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

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.