Ultrathin ZnIn2S4 Nanosheets Anchored on Ti3C2TX MXene for Photocatalytic H2 Evolution

Photocatalysts derived from semiconductor heterojunctions that harvest solar energy and catalyze reactions still suffer from low solar‐to‐hydrogen conversion efficiency. Now, MXene (Ti₃C₂T_X) nanosheets (MNs) are used to support the in situ growth of ultrathin ZnIn₂S₄ nanosheets (UZNs), producing sandwich‐like hierarchical heterostructures (UZNs‐MNs‐UZNs) for efficient photocatalytic H₂ evolution. Opportune lateral epitaxy of UZNs on the surface of MNs improves specific surface area, pore diameter, and hydrophilicity of the resulting materials, all of which could be beneficial to the photocatalytic activity. Owing to the Schottky junction and ultrathin 2D structures of UZNs and MNs, the heterostructures could effectively suppress photoexcited electron–hole recombination and boost photoexcited charge transfer and separation. The heterostructure photocatalyst exhibits improved photocatalytic H₂ evolution performance (6.6 times higher than pristine ZnIn₂S₄) and excellent stability.     

Introducing sulfur vacancies and in-plane SnS2/SnO2 heterojunction in SnS2 nanosheets to promote photocatalytic activity

Due to the relatively sluggish charge carrier separation in metal sulfides, the photocatalytic activity of them is still far lower than expected. Herein, sulfur vacancies and in-plane SnS₂/SnO₂ heterojunction were successfully introduced into the SnS₂ nanosheets through high energy ball-milling. These defective structures were studied by the electron paramagnetic resonance, Raman spectra, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscope analyses. The sulfur vacancies and in-plane heterojunctions strongly accelerate the separation of photoexcited electron-hole pairs, as confirmed by the photoluminescence emission spectra and time-resolved photoluminescence decay spectra. The introduction of sulfur vacancies and in-plane heterojunction in SnS₂ nanosheets results in roughly six times higher photodegrading rate for methyl orange and four times higher photocatalytic reduction rate of Cr⁶⁺ than those of pure SnS₂ nanosheets.     

Visible‐Light Photocatalytic Hydrogen Production Activity of ZnIn2S4 Microspheres Using Carbon Quantum Dots and Platinum as Dual Co‐catalysts

ZnIn₂S₄ microspheres (ZIS MSs) were for the first time decorated with carbon quantum dots (CQDs) and platinum nanoparticles (NPs) as dual co‐catalysts of for photocatalytic H₂ production. The ZIS MSs co‐loaded with CQDs and Pt exhibited a high photocatalytic H₂ production rate of 1032.2 μmol h^?1 g^?1 with an apparent quantum efficiency of 2.2 % (420 nm) in triethanolamine aqueous solution under visible‐light irradiation, which was much higher than the respective photocatalytic rates of pure ZIS, Pt loaded ZIS, and CQDs‐decorated ZIS. Such a great enhancement was attributed to the integrative effect of good crystallization, enhanced light absorption, high electrical conductivity of CQDs, and the vectorial electron transfer from ZIS to CQDs and Pt NPs (ZIS→CQDs→Pt).     

Nickel Doping in Atomically Thin Tin Disulfide Nanosheets Enables Highly Efficient CO2 Reduction

Engineering electronic properties by elemental doping is a direct strategy to design efficient catalysts towards CO₂ electroreduction. Atomically thin SnS₂ nanosheets were modified by Ni doping for efficient electroreduction of CO₂. The introduction of Ni into SnS₂ nanosheets significantly enhanced the current density and Faradaic efficiency for carbonaceous product relative to pristine SnS₂ nanosheets. When the Ni content was 5 atm %, the Ni‐doped SnS₂ nanosheets achieved a remarkable Faradaic efficiency of 93 % for carbonaceous product with a current density of 19.6 mA cm^?2 at ?0.9 V vs. RHE. A mechanistic study revealed that the Ni doping gave rise to a defect level and lowered the work function of SnS₂ nanosheets, resulting in the promoted CO₂ activation and thus improved performance in CO₂ electroreduction.     

Fe doped g-C3N4 composited ZnIn2S4 promoting Cr(VI) photoreduction

30% FeCN/ZIS (30% Fe doped g-C₃N₄ composited ZnIn₂S₄) was synthesized by a simple water bath method, via in-situ growth of abundant well-dispersed ZnIn₂S₄ nanosheets on the Fe doped g-C₃N₄ surface. Experimental results showed the optimized 30% FeCN/ZIS achieved the best photoreduction of Cr(VI) performance within a wide pH range, which was 9.5 times and 700 times higher than that of pure ZnIn₂S₄ and 30% FeCN (Fe doped g-C₃N₄). This is due to the intense synergy between the Fe-N_x bond and close interface contact produces a high-speed charge transfer channel, thus significantly improving the efficiency of optical carrier separation and migration. Meanwhile, UV-vis diffuse reflection spectra and photoluminescence spectroscopy showed that iron doping significantly narrowed the bandgap of g-C₃N₄, preventing electron-hole pair recombination. Further, the microstructures and charge separation properties were analyzed by scanning electron microscope, Photoluminescence Spectroscopy and time-resolved photoluminescence, which revealed the structure-activity relationship of composite structure and the synergistic mechanism of each functional component. This research should provide a viable technique for creating composites with high photocatalytic activity for the treatment of chromium-containing wastewater.     

Accelerating photocatalytic hydrogen evolution and pollutant degradation by coupling organic co-catalysts with TiO2

Accelerating the separation efficiency of photoexcited electron-hole pairs with the help of highly active co-catalysts has proven to be a promising approach for improving photocatalytic activity. Thus far, the most developed co-catalysts for semiconductor-based photocatalysis are inorganic materials; the employment of a specific organic molecule as a co-catalyst for photocatalytic hydrogen evolution and pollutant photodegradation is rare and still remains a challenging task. Herein, we report on the use of an organic molecule, oxamide (OA), as a novel co-catalyst to enhance electron-hole separation, photocatalytic H₂ evolution, and dye degradation over TiO₂ nanosheets. OA-modified TiO₂ samples were prepared by a wet chemical route and demonstrated improved light absorption in the visible-light region and more efficient charge transport. The photocatalytic performance of H₂ evolution from water splitting and rhodamine B (RhB) degradation for an optimal OA-modified TiO₂ photocatalyst reached 2.37 mmol g^-1 h^-1 and 1.43 × 10^?2 min^?1, respectively, which were 2.4 and 3.8 times higher than those of pristine TiO₂, respectively. A possible mechanism is proposed, in which the specific π-conjugated structure of OA is suggested to play a key role in the enhancement of the charge transfer and catalytic capability of TiO₂. This work may provide advanced insight into the development of a variety of metal-free organic molecules as functional co-catalysts for improved solar-to-fuel conversion and environmental remediation.     

Photoinduced Multiple Effects to Enhance Uranium Extraction from Natural Seawater by Black Phosphorus Nanosheets

Based on the photoinduced photothermal, photoelectric, and photocatalytic effects of black phosphorus (BP) nanosheets, a BP‐PAO fiber with enhanced uranium extraction capacity and high antibiofouling activity is fabricated by compositing BP nanosheets into polyacrylamidoxime (PAO). The photothermal effect increases the coordination interaction between UO₂²⁺ and the functional amidoxime group, and the photoelectric effect produces the surface positive electric field that exhibits electrostatic attraction to the negative [UO₂(CO₃)₃]^4?, which all increase the capacity for uranium adsorption. The photocatalytic effect endows the adsorbent with high antibiofouling activity by producing biotoxic reactive oxygen species. Owing to these three photoinduced effects, the photoinduced BP‐PAO fiber shows a high uranium adsorption capacity of 11.76 mg g^?1, which is 1.50 times of the PAO fiber, in bacteria‐containing natural seawater.     

Facile one‐step synthesis of broken case‐like carbon‐doped g‐C3N4 for photocatalytic degradation of benzene

Herein, a novel broken case‐like carbon‐doped g‐C₃N₄ photocatalyst was obtained via a facile one‐pot pyrolysis and cost‐effective method using glyoxal‐modified melamine as a precursor. The obtained carbon/g‐C₃N₄ photocatalyst showed remarkable enhanced photocatalytic activity in the degradation of gaseous benzene compared with that of pristine g‐C₃N₄ under visible light. The pseudo‐first‐order rate constant for gaseous benzene degradation on carbon/g‐C₃N₄ was 0.186 hr^?1, 5.81 times as large as that of pristine g‐C₃N₄. Furthermore, a possible photocatalytic mechanism for the improved photocatalytic performance over carbon/g‐C₃N₄ nanocomposites was proposed.     

Carbon-doped anatase TiO2 nanotube array/glass and its enhanced photocatalytic activity under solar light

To enhance the photocatalytic activity under solar light, highly ordered TiO₂ nanotube arrays (TNAs) film with anatase phase was fabricated on glass and successfully doped with carbon at various temperatures of 450–550 °C. The characterization results indicate that, after carbon doping, the TNAs still remained nanotubular structure with anatase phase. But their optical response shifted from UV to the visible light region and the recombination of photogenerated carriers was suppressed effectively. It is more important that the carbon-doped TNAs/glass (C-TNAs) samples exhibited high solar light photocatalytic activity, and 68%, 61% and 56% MO was photodegraded in 150 min by the C-TNAs calcined at 550, 500 and 450 °C, respectively. Especially, the apparent reaction rate constant of C-TNAs calcined at 550 (k, 0.065 min⁻¹) with the highest activity is 3.6 times that of pristine anatase TNAs (k, 0.018 min⁻¹). It is clear that carbon doping enhanced the photocatalytic activity under sunlight at optimized annealing temperature. The efficient activity could be attributed to the synergetic effects of strong visible light absorption, good crystallization, large surface, and enhanced separation of photoinduced carriers.     

超薄Ni掺杂ZnIn2S4纳米片用于光催化醇裂解同时制备C-C耦合产物及氢气

光催化析氢技术被认为是解决化石能源紧缺和环境污染问题的有效途径之一.在传统的光解水体系中,析氧半反应因涉及到复杂的四电子转移和O=O双键形成,成为光催化水分解的决速步骤.光生空穴牺牲试剂的引入虽然可以在一定程度上提高体系的光催化效率,但同时造成了光生空穴氧化能力的浪费,且增加了系统成本.相比之下,构建由光催化析氢和选择...     

Co doped ZnO nanowires as visible light photocatalysts

High aspect ratio cobalt doped ZnO nanowires showing strong photocatalytic activity and moderate ferromagnetic behaviour were successfully synthesized using a solvothermal method and characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS), vibrating sample magnetometry (VSM) and UV–visible absorption spectroscopy. The photocatalytic activities evaluated for visible light driven degradation of an aqueous methylene orange (MO) solution were higher than for Co doped ZnO nanoparticles at the same doping level and synthesized by the same synthesis route. The rate constant for MO visible light photocatalytic degradation was 1.9·10⁻³ min⁻¹ in case of nanoparticles and 4.2·10⁻³ min⁻¹ in case of nanowires. We observe strongly enhanced visible light photocatalytic activity for moderate Co doping levels, with an optimum at a composition of Zn_0.95Co_0.05O. The enhanced photocatalytic activities of Co doped ZnO nanowires were attributed to the combined effects of enhanced visible light absorption at the Co sites in ZnO nanowires, and improved separation efficiency of photogenerated charge carriers at optimal Co doping.     

Micelle‐Directing Synthesis of Ag‐Doped WO3 and MoO3 Composites for Photocatalytic Water Oxidation and Organic‐Dye Adsorption

In this paper, an Ag‐doped WO₃ (and MoO₃) composite has been prepared by following a simple micelle‐directed method and high‐temperature sintering route. The as‐prepared samples were characterized by X‐ray diffraction, inductively coupled plasma, transmission electron microscopy, X‐ray photoelectron spectroscopy, UV/Vis diffuse reflectance spectroscopy, Brunauer–Emmett–Teller, photoluminescence spectroscopy, and electrochemical impedance spectroscopy techniques. The photocatalytic experiments reveal that their oxygen‐production rates are up to 95.43 μmol (75.45 μmol) for Ag‐doped WO₃ (MoO₃), which is 9.5 (7.3) times higher than that of pure WO₃: 9.012 μmol (MoO₃: 9.00 μmol) under visible‐light illumination (λ ≥420 nm), respectively. The improvement of their photocatalytic activity is attributed to the enhancement of their visible‐light absorption and the separation efficiency of photogenerated carriers by Ag doping. Moreover, Ag‐doped WO₃ (MoO₃) also shows excellent adsorption of rhodamine B (RhB) and methylene blue (MB) in aqueous solution, with maximum adsorption capacities towards RhB and MB of 822 and 820 mg g⁻¹ for Ag‐doped WO₃, and 642 and 805 mg g⁻¹ for Ag‐doped MoO₃, respectively.     

Samarium and Nitrogen Co‐Doped Bi2WO6 Photocatalysts: Synergistic Effect of Sm3+/Sm2+ Redox Centers and N‐Doped Level for Enhancing Visible‐Light Photocatalytic Activity

Samarium and nitrogen co‐doped Bi₂WO₆ nanosheets were successfully synthesized by using a hydrothermal method. The crystal structures, morphology, elemental compositions, and optical properties of the prepared samples were investigated. The incorporation of samarium and nitrogen ions into Bi₂WO₆ was proved by X‐ray diffraction, energy dispersive X‐ray spectroscopy, and X‐ray photoelectron spectroscopy. UV/Vis diffuse reflectance spectroscopy indicated that the samarium and nitrogen co‐doped Bi₂WO₆ possessed strong visible‐light absorption. Remarkably, the samarium and nitrogen co‐doped Bi₂WO₆ exhibited higher photocatalytic activity than single‐doped and pure Bi₂WO₆ under visible‐light irradiation. Radical trapping experiments indicated that holes (h⁺) and superoxide radicals ( ^. O₂^?) were the main active species. The results of photoluminescence spectroscopy and photocurrent measurements demonstrated that the recombination rate of the photogenerated electrons and holes pairs was greatly depressed. The enhanced activity was attributed to the synergistic effect of the in‐built Sm³⁺/Sm²⁺ redox pair centers and the N‐doped level. The mechanism of the excellent photocatalytic activity of Sm‐N‐Bi₂WO₆ is also discussed.     

Enhanced visible‐light‐driven photocatalytic activity of F doped reduced graphene oxide ‐ Bi2WO6 photocatalyst

The reduced graphene oxide‐Bi₂WO₆ (rGO‐BWO) photocatalysts with the different R_F/O values (molar ratio of the F molar mass and the O's molar mass of Bi₂WO₆) had been successfully synthesized via one‐step hydrothermal method. The F‐doped rGO‐BWO samples were characterized by X‐ray diffraction patterns (XRD), field‐emission scanning electron microscopy (FE‐ESEM), transmission electron microscopy (TEM), Brunauer–Emmett–Teller surface area (BET), X‐ray photoelectron spectroscopy (XPS) and UV–vis diffuse reflectance spectra (DRS). The results indicate that F^? ions had been successfully doped into rGO‐BWO samples. With the increasing of the R_F/O values from 0 to 2%, the evident change of the morphology and the absorption edges of F‐doped rGO‐BWO samples and the photocatalytic activities had been enhanced. Moreover, the photocatalytic activity of F‐doped rGO‐BWO with R_F/O = 0.05 were better than rGO‐BWO and the other F‐doped rGO‐BWO under 500 W Xe lamp light irradiation. The enhanced photocatalytic activity can be attributed to the morphology of the intact microsphere that signify the bigger specific surface area for providing more possible reaction sites for the adsorption–desorption equilibrium of photocatalytic reaction, the introduction of F^? ions that may cause the enhancement of surface acidity and creation of oxygen vacancies under visible light irradiation, the narrower band gap which means needing less energy for the electron hole pair transition.     

Understanding the synergistic effects,optical and electronic properties of ternary Fe/C/S‐doped TiO2 anatase within the DFT + U approach

Although TiO₂ is an efficient photocatalyst, its large band gap limits its photocatalytic activity only to the ultraviolet region. An experimentally synthesized ternary Fe/C/S‐doped TiO₂ anatase showed improved visible light photocatalytic activity. However, a theoretical study of the underlying mechanism of the enhanced photocatalytic activity and the interaction of ternary Fe/C/S‐doped TiO₂ has not yet been investigated. In this study, the defect formation energy, electronic structure and optical property of TiO₂ doped with Fe, C, and S are investigated in detail using the density functional theory + U method. The calculated band gap (3.21 eV) of TiO₂ anatase agree well with the experimental band gap (3.20 eV). The defect formation energy shows that the co‐ and ternary‐doped systems are thermodynamically favorable under oxygen‐rich condition. Compared to the undoped TiO₂, the absorption edge of the mono‐, co‐, and ternary‐doped TiO₂ is significantly enhanced in the visible light region. We have shown that ternary doping with C, S, and Fe induces a clean band structure without any impurity states. Moreover, the ternary Fe/C/S‐doped TiO₂ exhibit an enhanced photocatalytic activity, a smaller band gap and negative formation energy compared to the mono‐ and co‐doped systems. Moreover, the band edges of Fe/C/S‐doped TiO₂ align well with the redox potentials of water, which shows that the ternary Fe/C/S‐doped TiO₂ is promising photocatalysts to split water into hydrogen and oxygen. These findings rationalize the available experimental results and can assist the design of TiO₂‐based photocatalyst materials.     

Fluorine‐Doped Porous Single‐Crystal Rutile TiO2 Nanorods for Enhancing Photoelectrochemical Water Splitting

Fluorine‐doped hierarchical porous single‐crystal rutile TiO₂ nanorods have been synthesized through a silica template method, in which F^? ions acts as both n‐type dopants and capping agents to make the isotropic growth of the nanorods. The combination of high crystallinity, abundant surface reactive sites, large porosity, and improved electronic conductivity leads to an excellent photoelectrochemical activity. The photoanode made of F‐doped porous single crystals displays a remarkably enhanced solar‐to‐hydrogen conversion efficiency (≈0.35 % at ?0.33 V vs. Ag/AgCl) under 100 mW cm^?2 of AM=1.5 solar simulator illumination that is ten times of the pristine solid TiO₂ single crystals.     

Boron‐Doped,Carbon‐Coated SnO2/Graphene Nanosheets for Enhanced Lithium Storage

Heteroatom doping is an effective method to adjust the electrochemical behavior of carbonaceous materials. In this work, boron‐doped, carbon‐coated SnO₂/graphene hybrids (BCTGs) were fabricated by hydrothermal carbonization of sucrose in the presence of SnO₂/graphene nanosheets and phenylboronic acid or boric acid as dopant source and subsequent thermal treatment. Owing to their unique 2D core–shell architecture and B‐doped carbon shells, BCTGs have enhanced conductivity and extra active sites for lithium storage. With phenylboronic acid as B source, the resulting hybrid shows outstanding electrochemical performance as the anode in lithium‐ion batteries with a highly stable capacity of 1165 mA h g^?1 at 0.1 A g^?1 after 360 cycles and an excellent rate capability of 600 mA h g^?1 at 3.2 A g^?1, and thus outperforms most of the previously reported SnO₂‐based anode materials.     

A Multiple Structure‐Design Strategy towards Ultrathin Niobate Perovskite Nanosheets with Thickness‐Dependent Photocatalytic Hydrogen‐Evolution Performance

Hydrogen production by catalytic water splitting using sunlight holds great promise for clean and sustainable energy source. Despite the efforts made in the past decades, challenges still exist in pursuing solid catalysts with light‐harvesting capacity, large surface areas and efficient utilities of the photogenerated carrier, at the same time. Here, a multiple structure design strategy leading to highly enhanced photocatalytic performance on hydrogen production from water splitting in Dion–Jacobson perovskites KCa₂Na_{n ‐3}Nb_n O_{3n +1} is described. Specifically, chemical doping (N/Nb⁴⁺) of the parent oxides via ammoniation improved the ability of sunlight harvesting efficiently; subsequent liquid exfoliation of the doped perovskites yielded ultrathin [Ca₂Na_{n ‐3}Nb_n O_{3n +1}]⁻ nanosheets with greatly increased surface areas. Significantly, the maximum hydrogen evolution appears in the n =4 nanosheets, which suggests the most favorable thickness for charge separation in such perovskite‐type catalysts. The optimized black N/Nb⁴⁺‐[Ca₂NaNb₄O₁₃]⁻ nanosheets show greatly enhanced photocatalytic performance, as high as 973 μmol h⁻¹ with Pt loading, on hydrogen evolution from water splitting. As a proof‐of‐concept, this work highlights the feasibility of combining various chemical strategies towards better catalysts and precise thickness control of two‐dimensional materials.     

Visible‐light‐driven photocatalytic degradation using Mn‐doped SrMoO4 nanoparticles

Mn‐doped SrMoO₄ nanocrystals were synthesized by thermal decomposition of metal–organic salt in an organic solvent with the doping content in the range 0–12 mol%. The structures, morphologies and optical properties were characterized using various techniques. The results suggest that Mo sites in the SrMoO₄ lattice are substituted by the Mn dopant, the adsorption bands are found to be shifted toward the visible light region and the band gap becomes narrower correspondingly. The photocatalytic performance of the as‐synthesized product was determined using the degradation of methylene blue by visible light irradiation. The photocatalytic performance is enhanced with Mn doping, and the optimal degradation rate is 85% in 140 min for 5 mol% Mn doping. The enhanced photocatalytic activity with Mn doping may be ascribed to the energy band adjustment and effective photogenerated electron–hole separation caused by the Mn doping. A possible photocatalytic mechanism is also discussed.     

Engineering surface oxygen vacancy of mesoporous CeO2 nanosheets assembled microspheres for boosting solar-driven photocatalytic performance

Surface oxygen vacancy defects of mesoporous CeO₂ nanosheets assembled microspheres（D-CeO₂） are engineered by polymer precipitation, hydrothermal and surface hydrogenation strategies. The resultant D-CeO₂ with a main pore diameter of 9.3 nm has a large specific surface area（～102.3 m²/g） and high thermal stability. The mesoporous nanosheets assembled microsphere structure prevents the nanosheets from aggregation, which is beneficial to effective mass tr...