72 research outputs found
TiO2 Photocatalysis for the Transformation of Aromatic Water Pollutants into Fuels
The growing world energy consumption, with reliance on conventional energy sources and the associated environmental pollution, are considered the most serious threats faced by man-kind. Heterogeneous photocatalysis has become one of the most frequently investigated technolo-gies, due to its dual functionality, i.e., environmental remediation and converting solar energy into chemical energy, especially molecular hydrogen. H2 burns cleanly and has the highest gravimetric gross calorific value among all fuels. However, the use of a suitable electron donor, in what so-called âphotocatalytic reformingâ, is required to achieve acceptable efficiency. This oxidation half-reaction can be exploited to oxidize the dissolved organic pollutants, thus, simultaneously improving the water quality. Such pollutants would replace other potentially costly electron donors, achieving the dual-functionality purpose. Since the aromatic compounds are widely spread in the environment, they are considered attractive targets to apply this technology. In this review, different aspects are highlighted, including the employing of different polymorphs of pristine titanium dioxide as pho-tocatalysts in the photocatalytic processes, also improving the photocatalytic activity of TiO2 by loading different types of metal co-catalysts, especially platinum nanoparticles, and comparing the effect of various loading methods of such metal co-catalysts. Finally, the photocatalytic reforming of aromatic compounds employing TiO2-based semiconductors is presented
Solar and Visible Light Driven Photocatalysis for Sacrificial Hydrogen Generation and Water Detoxification with Chemically Modified Ti02
Photocatalysis is a recognized approach where light energy is employed to excite the semiconductor material producing electron/hole pair which eventually involves in the detoxification of pollutants and/or water splitting producing hydrogen. Existing photocatalysts suffer from poor activity or no activity in visible light irradiation which restricts them from solar light utilization. This work is focused on two key applications of photocatalysis (i) sacrificial hydrogen generation, and (ii) phenol degradation in visible and/or solar light. Platinum was loaded on TiO2 photocatalyst by solar photo-deposition method. Eosin Y dye was used as a sensitizer for sensitization of platinum loaded TiO2 photocatalyst. The photocatalyst was irradiated from the top with a solar simulator. The light source was equipped with AM 1.5 G as well as a 420 nm cutoff filter to remove all the UV light. A factorial design at two levels and four factors has been carried out in order to investigate the potential for hydrogen generation using Eosin Y-sensitized TiO2/Pt catalyst under visible solar light in presence of triethanolamine as electron donor. Experimental data were analyzed using both âPareto analysisâ as well as conventional regression analysis techniques. A regression function was proposed that satisfactorily predicts hydrogen generation as a function of various operating parameters. Later, the photocatalytic behavior of the eosin Yâsensitized photocatalyst was studied in solar-UV (300-388 nm), solar-visible (420-650 nm) and full solar spectrum (300-650 nm) to explore the optimum reaction conditions such as (i) light intensity (100 mW cm-2), (ii) solution pH (7.0), (iii) platinum content (wt %) on TiO2 (0.25 %), (iv) mass of eosin Y-TiO2/ Pt (1-1.3 g L-1) , (v) concentration of trietanolamine (0.25 M), and (vi) mass ratio of eosin Y to TiO2/Pt (1:10). The reaction mechanisms were different in solar and visible lights, although in both cases formaldehyde was detected as an intermediate product.
Studies in a pulsating flow reactor showed positive effects of pre-sonication, increased flow rate and bi-directional mixing mode in solar hydrogen generation. A detailed study on the photocatalytic behavior of formaldehyde for sacrificial hydrogen generation was performed for better understanding of the process. Photocatalytic hydrogen generation from formaldehyde was influenced by solution pH, platinum content (wt %) on TiO2, catalyst concentration, light intensity, and initial formaldehyde concentration. A Langmuir-type model was well fitted with the experimental data for photocatalytic hydrogen generation from both triethanolamine and formaldehyde as sacrificial agents. Apparent quantum yield (QY) was much higher for UV light driven hydrogen generation. In solar and visible light the QYs were a function of the light intensity and the wavelength range considered for the calculation. Phenol degradation with eosin Y-sensitized TiO2/Pt photocatalyst under solar-visible light was performed with triethanolamine as electron donor. About 93 % degradation of 40 ppm phenol solution was achieved within 90 minutes using Eosin Y-TiO2/Pt photocatalyst at optimum conditions (pH = 7.0, catalyst loading = 0.8 g L-1, triethnolamine concentration = 0.2 M, 0.5 % Pt loading on TiO2, visible solar light of 100 mW cm-2). Kinetic rate constant and adsorption equilibrium constant were determined and a Langmuir-Hinshelwood type equation was proposed to describe phenol degradation on TiO2 at different visible light intensities. The model equation predicts experimental results quite well
Recent Developments in Environmental Photocatalytic Degradation of Organic Pollutants: The Case of Titanium Dioxide NanoparticlesâA Review
The presence of both organic and inorganic pollutants in water due to industrial, agricultural, and domestic activities has led to the global need for the development of new, improved, and advanced but effective technologies to effectively address the challenges of water quality. It is therefore necessary to develop a technology which would completely remove contaminants from contaminated waters. TiO2 (titania) nanocatalysts have a proven potential to treat âdifficult-to-removeâ contaminants and thus are expected to play an important role in the remediation of environmental and pollution challenges. Titania nanoparticles are intended to be both supplementary and complementary to the present water-treatment technologies through the destruction or transformation of hazardous chemical wastes to innocuous end-products, that is, CO2 and H2O. This paper therefore explores and summarizes recent efforts in the area of titania nanoparticle synthesis, modifications, and application of titania nanoparticles for water treatment purposes
Degradation of emerging contaminants using metal organic frameworks (MOFs) by photocatalysis
Tesis Doctoral inĂ©dita leĂda en la Universidad AutĂłnoma de Madrid, Facultad de Ciencias, Departamento de QuĂmica FĂsica Aplicada. Fecha de Lectura: 16-12-2022La realizaciĂłn de este trabajo ha sido posible gracias al apoyo econĂłmico del Ministerio de EconomĂa y Competitividad (MINECO) a travĂ©s del proyecto CTQ2016-78576-R, a la Agencia Estatal de InvestigaciĂłn (AEI) por el proyecto PID2019-106186RB-I00/AEI/10.13039/501100011033 y a la concesiĂłn de un contrato de FormaciĂłn de Personal Investigador (FPI) del MINECO (Referencia BES-2017- 082613
Photocatalytic production of hydrogen from biomass-derived feedstocks
[EN] The application of photocatalysis for the utilisation of sunlight energy is intensely investigated in present times, particularly in prospect of generating solar fuels by hydrogen production or CO2 reduction processes as tools for societies aiming to relief their thirst for fossil resources. From the perspective of sustainability, the rational use of biomass-derived feedstocks for photocatalytic H2 production is a feasible, proven and highly efficient process. In this review, in addition to delving into physico-chemical fundamentals of photocatalytic processes on semiconductors, the research activity on this topic related to the design of revolutionary semiconductor-based materials, generally including metallic nanoparticles or complexes as hydrogen-evolving co-catalysts, is outlined and critically evaluated. Moreover, the use of sunlight and renewable feedstocks for the generation of hydrogen, as a compelling opportunity for the energy sector, is emphasised. Special focus is also set on the valorisation of biorefinery products, agricultural residues and industrial or municipal waste.Financial support from the Spanish Government-MINECO through "Severo Ochoa" (SEV 2012-0267) is acknowledged. The European Union is also acknowledged for the SynCatMatch project (ERC-AdG-2014-671093).Puga, AV. (2016). Photocatalytic production of hydrogen from biomass-derived feedstocks. Coordination Chemistry Reviews. 315:1-66. https://doi.org/10.1016/j.ccr.2015.12.009S16631
Novel strategies to design and construct efficient semiconductor-based photocatalyst for enhancing photocatalytic hydrogen evolution and nitrogen fixation under sunlight irradiation
L'Ă©nergie solaire est la source d'Ă©nergie la plus abondante au monde et elle peut ĂȘtre convertie en Ă©nergie chimique via des processus photocatalytiques. Au cours des derniĂšres dĂ©cennies, la photocatalyse sous la lumiĂšre du soleil est apparue comme une alternative innovante aux combustibles fossiles afin de rĂ©soudre et prĂ©venir des problĂšmes graves liĂ©s Ă la crise environnementale et Ă©nergĂ©tique. Actuellement, les matĂ©riaux Ă base de semi-conducteurs (tels que TiOâ, CâNâ, InâOâ, WOâ) sont intensivement Ă©tudiĂ©s pour diverses applications photocatalytiques, y compris la rĂ©action dâĂ©volution d'hydrogĂšne (HER) et la rĂ©duction de l'azote en ammoniac (NRR). Par consĂ©quent, diverses approches telles que l'ingĂ©nierie structurelle, les hĂ©tĂ©rojonctions nanocomposites ont Ă©tĂ© Ă©tudiĂ©es afin de surmonter les problĂšmes de ces matĂ©riaux et ainsi augmenter l'activitĂ© catalytique. Dans le cadre de cette thĂšse, nous avons dĂ©veloppĂ© des nouvelles stratĂ©gies pour la synthĂšse des quatre types de photocatalyseurs efficaces pour la production d'hydrogĂšne et la fixation de l'azote sous la lumiĂšre du soleil. Nos matĂ©riaux prĂ©sentent une structure unique, qui favorise l'absorption de la lumiĂšre visible, la sĂ©paration des charges Ă©lectrons-trous et lâaugmentation du nombre de sites actifs.Pour l'application de la gĂ©nĂ©ration d'hydrogĂšne photocatalytique, nous avons d'abord synthĂ©tisĂ© les sphĂšres de type Ă©ponge CdIânSâ monophasĂ©es via une mĂ©thode solvothermique suivie d'un traitement au gaz contenant HâS. La formation du complexe Cd/In avec une distribution uniforme de CdÂČâș et InÂłâș a jouĂ© un rĂŽle crucial dans la formation du spinelle monophasĂ© CdInâSâ. L'Ă©nergie de la bande interdite s'est avĂ©rĂ©e ĂȘtre significativement rĂ©duite, ce qui permet une absorption Ă©tendue de la lumiĂšre visible jusqu'Ă 700 nm, ceci est principalement attribuĂ© Ă la dispersion d'espĂšce sulfure sur la bande de valence du CdInâSâ monophasĂ©. Avec le dĂ©pĂŽt de Ni mĂ©tallique comme cocatalyseur de rĂ©duction, le photocatalyseur hybride Ni-CdInâSâ a montrĂ© une efficacitĂ© amĂ©liorĂ©e pour la production d'hydrogĂšne sous la lumiĂšre solaire, ce qui reprĂ©sente une augmentation de lâactivitĂ© dâenviron, respectivement, 5,5 et 3,6 fois que celle des Ă©chantillons Pt-CdInâSâ et Pd-CdInâSâ. Le deuxiĂšme systĂšme photocatalytique dĂ©veloppĂ© implique la prĂ©paration de nitrure de carbone graphitique dopĂ© au S (Ni-SCN). Ce dernier est chimiquement ancrĂ© au nickel par une technique connue sous le nom de processus de photo-dĂ©pĂŽt assistĂ© par sulfuration. L'origine de la structure distinctive du Ni-SCN est dĂ» Ă l'existence de liaisons chimiques NiS-C-N dans le systĂšme, ce qui favorisait la sĂ©paration des charges photogĂ©nĂ©rĂ©es et amĂ©liorait la capacitĂ© dâabsorption lumineuse du photocatalyseur. Par consĂ©quent, lâĂ©chantillon NiSCN synthĂ©tisĂ© prĂ©sente une excellente activitĂ© photocatalytique pour la production d'hydrogĂšne sous la lumiĂšre du soleil. En effet, ce systĂšme prĂ©sente une activitĂ© beaucoup plus Ă©levĂ©e que celle des systĂšmes g-CâNâ dopĂ©s au S, Ni supportĂ© g-CâNâ et Pt supportĂ© g-CâNâ dopĂ©s au S. Pour une application photo (Ă©lectro) catalytique de fixation de l'azote, nos travaux sont les premiers Ă rapporter la synthĂšse de nanoparticules d'Au chargĂ©es de nanoparticules WââOââ dopĂ©es au Fe (notĂ©es WOF-Au) par une synthĂšse solvothermique suivie d'un dĂ©pĂŽt in situ des nanoparticules d'Au. L'incorporation de dopants Fe peut non seulement guĂ©rir les Ă©tats de dĂ©faut de masse dans les rĂ©seaux non stĆchiomĂ©triques WââOââ, mais Ă©galement favoriser la sĂ©paration et la migration interfaciale des Ă©lectrons du photocatalyseur vers les molĂ©cules Nâ chimisorbĂ©es; tandis que les nanoparticules Au dĂ©corĂ©es sur la surface dopĂ©e au Fe WââOââ ont fourni les Ă©lectrons Ă haute Ă©nergie pour la rĂ©duction de Nâ via l'effet de rĂ©sonance plasmonique de surface localisĂ© (LSPR). Le systĂšme WOF-Au plasmonique rĂ©sultant montre un rendement amĂ©liorĂ© pour la production de NHâ, beaucoup plus Ă©levĂ© que celui du WââOââ pur ainsi qu'une trĂšs grande stabilitĂ©. L'amĂ©lioration des performances photoĂ©lectrocatalytiques est principalement due Ă l'effet synergique des dopants Fe et des nanoparticules Au dans l'hĂŽte WââOââ. Enfin, les cacahuĂštes creuses de InâOâ dopĂ©es au Ru (dĂ©notĂ©es Ru-InâOâ HPN) ont Ă©tĂ© fabriquĂ©es par la nouvelle stratĂ©gie d'auto-matrice suivie de la calcination des prĂ©curseurs synthĂ©tisĂ©s. Les nanoparticules uniformes InâOâ sont Ă©troitement agglomĂ©rĂ©es ensemble pour former une structure de cacahuĂšte creuse, ce qui facilite la sĂ©paration et le transport des l'Ă©lectrons-trous photoexcitĂ©s, amĂ©liorant lâabsorption de la lumiĂšre par multi-rĂ©flexion. De plus, l'introduction des dopants Ru induit de nombreuses lacunes en oxygĂšne Ă la surface et rĂ©duit l'Ă©nergie de la bande interdite du systĂšme photocatalytique. Ces lacunes d'oxygĂšne agissent comme des centres de piĂ©geage, facilitant la sĂ©paration des Ă©lectrons trous photoexcitĂ©s. Par consĂ©quent, le taux de production d'ammoniac des Ru-InâOâ HPNs est 5,6 fois plus Ă©levĂ© que celui des InâOâ HPNs purs et largement supĂ©rieur au matĂ©riau en vrac d'InâOâ, lorsquâil est soumis Ă lâirradiation solaire.Solar energy is the most abundant energy source in the world, and it can be converted into chemical energy via photocatalytic processes. Over the last decades, sunlight-driven photocatalysis has emerged as an innovative alternative to fossil fuels for solving the severe problems related to environmental diseases and the energy crisis. Currently, semiconductorbased materials (such as TiOâ, CâNâ, InâOâ, WOâ, BiVOâ) have been intensively studied for diverse photocatalytic applications, including the hydrogen evolution reaction (HER) and the nitrogen reduction reaction (NRR) to produce ammonia. However, the drawbacks of weak visible light absorption, low electron-hole separation with high recombination rate, and lack of surface active-sites have limited the photocatalytic performance of these semiconductorbased photocatalysts. Therefore, various approaches such as structural engineering, nanocomposite heterojunctions have been applied to overcome the limitations of these materials and boosting the catalytic activity. In this thesis, we employed novel strategies to develop four efficient photocatalytic systems for hydrogen production and nitrogen fixation. Our materials possessed a unique structure, which is advantageous to promote the visiblelight absorption, facilitate the separation of charge carrier, and increase the number of surface-active sites. For the photocatalytic hydrogen evolution application, we firstly synthesized the singlephase CdInâSâ sponge-like spheres via solvothermal method followed by HâS gas treatment. The formation of CdIn-complex with uniform distribution of CdÂČâș and InÂłâș played a crucial role in achieving the spinel structured-single phase CdInâSâ. The bandgap energy was found to be significantly reduced, resulting in the extended visible light absorption up to 700 nm, which was primarily attributed to the sulfide species-mediated modification of the valence band in CdInâSâ single-phase. With the deposition of Ni metal as a reduction cocatalyst, the hybrid Ni-CdInâSâ photocatalyst showed enhanced solar light-driven photocatalytic hydrogen evolution efficiency, which is around 5.5 and 3.6 folds higher than that of Pt-CdInâSâ and Pd-CdInâSâ samples, respectively. The second developed photocatalytic system involved the preparation of chemically bonded nickel anchored S-doped graphitic-carbon nitride (Ni-SCN) through a technique known as sulfidation assisted photo-deposition process. The origin of the distinctive structure of Ni-SCN was due to the existence of Ni-S-C-N chemical bonds in the system, which fundamentally favored the separation of photogenerated electron-hole and improved the light-harvesting capabilities of the photocatalyst. Consequently, the synthesized Ni-SCN exhibited an excellent sunlight-driven photocatalytic activity toward hydrogen evolution, which was several times higher than Sdoped g-CâNâ, Ni supported g-CâNâ and Pt loaded S-doped CâNâ systems. For photo(electro)catalytic nitrogen fixation application, our work is the first to report the synthesis of Au nanoparticles loaded Fe doped WââOââ (denoted as WOF-Au) nanorods through a solvothermal synthesis following by in situ deposition of Au nanoparticles. The incorporation of Fe dopants can not only heal the bulk-defect-states in nonstoichiometric WââOââ lattices but also promote the separation and interfacial migration of electrons from photocatalyst to chemisorbed Nâ molecules; while Au nanoparticles decorated on the Fe doped WââOââ surface provided the high energetic electrons for Nâ reduction via the localized surface plasmon resonance effect (LSPR). The obtained plasmonic WOF-Au system shows an enhanced NHâ yield, which is much higher than that of the bare WââOââ, as well as very high stability. The enhancement in photoelectrocatalytic performance is mainly contributed by the synergetic effect of Fe dopants and plasmonic Au nanoparticles on the WââOââ host. Lastly, Ru doped InâOâ hollow peanuts (demoted as Ru-InâOâ HPNs) were fabricated by the novel self-template strategy followed by the calcination of the as-synthesis precursors. The uniform InâOâ nanoparticles were closely packed together to form a hollow peanut structure, which facilitated the separation and transportation of photoinduced electron-hole and favored the light-harvesting ability by the internal multi-reflection process. Furthermore, the introduction of Ru dopants induced numerous surface oxygen vacancies and narrow down the bandgap energy of the photocatalytic system. These oxygen vacancies act as trapping centers, facilitating the separation of photoexcited electrons and holes. Consequently, the ammonia production rate of Ru-InâOâ HPNs was 5.6 times and much higher as compared to pure InâOâ HPNs and bulk material of InâOâ under solar light irradiation
Treatment of Perfluorinated Compounds and Nitroaromatics by Photocatalysis in the Presence of Ultraviolet and Solar Light
Nitroaromatic compounds (NACs) and perfluorinated compounds (PFCs) are two classes of water contaminants of DoD concern due to their risk to the environment, personnel, and mission. This study investigated the potential of an innovative technology, oxidation using titanium dioxide (TiO2) and TiO2 doped with silver (Ag-TiO2) as photocatalyst, to effectively and energy efficiently treat NAC and PFC-contaminated water. Three model contaminants, 2,4-DNT (NAC), and PFOA and PFOS (PFCs), were degraded using TiO2 and Ag-TiO2 immobilized on glass slides under sunlight and UV light in atmospheric conditions and at neutral pH. 2,4-DNT degraded 14% and 15% in the presence of Ag-TiO2 and TiO2, respectively, under sunlight after 8 hours. After 8 hours under UV light, 2,4-DNT degraded 13% and 29% in the presence of Ag-TiO2 and TiO2, respectively. Results indicate that PFOA and PFOS do not degrade under the conditions of the experiment. Further study is needed to investigate the viability of the technology to treat NAC- and PFC-contaminated water
3rd International Conference on Nanomaterials Science and Mechanical Engineering: book of abstracts
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