Time-dependent surface polarization breaks static scaling relationship for selective acetylene hydrogenation

Controlling the surface-adsorbates interactions is critical to advancing numerous chemical processes. Static scaling correlations between adsorption energies of chemically related surface species impose limits on selectivity in chemical processes, as exemplified by constraints in heterogeneous catalysis. Here we demonstrate that dynamic surface polarization under oscillating electric potentials can overcome this limitation in Pd-catalysed acetylene semi-hydrogenation. Unlike static polarization, which only imparts a minor improvement to ethylene selectivity, dynamic polarization drastically enhances selectivity without further sacrificing conversion, yielding a high ethylene productivity. Mechanistic insights from hydrogenation kinetics, in situ diffuse reflectance infrared Fourier transform spectroscopy, X-ray absorption spectroscopy and density functional theory reveal that time-dependent polarization dynamically modulates the Pd's electronic structure and adsorption energetics. Alternating between strong-binding states with positive polarization during acetylene hydrogenation and weak-binding states with negative polarization during ethylene formation effectively suppresses over-hydrogenation while maintaining semi-hydrogenation activity. This work establishes dynamic electric surface modulation as a powerful strategy for decoupling adsorption-energy correlations to improve heterogeneous catalysis and other adsorption-mediated processes.