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Inorganic Chemistry – Reactivity Group
  

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Research Topic:
  Development of cost-effective electrocatalysis for the anodic oxygen evolution reaction (OER)
Cyriac Massué

Electrocatalytic water splitting offers the opportunity of implementing chemical energy storage based on hydrogen production into power grids based on a variety of renewable energy sources. A major bottleneck, which so far limits the commercial relevance of such systems is the development of stable and cost-effective electrocatalysts for the anodic oxygen evolution reaction (OER). The target of our research is the synthetic development of optimized metal oxide composite materials for the OER and a better modelling of the relevant structure-activity relationships involved.

Several groups within the department have joined efforts and resources to focus on Ir-based systems. Indeed iridium-based OER-electrocatalysts have proven so far to be the only systems combining high activitiy and stability under acidic OER-conditions. [1] The comparison of benchmark Ir-compounds (see graph) indicates striking differences between crystalline IrO2 and amorphous IrOx(OH)y. These findings are well in line with recent reports that the optimum for high OER-activity and -stability might be reached for such Ir-oxohydroxides. [2] [3] In order to gain a full understanding of the influence of the chemical nature of Ir-compounds on their OER-performance, we have produced an extensive portfolio of Ir-compounds ranging from IrO2 to IrOx(OH)y via the full range of synthesis methods available in the department. Within the framework of the “Ekolyser”-project optimized systems are tested under commercially relevant conditions. (collaboration with Dr. Ranjan at MPI-CEC, Research Center Jülich, Solvicore, Fumatech, Gräbener Maschinenbau, financed by BMWI)

In parallel to the evaluation of the electrochemical OER-performance, we have deployed significant efforts to study the behavior of electrocatalysts during OER. Analytical tools adapted for electrocatalytic in-situ studies of the surface structure and chemistry are being developed for grazing incidence X-ray diffraction studies (GIXRD) and synchrotron experiments by the Electron Microscopy group and the Electronic Structure group. This combined approach should eventually lead to pinpointing which structural and chemical features of Ir-based compounds determine their OER-performance. In turn this will allow to further optimize synthesis procedures for the production of commercially relevant OER-electrocatalysts.

The comparison of benchmark Ir-compounds
indicates striking differences between
crystalline IrO2 and amorphous IrOx(OH)y.

(to see full size, click on the image)
References
  1. McCrory, C. C. L.; Jung, S.; Ferrer, I. M.; Chatman, S. M.; Peters, J. C.; Jaramillo, T. F. J.
    Am. Chem. Soc. 2015, 137, 4347.
  2. Cherevko, S.; Reier, T.; Zeradjanin, A. R.; Pawolek, Z.; Strasser, P.; Mayrhofer, K. J. J.
    Electrochemistry Communications 2014, 48, 81.
  3. Reier, T.; Teschner, D.; Lunkenbein, T.; Bergmann, A.; Selve, S.; Kraehnert, R.; Schlögl, R.; Strasser, P. J.
    Electrochem. Soc. 2014, 161, F876.
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