Unveiling Alkali-Induced Redox Modulation: In-Situ Spectroscopic Insights from RWGS on Alkali-Modified ZrO₂-Supported...

Alkali-modified solid catalysts represent a promising class of heterogeneous catalysts for various applications. Despite extensive research, the role of alkali metals remains debated. In this study, Na-modified ZrO₂-supported Cu catalysts are synthesized using different methods for the reverse water-gas shift (RWGS) reaction to elucidate the role of Na⁺. Catalytic results show that activity strongly depends on the preparation method, with the one-pot approach yielding three times higher activity than wet impregnation. The one-pot method significantly enhances Cu⁰ dispersion, preventing the loss of Cu sites due to agglomeration or coverage by Alkali. Although the prevailing view suggests that alkali metals favor the associative mechanism for CO formation. Combined in-situ studies demonstrate that the redox mechanism is the main pathway for CO formation. In-situ EPR and in-situ CO-DRIFTS results indicate that Na⁺ plays a critical role in facilitating the reoxidation of reduced Cu⁰ sites by CO₂ dissociation during the reaction, eventually leading to CO formation. The results show that a high density of accessible Cu⁰ sites with enhanced redox activity is essential for achieving superior catalytic performance. These findings are expected to advance the rational engineering of alkali-modified surfaces, with enriched active sites and finely tuned redox behavior.