The Pros and Cons of Polydopamine-Sensitized Titanium Oxide for the Photoreduction of CO2

Abstract

Photocatalytic reduction of CO 2 into fuels is a promising route to reduce greenhouse gas emission, and it demands high-performance photocatalysts that can use visible light in the solar spectrum. Due to its broadband light adsorption, polydopamine (PDA) is considered as a promising photo-sensitization material for semiconductor photocatalysts. In this work, titanium oxides have been coated with PDA through an in-situ oxidation polymerization method to pursue CO 2 reduction under visible light. We have shown that the surface coated PDA with a thickness of around 1 nm can enhance the photocatalytic performance of anatase under visible light to reduce CO 2 into CO. Assisted with additional UV-vis adsorption and photoluminescence characterizations, we confirmed the sensitization effect of PDA on anatase. Furthermore, our study shows that thicker PDA coating might not be favorable, as PDA could decompose under both visible and UV-vis light irradiations. 13 C solid-state nuclear magnetic resonance showed structural differences between thin and thick PDA coatings and revealed compositional changes of PDA after light irradiation.

Characterization and Effect of Ag(0) vs. Ag(I) Species and Their Localized Plasmon Resonance on Photochemically Inactive TiO2

“…Therefore, much effort has been focused on enhancing the photocatalytic activity of TiO 2 , including doping with metal or non-metal species [17,18], surface sensitization [19,20], and noble metal deposition [21][22][23][24][25]. In particular, the noble metal deposition has attracted a lot of attention since it can improve e − -h + separation and enhance the semiconductor's absorption in the visible light region [26,27].…”

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).…”

“…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]. Six other papers focus on conventional catalysis ("dark" reactions), reporting efficient H 2 production [28,29], synthesis of ethanol and butanol [30], direct conversion of CO 2 and methanol to dimethyl carbonate [31], water purification [32], and advanced characterization of catalysts by X-ray absorption fine structure (EXAFS) spectroscopy [33].…”

“…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.…”

“…They reported visible light activity of this material towards CO 2 reduction under a simulated flue gas system. Visible light-induced photoreduction of CO 2 was also conducted with polydopamine-sensitized TiO 2 by Wang et al [27]. The successful titania modifications with D-glucose was achieved by Markowska-Szczupak et al [24], where the photocatalytic activities of suspended and immobilized photocatalysts were compared.…”