Pressure-dependent surface chemistry of a catalytic material such as single crystals in a gaseous environment of a reactant gas is reported in literature. It can be tracked with an ambient pressure X-ray photoelectron spectrometer by introducing a reactant gas to a chamber; the reactant gas remains static as the volume of a chamber is quite large. To track surface of a catalyst during catalysis it is necessary to flow the mixture of reactant gases through the catalyst during data acquisition. A new reaction cell was developed for tracking surface chemistry of a catalyst in a flowing gaseous environment instead of a static one. Due to the small volume of mixture of reactant gases in the reaction cell, the gas flows much faster in such a reaction cell than a UHV chamber under the same pump capacity. Flow rate of mixture of reactant gases is tunable in the range of 0.1-6 ml/min, approximately equivalent with the flow rate of 2-120 ml/min of 5% reactant gas balanced with inert gas. The passivation of the internal surface of the cell with electrochemically deposited Au film prevents the cell from participating into a catalytic reaction. Catalyst is heated through a tunable laser beam. The laser beam with high density of power largely minimizes any heating around the sample; the sample holder remains at 40C when the sample is at 700C. Catalytic performance is evaluated with an on-line mass spectrometer which measures gas composition near to surface of the catalyst. A correlation between in-situ surface chemistry of a catalyst tracked with the reaction-based AP-XPS and its corresponding catalytic performance evaluated with the on-line mass spectrometer will be illustrated.

Tracking surface chemistry of a catalyst during catalysis with a lab-based ambient pressure X-ray photoelectron spectrometer

250th National Meeting (2015)

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