The Role of Pt₃/TiO₂(h K l) Interface in Hydrogen and Water Splitting: A DFT Perspective on Reactivity and Limitations

The Pt/TiO2 interface has shown promise as a photocatalyst for hydrogen evolution reactions (HER). However, understanding hydrogen and water splitting reactions on the Pt surface of the Pt/TiO2 interface remains a significant challenge. The Pt3/TiO2(h k l) interface was characterized using X-ray diffraction (XRD) with Rietveld refinement analysis, which revealed reflections attributed to Pt(1 1 1) and anatase TiO2(h k l). Theoretical modeling of the Pt3/TiO2(h k l) interface consists of approximately 60% TiO2 and 40% Pt, as determined by Rietveld refinement. The electronic properties were obtained using density functional theory (DFT)/plane-wave calculations on a model consisting of 39 atoms. The band structure and projected density of states (PDOS) of Pt3/TiO2(h k l) showed a new state between the valence and conduction bands, with contributions from the Pt 5d state, indicating metallic behavior. The initial steps of hydrogen and water splitting, as well as the transition states, were determined using the nudged elastic band (NEB) method for the reactions H2→Hads*+Hads* and H2Oads→OHads*+Hads* on the Pt3 surface of the Pt3/TiO2(h k l) interface. The Pt3/TiO2(1 0 1) interface exhibited the lowest activation energy (0.19 eV) for hydrogen molecule splitting, an exothermic reaction. Both Pt3/TiO2(h k l) interfaces exhibited an activation energy of approximately 1.4 eV for water splitting, an endothermic reaction. Therefore, hydrogen molecule splitting on the Pt3 surface is favorable, whereas water splitting is not, which may limit the hydrogen production rate (HGR) compared to other catalysts.