In situ intermediate-energy X-ray catalysis research at the advanced photon source beamline 9-BM

A specially-designed catalysis reaction cell was used for acquiring X-ray Absorption Near Edge Structure (XANES) with heating and gas treatment in an intermediate-X-ray energy regime (∼2.1–4 keV) at the Advanced Photon Source beamline 9-BM. In situ X-ray measurements in this energy range can be complicated due to absorption by cell components, the reaction gases themselves, air surrounding the reaction cell, and a host of other reasons. As a proof of concept, bimetallic palladium catalysts were examined from the Pd LII and LIII edges, at approximately 3.2 keV. The XANES edge position, the height of the “white line” peak, and the shape of the peak display significant changes with alloy formation and CO adsorption. This in turn shows that the Pd L-edge XANES are very sensitive to changes in the d-band density-of-states and can be used to derive rich information about how a supported Pd, or other 4d transition metal catalyst, behaves when under reaction conditions or upon alloy formation.