Depth-Resolved Redox Heterogeneity in Inverse CeO2/CuO Catalysts for N2O Decomposition

Efficient nitrous oxide (N2O) decomposition relies on coupled redox cycles, yet it remains unclear how deeply into the catalyst these redox changes extend under working conditions and what oxygen-exchange depth is required to sustain turnover. Here we combine inverse CeO2/CuO architectures with depth-resolved X-ray spectroscopy to identify the active redox motif and the operative oxygen-exchange zone. 20 wt % CuO/CeO2 and inverse CeO2/90 wt % CuO catalysts were prepared by flame spray pyrolysis (FSP) and coprecipitation (CP), generating distinct Cu–Ce interfacial structures for N2O conversion. The inverse 90FSP is more active than the conventional 20FSP and coprecipitated 90CP catalysts under the conditions studied. Bulk-sensitive Cu K-edge HERFD-XANES reveals only minor changes in Cu oxidation state under reaction conditions, showing that bulk-averaged Cu redox is not the descriptor for the activity trend. In contrast, surface-sensitive Cu L-edge spectra uncover pronounced, reversible Cu2+/Cu+ cycling that is strongly localized in the surface and subsurface regions and, critically, a sustained surface-subsurface Cu2+/Cu+ redox gradient that is unique to the most active 90FSP catalyst. Mechanistically, this pronounced surface-subsurface Cu2+/Cu+ ratio contrast indicates that N2O-driven surface Cu redox turnover is sufficiently fast that it cannot be fully equilibrated by lattice oxygen exchange (O2– equilibration) with the subsurface. These results identify interface density and temperature-dependent redox depth as a design and diagnostic principle for metal–oxide redox catalysis.