Here, we will introduce the progress of g-C3N4 photocatalysts in hydrogen production from the aspects of changing the ratio of C and N, morphology, element doping and constructing heterostructures. ...Discuss the excellent results of various types of photocatalysts.
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g-C3N4 have been widely used in the fields of photocatalytic hydrogen production, photocatalytic degradation of dyes and oxidative degradation of toxic gases due to their excellent performance. It has attracted extensive attention in recent years due to its highly efficient photocatalytic capacity of hydrogen generation, water oxidation, carbon dioxide reduction and degradation of organic pollutants. Because of the abundant carbon and nitrogen composition of the earth, large-scale production and industrial applications of this material are possible. The modification of this material makes its performance more excellent so that this new material can obtain a steady stream of vitality. These outstanding works have become important materials and milestones on the road to mankind’s photocatalytic hydrogen production. This review will begin with the basic idea of designing, synthesizing and improving g-C3N4 based photocatalytic materials, and introduce the latest development of g-C3N4 photocatalysts in hydrogen production from four aspects of controlling the carbon/nitrogen ratio, morphology, element doping and heterojunction structure of g-C3N4 materials.
Photocatalytic overall water splitting is an interesting research topic in the field of energy and outer space exploration. Here, we designed a P/MoS2 composite photocatalyst with ...self-water-absorption performance by compositing MoS2 nanosheets and polycrystalline black phosphorus nanosheets. The composite photocatalyst produced a sufficient amount of hydrogen in the absence of any precious metal. This also demonstrated photocatalytic overall water-splitting ability in the absence of any sacrificial agent. More interestingly, it effectively absorbed water and demonstrated good overall water-splitting performance under the simulated Mars conditions; the average hydrogen production rate was 17.68 μmol h−1 g−1, and the oxygen production rate was 7.61 μmol h−1 g−1 over a period of 70 h. A comprehensive investigation of the ability of the composite photocatalyst to absorb water and produce hydrogen was performed.
Here, we designed a P/MoS2 composite photocatalyst with self-water-absorption performance. It demonstrated good water absorption and overall water-splitting properties under simulated Mars conditions. Display omitted
•We designed the first P/MoS2 composite photocatalyst with self-water-absorption performance.•The composite photocatalyst effectively produced hydrogen and absorbed water in the absence of any precious metals.•The ability of the photocatalyst to absorb water and perform overall water splitting was confirmed.
Two-dimensional (2D) carbon nitride (CN) photocatalysts are attracting extensive attention owing to their excellent photocatalytic properties. In this study, we successfully prepared CN materials ...with heterogeneous structures via hydrothermal treatment, high-temperature roasting, ball milling, sintering, and other processes. Benefitting from interface interactions in hybrid architectures, the CN photocatalysts exhibited high photocatalytic activity. The rate of hydrogen production using these CN photocatalysts reached 17028.82 μmol h−1 g−1, and the apparent quantum efficiency was 11.2% at 420 nm. The ns-level time-resolved photoluminescence (PL) spectra provided information about the time-averaged lifetime of fluorescence charge carriers; the lifetime of the charge carriers causing the fluorescence of CN reached 9.99 ns. Significantly, the CN photocatalysts displayed satisfactory results in overall water splitting without the addition of sacrificial agents. The average hydrogen and oxygen production rates were 270.95 μmol h−1 g−1 and 115.21 μmol h−1 g−1 in 7 h, respectively, which were promising results for the applications of the catalysts in overall water splitting processes. We investigated the high efficiency of the prepared CN photocatalysts via a series of tests (UV-vis diffuse reflectance spectroscopy, photocurrent response measurements, PL emission spectroscopy, time-resolved PL spectroscopy, and Brunauer-Emmett-Teller analysis). Furthermore, the Mott-Schottky plot and current-voltage curve were acquired via electrochemical tests. The fabricated CN photocatalyst had a small p-n junction in its heterogeneous structure, which further enhanced its photocatalytic efficiency. Therefore, this work can promote the development of CN photocatalysts.
In this work, we successfully prepared a CN material with a heterogeneous structure via a clever design for the first time. Benefitting from the interface interactions in hybrid architectures, the CN photocatalysts exhibited high photocatalytic activity.
Here, we proposed a multistep ion exchange (cation exchange and anion exchange) strategy to synthesize amorphous Ni-Co-S and polycrystalline β-Co(OH)2 hybrid nanomaterials with a hollow polyhedron ...structure. Benefiting from synergistic effects of different components and the remarkable superiorities of hollow structure, the electrode material possesses higher energy storage performance with the higher capacity of 1440.0 C/g at 1 A/gand the corresponding hybrid supercapacitor enjoys a high energy density of 58.4 Wh/kgat the power density of 0.8 kW/kg.
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In power storage technology, ion exchange is widely used to modify the electronic structures of electrode materials to stimulate their electrochemical properties. Here, we proposed a multistep ion exchange (cation exchange and anion exchange) strategy to synthesize amorphous Ni-Co-S and β-Co(OH)2 hybrid nanomaterials with a hollow polyhedron structures. The synergistic effects of different components and the remarkable superiorities of hollow structure endow Ni-Co-S/Co(OH)2 electrode with outstanding electrochemical performance, including ultra-high specific capacity (1440.0 C/g at 1 A/g), superior capacitance retention rate (79.1% retention at 20A/g) and long operating lifespan (81.4% retention after 5000 cycles). Moreover, the corresponding hybrid supercapacitor enjoys a high energy density of 58.4 Wh/kg at the power density of 0.8 kW/kg, and a decent cyclability that the capacitances are maintained at 80.8% compared with the initial capacitance. This research presents a high-performance electrode material and provides a promising route for the construction of electrode materials for supercapacitors with both structural and component advantages.
Developing highly durable and active Pt-supported catalysts is currently the most prominent and practicable electrocatalyst design strategy for direct methanol fuel cells (DMFC) due to their high ...electrocatalytic stability and activity. Herein, we fabricated CeO
2
nanorods with tiny Pt nanoparticles that possess good electrocatalytic behavior for methanol oxidation reaction (MOR). In addition, the presence of Ce
3+
and small Pt nanoparticles (3.46 nm) enhanced strong metal interaction, facilitating the formation of oxygen vacancies on the CeO
2
surface to boost the MOR performance. Hence, the Pt-CeO
2
catalyst revealed high mass activity (1414.0 mA mg
−1
) and areal-specific activity (1.615 mA cm
−2
) towards MOR in an acidic electrolyte, which was three times that of the 20% Pt/C catalyst (545.4 mA mg
−1
and 0.856 mA cm
−2
). Besides, the Pt-CeO
2
catalyst exhibited excellent performance of MOR in an alkaline electrolyte and retained 90.44% of its initial mass activity after 5000 cycles due to the unique morphology and synergistic effects between Pt and CeO
2
. Pt-CeO
2
is regarded as a promising MOR electrocatalyst for DMFC applications.
Graphical Abstract
Highlights
• 10% Pt-CeO
2
nanorods catalyst has excellent MOR performance in acidic and alkaline electrolytes.
• The high surface area of CeO
2
nanorod enhances the stability of Pt metal.
• Redox pair (Ce
3+
/Ce
4+
) and Pt-O induced oxygen vacancy may enhance the active surface area.
• Strong metal interaction leads to the synergistic effect of Pt-CeO
2
catalyst.
Here, the influence of the band gap was revealed by fluorination and hydroxylation of CN photocatalyst based on first theoretical principle. With F atoms and OH doping, the band gap of CN was ...significantly improved, conduction band and valence band moved up. Then, FCN photocatalyst with F atoms and OH was successfully synthesized by a hydrothermal fluorinated method. Next, the reasons why FCN photocatalyst was more effective than that of traditional CN photocatalyst was fully discussed.
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Carbon nitride (CN) photocatalysts have attracted much attention due to their excellent photocatalytic properties. And hydrothermal fluorination is a common method to improve the photocatalytic effect of CN photocatalyst. Here, the influence of the band gap was first revealed of fluorination and hydroxylation of CN photocatalyst based on the first theoretical principle. Here, the effect of fluorination and hydroxylation on the CN band gap was discussed for the first time using the first theoretical principle. With F atoms and OH doping, the band gap of CN was significantly improved, conduction band and valence band moved up. Then, FCN photocatalyst with F atoms and OH was successfully synthesized by a hydrothermal fluorinated method. Next, the reasons why FCN photocatalyst was more effective than that of traditional CN photocatalyst were fully discussed. From the photocatalytic effect of photocatalyst (12,593.2 μmol g−1 h−1 to the morphology (super-small nanosheets), structure (homojunctions), composition (metal‐free), specific surface area (54.1 m2/g), visible light absorption response (AQE is 10.9% at 420 nm) and photo-induced carrier life (14.13 ns). Therefore, this work has a great guiding effect on the development of CN photocatalyst.
The successful preparation and application of graphene shows that it is feasible for the materials with a thickness of a single atom or few atomic layers to exist stably in nature. These materials ...can exhibit unusual physical and chemical properties due to their special dimension effects. At present, researchers have made great achievements in the preparation, characterization, modification, and theoretical research of 2D materials. Because the structure of 2D materials is often similar, it has a certain degree of qualitative versatility. Besides, 2D materials often carry good catalytic performance on account of their more active sites and adjustable harmonic electronic structure. In this review, taking 2D materials as examples graphene, boron nitride (h-BN), transition metal sulfide and so on, we review the crystal structure and preparation methods of these materials in recent years, focus on their photocatalyst properties (carbon dioxide reduction and hydrogen production), and discuss their applications and development prospects in the future.
With the rise in biometric-based identity authentication, facial recognition software has already stimulated interesting research. However, facial recognition has also been subjected to criticism due ...to security concerns. The main attack methods include photo, video, and three-dimensional model attacks. In this paper, we propose a multifeature fusion scheme that combines dynamic and static joint analysis to detect fake face attacks. Since the texture differences between the real and the fake faces can be easily detected, LBP (local binary patter) texture operators and optical flow algorithms are often merged. Basic LBP methods are also modified by considering the nearest neighbour binary computing method instead of the fixed centre pixel method; the traditional optical flow algorithm is also modified by applying the multifusion feature superposition method, which reduces the noise of the image. In the pyramid model, image processing is performed in each layer by using block calculations that form multiple block images. The features of the image are obtained via two fused algorithms (MOLF), which are then trained and tested separately by an SVM classifier. Experimental results show that this method can improve detection accuracy while also reducing computational complexity. In this paper, we use the CASIA, PRINT-ATTACK, and REPLAY-ATTACK database to compare the various LBP algorithms that incorporate optical flow and fusion algorithms.
In this paper, a caterpillar like nanorod-like structure (Ag2S-NiCo2S4/CF) is synthesized by sulfur modification of the Ag-NiCo-THs nanoneedles. Due to the synergic effect of Ag2S and NiCo2S4 in the ...hybrid architecture, the electrode material has excellent performance with a capacity of 179.7 mAh g−1 at 1 A g−1 and a high energy density of 35.978 Wh kg−1 at 800 W kg−1.
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Hybrid supercapacitors have the advantages of fast charging and discharging and long service life, which are an efficient and practical energy storage device. Therefore, the design of hybrid supercapacitors is the focus of current research. In this paper, the silver modified spinel NiCo2S4 nanorods (Ag2S-NiCo2S4/CF) are synthesized by an efficient and economical method, which has excellent electrochemical performance. The Ag2S-NiCo2S4/CF shows a high specific capacity of 179.7 mAh g−1 at current density of 1 A g−1, and excellent rate capability (capacitance retention of ~87% at 20 A g−1). The corresponding Ag2S-NiCo2S4/CF//AC/CF hybrid supercapacitor is assembled by Ag2S-NiCo2S4/CF as the positive electrode, which can provide an energy density of 35.978 Wh kg−1 at a high-power density of 800 W kg−1 and has significant cyclic stability (~80% of the initial capacitor after ~9600 cycles). Therefore, Ag2S-NiCo2S4/CF material is a promising electrode material that can be applied to hybrid supercapacitors.
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