The design, synthesis, and photoelectrochemical characterization of Co3(PO4)2, a hydrogen evolving catalyst modified with reduced graphene oxide (RGO), is reported. The 3D flowerlike Co3(PO4)2 ...heterojunction system, consisting of 3D flowerlike Co3(PO4)2 and RGO sheets, was synthesized by a one-pot insitu photoassisted method under visible-light irradiation, which was achieved without the addition of surfactant or a structure-directing reagent. For the first time, Co3(PO4)2 is demonstrated to act as a hydrogen evolving catalyst rather than being used as an oxygen evolving photoanode. In particular, 3D flowerlike Co3(PO4)2 anchored to RGO nanosheets is shown to possess dramatically improved photocatalytic activity. This enhanced photoactivity is mainly due to the staggered typeII heterojunction system, in which photoinduced electrons from 3D flowerlike Co3(PO4)2 transfer to the RGO sheets and result in decreased charge recombination, as evidenced by photoluminescence spectroscopy. The band gap of Co3(PO4)2 was calculated to be 2.35eV by the Kubelka-Munk method. Again, the Co3(PO4)2 semiconductor displays n-type behavior, as observed from Mott-Schottky measurements. These RGO-Co3(PO4)2 conjugates are active in the visible range of solar light for water splitting and textile dye degradation, and can be used towards the development of greener and cheaper photocatalysts by exploiting solar light.
The replacement of expensive noble-metals cocatalysts with inexpensive, earth-abundant, metallic nonmetal materials in most semiconductor-based photocatalytic systems is highly desirable. Herein, we ...report the fabrication of stable 1T-MoS2 slabs insitu grown on CdS nanorods (namely, 1T-MoS2@CdS) by using a solvothermal method. As demonstrated by ultrafast transient absorption spectroscopy, in combination with steady-state and time-resolved photoluminescence, the synergistic effects resulting from formation of the intimate nanojunction between the interfaces and effective electron transport in the metallic phase of 1T-MoS2 largely contribute to boosting the photocatalytic activity of CdS. Notably, the heterostructure with an optimum loading of 0.2wt% 1T-MoS2 exhibits an almost 39-fold enhancement in the photocatalytic activity relative to that exhibited by bare CdS. This work represents a step towards the insitu realization of a 1T-phase MoS2-based heterostructure as a promising cocatalyst with high performance and low cost.
A new series of inorganic–organic hybrid perovskite materials were prepared by microwave-assisted grafting reactions. Simple carboxylic acids, acetic acid, and propionic acid, as well as ...hydroxyaromatic carboxylic acids, 3,5-dihydroxy benzoic acid (DBA), 5-hydroxyisophthalic acid (HPA), 4-hydroxybenzoic acid (HBA), and 4-hydroxy-4-biphenyl carboxylic acid (HBCA), were reacted with the Dion–Jacobson double-layered perovskite, HLaNb2O7, and its alcoxy derivatives. Grafting was found to not occur with simple carboxylic acids, while those molecules with hydroxyls were all attached to the perovskite interlayers. Reactivity of the hydroxyaromatic carboxylic acids varied with the different layered perovskite hosts where reactions with HLaNb2O7 did not occur, and those with n-propoxy-LaNb2O7 were limited; the greatest extent of reactivity was seen with n-decoxy-LaNb2O7. This is attributed to the larger interlayer spacing available for the insertion of the various hydroxyaromatic carboxylic acid compounds. The loading exhibited by the grafting species was less than that seen with well-known long-chain alkoxy grafting groups. It is expected that the width of the molecules contributes to this where, due to the benzyl groups, the interlayer volume of the grafted moieties occupies a larger horizontal fraction, therefore minimizing the loading to the below half. X-ray powder diffraction and transmission electron microscopy studies found that grafting of the n-decoxy-LaNb2O7 intermediates with the series of hydroxyaromatics resulted in a reduction in crystallinity along with a disruption of the layer structure. Raman data on the series show little variation in local structure except for HBCA, where there appears to be a lengthening of the Nb-O apical linkage and a possible reduction in the distortion of inner-layer NbO6 octahedra. The optical properties of the hydroxyaromatic carboxylic acid grafted perovskites were also investigated using diffuse-reflectance UV-Vis spectroscopy. The band gaps of DBA, HPA, and HBA were found to be similar to the parent (Eg ≈ 3.4 eV), while the HBCA was significantly less by ca. 0.6 eV. This difference is attributed to electron withdrawal from the perovskite block to the HBCA ligand, leading to a lower band gap for the HBCA compound. The methods described herein allow for the formation of a new series of inorganic–organic hybrid materials where the products are of interest as precursors to more complex architectures as well as models for band gap modification of metal oxide photocatalysts.
Dinitrogen reduction to ammonia using transition metal catalysts is central to both the chemical industry and the Earth's nitrogen cycle. In the Haber-Bosch process, a metallic iron catalyst and high ...temperatures (400 °C) and pressures (200 atm) are necessary to activate and cleave NN bonds, motivating the search for alternative catalysts that can transform N
to NH
under far milder reaction conditions. Here, the successful hydrothermal synthesis of ultrathin TiO
nanosheets with an abundance of oxygen vacancies and intrinsic compressive strain, achieved through a facile copper-doping strategy, is reported. These defect-rich ultrathin anatase nanosheets exhibit remarkable and stable performance for photocatalytic reduction of N
to NH
in water, exhibiting photoactivity up to 700 nm. The oxygen vacancies and strain effect allow strong chemisorption and activation of molecular N
and water, resulting in unusually high rates of NH
evolution under visible-light irradiation. Therefore, this study offers a promising and sustainable route for the fixation of atmospheric N
using solar energy.
Background: In the present study, the photocatalytic (TiO2/UV) batch process has been used for the methyl orange (MO) degradation. Methods: In the catalyst range from 0.25 to 1.5 g/L, the optimum ...concentration of TiO2 was found to be 0.5 g/L. The kinetic behavior of MO degradation has been evaluated using the non-linear form of pseudo-first order and pseudo-second order models. Results: The goodness of the fit was evaluated using the correlation coefficient R2 value and the mean square error (MSE) function. Conclusion: The kinetic studies revealed that the pseudo-first order model (k1 = -0.0593 min-1) is more suitable to fit the experimental data (R2 = 0.957, MSE = 0.00271) of MO degradation.
Piezoelectric‐based catalysis that relies on the charge energy or separation efficiency of charge carriers has attracted significant attention. The piezo‐potential induced by strain or stress can ...induce a giant electric field, which has been demonstrated to be an effective means for charge energy shifting or transferring electrons and holes. In recent years, intense efforts have been made in this subject, and the research has mainly focussed on two aspects: i) Alteration of surface charge energy by piezo‐potential in piezocatalysis; ii) the separation of photo‐generated charge carriers and the catalytic activity enhancement of an integrated piezoelectric semiconductor or coupled system composed of piezoelectrics and semiconductors. Systematically summarizing the advances of the above two aspects is helpful in the context of deepening understanding of the relevant issues and developing new ideas for piezoelectric‐based catalysis. In this review, a comprehensive summary on piezocatalysis and piezo‐photocatalysis is provided. The charge transfer behaviors and catalytic mechanisms over a large variety of piezocatalysts and piezo‐photocatalysts are systematically analyzed. In addition, the types of mechanical energy, strategies for enhancing piezocatalysis, and the advanced applications of piezocatalysis and piezo‐photocatalysis are discussed. Finally, the promising development directions of piezocatalysis and piezo‐photocatalysis, such as materials, assembly forms, and applications in the future are proposed.
Mechanical energy and solar energy can enable charge energy alteration or effective separation of electron–hole pairs, which trigger various catalytic reactions. The recent research progress on piezocatalysis and piezo‐photocatalysis is summarized, concentrating especially on the typical piezocatalysts, mechanical energy forms, piezocatalysis modulation strategies, piezo‐photocatalyst types, and catalytic applications to offer a guideline for the development of piezoelectric‐based catalysts.
The built‐in electric field can be generated in the piezoelectric materials under mechanical stress. The resulting piezoelectric effect is beneficial to charge separation in photocatalysis. ...Meanwhile, the mechanical stress usually gives rise to accelerated mass transfer and enhanced catalytic activity. Unfortunately, it remains a challenge to differentiate the contribution of these two factors to catalytic performance. Herein, for the first time, isostructural metal–organic frameworks (MOFs), i.e., UiO‐66‐NH2(Zr) and UiO‐66‐NH2(Hf), are adopted for piezo‐photocatalysis. Both MOFs, featuring the same structures except for diverse Zr/Hf‐oxo clusters, possess distinctly different piezoelectric properties. Strikingly, UiO‐66‐NH2(Hf) exhibits ≈2.2 times of activity compared with that of UiO‐66‐NH2(Zr) under simultaneous light and ultrasonic irradiation, though both MOFs display similar activity in the photocatalytic H2 production without ultrasonic irradiation. Given their similar pore features and mass transfer behaviors, the activity difference is unambiguously assignable to the piezoelectric effect. As a result, the contributions of the piezoelectric effect to the piezo‐photocatalysis can be clearly distinguished owing to the stronger piezoelectric property of UiO‐66‐NH2(Hf).
Two isostructural metal–organic frameworks (MOFs) with distinctly different piezoelectric responses are used in piezo‐photocatalysis. Remarkably, the H2 production efficiency of Hf‐MOF is 2.2 times that of Zr‐MOF under simultaneous light and ultrasonic irradiation. The role of the piezoelectric effect can be distinguished owing to their similar pore features and mass transfer behaviors.
With the ambition of solving the challenges of the shortage of fossil fuels and their associated environmental pollution, visible‐light‐driven splitting of water into hydrogen and oxygen using ...semiconductor photocatalysts has emerged as a promising technology to provide environmentally friendly energy vectors. Among the current library of developed photocatalysts, organic conjugated polymers present unique advantages of sufficient light‐absorption efficiency, excellent stability, tunable electronic properties, and economic applicability. As a class of rising photocatalysts, organic conjugated polymers offer high flexibility in tuning the framework of the backbone and porosity to fulfill the requirements for photocatalytic applications. In the past decade, significant progress has been made in visible‐light‐driven water splitting employing organic conjugated polymers. The recent development of the structural design principles of organic conjugated polymers (including linear, crosslinked, and supramolecular self‐assembled polymers) toward efficient photocatalytic hydrogen evolution, oxygen evolution, and overall water splitting is described, thus providing a comprehensive reference for the field. Finally, current challenges and perspectives are also discussed.
Molecular design strategies of various conjugated polymers for photocatalytic water splitting are reviewed. The structure–property relationships between functional groups, building blocks, and photocatalytic water splitting in a variety of conjugated polymers are explored. Furthermore, key factors that contribute to a highly efficient polymer photocatalyst in visible‐light‐driven water splitting are outlined.
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