Reverse water-gas shift reaction: steady state isotope switching study of the reverse water-gas shift reaction using in situ DRIFTS and a Pt/ceria catalyst

A previous investigation using steady state isotope switching in combination with DRIFTS demonstrated that surface formates exchange rapidly in a low temperature shift feed for the forward reaction. Transient decomposition of the pseudo-stable formate indicated that water autocatalyzes the forward shift reaction. In the present study, and including water in the RWGS feed (H2 and CO2), surface formates were found to exchange more rapidly during RWGS over Pt/ceria than when a dry feed was used. An earlier claim suggested that PtCO and carbonate were intermediates, as they exchange rapidly during RWGS. However, in the present study of 12CO2 to 13CO2 switching, PtCO and carbonate exchange rapidly even in the absence of reaction. Furthermore, the formate exchange rate during RWGS in the absence of added water proceeds at a much slower rate, indicating that conclusions on the mechanism of forward shift cannot be inferred on the basis of dry RWGS results.