Decoupling electronic and geometric effects in Pd catalysts via thermal surface reconstruction for selective hydrogenation.

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.