A perspective on chromium-Free iron oxide-based catalysts for high temperature water-gas shift reaction

Recent efforts to replace toxic hexavalent chromium oxide in commercial copper-chromium-iron oxide catalysts for the High-Temperature Water-Gas Shift (HT-WGS) reaction are reviewed. Advances in understanding the fundamentals of the HT-WGS reaction catalyzed by copper-chromium-iron oxide reveal that the role of chromium is to act as textural promoter to stabilize the surface area of the iron oxide phase towards sintering. The lack of in situ/operando spectroscopic characterization of the bulk and surface phases of the newly designed promoted catalysts, however, severely hampers a thorough understanding of the chemical states as well as the exact role of the non-Cr promoters. Future research studies will need to perform in situ/operando spectroscopy studies to fill this void to allow for the rational design of advanced HT-WGS catalysts.