TiO₂ Facets Shaped by Concentration-Dependent Surface Diffusion of Dopamine

Facet engineering highlights the fundamental understanding of kinetic growth of facets with capping agents. Here, we provide a roadmap for modulating TiO₂ facets using dopamine as a capping agent inspired by density functional theory calculations and molecular dynamics simulations. Our calculations revealed that the surface diffusion of dopamine and their facet-specific affinity direct the kinetic growth of TiO₂{100} and {101} facets into a nonequilibrium crystal shape. Our TiO₂ synthesis agreed well with the theoretical predictions, suggesting that the concentration-dependent diffusion is central in accurately tuning a desirable ratio of mixed facets. Our findings shed new light on the diffusion-limited kinetically controlled facet growth mechanism, and this fine-tuning of mixed facets on a single crystal provides a general approach to design and fabricate facets on metal oxides.