Editorial

6 pages, 242 KiB

Open AccessEditorial

Surface Aspects of Semiconductor Photochemistry

by Maria Vittoria Dozzi and Elena Selli

Surfaces 2020, 3(3), 467-472; https://doi.org/10.3390/surfaces3030033 - 02 Sep 2020

Cited by 1 | Viewed by 2032

The Surfaces Special Issue entitled “Surface Aspects of Semiconductor Photochemistry” is mainly devoted to the 7th International Conference on Semiconductor Photochemistry (SP7), which was held on 11–14 September 2019 in Milano, Italy, in the beautiful Renaissance “Ca’ Granda” main building of [...] Read more.

The Surfaces Special Issue entitled “Surface Aspects of Semiconductor Photochemistry” is mainly devoted to the 7th International Conference on Semiconductor Photochemistry (SP7), which was held on 11–14 September 2019 in Milano, Italy, in the beautiful Renaissance “Ca’ Granda” main building of the University Milan [...] Full article

(This article belongs to the Special Issue Surface Aspects of Semiconductor Photochemistry)

Research

Jump to: Editorial, Review

14 pages, 3154 KiB

Open AccessArticle

Ni-Doped Titanium Dioxide Films Obtained by Plasma Electrolytic Oxidation in Refrigerated Electrolytes

by Hamed Arab, Gian Luca Chiarello, Elena Selli, Giacomo Bomboi, Alberto Calloni, Gianlorenzo Bussetti, Guglielmo Albani, Massimiliano Bestetti and Silvia Franz

Surfaces 2020, 3(2), 168-181; https://doi.org/10.3390/surfaces3020013 - 17 Apr 2020

Cited by 7 | Viewed by 2888

Abstract

Porous crystalline Ni-doped TiO₂ films were produced using DC plasma electrolytic oxidation in refrigerated H₂SO₄ aqueous solutions containing NiSO₄. The crystalline phase structure consisted of a mixture of anatase and rutile, ranging from ~30 to ~80 wt [...] Read more.

Porous crystalline Ni-doped TiO₂ films were produced using DC plasma electrolytic oxidation in refrigerated H₂SO₄ aqueous solutions containing NiSO₄. The crystalline phase structure consisted of a mixture of anatase and rutile, ranging from ~30 to ~80 wt % rutile. The oxide films obtained at low NiSO₄ concentration showed the highest photocurrent values under monochromatic irradiation in the UV-vis range, outperforming pure TiO₂. By increasing NiSO₄ concentration above a threshold value, the photoelectrochemical activity of the films decreased below that of undoped TiO₂. Similar results were obtained using cyclic voltammetry upon polychromatic UV-vis irradiation. Glow discharge optical emission spectrometry (GD-OES) analysis evidenced a sulfur signal peaking at the TiO₂/Ti interface. XPS spectra revealed that oxidized Ni²⁺, S⁴⁺ and S⁶⁺ ions were included in the oxide films. In agreement with photocurrent measurements, photoluminescence (PL) spectra confirmed that less intense PL emission, i.e., a lower electron-hole recombination rate, was observed for Ni-doped samples, though overdoping was detrimental. Full article

(This article belongs to the Special Issue Surface Aspects of Semiconductor Photochemistry)

► Show Figures

Graphical abstract

11 pages, 3477 KiB

Open AccessArticle

Multilayer WO₃/BiVO₄ Photoanodes for Solar-Driven Water Splitting Prepared by RF-Plasma Sputtering

by Matteo Pedroni, Gian Luca Chiarello, Espedito Vassallo and Elena Selli

Surfaces 2020, 3(1), 105-115; https://doi.org/10.3390/surfaces3010010 - 13 Mar 2020

Cited by 7 | Viewed by 3350

Abstract

A series of WO₃, BiVO₄ and WO₃/BiVO₄ heterojunction coatings were deposited on fluorine-doped tin oxide (FTO), by means of reactive radio frequency (RF) plasma (co)sputtering, and tested as photoanodes for water splitting under simulated AM 1.5 G [...] Read more.

A series of WO₃, BiVO₄ and WO₃/BiVO₄ heterojunction coatings were deposited on fluorine-doped tin oxide (FTO), by means of reactive radio frequency (RF) plasma (co)sputtering, and tested as photoanodes for water splitting under simulated AM 1.5 G solar light in a three-electrode photoelectrochemical (PEC) cell in a 0.5 M NaSO₄ electrolyte solution. The PEC performance and time stability of the heterojunction increases with an increase of the WO₃ innermost layer up to 1000 nm. A two-step calcination treatment (600 °C after WO₃ deposition followed by 400 °C after BiVO₄ deposition) led to a most performing photoanode under back-side irradiation, generating a photocurrent density of 1.7 mA cm⁻² at 1.4 V vs. SCE (i.e., two-fold and five-fold higher than that generated by individual WO₃ and BiVO₄ photoanodes, respectively). The incident photon to current efficiency (IPCE) measurements reveal the presence of two activity regions over the heterojunction with respect to WO₃ alone: The PEC efficiency increases due to improved charge carrier separation above 450 nm (i.e., below the WO₃ excitation energy), while it decreases below 450 nm (i.e., when both semiconductors are excited) due to electron–hole recombination at the interface of the two semiconductors. Full article

(This article belongs to the Special Issue Surface Aspects of Semiconductor Photochemistry)

► Show Figures

Graphical abstract

12 pages, 3427 KiB

Open AccessArticle

Hydrogenation of ZnFe₂O₄ Flat Films: Effects of the Pre-Annealing Temperature on the Photoanodes Efficiency for Water Oxidation

by Annalisa Polo, Charles R. Lhermitte, Maria Vittoria Dozzi, Elena Selli and Kevin Sivula

Surfaces 2020, 3(1), 93-104; https://doi.org/10.3390/surfaces3010009 - 12 Mar 2020

Cited by 10 | Viewed by 2758

Abstract

The effects induced by post-synthesis hydrogenation on ZnFe₂O₄ flat films in terms of photoelectrochemical (PEC) performance of photoanodes for water oxidation have been deeply investigated as a function of the pre-annealing temperature of the materials. The structure and morphology of [...] Read more.

The effects induced by post-synthesis hydrogenation on ZnFe₂O₄ flat films in terms of photoelectrochemical (PEC) performance of photoanodes for water oxidation have been deeply investigated as a function of the pre-annealing temperature of the materials. The structure and morphology of the films greatly affect the efficacy of the post synthesis treatment. In fact, highly compact films are obtained upon pre-annealing at high temperatures, and this limits the exposure of the material bulk to the reductive H₂ atmosphere, making the treatment largely ineffective. On the other hand, a mild hydrogen treatment greatly enhances the separation of photoproduced charges in films pre-annealed at lower temperatures, as a result of the introduction of oxygen vacancies with n-type character. A comparison between present results and those obtained with ZnFe₂O₄ nanorods clearly demonstrates that specific structural and/or surface properties, together with the initial film morphology, differently affect the overall contribution of post-synthesis hydrogenation on the efficiency of zinc ferrite-based photoanodes. Full article

(This article belongs to the Special Issue Surface Aspects of Semiconductor Photochemistry)

► Show Figures

Graphical abstract

11 pages, 5701 KiB

Open AccessArticle

Citric Acid Regulated Fabrication of Macroporous TiO₂

by Rui Chen, Ningning Shao, Xiaoquan Zhou and Tiehong Chen

Surfaces 2020, 3(1), 50-60; https://doi.org/10.3390/surfaces3010006 - 03 Feb 2020

Cited by 4 | Viewed by 2838

Abstract

Macroporous TiO₂ monolith was prepared by a microphase separation method. After citric acid was added to the synthesis procedure, the yield of the titanium precursor has been significantly increased, and the stability of macroporous structure can be obviously enhanced. Anatase and rutile [...] Read more.

Macroporous TiO₂ monolith was prepared by a microphase separation method. After citric acid was added to the synthesis procedure, the yield of the titanium precursor has been significantly increased, and the stability of macroporous structure can be obviously enhanced. Anatase and rutile phase of TiO₂ were obtained after a 550 °C and 800 °C calcination, respectively. Full article

(This article belongs to the Special Issue Surface Aspects of Semiconductor Photochemistry)

► Show Figures

Figure 1

15 pages, 5880 KiB

Open AccessArticle

Digitally Printed AgNPs Doped TiO₂ on Commercial Porcelain-Grès Tiles: Synergistic Effects and Continuous Photocatalytic Antibacterial Activity

by Claudia Letizia Bianchi, Giuseppina Cerrato, Bianca Maria Bresolin, Ridha Djellabi and Sami Rtimi

Surfaces 2020, 3(1), 11-25; https://doi.org/10.3390/surfaces3010002 - 14 Jan 2020

Cited by 18 | Viewed by 3727

Abstract

In the present study, we use commercial digitally printed ceramic tiles, functionnalized by AgNPs doped micro–TiO₂, to investigate the mechanism of Ag in the continouos photocatalytic antibacterial activity. The novelty of the research lies in the attempt to understand the mechanism [...] Read more.

In the present study, we use commercial digitally printed ceramic tiles, functionnalized by AgNPs doped micro–TiO₂, to investigate the mechanism of Ag in the continouos photocatalytic antibacterial activity. The novelty of the research lies in the attempt to understand the mechanism of Ag, supported on TiO₂, able to exhibit the same antibacterial activity of a standard system containing Ag species, but here, totally embedded on the tile surface, and thus not free to move and damage the bacteria cell. UV/vis diffuse reflectance spectroscopy (DRS) of AgNPs–TiO₂ tiles indicated an enhanced visible light response, wherein a new absorption band was produced around 18,000–20,000 cm⁻¹ (i.e., in the 400–600 nm range) owing to the surface plasmon resonance (SPR) of AgNPs. The antibacterial photocatalytic experiments were conducted towards the inactivation of E. coli under solar light and indoor light. It was found that the degradation speed of E. coli in the presence of AgNPs–TiO₂ tiles is solar light-intensity depending. This justifies the semiconductor behavior of the material. Furthermore, the AgNPs–TiO₂ tiles exhibit a high ability for the inactivation of E. coli at a high load (10⁴–10⁷ colony-forming unit (CFU)/mL). Additionally, AgNPs–TiO₂ tiles showed a remarkable antibacterial activity under indoor light, which confirms the good photocatalytic ability of such tiles. On the basis of the reactive oxygen species (ROS) quenching experiments, O₂^•− species and h⁺ were more reactive for the inactivation of E. coli rather than ^•OH species. This is because of the different lifetime (bacteria are more likely oxidized by ROS with longer lifetime); in fact, O₂^•− and h⁺ exhibit a longer lifetime compared with ^•OH species. The generation of H₂O₂ as the most stable ROS molecule was also suggested. Full article

(This article belongs to the Special Issue Surface Aspects of Semiconductor Photochemistry)

► Show Figures

Graphical abstract

14 pages, 4357 KiB

Open AccessArticle

UV Light Driven Selective Oxidation of Cyclohexane in Gaseous Phase Using Mo-Functionalized Zeolites

by Vincenzo Vaiano and Diana Sannino

Surfaces 2019, 2(4), 546-559; https://doi.org/10.3390/surfaces2040040 - 09 Dec 2019

Cited by 2 | Viewed by 2519

Abstract

Heterogeneous photocatalysis in the gas phase has been applied as a promising technique for organic syntheses in mild conditions. Modified zeolites have been used under UV irradiation as novel photocatalysts. In this study, we preliminarily investigated the photoxidation of cyclohexane on ferrierite and [...] Read more.

Heterogeneous photocatalysis in the gas phase has been applied as a promising technique for organic syntheses in mild conditions. Modified zeolites have been used under UV irradiation as novel photocatalysts. In this study, we preliminarily investigated the photoxidation of cyclohexane on ferrierite and MoO_x-functionalized ferrierite in a gas–solid continuous flow reactor. In the presence of UV light, MoO_x-functionalized ferrierite showed the formation of benzene and cyclohexene as reaction products, indicating the occurrence of photocatalysed cyclohexane oxydehydrogenation. By contrast, unmodified ammonium ferrierite exhibited relevant activity for total oxidation of cyclohexane to carbon dioxide and water. The influence of Mo loading on cyclohexane conversion and products selectivity was evaluated. Full article

(This article belongs to the Special Issue Surface Aspects of Semiconductor Photochemistry)

► Show Figures

Graphical abstract

Review

Jump to: Editorial, Research

21 pages, 3999 KiB

Open AccessReview

Recent Advancements in the Understanding of the Surface Chemistry in TiO₂ Photocatalysis

by Alexander V. Vorontsov, Héctor Valdés, Panagiotis G. Smirniotis and Yaron Paz

Surfaces 2020, 3(1), 72-92; https://doi.org/10.3390/surfaces3010008 - 18 Feb 2020

Cited by 19 | Viewed by 4304

Abstract

Surface chemistry plays a major role in photocatalytic and photoelectrochemical processes taking place with the participation of TiO₂. The synthesis methods, surface characterizations, theoretical research methods, and hardware over the last decade generated opportunities for progress in the surface science of [...] Read more.

Surface chemistry plays a major role in photocatalytic and photoelectrochemical processes taking place with the participation of TiO₂. The synthesis methods, surface characterizations, theoretical research methods, and hardware over the last decade generated opportunities for progress in the surface science of this photocatalyst. Very recently, attention was paid to the design of photocatalysts at the nanoscale level by adjusting the types of exposed surfaces and their ratio, the composition and the surface structure of nanoparticles, and that of individual surfaces. The current theoretical methods provide highly detailed designs that can be embodied experimentally. The present review article describes the progress in the surface science of TiO₂ and TiO₂-based photocatalysts obtained over the last three years. Such aspects including the properties of macro- and nano-scale surfaces, noble-metal-loaded surfaces, doping with Mg and S, intrinsic defects (oxygen vacancies), adsorption, and photoreactions are considered. The main focus of the article is on the anatase phase of TiO₂. Full article

(This article belongs to the Special Issue Surface Aspects of Semiconductor Photochemistry)

► Show Figures

Graphical abstract

Journal Menu

Journal Browser

Surface Aspects of Semiconductor Photochemistry

Share This Special Issue

Special Issue Editors

Special Issue Information

Keywords

Published Papers (8 papers)

Editorial

Research

Review

Further Information

Guidelines

MDPI Initiatives

Follow MDPI