Tailoring Pt-CeO 2 Interactions to Bypass Activity-Selectivity Trade-Off for C 2 H 2 Semi-Hydrogenation

CeO 2 -supported platinum-group metals with small nanoparticles allow fine-tuning of their electronic properties through enhanced electronic interactions with the support. Here, we modify the electronic properties of a Pt/CeO 2 catalyst with 1.5 nm Pt nanoparticles by varying the near-surface oxygen vacancy concentration. In-situ infrared, X-ray photoelectron, and X-ray absorption spectroscopies show that roomtemperature oxidation followed by re-reduction at 100 o C decreases near-surface oxygen vacancies by ∼3-fold without altering Pt size, resulting in ∼25-fold increase in C 2 H 2 hydrogenation turnover frequency while C 2 H 4 selectivity remains unchanged at ∼90%. These findings are exceptional for C 2 H 2 semi-hydrogenation since C 2 H 4 selectivity typically decreases with increasing C 2 H 2 activity due to the well-known linear scaling relationship and Brønsted-Evans-Polanyi relation. X-ray absorption spectroscopy and density functional theory calculations reveal that lowering subsurface oxygen vacancy concentration unevenly depletes Pt d -electron density, altering projected density of states exclusively for apex Pt sites. Competitive adsorption modeling reveals that apex Pt sites preferentially adsorb C 2 H 2 , while basal Pt sites favor C 2 H 4 , leading to a stronger effect on C 2 H 2 binding and resulting in the observed deviation from the typical activity-selectivity trade-off. Our study demonstrates that tailoring Pt-CeO 2 interactions enables site- and molecule-specific adsorption modulation to overcome the conventional activity–selectivity trade-off.