Operando UV-vis spectroscopy for real-time monitoring of nanoparticle size in reaction conditions: a case study on r WGS over Au nanoparticles.

We propose the use of surface plasmon resonance (SPR) as a distinctive marker for real-time monitoring in reaction conditions of gold nanoparticles supported on α-Al 2 O 3 . The study leverages the SPR shape-and-size dependency to monitor metal nanoparticles in reaction conditions, evidencing an influence of both dimensions and agglomerations on the SPR peak position. Operando measurements, coupling UV-vis spectroscopy and catalytic testing, allows to follow the dynamics during nanoparticle formation (Au 3+ to Au 0 reduction) and during the reverse water gas shift reaction (CO 2 + H 2 → CO + H 2 O). The catalyst structure and stability in reaction conditions was further confirmed by operando X-ray spectroscopy and PXRD data. Overall, this approach enables the direct acquisition of information on the structure-activity relationship of metal-based supported catalysts under actual reaction conditions.