TiO₂ Nanotube Arrays Modified with Cr‐Doped SrTiO₃ Nanocubes for Highly Efficient Hydrogen Evolution under Visible Light

Abstract

In recent decades, solar-driven hydrogen production over semiconductors has attracted tremendous interest owing to the global energy and environmental crisis. Among various semiconductor materials, TiO2 exhibits outstanding photocatalytic properties and has been extensively applied in diverse photocatalytic and photoelectric systems. However, two major drawbacks limit practical applications, namely, high charge-recombination rate and poor visible-light utilization. In this work, heterostructured TiO2 nanotube arrays grafted with Cr-doped SrTiO3 nanocubes were fabricated by simply controlling the kinetics of hydrothermal reactions. It was found that coupling TiO2 nanotube arrays with regular SrTiO3 nanocubes can significantly improve the charge separation. Meanwhile, doping Cr cations into SrTiO3 nanocubes proved to be an effective and feasible approach to enhance remarkably the visible-light response, which was also confirmed by theoretical calculations. As a result, the rate of photoelectrochemical hydrogen evolution of these novel heteronanostructures is an order of magnitude larger than those of TiO2 nanotube arrays and other previously reported SrTiO3 /TiO2 nanocomposites under visible-light irradiation. Furthermore, the as-prepared Cr-doped SrTiO3 /TiO2 heterostructures exhibit excellent durability and stability, which are favorable for practical hydrogen production and photoelectric nanodevices.

One‐dimensional TiO2 Nanotube Photocatalysts for Solar Water Splitting

“…Moreover, Sr doping of TiO 2 nanotubes showed a red shift in the absorption edge, which resulted in an electrode photoconversion efficiency of 0.69%, more than 3 times higher than that of the undoped nanotube arrays (0.2%) under the same conditions. Additionally, metallic elements such as Nb, Cr are usually doped into TiO 2 /SrTiO 3 nanotubular heterostructures to enhance their photoelectrocatalytic activities 222, 223. For example in the SrTiO 3 /TiO 2 composites, the electrons of pure SrTiO 3 can only be excited from the valence band (O 2p) to the conduction band (Ti 3d) by photons with energy greater than 3.2 eV.…”

Photochemical charge transfer observed in nanoscale hydrogen evolving photocatalysts using surface photovoltage spectroscopy

“…17,[21][22][23][24][25][26][27][28] As a model system we use single crystalline nanoparticles of Rh-doped SrTiO 3 . SrTiO 3 is an established photocatalyst for overall water splitting under UV light only, 18,21,[29][30][31] but it can be converted into a visible light responsive material upon doping with Cr, 32 Cr/Sb, 33,34 Cr/Ta, 35 Rh, 36,37 Ni/Ta, 38 and…”

Hydrogenated TiO2/SrTiO3 porous microspheres with tunable band structure for solar-light photocatalytic H2 and O2 evolution

“…The visible-light photocatalytic performance of a catalyst strongly depends on the nature of the catalyst in terms of defect states, components, etc. Various strategies have been proposed to shift the photoabsorption region of wide-band-gap photocatalysts toward the visible-light region, such as doping with metals (e.g., Cr or Fe) and nonmetal ions (e.g., N or S) [15][16][17][18][19] or coupling with other narrow-band-gap semiconductors [20,21]. Furthermore, recent studies have shown that, through the partial reduction method, semiconductors modified by hydrogen treatment (e.g., TiO2 and CeO2) present oxygen vacancies and exhibit visible-light response for robust charge generation [22][23][24].…”