The Role of Pt/TiO() Interface in Hydrogen and Water Splitting: A DFT Perspective on Reactivity and Limitations.

The Pt/TiO 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/TiO interface remains a significant challenge. The Pt/TiO() interface was characterized using X-ray diffraction (XRD) with Rietveld refinement analysis, which revealed reflections attributed to Pt-() and anatase TiO(). Theoretical modeling of the Pt/TiO() interface consists of approximately 60% TiO 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 Pt/TiO() showed a new state between the valence and conduction bands, with contributions from the Pt 5 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 and on the Pt surface of the Pt/TiO() interface. The Pt/TiO() interface exhibited the lowest activation energy (0.19 eV) for hydrogen molecule splitting, an exothermic reaction. Both Pt/TiO() interfaces exhibited an activation energy of approximately 1.4 eV for water splitting, an endothermic reaction. Therefore, hydrogen molecule splitting on the Pt surface is favorable, whereas water splitting is not, which may limit the hydrogen production rate (HGR) compared to other catalysts.