KOH-promoted Pt/Al2O3 catalysts for water gas shift and methanol steam reforming: An operando DRIFTS-MS study

•WGS and MSR are investigated on alumina-supported Pt catalysts.•Significantly improved activity and selectivity by applying a thin KOH-coating.•Strong modification of Pt by doping with K.•Hygroscopicity and basicity of KOH essential for enhanced performance.•Reaction pathway influenced by coating.

The performance of KOH-modified Pt/Al2O3 catalysts has been investigated under the conditions of the water-gas shift (WGS) reaction and methanol steam reforming (MSR) with diffuse reflectance infrared Fourier-transform spectroscopy (DRIFTS) coupled with online quadrupole mass spectrometry (QMS). We demonstrate that both the activity and the selectivity are enhanced in comparison to the uncoated catalyst by applying a thin coating of KOH. By means of IR spectroscopy, we were able to follow the formation of surface species on two different types of catalysts. During reaction, primarily formates are observed on the uncoated catalyst while a film of hydroxides and carbonates is observed on the KOH-coated sample. Additionally, the vibrational bands of CO adsorbed on Pt suggest a strong modification of the electronic structure of the Pt particles by K-coadsorption, leading to a weakening CO bond and a strengthening of the PtC bond. As a result, we observe an increased selectivity to CO2 on the KOH modified system.

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