Second-harmonic generation and theoretical studies of protonation at the water/α-TiO2 (1 1 0) interface

The pH of zero net surface charge (pHpzc) of the α-TiO2 (1 1 0) surface was characterized using second-harmonic generation (SHG) spectroscopy. The SHG response was monitored during a series of pH titrations conducted at three NaNO3 concentrations. The measured pHpzc is compared with a pHpzc value calculated using the revised MUltiSIte Complexation (MUSIC) model of surface oxygen protonation. MUSIC model input parameters were independently derived from ab initio calculations of relaxed surface bond lengths for a hydrated surface. Model (pHpzc 4.76) and experiment (pHpzc 4.8 ± 0.3) agreement establishes the incorporation of independently derived structural parameters into predictive models of oxide surface reactivity.