Effects of Matching Facet Pairs of TiO₂ on Photoelectrochemical Water Splitting Behaviors

Abstract

Engineering crystal facets have been proved as one of the most promising strategies for promoting photocatalytic performance of titanium dioxide (TiO2). The earlier research in this field focused on trying to obtain as high ratio of the high energy {001} facet as possible, while later found that the co‐existence of facets is more beneficial. However, controlling crystals to expose suitable facet pairs and facet ratios remains challenging. In this work, we not only comprehensively match possible low‐index facets such as {101}‐{001} and {010}‐{001} facet pairs, but also systematically tune their ratios. Moreover, these faceted particles can be directly grown onto the transparent conductive substrate, which can be directly used as a photoanode. So, their intrinsic behaviors can be precisely evaluated without interference from other exogenous factors such as binders, additives, or assembly skills. Various characterization techniques reveal that both the types of facet pairs and the ratios of facets play crucial roles on photocatalytic behaviors, due to the different electron affinity and dissociative adsorption ability of water molecules on a particular facet. Charge transport and surface chemistry have been thoroughly investigated to identify the underlying mechanism. This work sheds light on a material design strategy considering a suitable match of facet pairs for optimizing photocatalytic performance for a wide variety of applications.

Three-Dimensional Hierarchical Porous TiO2 for Enhanced Adsorption and Photocatalytic Degradation of Remazol Dye

“…Among semiconductor photocatalysts, titanium dioxide (TiO 2 ) has been widely used in photocatalytic degradation of pollutants because of its respectable photocatalytic properties, chemical and biological inertness, no secondary pollution, and low cost [ 6 , 11 ]. There have been numerous reports about using TiO 2 and its composites in various photocatalytic environmental remediations such as waste degradation [ 1 , 11 , 12 , 13 ], water and air purification [ 7 , 11 , 14 ], carbon dioxide reduction [ 15 , 16 , 17 , 18 ], conversion of biomass-derived wastes to valuable chemicals [ 19 , 20 , 21 ], and photocatalytic water splitting for alternative hydrogen energy [ 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 ]. However, the main drawbacks of unmodified TiO 2 are the undesirable recombination of electrons and holes, the low efficiency under visible light irradiation, and the limited adsorption of dyes on the catalyst’s surface.…”

Enhanced Water Splitting Reaction Performance using TiO2 Deposited with Graphene Quantum Dots Grafted onto Gold Nanoparticles

“…Several types of photoanode have been used in PEC water splitting reactions, such as titanium dioxide (TiO 2 ), [2][3][4] graphitic carbon nitride (gÀ C 3 N 4 ), [5][6][7] and heterojunction catalysts. [8][9] Particularly, TiO 2 has been used extensively due to its high chemical/thermal stability.…”

“…[13][14] Owing to the cooperative effect between oxidative and reductive surfaces on the TiO 2 itself, TiO 2 with coexposed {001}-{010} facet has been used as an effective photoanode in solar driven photocatalytic water splitting reactions. [4,15] However, some studies have shown that improvement in PEC performance of the TiO 2 based photocatalyst via incorporation of {001} was not always the case. [4,13] The discrepancies depend on the ratio of {001} compared to other facets in the TiO 2 particles.…”

“…[4,15] However, some studies have shown that improvement in PEC performance of the TiO 2 based photocatalyst via incorporation of {001} was not always the case. [4,13] The discrepancies depend on the ratio of {001} compared to other facets in the TiO 2 particles. In addition, based on density functional theory (DFT) calculations, the different electron affinity which is the ability to attract electrons of each facet can strongly affect the dissociative absorption ability of water molecules on the catalyst and the charge separation efficiency of the system.…”

“…In addition, based on density functional theory (DFT) calculations, the different electron affinity which is the ability to attract electrons of each facet can strongly affect the dissociative absorption ability of water molecules on the catalyst and the charge separation efficiency of the system. [4] Ideally, the photoexcited electrons should be accumulated at {010} surface for reduction and the holes density should be high on {001} surface for oxidation. In addition, theses photogenerated charges should be separated effectively, overcoming the electron affinity effect and completely consumed during the redox reaction.…”