Abstract
The entangled electronic and geometric effects in heterogeneous catalysis have long obscured precise attribution of their individual roles. By employing a thermal-induced surface reconstruction strategy to progressively enhance metal-support interactions, we achieve continuous tuning of Pd's electronic and geometric structures. Using alkyne semi-hydrogenation as a prototypical structure-sensitive probe reaction, we demonstrate that despite the linear coupling of electronic and geometric structures during Pd reconstruction, the turnover frequency scales solely with the geometric descriptor W (quantifying Pd particle flattening), while selectivity regulation bifurcates into two distinct regimes: Below a critical W, electron-deficient Pd sites offset geometric constraints, yielding a non-structure-sensitive selectivity plateau; whereas above this threshold, electron-rich surfaces establish unequivocal geometric control. Moreover, surface reconstruction drastically shrinks the electronic-geometric space of Pd sites for over-hydrogenation side reaction. These insights provide a blueprint for metal catalysts regulation in hydrogenation and may open avenues for quantifying electronic-geometric interplay in other structure-sensitive reactions.