The influence of adsorbed substances on alkaline methanol electro-oxidation

Alkaline methanol electro-oxidation shows a strong decrease in current during chronoamperometry (CA) measurements. In this paper, we investigate which processes and conditions cause this behavior. One explanation previously discussed in literature is glass ions blocking the catalyst surface. Alkaline electrolytes are well-known for their glass corrosive potential. The impact of glass-ions on dynamic and stationary measurements is quantified by comparing a glass-cell and a PTFE cell. We confirm that the cell material has an influence on the recorded current over time during chronoamperometric measurements. However, the strong decay of current also occurs in PTFE, showing that glass ions are not the main reason for the current decline in CA measurements. Although a carbon-supported Pt catalyst is not stable, smooth Pt catalyst features stable behavior during dynamic measurements. In order to investigate the reason for the current decay in CA measurements, we use insitu FTIR spectroscopy to identify possible adsorbed reaction intermediates and products on the catalyst surface over time. We find that the bicarbonate surface coverage constantly increases during CA, whereas the amount of other detected species decrease. This suggests that the strongly adsorbed bicarbonate at the catalyst surface might be the blocking species, which is responsible for the current loss.