In situ high temperature surface enhanced Raman spectroscopy for the study of interface phenomena: Probing a solid acid on alumina

Herein, we utilize surface enhanced Raman spectroscopy (SERS) for the in situ analyses of catalyst structure while operating at elevated temperatures in various atmospheres. In order to accomplish this, robust SERS substrates were generated by depositing an ultrathin protective coating of alumina on top of silver nanowires (NWs) via atomic layer deposition (ALD). In situ studies were then conducted by analyzing the effects of heating a solid acid, phosphotungstic acid (PTA), on the alumina surface in either an oxygen or hydrogen environment at temperatures up to 400 °C. Interestingly, the distance-dependent decay of the enhancement factor of the SERS signal from the underlying NWs allowed us to probe with great detail the interfacial region between the PTA and the alumina surface. The ability to analyze the area closest to the alumina surface was further confirmed by assembling vanadia onto the substrate and monitoring the intensity differences between the V-O-Al and outer V ? - ? O bonds.