Periodic DFT Study of Rutile IrO₂: Surface Reactivity and Catechol Adsorption

IrO 2 is a key material for photocatalytic applications as water oxidation catalyst. Despite its increasing interest, little is known about its molecular structure and reactivity. In this study, the surface properties of stoichiometric rutile IrO 2 are investigated by means of periodic density functional theory (DFT), including the structural, energetic, electronic properties, and chemical reactivity toward catechol, a probe molecule mimicking photocatalytic linkers. Our results show that the (110)-IrO 2 rutile termination is the most stable, and we discuss the role of the number and type of surface sites in the relative stability compared with (100), (001), and (101) terminations. Regarding the reactivity of the surfaces with catechol, our results show that the molecule dissociates and binds in bidentate, chelate, and monodentate modes. Interestingly, we find the chelated mode selectively favored over the (001) termination with the highest adsorption energy, −3.93 eV, being unstable on other terminations. The bidentate mode is preferred on (110) −3.83 eV, (100) −3.24 eV, and (101) −2.23 eV. The selective stabilization of the chelated mode, suggested in the literature to be responsible for the optical absorption in TiO 2 nanoparticles, could guide in the search of tailored iridia-based interfaces for photocatalytic applications.