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.
Bismuth-rich bismuth oxyhalides (Bi–O–X; X = Cl, Br, I) display high photocatalytic reduction activity due to the promoting conduction band potential. In this work, two Bi5O7I nanosheets with ...different dominant facets were synthesized using either molecular precursor hydrolysis or calcination. Crystal structure characterizations, included X-ray diffraction patterns (XRD), field emission electron microscopy and fast Fourier transformation (FFT) images, showed that hydrolysis and calcination resulted in the dominant exposure of {100} and {001} facets, respectively. Photocatalytic data revealed that Bi5O7I–001 had a higher activity than Bi5O7I–100 for N2 fixation and dye degradation. Photoelectrochemical data revealed that Bi5O7I–001 had higher photoinduced carrier separation efficiency than Bi5O7I–100. The band structure analysis also used to explain the underlying photocatalytic mechanism based on the different conduction band position. This work presents the first report about the facet-dependent photocatalytic performance of bismuth-rich Bi–O–X 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.
The exploitation and preparation of novel non-noble-metal cocatalysts are particularly crucial to develop high-activity photocatalytic hydrogen-generation materials. In this study, metallic Sn ...nanoparticle, a new hydrogen-generation cocatalyst, was effectively integrated with the conventional TiO2 photocatalyst to greatly boost the hydrogen-production reaction via a direct photoinduced method. Herein, the direct photoinduced synthesis of Sn nanoparticle-deposited TiO2 photocatalysts and their enhanced H2-generation activity can be easily and simultaneously realized in an ethylene glycol–ethanol system. The Sn nanoparticles were very small (ca. 2 nm) and uniformly deposited onto the TiO2 surface to synthesize highly efficient Sn/TiO2 photocatalysts via the formation of Sn(II)-EG complex molecules and their following in situ photoreduction method. Photocatalytic results indicated that metallic Sn cocatalyst could dramatically promote the H2-generation activity of TiO2 photocatalyst, and the resultant Sn/TiO2(3 wt %) presented the highest H2-production rate with a value of 553.1 μmol h–1 g–1, which is 43.9 times as that of pure TiO2 (12.6 μmol h–1 g–1). Thus, an electron-cocatalyst-mediated mechanism is raised to explain the promoted H2-generation efficiency of TiO2 photocatalyst, namely, the metallic Sn cocatalyst can act as the electron receiver to quickly capture photoexcited electrons and serve as the interfacial hydrogen-generation site to enhance the hydrogen-generation rate. Considering the facile synthetic route, earth abundance, and high activity, the metallic Sn cocatalyst would have enormous prospect for the development of efficient photocatalysts applied in different fields.
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