Chinese Journal of Catalysis ›› 2021, Vol. 42 ›› Issue (12): 2206-2215.DOI: 10.1016/S1872-2067(20)63766-4

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Optimizing the nickel boride layer thickness in a spectroelectrochemical ATR-FTIR thin-film flow cell applied in glycerol oxidation

Steffen Cychya, Sebastian Lechlera, Zijian Huanga, Michael Braunb, Ann Cathrin Brixc, Peter Blümlerd, Corina Andronescub, Friederike Schmidd, Wolfgang Schuhmannc, Martin Muhlera,*()   

  1. aLaboratory of Industrial Chemistry, Department of Chemistry and Biochemistry, Ruhr University Bochum, Universitätsstr. 150, D-44801 Bochum, Germany
    bTechnical Chemistry III and CENIDE, Faculty of Chemistry, University of Duisburg-Essen, Universitätsstr. 7, D-45141, Essen, Germany
    cAnalytical Chemistry - Center for Electrochemical Sciences (CES), Faculty of Chemistry and Biochemistry, Ruhr University Bochum, Universitätsstr. 150, D-44801 Bochum, Germany
    dInstitute of Physics, Johannes Gutenberg-University Mainz, Staudingerweg 9, D-55128 Mainz, Germany
  • Received:2020-12-23 Accepted:2020-12-23 Online:2021-12-18 Published:2021-05-06
  • Contact: Martin Muhler
  • About author:* E-mail: muhler@techem.rub.de

Abstract:

The influence of the drop-casted nickel boride catalyst loading on glassy carbon electrodes was investigated in a spectroelectrochemical ATR-FTIR thin-film flow cell applied in alkaline glycerol electrooxidation. The continuously operated radial flow cell consisted of a borehole electrode positioned 50 µm above an internal reflection element enabling operando FTIR spectroscopy. It is identified as a suitable tool for facile and reproducible screening of electrocatalysts under well-defined conditions, additionally providing access to the selectivities in complex reaction networks such as glycerol oxidation. The fast product identification by ATR-IR spectroscopy was validated by the more time-consuming quantitative HPLC analysis of the pumped electrolyte. High degrees of glycerol conversion were achieved under the applied laminar flow conditions using 0.1 M glycerol and 1 M KOH in water and a flow rate of 5 µL min-1. Conversion and selectivity were found to depend on the catalyst loading, which determined the catalyst layer thickness and roughness. The highest loading of 210 µg cm-2 resulted in 73% conversion and a higher formate selectivity of almost 80%, which is ascribed to longer residence times in rougher films favoring readsorption and C-C bond scission. The lowest loading of 13 µg cm-2 was sufficient to reach 63% conversion, a lower formate selectivity of 60%, and, correspondingly, higher selectivities of C2 species such as glycolate amounting to 8%. Thus, only low catalyst loadings resulting in very thin films in the few μm thickness range are suitable for reliable catalyst screening.

Key words: Catalyst layer thicknes, Electrocatalyst, Nickel boride, Operando ATR-IR, High performance liquid chromatography, Flow cell, Thin film, Anodic glycerol oxidation