Abstract
Clean water and the increased use of renewable energy are considered to be two of the main goals in the effort to achieve a sustainable living environment. The fulfillment of these goals may include the use of solar-driven photocatalytic processes that are found to be quite effective in water purification, as well as hydrogen generation. H2 production by water splitting and photocatalytic degradation of organic pollutants in water both rely on the formation of electron/hole (e−/h+) pairs at a semiconducting material upon its excitation by light with sufficient photon energy. Most of the photocatalytic studies involve the use of TiO2 and well-suited model compounds, either as sacrificial agents or pollutants. However, the wider application of this technology requires the harvesting of a broader spectrum of solar irradiation and the suppression of the recombination of photogenerated charge carriers. These limitations can be overcome by the use of different strategies, among which the focus is put on the creation of heterojunctions with another narrow bandgap semiconductor, which can provide high response in the visible light region. In this review paper, we report the most recent advances in the application of TiO2 based heterojunction (semiconductor-semiconductor) composites for photocatalytic water treatment and water splitting. This review article is subdivided into two major parts, namely Photocatalytic water treatment and Photocatalytic water splitting, to give a thorough examination of all achieved progress. The first part provides an overview on photocatalytic degradation mechanism principles, followed by the most recent applications for photocatalytic degradation and mineralization of contaminants of emerging concern (CEC), such as pharmaceuticals and pesticides with a critical insight into removal mechanism, while the second part focuses on fabrication of TiO2-based heterojunctions with carbon-based materials, transition metal oxides, transition metal chalcogenides, and multiple composites that were made of three or more semiconductor materials for photocatalytic water splitting.
Highlights
Nowadays, accessible clean water and energy resources are among the highest priorities for sustainable economic growth and societal wellbeing
A similar improvement was obtained by comparing performances of the same materials in the case of DCF degradation [67] (Table 6). The reason for such improvement relies on the potential of photogenerated e− in conduction band band (CB) of SnS2 to migrate to CB of TiO2, while h+ remained at the valence band (VB) of SnS2
The as-prepared composite showed high hydrogen evolution rate (HER) of 129 μmol/h/g under visible light, which can be attributed to the efficient charge separation in the constructed Z-scheme system, the broadened visible-light response range, owing to the surface plasmon resonance (SPR) effects on
Summary
Accessible clean water and energy resources are among the highest priorities for sustainable economic growth and societal wellbeing. H2 production by water splitting and photocatalytic degradation of organic pollutants in water both rely on the formation of electron/hole (e- /h+ ) pairs at a semiconducting material upon its excitation by light with sufficient photon energy [9,10,11,12] These processes, which can be conducted under environmentally friendly and mild conditions, are economically viable, possessing a potential of becoming effective methods to produce clean energy and water, owing to their low-cost, long-term stability, and usage of solar energy [13]. Thematerials, second part targets the mostoxides, recent transition metal chalcogenides, and multiple composites that were made of three or more achievements in the field of fabrication of TiO2 -based heterojunctions with carbon based materials, semiconductor materials for photocatalytic water splitting. Transition metal oxides, transition metal chalcogenides, and multiple composites that were made of three or more semiconductor materials for photocatalytic water splitting
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