar resources, especially in the time periods known as “dunkelflauten”. Whilst costs vary substantially around the world, contemporary costs of reliable green hydrogen are estimated to be, on average, 18–22 USD per kgH2 with a minimum of 5 USD per kgH2, depending on the ability to monetise “surplus” or “excess” renewable energy. The primary cost driver is renewable energy capacity, with electrolysers and energy storage costs exerting a second-order effect. With cost reduction, future costs are anticipated to be, on average, 8–10 USD per kgH2 with a minimum of 3 USD per kgH2, again as a function of the ability to monetise otherwise curtailed power. Another key factor in future costs is found to be hurdle rates for capital investments. Finally, we observe that continued cost reduction of renewable power is key to reducing overall system costs of green hydrogen production.
  • Photoelectrochemical glycerol oxidation on Mo-BiVO4 photoanodes shows high photocharging current density and enhanced H2 evolution
    Item type: Journal Article
    Bora, Debajeet K.; Nadjafi, Manouchehr; Armutlulu, Andac; et al. (2022)
    Energy Advances
    Mo-doped BiVO4's lower efficiency can be attributed in part to exciton recombination losses. Recombination losses during photoelectrochemical water oxidation can be eliminated by using glycerol as a hole acceptor. This results in an enhanced photocurrent density. In this research, we present the synthesis of a Mo-doped BiVO4 photoelectrode with a greater photocurrent density than a traditional pristine photoanode system. Increased photon exposure duration in the presence of glycerol leads to 8 mA cm-2 increase in photocurrent density due to the creation of a capacitance layer and a decrease in charge transfer resistance on the photoelectrode in a neutral-phosphate buffer solution thus confirming the photo charging effect. Glycerol photooxidation improves the photoelectrode's rate of hydrogen evolution. Research into the effects of electrolyte and electrode potential on photoelectrodes has revealed that when the applied potential increases, the light absorbance behaviour changes following its absorption distribution over the applied potential. Under a transmission electron microscope (TEM), a unique dynamical crystal fringe pattern is found in the nanoparticles scratched from the photoelectrode.
Publications 1 - 3 of 3