Synergistic Effect of Cu2O and Urea as Modifiers of TiO2 for Enhanced Visible Light Activity

Abstract

Low cost compounds, i.e., Cu 2 O and urea, were used as TiO 2 modifiers to introduce visible light activity. Simple and cheap methods were applied to synthesize an efficient and stable nanocomposite photocatalytic material. First, the core-shell structure TiO 2-polytriazine derivatives were prepared. Thereafter, Cu 2 O was added as the second semiconductor to form a dual heterojunction system. Enhanced visible light activity was found for the above-mentioned nanocomposite, confirming a synergistic effect of Cu 2 O and urea (via polytriazine derivatives on titania surface). Two possible mechanisms of visible light activity of the considered material were proposed regarding the type II heterojunction and Z-scheme through the essential improvement of the charge separation effect.

Nanomaterials for Environmental Purification and Energy Conversion

“…Most papers discussed photocatalytic reactions on nanomaterials (heterogeneous photocatalysis). Titania (titanium(IV) oxide, TiO 2 ) is one of the most well-known and widely studied photocatalysts, due to its advantages, such as high activity, stability, low-cost, and nontoxicity (excluding toxicity of nanomaterials), as also confirmed in this issue (seven papers [17][18][19]21,24,26,27]). However, titania has two main shortcomings, i.e., recombination of charge carriers (typical for all semiconductors) and inactivity under visible light irradiation (due to wide bandgap).…”

“…In this study, it was shown for the first time that titania modification with monosaccharides could be efficient for water disinfection, and the immobilization of the photocatalyst on the concrete discs might be a prospective method for public water supplies and water storage tanks (as exemplified for a home aquarium in Figure 2a). The synergistic effect was observed by Janczarek et al for titania bi-modification with urea (formed poly(amino-s-triazine) [35]) and Cu 2 O [19]. Two types of possible mechanisms of visible light activity were proposed, i.e., the type II heterojunction and Z-scheme.…”

“…Accordingly, the Special Issue "Nanomaterials for Environmental Purification and Energy Conversion" is a collection of 17 papers, including 16 research papers and one review. Eleven papers present heterogeneous photocatalysis for efficient degradation of organic pollutants (phenol [17,18], 2-propanol [19], dyes [20][21][22], humic acid [23]), inactivation of microorganisms (Escherichia coli, Staphylococcus epidermidis [24], Bacillus subtilis, and Clostridium sp. [18]), H 2 evolution [25], and CO 2 reduction [26,27].…”

“…The comprehensive review by Giovannetti et al on recent advances in graphene-based TiO 2 nanocomposites for synthetic dye degradation shows the increasing potential of titania photocatalysts based on graphene matrix, in the field of extending the light absorption of TiO 2 from UV into the visible light range of radiation [21]. In this regard, the idea of titania modification is strongly present in the papers collected in the issue, e.g., titania surface modification with copper oxides (Cu 2 O [19] and Cu x O y [18]), organic compounds (glucose [24] and urea [19]), polymers (polydopamine [27]), graphene [21], carbon/nitrogen [17], and titania doping (self-doped or hydrogenated) [34]. All kinds of modifications resulted in enhanced activity under either UV, visible light or solar radiation.…”

Morphology-Governed Performance of Plasmonic Photocatalysts

“…The recombination results in an obvious decrease in photocatalytic efficiency, reaching quantum yields much lower than expected 100%. Accordingly, various methods have been proposed to limit this recombination [6], including properties' improvements, e.g., higher crystallinity, less defects' content, perfect crystal morphology (faceted particles) [7][8][9][10][11], larger content of shallow than deep electron traps (ETs) [12]), and various modifications, e.g., doping [13][14][15], surface modifications [16][17][18][19], heterojunction formation (coupled semiconductors) [20][21][22]. One of the most efficient methods to inhibit the charge carriers' recombination is the surface modification of photocatalyst with deposits of noble metals, because noble metals work as an electrons' scavenger ( Figure 1b) because of larger work function of metals than the electron affinity of oxide semiconductors, as first found for platinum-modified titania almost half century ago by Bard [23].…”