The　intrinsic　nature　of　irreducible　oxides　(e.g.　Al2O3)　makes　it　hard　to　tune　the　charge　state　of　supported　late-transition　metals,　then　difficult　to　adjust　the　selectivity　of　catalysts　in　CO2　hydrogenation.　Herein,　we　find　that　modifying　the　Pd/Al2O3　catalyst　with　alkali　metals　(especially　potassium)　is　efficient　to　boost　the　CO　formation　in　CO2　hydrogenation.　In　comparison　to　Pd/Al2O3,　approximately　twenty-fold　promotion　in　reverse　water–gas　shift　(RWGS)　rate　was　achieved　on　K-modified　catalysts　with　proper　K/Pd　proportions.　Combined　structural　characterizations　demonstrate　that　the　enhanced　Pd-O　interactions　through　K　mediation　stabilize　the　ca.　2　nm　sized　Pd　particles　as　well　as　the　electron-deficient　state　of　Pd,　which　are　robust　enough　during　long-termed　evaluation　with　undamped　performance.　In　situ　spectroscopy　unveils　a　bi-dentate　*HCOO　associated　reaction　mechanism　taking　effect　on　alkali-modified　catalysts,　which　contributes　to　∼　100　%　of　CO　selectivity　and　3318.1　mmol∙gPd-1∙h−1　of　CO　formation　rate　at　340°C.　©　2024　Elsevier　B.V.