Facet-Dependent Photoelectrochemical Performance of TiO₂ Nanostructures: An Experimental and Computational Study

Abstract

The behavior of crystalline nanoparticles depends strongly on which facets are exposed. Some facets are more active than others, but it is difficult to selectively isolate particular facets. This study provides fundamental insights into photocatalytic and photoelectrochemical performance of three types of TiO(2) nanoparticles with predominantly exposed {101}, {010}, or {001} facets, where 86-99% of the surface area is the desired facet. Photodegradation of methyl orange reveals that {001}-TiO(2) has 1.79 and 3.22 times higher photocatalytic activity than {010} and {101}-TiO(2), respectively. This suggests that the photochemical performance is highly correlated with the surface energy and the number of under-coordinated surface atoms. In contrast, the photoelectrochemical performance of the faceted TiO(2) nanoparticles sensitized with the commercially available MK-2 dye was highest with {010}-TiO(2) which yielded an overall cell efficiency of 6.1%, compared to 3.2% for {101}-TiO(2) and 2.6% for {001}-TiO(2) prepared under analogous conditions. Measurement of desorption kinetics and accompanying computational modeling suggests a stronger covalent interaction of the dye with the {010} and {101} facets compared with the {001} facet. Time-resolved THz spectroscopy and transient absorption spectroscopy measure faster electron injection dynamics when MK-2 is bound to {010} compared to other facets, consistent with extensive computational simulations which indicate that the {010} facet provides the most efficient and direct pathway for interfacial electron transfer. Our experimental and computational results establish for the first time that photoelectrochemical performance is dependent upon the binding energy of the dye as well as the crystalline structure of the facet, as opposed to surface energy alone.

Roles of Crystal Surface in Pt-Loaded Titania for Photocatalytic Conversion of Organic Pollutants: A First-Principle Theoretical Calculation

“…64 Moreover, the first-principles studies also indicate that the adsorption of gold on TiO 2 (001) is much stronger than that on the (101) surface. 19 In addition, TiO 2 /graphene composites have a higher photocatalytic activity compared with the P25 under UV light due to the effective exposure of highly reactive (001) surface.…”

Flow-Based Surface Decoration of Microparticles with Titania and Other Transition Metal Oxide Nanoparticles

“…To demonstrate that these materials are suitable for catalytic applications, we used them as a catalyst for the photodegradation of MO, a dye commonly used in such studies [36]. Importantly for photocatalysis, the TiO 2 on these particles is predominantly anatase (see above), which performs better as a photocatalyst compared to other phases due to slower charge recombination and greater electron mobility [36][37][38].…”

“…Importantly for photocatalysis, the TiO 2 on these particles is predominantly anatase (see above), which performs better as a photocatalyst compared to other phases due to slower charge recombination and greater electron mobility [36][37][38]. To showcase the dimensions of the composite particles -relatively large compared to the TiO 2 nanocrystals themselves -we ran these experiments in a miniature packed-bed reactor.…”

Dissimilar anisotropy of electron versus hole bulk transport in anatase TiO2 : Implications for photocatalysis

“…In this regard, the work of Yang et al [11] is greatly noteworthy: they, for the first time, demonstrated that morphological control was possible using hydrofluoric acid as a shape-controlling agent. This work enables a variety of particle shapes to be tested in PC and to be compared in terms of activities [12][13][14][15][16][17]. These experiments have led to the interesting consensus that reduction and oxidation reactions preferably occur on different facets, i.e., reductions on (100)/(101) and oxidations on (001), respectively; now, these results require a fundamental understanding of their origin.…”