Visible‐Light Responsive TiO₂‐Based Materials for Efficient Solar Energy Utilization

Abstract

currents, geothermal, biomass, and solar, have been developed as alternatives. Among them, solar energy is the most abundant, inexpensive, nonpolluting, and sustainable. [5][6][7][8] Some semiconductors, so called photocatalysts, which possess the capacity to harvest solar energy to drive catalytic reactions for valuable chemical production, have been designed and fabricated to achieve efficient solar energy utilization. [9][10][11][12][13][14][15][16][17][18][19] Typically, TiO 2 is recognized as one of the most promising candidates due to its chemical stability, nontoxicity, and high resistance to photocorrosion. [20][21][22][23][24][25] In general, TiO 2 possesses three major phases, including anatase, rutile and brookite, and many other minor phases, such as monoclinic TiO 2 (B). All of them have wide bandgaps of 3.0-3.2 eV. Hence, TiO 2 can only absorb ultraviolet light (UV), while the visible light accounting for ≈43% of solar energy cannot be utilized. Furthermore, the rapid recombination of photogenerated electrons and holes severely limits its quantum efficiency. Thus, overall photocatalytic activity of TiO 2 is very limited, especially under visiblelight irradiation. [26][27][28] A complete photocatalytic reaction using TiO 2 -based photocatalysts involves three major steps: i) light absorption and The photocatalytic properties of TiO 2 have aroused a broad range of research interest since 1972 due to its abundance, chemical stability, and easily available nature. To increase its overall activity, in the past few decades, much effort has been devoted to the fabrication of advanced TiO 2 -based photocatalysts with visible-light response and these photocatalysts have shown great potential in the field of solar energy utilization. Here, recent progress in the investigation of visible-light responsive TiO 2 -based materials are reviewed. Notably, the fabrication strategies and corresponding chemical/ physical properties of visible-light responsive TiO 2 -based materials are described in detail, with a focus on bandgap engineering and junction engineering from the perspective of light absorption, charge transfer and separation, and surface reactions. Their applications in solar-fuel production, organic synthesis, bacterial disinfection, pollutant degradation and nitrogen fixation are also discussed. Moreover, the new trends and ongoing challenges in this field are proposed and highlighted.

Interfacial Assembly and Applications of Functional Mesoporous Materials

“…Therefore, a series of mesoporous semiconductors with different mesostructures and compositions have been fabricated (Table ). , …”

“…Therefore, a series of mesoporous semiconductors with different mesostructures and compositions have been fabricated (Table 3). 338,339 As a typical one, mesoporous TiO 2 has been a promising candidate for photocatalyst benefiting from its intrinsic properties such as natural abundance, environmental friendliness, excellent chemical stability, low cost, plentiful polymorphs, and good optical performances. 361,362 A series of functional mesoporous TiO 2 -based photocatalysts have been fabricated via the interfacial assembly in the past few decades, and their performance still is greatly influenced by the wide bandgap and low quantum efficiencies.…”

Assembly of a Titanium-Oxo Cluster and a Bismuth Iodide Cluster, a Single-Source Precursor of a p–n-Type Photocatalyst

“…However, its applications are limited in the ultraviolet solar energy region for the wide band gap of TiO 2 . Therefore, numerous challenges to developing visible light-driven TiO 2 materials with high photoabsorption efficiency have been overcome through metal or non-metal doping, − dye sensitizing, − and designing nanostructured heterojunctions with other semiconductors. − Physically or chemically modulated TiO 2 , in particular nano TiO 2 , has been proven to be an efficient photocatalyst for versatile applications in splitting water, degradation of organic pollutants, solar cells, and other photoelectronic devices. − …”

Heterostructure-Induced Light Absorption and Charge-Transfer Optimization of a TiO2 Photoanode for Photoelectrochemical Water Splitting

“…Conversion of solar energy into chemical fuels is an effective strategy to relieve the environmental and energy crises and meet the growing energy demand. , Photoelectrochemical (PEC) water splitting has been considered an attractive strategy for producing renewable hydrogen from water. , Generally, the PEC water splitting process involves three steps . First, the semiconductor layer absorbs photons and generates photoexcited electron–hole pairs.…”