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

Cychy, S. and Lechler, S. and Huang, Z. and Braun, M. and Brix, A.C. and Blümler, P. and Andronescu, C. and Schmid, F. and Schuhmann, W. and Muhler, M.

Volume: 42 Pages: 2206-2215
DOI: 10.1016/S1872-2067(20)63766-4
Published: 2021

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. © 2021 Dalian Institute of Chemical Physics, the Chinese Academy of Sciences

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