Effects of Metal Doping on the Structure and Water–Gas Shift Reaction Performance of Copper–Manganese Catalysts

Cu-Mn catalysts modified with Zr, Ce, Fe, Al, and Zn were prepared by co-precipitation and evaluated for the water–gas shift reaction (WGSR) using a common conditioning and cooling protocol. Among the tested compositions, the 5 mol% Zr sample gave the highest reported mean CO conversion at 200 °C, 60.1%, compared with 23.1% for undoped CuMn. XRD, BET, H2-TPR, NH3-TPD, N2O-assisted surface reduction (s-TPR), and XPS were used to compare phase composition and surface properties. Within the Zr series, the 5 mol% sample also had the largest model-derived Cu surface area per catalyst mass, 44.1 m2 g−1, whereas the apparent fractional Cu dispersion was highest at 8 mol% Zr. CO conversion did not increase monotonically with Zr loading, and the higher-conversion 5 mol% sample had larger spent Cu crystallites than undoped CuMn. These comparisons distinguish nominal loading, fractional dispersion, and mass-specific Cu area as separate descriptors when relating composition to WGSR performance. Mechanistic interpretations and long-term durability require further evidence.