PEM water electrolysis cells with catalyst coating by atomic layer deposition

The limited annual mining capacity and high costs of platinum metal group catalysts (PMG) are confining the production of hydrogen from PEM electrolysis. Therefore, a significant reduction of catalyst needs is crucial to reduce system costs and increase production capacity. This study demonstrates the feasibility of a PEM water electrolysis cell design using porous transport electrodes (PTE) with catalyst coating by atomic layer deposition (ALD) and operation in 1 mol/L sulphuric acid at 60 °C. Though the catalyst loading has been reduced to 0.12 mg/cm iridium on the anode and 0.28 mg/cm platinum on the cathode, a current density of 168 mA/cm and mean high mass activity of 1400 A/g iridium could be achieved at 1.7 V. The characterization of three high loading PTE cells is combined with a detailed overpotential analysis from polarization curve fits and demonstrates a reproducible cell setup. Further analysis steps show an increasing cell performance with increasing coating cycle numbers and the consistency of the anode performance in the three electrode setup with the complete cell. The ALD coated PTE design turns out to be a promising candidate for catalyst loading reduction in PEM electrolysis.This work was done within the research project Tubulyze and was supported by the German Federal Ministry of Education and Research (BMBF FKZ:03FS0564B). The authors thank B. Sánchez Batalla and C.Weidlich (DECHEMA) for the ICP-MS measurements

Genesis of spodic material underneath peat bogs in a Danish wetland

9 pages, 5 figures, 3 tables, 41 references.The chemistry of wet Spodosols (Aquods) differs from well-drained Spodosols. Two different hypotheses have been suggested to explain the contrasting genesis of wet spodic horizons. This study attempted to determine whether Aquods at a Danish peat-bog wetland site are a result of (i) in situ illuviation under a fluctuating water table, or (ii) degradation of a former Fe-rich, well-drained spodic horizon. Methods included soil surveys, wet chemical analyses, micromorphology, pollen analysis, and radiocarbon dating of soil organic matter (OM) fractions. Aquods, and soil material with spodic features, were exclusively found in sandy material at the margins of or underneath sphagnum peat bogs, whereas Inceptisols were found on well-drained sandy deposits only. Aluminum content was very high and Fe low in spodic materials with ortstein properties. Solid-state 13C nuclear magnetic resonance (NMR) spectra of wet sandy 2Bs horizons were dominated by alkyl C (70%) from water-insoluble OM and were clearly distinct from NMR spectra of overlying 2Bhsm material. Pollen analysis revealed that an open forest with a thick mor layer dominated until shortly after 5000 yr BP, when sphagnum was first recorded. Radiocarbon ages of bulk soil C in the spodic horizons had mean residence times of 4500 to 4400 yr. Accordingly, the spodic B horizon was probably formed by strong in situ illuviation of Al-OM complexes before the sphagnum peat bog formation. This suggests that spodic material formation and thus strong C accumulation underneath this Danish peat bog took place for a limited period, only in susceptible parent material, and at the margins of the expanding peat bogThe financial support from The Danish Veterinary and Agricultural Research Council is acknowledged.Peer Reviewe