Satyabadi Martha

Facile synthesis of highly active g-C3N4 for efficient hydrogen production under visible light

A highly active graphitic C3N4 photocatalyst prepared from a mixture of urea and melamine with advanced structural, optical and electronic properties and enhanced photocatalytic activity for the production of hydrogen gas is explored. The prepared photocatalyst is able to generate a high rate of hydrogen gas production (135 μmol h−1) by loading with 1 wt% Pt as a co-catalyst. The good separation of C3N4 sheets, lower recombination rate of excitons and the high amount of generated photocurrent have significantly contributed towards the photocatalytic activity of graphitic carbon nitride prepared from a mixture of urea and melamine.

Facile Synthesis of Au/g-C3N4 Nanocomposites: An Inorganic/Organic Hybrid Plasmonic Photocatalyst with Enhanced Hydrogen Gas Evolution Under Visible-Light Irradiation

Noble‐metal Au nanoparticles deposited on graphitic carbon nitride polymer (g‐C3N4) photocatalyst by a facile deposition–precipitation method exhibited high photocatalytic activity for hydrogen gas production under visible‐light irradiation. The Au/g‐C3N4 nanocomposite plasmonic photocatalysts were characterized by X‐ray diffraction spectroscopy, diffuse reflectance UV/Vis spectroscopy, FTIR spectroscopy, field‐emission scanning electron microscopy, high‐resolution transmission electron microscopy, selected‐area electron diffraction, X‐ray photoelectron spectroscopy, photoluminescence spectroscopy, and photoelectrochemical measurements. We studied the effect of Au deposition on the photocatalytic activity of g‐C3N4 by investigation of optical, electronic, and electrical properties. Enhanced photocatalytic activity of Au/g‐C3N4 naocomposite for hydrogen production was attributed to the synergic mechanism operating between the conduction band minimum of g‐C3N4 and the plasmonic band of Au nanoparticles including high optical absorption, uniform distribution, and nanoscale particle size of gold. The mechanism of te photocatalytic activity of the nanocomposite photocatalyst is discussed in detail. Deposition of Au nanoparticles on g‐C3N4 was optimized and it was found that 1 wt % Au‐loaded g‐C3N4 composite plasmonic photocatalyst generated a photocurrent density of 49 mA cm−2 and produced a hydrogen gas amount of 532 μmol under visible light, which were more than 3000 times higher and 23 times higher, respectively, than the values of neat g‐C3N4.

Fabrication of Novel p-BiOI/n-ZnTiO3 Heterojunction for Degradation of Rhodamine 6G under Visible Light Irradiation

With the purpose of efficient electron-hole separation and enhancement of photocatalytic performance in the visible region, we have fabricated a novel p-BiOI/n-ZnTiO3 heterojunction by a precipitation-deposition method and studied its activity toward dye degradation. The physicochemical characteristics of the fabricated BiOI/ZnTiO3 heterojunctions were surveyed by powder X-ray diffraction pattern (PXRD), BET-surface area, diffuse reflectance UV-vis (DRUV-vis), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), photoluminescence spectroscopy (PL spectra), X-ray photoelectron spectroscopy (XPS), and photoelectrochemical measurement. The photosensitization effect of BiOI enhanced the spectral response of ZnTiO3 from UV to visible region, making all the BiOI/ZnTiO3 heterojunctions active under visible light. The PEC measurement confirmed the p-type character of BiOI and n-type character of ZnTiO3. The optimal amount of BiOI in BiOI/ZnTiO3 heterojunctions was found to be 50% which degraded 82% of 50 ppm Rh 6G under visible light irradiation. The degradation rate of 50% BiOI/ZnTiO3 heterojunction was found to be 9.8 and 11.1 times higher than that of bare BiOI and ZnTiO3, respectively. The photosensitization effect of BiOI and the formed heterojunction between p-type BiOI and n-type ZnTiO3 contribute to improved electron-hole separation and enhancement in photocatalytic activity.

Facile synthesis of visible light responsive V2O5/N,S–TiO2 composite photocatalyst: enhanced hydrogen production and phenol degradation

A series of novel V2O5/N,S–TiO2 composite photocatalysts were fabricated by a solid state reaction route. The investigated composite materials were successfully characterised by XRD, DRUV-vis spectra, SEM, TEM, XPS, FTIR, NH3-TPD, BET-surface area and photoresponse studies. The photocatalytic applications of the composite materials were evaluated for hydrogen production under visible light irradiation (λ ≥ 400 nm) and phenol degradation under direct solar light. The V2O5 component played a key role for the visible light activity of the composite system at longer wavelengths. Among all the prepared materials, V2O5/N,S–TiO2 activated at 500 °C showed promising activity towards hydrogen production (296.6 μmol h−1) under visible light and successively degraded 88% of 100 mg L−1 phenol solution under direct solar light irradiation in just 4 h. The present investigation is of great importance in view of energy and environmental applications.

An overview of the structural, textural and morphological modulations of g-C3N4 towards photocatalytic hydrogen production

Graphitic carbon nitride (g-C3N4) is gaining more and more importance as a photocatalytic material due to its promising electronic band structure and high thermal and chemical stability. Very recently, a variety of nanostructured g-C3N4 photocatalysts with varying shapes, sizes, morphologies and electronic band structures have been reported for application in photocatalytic research. This critical review represents an extensive overview of the synthesis of a variety of g-C3N4 nanostructured materials with a controllable structure, morphology and surface modification for superior electronic properties. This article highlights the design of efficient photocatalysts for the splitting of water into hydrogen gas using solar energy. Finally, in the summary and outlook, this article highlights the ongoing challenges and opportunities of g-C3N4. It is also hoped that this review will stimulate further investigation and will open up new possibilities to develop new hybrid g-C3N4 materials with new and exciting applications.

An overview of the modification of g-C3N4 with high carbon containing materials for photocatalytic applications

In recent years, graphitic carbon nitride has become one of the very exciting sustainable materials, due to its unusual properties and promising applications as a heterogeneous catalyst in water splitting and organic contaminant degradation. A variety of modifications have been reported for this nanostructured material with the use of carbonaceous materials to enhance its potential applications. This review summarizes the ongoing developments towards the use of carbonaceous materials like activated carbon (AC), ordered mesoporous carbon (OMC), carbon nanotubes (CNTs), fullerene (C60) and graphene (GE) for the enhancement of the photocatalytic performance of metal free semiconductor photocatalysts because of their special structures and unique electronic properties. Also this review highlights the recent strategies aiming to promote the activity by coupling with polymers (having higher carbon content). Our study reveals that in addition to the charge transfer effects, morphological changes in g-C3N4 are also introduced by combination of g-C3N4 with carbonaceous materials to tailor its pristine properties and to extend its applications.

Fabrication of In2O3 modified ZnO for enhancing stability, optical behaviour, electronic properties and photocatalytic activity for hydrogen production under visible light

With the purpose of enhancing the stability, optical behaviour, electronic properties and photocatalytic activity for hydrogen production under visible light, ZnO has been modified by In2O3. The thriving modification of ZnO by In2O3 was confirmed from X-ray diffraction, DRUV-vis spectra, X-ray photoelectron spectroscopy, transmission electron microscopy, photoluminescence spectroscopy and photoelectrochemical measurement. DRUV-vis spectra showed that the optical absorption of ZnO was significantly enhanced to the visible region by modification with In2O3. TEM study confirmed that the particle size of ZnO was drastically reduced by the modification with In2O3 which helped to retard the recombination of charge carriers and enhanced the photocatalytic activity. Moreover, In2O3 modification greatly enhanced the stability of ZnO in aqueous medium which is a really challenging task in the photocatalytic chemistry of ZnO. All the In2O3 modified ZnO samples showed high photocatalytic activity for hydrogen production under visible light.

Synthesis of multifunctional nanostructured zinc-iron mixed oxide photocatalyst by a simple solution-combustion technique.

A series of nanostructure zinc-iron mixed oxide photocatalysts have been fabricated by solution-combustion method using urea as the fuel, and nitrate salts of both iron and zinc as the metal source. Different characterization tools, such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), diffuse reflectance UV-visible spectra (DRUV-vis), electron microscopy, and photoelectrochemical measurement were employed to establish the structural, electronic, and optical properties of the material. Electron microscopy confirmed the nanostructure of the photocatalyst. The synthesized photocatalysts were examined towards photodegradation of 4-chloro-2-nitro phenol (CNP), rhodamine 6G (R6G), and photocatalytic hydrogen production under visible light (λ ≥ 400 nm). The photocatalyst having zinc to iron ratio of 50:50 showed best photocatalytic activity among all the synthesized photocatalysts.

The effect of sulfate pre-treatment to improve the deposition of Au-nanoparticles in a gold-modified sulfated g-C3N4 plasmonic photocatalyst towards visible light induced water reduction reaction

In continuation of our earlier work on Au-g-C3N4 and to improve its activity further, Au incorporated sulfated carbon nitride (g-C3N4) has been designed by using a simple impregnation cum borohydrate reduction method for the visible light induced water reduction reaction for hydrogen generation. The photocatalysts were characterized using various instrumental methods such as PXRD, UV-Vis DRS, SEM, HR-TEM, XPS, PL and TRPL spectral analysis. Functionalisation by the -HSO3 group and incorporation of AuNPs in the g-C3N4 skeleton lead to the extension of its pi-conjugated system, modification of its semiconductor properties, such as band structure engineering with a tunable bandgap, red-shift of the optical absorption band and promotion of charge migration and separation. The sulfate pre-treated g-C3N4 samples are supposed to have a defected surface due to oxygen vacancies, which increases the adsorption of AuNPs onto the vacant oxygen sites. Thus the AuNPs get adsorbed on the reduced surfaces, increasing the extent and effectiveness of the electronic communication between gold and the g-C3N4 interface. The improved photocatalytic activity could be attributed to the surface plasmon resonance (SPR) effect of AuNPs, which synergistically facilitates the photocatalysis process. The photocatalytic activity of Au-sulfated g-C3N4 for photocatalytic splitting of water to produce H2 was increased 1.5 times compared to that of Au-g-C3N4, 2.5 times compared to that of sulphated-g-C3N4 and 35 times compared to that of single-phase g-C3N4.

Plasmon Induced Nano Au Particle Decorated over S,N-Modified TiO2 for Exceptional Photocatalytic Hydrogen Evolution under Visible Light

Nano Au deposited mesoporous S,N-TiO2 (SNT) nanocomposites have been fabricated through deposition precipitation technique by employing urea as the hydrolyzing agent. To investigate the structural, optical, and electronic properties, the photocatalysts are characterized through X-ray diffraction (XRD), UV-vis diffuse reflectance spectra, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and photoelectrochemical measurements. Here in addition to the co-catalyst nature of nano Au particles, surface plasmon resonance (SPR) effect in visible region enhances the light harvestation ability as well as transfer electrons to the conduction band of SNT. Furthermore, easy channelization of photogenerated charge carriers through sulfate facilitated redox couple makes the system more potential towards H2 evolution. TEM study exhibits well interconnective morphology in the matrix which helps easy channelization of electrons in the SNT nanocomposites. The photocatalytic activities have been evaluated for hydrogen generation under the irradiation of visible light and an enhanced activity has been observed for the Au promoted SNT due to the presence of nano Au particles, that is, 3.5 nm. The hydrogen generation activity of 3Au-SNT is nearly 9 times higher than that of neat SNT, and the energy conversion efficiency was found to be 17.6 %.