Atomic-level design of Pt-Pd dual sites on TiO2: Overcoming single-atom limitations for enhanced photocatalysis

Photocatalytic technology, as an environmentally friendly and sustainable approach for hydrogen production, demonstrates significant market potential，where bimetallic single-atom catalysts (SACs) demonstrate superior performance compared to monometallic counterparts through heteronuclear synergistic effects, establishing them as a critical research focus in modern catalytic science. In this investigation, TiO₂ nanosheets were employed as catalytic supports, with oxygen vacancy defects being strategically introduced via H₂-Ar atmosphere thermal reduction to immobilize both monometallic Pt and bimetallic Pt-Pd single atoms. The hydrogen evolution rates were quantified as 1956.45 μmol·h⁻¹ ·g cat ⁻¹ for Pt-loaded catalysts and 3522.65 μmol·h⁻¹ ·g cat ⁻¹ for Pt-Pd-loaded systems, corresponding to 72.3-fold and 130.2-fold improvements relative to unmodified TiO₂. This performance enhancement is attributed to optimized charge carrier separation facilitated by oxygen vacancies and the complementary electronic interactions between Pt and Pd atoms in bimetallic configurations, which collectively promote efficient surface reactions and hydrogen generation kinetics. The remarkable advantages of bimetallic systems in photocatalytic hydrogen evolution are demonstrated through these findings, with Density Functional Theory (DFT) revealing that Pd incorporation not only modulates charge density and band structure through its role as a cocatalyst but also actively participates in the hydrogen evolution reaction as catalytic sites. The formation of Ti-Pt-Ti and Ti-Pd-Ti configurations is observed to effectively reduce reaction energy barriers while suppressing competitive adsorption at isolated metal sites, resulting in enhanced catalytic performance. A strategy for designing efficient photocatalysts is established through this work, supported by mechanistic insights into energy barrier reduction and adsorption regulation, which provides critical theoretical foundations with both scientific and practical significance.