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Journal ArticleDOI: 10.1039/D0TA08334H

Heterogenization of homogeneous photocatalysts utilizing synthetic and natural support materials

02 Mar 2021-Journal of Materials Chemistry (The Royal Society of Chemistry)-Vol. 9, Iss: 8, pp 4454-4504
Abstract: Homogeneous photocatalysis has considerably contributed to green applications such as energy production and environmental decontamination. Currently, researchers mainly focus on the search for sustainable processes that can generate valuable chemical compounds with high selectivity and aid in the complete mineralization of hazardous compounds. Although homogeneous photocatalysts exhibit superior performance, their recovery after the reaction is difficult. The 3Rs process, i.e., recovery, recycling and reuse of photocatalysts respectively, is critical to make a photocatalytic process eco-friendly. Heterogenization of homogeneous photocatalysts is considered as an effective method to not only realize the recycling of homogeneous photocatalysts, but also enhance the overall photocatalytic activity. Conventional methods have employed synthetic materials for the heterogenization of homogeneous photocatalysts. Nevertheless, scientists have discovered that natural polymer sources can be alternatives due to their excellent chemical, mechanical, and electrical properties for applications under harsh reaction conditions. In this review, we have summarized state-of-the-art techniques employed for the heterogenization of homogeneous photocatalysts using various supporting materials in terms of design and preparation. First, we have organized these strategies into different categories, such as microporous encapsulation, dye-sensitized semiconductors, metal–organic framework (MOF) construction, carbon material fixation, synthetic polymer attachment and natural origin supports. To provide readers with deeper insights into this field, we have presented some fundamentals of homogeneous photocatalysis with respect to environmental applications and its heterogeneous strategies. Furthermore, we have discussed the performance of heterogeneous photocatalysts prepared from these methods, including photocatalytic performance, product selectivity and reusability. Finally, we have concluded with different aspects on the current challenges and new aspects in emerging technologies.

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10 results found


Open access
Chen Wang1, Jun Li1, Giuseppe Mele, Gaomai Yang1  +3 moreInstitutions (2)
01 Jan 2007-
Abstract: The novel porphyrins 5,10,15,20-tetra-[4-(3-phenoxy)-propoxy]phenyl porphyrin, H2Pp(a) and 5,10,15,20-tetra-[2-(3-phenoxy)-propoxy]phenyl porphyrin, H2Pp(b) and their corresponding copper(II) complexes CuPp(a), CuPp(b) were synthesized and characterized by using various spectroscopic techniques. The photocatalytic activity of polycrystalline TiO2 samples impregnated with H2Pp(a), H2Pp(b), CuPp(a) and CuPp(b) as sensitizers have been investigated by carrying out the photo-degradation of 4-nitrophenol (4-NP) as a probe reaction in aqueous suspension and under visible light. The maximum photocatalytic activity was obtained using TiO2 loaded with a monolayer of the copper porphyrin CuPp(b) in the amount of 18 μmol per gram of TiO2. The photocatalytic efficiency decreased in the following order: TiO2-CuPp(b), TiO2-CuPp(a), TiO2-H2Pp(b), TiO2-H2Pp(a). A possible mechanism of the photocatalytic degradation is also proposed.

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Topics: Porphyrin (54%)

121 Citations


Journal ArticleDOI: 10.1039/D0SE01901A
Yong Peng1, Hao Wu1, Mingjian Yuan2, Fang-Fang Li3  +3 moreInstitutions (4)
Abstract: Bismuth vanadate (BiVO4) is one of the highly promising photoanodes for photoelectrochemical (PEC) water splitting but suffers from severe carrier recombination and undesirable charge transfer at the semiconductor–electrolyte interface. Herein, we employ an effective surface-engineered sulfite treatment to improve the PEC performance of BiVO4 without illumination. This post-synthetic treatment on BiVO4 photoanodes can substantially enhance the interfacial charge transfer efficiency because of decreased charge carrier recombination arising from both surface oxygen vacancies (Ovac) and surface disordered layers. The as-prepared BiVO4 exhibits a photocurrent density of 2.2 mA cm−2 at 1.23 V vs. the reversible hydrogen electrode (RHE) under 1-sun illumination, which is 1.7-times higher than that of pristine BiVO4. By coating the amorphous FeOOH cocatalyst, the photocurrent density can be further improved to 2.8 mA cm−2. We demonstrate that the chemical reaction employing a reducing agent with a mild reduction activity can controllably alter the surface states of BiVO4 photoanodes, providing a facile, efficient, and low-cost strategy to achieve high-performance photoelectrodes.

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Topics: Water splitting (53%), Bismuth vanadate (52%), Photocurrent (51%) ... show more

4 Citations


Journal ArticleDOI: 10.1016/J.IJBIOMAC.2021.10.044
Abstract: The development of porous adsorbent materials from renewable resources for water and wastewater treatment has received considerable interest from academia and industry. This work aims to synthesize composite hydrogel from the combination of guar gum (a neutral galactomannan polysaccharide) and TiO2. The TiO2-embedded guar gum hydrogel (TiO2@GGH) was utilized to remove methylene blue through adsorption and photodegradation. The presence of TiO2 particles in the hydrogel matrix (TiO2@GGH) was confirmed by scanning electron microscopy-energy dispersive X-ray and X-ray photoelectron spectroscopy analysis. The mercury intrusion and N2 sorption isotherm indicate the macroporous structure of the TiO2@GGH composite, showing the presence of pore sizes ~420 μm. The dye removal efficiency of the GGH and TiO2@GGH was evaluated in batch mode at ambient temperature under varying pH. The effect of UV radiation on the dye removal efficiency was also assessed. The results demonstrated that the highest dye removal was recorded at pH 10, with the equilibrium condition achieved within 5 h. UV radiation was shown to enhance dye removal. The maximum adsorption capacity of TiO2@GGH is 198.61 mg g−1, while GGH sorbent is 188.53 mg g−1. The results imply that UV radiation gives rise to the photodegradation effect.

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Topics: Guar gum (58%), Adsorption (53%), Photodegradation (52%)

Open accessJournal ArticleDOI: 10.1039/D1TA05935A
Yong Peng1, Chun Hong Mak1, Ji-Jung Kai1, Minshu Du2  +7 moreInstitutions (8)
Abstract: For the global energy demand and climate change challenges, seeking renewable, sustainable energy sources is of great significance. Photoelectrochemical (PEC) water splitting is one of the promising technologies for converting intermittent solar energy into storable hydrogen energy, to tackle these issues. As the core component in a PEC system, photoelectrodes have been modified by various strategies including nanostructuring, facet-engineering, elemental doping, and heterostructured engineering. Apart from these techniques, numerous effective post-synthetic treatments have also been used to facilely and powerfully boost the physicochemical properties of photoelectrodes, for the enhancement of their PEC performance. Among them, a number of post-treatments can selectively influence photoelectrode surface and subsurface areas, altering surface states that play crucial roles in the hydrogen/oxygen evolution reaction. In virtue of such post-treatments, we summarize recently reported post-synthetic treatments for enhanced PEC applications. Post-treatment methods are classified into three sections: chemical treatments, electrochemical and irradiation-based treatments, and post-annealing treatments. In the end, a summary and outlook section regarding the utilization of post-treatments for PEC applications have been provided. This review can provide inspiration for further studies about post-treatments, not only in the PEC water splitting field, but also in other aspects, such as electrolysis.

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Topics: Water splitting (52%)

Journal ArticleDOI: 10.1016/J.JCIS.2021.10.063
Yong Peng1, Minshu Du2, Xingli Zou3, Guohua Jia4  +5 moreInstitutions (8)
Abstract: Nickel oxyhydroxide (NiOOH) is regarded as one of the promising cocatalysts to enhance the catalytic performance of photoanodes but suffers from serious interfacial charge-carrier recombination at the photoanode||NiOOH interface. In this work, surface-engineered BiVO4 photoanodes are fabricated by sandwiching an oxygen vacancy (Ovac) interlayer between BiVO4 and NiOOH. The surface Ovac interlayer is introduced on BiVO4 by a chemical reduction treatment using a mild reducing agent, sodium hypophosphite. The induced Ovac can alleviate the interfacial charge-carrier recombination at the BiVO4||NiOOH junction, resulting in efficient charge separation and transfer efficiencies, while an outer NiOOH layer is coated to prevent the Ovac layer from degradation. As a result, the as-prepared NiOOH-P-BiVO4 photoanode exhibits a high photocurrent density of 3.2 mA cm−2 at 1.23 V vs. RHE under the irradiation of 100 mW/cm2 AM 1.5G simulated sunlight, in comparison to those of bare BiVO4, P-BiVO4, and NiOOH-BiVO4 photoanodes (1.1, 2.1 and 2.3 mA cm−2, respectively). In addition to the superior photoactivity, the 5-h amperometric measurements illustrate improved stability of the surface-engineered NiOOH-P-BiVO4 photoanode. Our work showcases the feasibility of combining cocatalysts with Ovac, for improved photoactivity and stability of photoelectrodes.

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References
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213 results found


Journal ArticleDOI: 10.1038/353737A0
24 Oct 1991-Nature
Abstract: THE large-scale use of photovoltaic devices for electricity generation is prohibitively expensive at present: generation from existing commercial devices costs about ten times more than conventional methods1. Here we describe a photovoltaic cell, created from low-to medium-purity materials through low-cost processes, which exhibits a commercially realistic energy-conversion efficiency. The device is based on a 10-µm-thick, optically transparent film of titanium dioxide particles a few nanometres in size, coated with a monolayer of a charge-transfer dye to sensitize the film for light harvesting. Because of the high surface area of the semiconductor film and the ideal spectral characteristics of the dye, the device harvests a high proportion of the incident solar energy flux (46%) and shows exceptionally high efficiencies for the conversion of incident photons to electrical current (more than 80%). The overall light-to-electric energy conversion yield is 7.1-7.9% in simulated solar light and 12% in diffuse daylight. The large current densities (greater than 12 mA cm-2) and exceptional stability (sustaining at least five million turnovers without decomposition), as well as the low cost, make practical applications feasible.

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Topics: Solar cell (58%), Polymer solar cell (56%), Photovoltaic system (56%) ... show more

25,199 Citations


Journal ArticleDOI: 10.1038/238037A0
Akira Fujishima1, Kenichi Honda2Institutions (2)
07 Jul 1972-Nature
Abstract: ALTHOUGH the possibility of water photolysis has been investigated by many workers, a useful method has only now been developed. Because water is transparent to visible light it cannot be decomposed directly, but only by radiation with wavelengths shorter than 190 nm (ref. 1).

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24,267 Citations


Journal ArticleDOI: 10.1002/ANIE.200460587
30 May 2005-Angewandte Chemie
Abstract: As the most important skeletal component in plants, the polysaccharide cellulose is an almost inexhaustible polymeric raw material with fascinating structure and properties. Formed by the repeated connection of D-glucose building blocks, the highly functionalized, linear stiff-chain homopolymer is characterized by its hydrophilicity, chirality, biodegradability, broad chemical modifying capacity, and its formation of versatile semicrystalline fiber morphologies. In view of the considerable increase in interdisciplinary cellulose research and product development over the past decade worldwide, this paper assembles the current knowledge in the structure and chemistry of cellulose, and in the development of innovative cellulose esters and ethers for coatings, films, membranes, building materials, drilling techniques, pharmaceuticals, and foodstuffs. New frontiers, including environmentally friendly cellulose fiber technologies, bacterial cellulose biomaterials, and in-vitro syntheses of cellulose are highlighted together with future aims, strategies, and perspectives of cellulose research and its applications.

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Topics: Cellulose fiber (66%), Bacterial cellulose (65%), Cellulose (59%)

5,229 Citations


Open accessJournal ArticleDOI: 10.1038/NCOMMS4460
Taras Palasyuk1, I. A. Troyan1, Mikhail Eremets1, Vadym Drozd2  +7 moreInstitutions (3)
Abstract: Ionization of highly compressed ammonia has previously been predicted by computation. Here, the authors provide experimental evidence for this autoionization process at high pressures, showing the transformation of molecular ammonia into ammonium amide.

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Topics: Chemical ionization (59%), Ionization (55%), Ammonia (54%) ... show more

3,629 Citations


Journal ArticleDOI: 10.1002/IJCH.197000029
Dieter Rehm1, Albert Weller1Institutions (1)
Abstract: Fluorescence quenching rate constants, kq, ranging from 106 to 2 × 1010 M−1 sec−1, of more than 60 typical electron donor-acceptor systems have been measured in de-oxygenated acetonitrile and are shown to be correlated with the free enthalpy change, ΔG23, involved in the actual electron transfer process in the encounter complex and varying between + 5 and −60 kcal/mole. The correlation which is based on the mechanism of adiabatic outer-sphere electron transfer requires ΔG≠23, the activation free enthalpy of this process to be a monotonous function of ΔG23 and allows the calculation of rate constants of electron transfer quenching from spectroscopic and electrochemical data. A detailed study of some systems where the calculated quenching constants differ from the experimental ones by several orders of magnitude revealed that the quenching mechanism operative in these cases was hydrogen-atom rather than electron transfer. The conditions under which these different mechanisms apply and their consequences are discussed.

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3,340 Citations


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