Low Photocatalytic Activity Research Articles

Interfacial interaction of graphitic carbon nitride/nanodiamond nanocomposites toward synergistic enhancement of photocatalytic degradation of organic contaminants

Graphitic carbon nitride (g-C3N4) has been widely used in various photocatalyst applications. However, compared with conventional metal-based photocatalysts, it exhibits low photocatalytic activity because of the low mobility of its charge carriers. In this study, g-C3N4/nanodiamond (ND) nanocomposites were fabricated via a facile single-step heating strategy. Under visible-light irradiation, the optimal g-C3N4/ND nanocomposites with 1.0 wt% ND content exhibited an RhB degradation rate more than two times greater than that of the g-C3N4. In addition, reutilization experiments showed that the g-C3N4/ND nanocomposites exhibit good stability and reusability. This remarkable enhancement of the photocatalytic activity was attributed to the interfacial effect between g-C3N4 and ND, which reduces energy-wasteful electron–hole recombination and promotes charge-separation efficiency. Such an approach could accelerate the development of composites for photocatalyst applications and provide more rational guidance and fundamental understanding toward realizing the theoretical limits of interfaces.

Photocatalytic Degradation of Methylene Blue Dye by Electrospun Binary and Ternary Zinc and Titanium Oxide Nanofibers

Synthetic dyes, dispersed in water, have harmful effects on human health and the environment. In this work, Ti and/or Zn oxide nanofibers (NFs) with engineered architecture and surface were produced via electrospinning followed by calcination. Calcination and subsequent cooling were operated at fast rates to generate porous NFs with capture centers to reduce the recombination rate of the photogenerated charges. After morphological and microstructural characterisation, the NFs were comparatively evaluated as photocatalysts for the removal of methylene blue from water under UV irradiation. The higher band gap and lower crystallinity were responsible for the lower photocatalytic activity of the ternary oxides (ZnTiO3 and Zn2TiO4) towards the degradation of the dye. The optimal loads of the highly performing binary oxides were determined. By using 0.66 mg mL−1 wurtzite ZnO for the discoloration of an aqueous solution with a dye concentration of 15 µM, a higher rate constant (7.94 × 10−2 min−1) than previously reported was obtained. The optimal load for anatase TiO2 was lower (0.33 mg mL−1). The corresponding rate constant (1.12 × 10−1 min−1) exceeds the values reported for the commonly used P25–TiO2 benchmark. The catalyst can be reused twice without any regeneration treatment, with 5.2% and 18.7% activity decrease after the second and third use, respectively.

Boosting the photocatalytic H2 production performance and stability of C3N4 nanosheets via the synergistic effect between SnO2 nanoparticles and Pt nanoclusters

Low photocatalytic activity and unsatisfactory stability impede the commercialization of C3N4-based photocatalysts. Herein, a photocatalyst with outstanding performance was fabricated using C3N4 nanosheets, SnO2 nanoparticles and Pt nanoclusters. The H2 evolution rate over it is 1.06 mmol g-1h−1, which is about 177 times that over pristine C3N4 nanosheets and 2.3 times that over the Pt loaded C3N4 nanosheets. Besides, it also shows remarkable stability. After ten cycles of repeated photocatalytic experiments, its photocatalytic activity can remain 93% compared to the first cycle. This study provides a helpful strategy for boosting the photocatalytic activity and stability of C3N4-based photocatalysts.

Improved photocatalytic activity and stability of InGaN quantum dots/C3N4 heterojunction photoelectrode for CO2 reduction and hydrogen production

Photocatalytic conversion of CO2 to produce fuel is considered a promising approach to reduce CO2 emissions and tackle energy crisis. GaN-based materials have been studied for CO2 reduction because of their excellent optical properties and band structure. However, low photocatalytic activity and severe photocorrosion of GaN-based photoelectrode greatly limit their applications. In this work, photocatalytic activity was improved by adopting InGaN quantum dots (QDs) combined with C3N4 nano-sheets as photoanode, and thus the efficiency of CO2 reduction and the selectivity of hydrogen production were increased significantly. In addition, the photoelectron-chemical corrosion of photoelectrodes has been apparently controlled. InGaN QDs/C3N4 has the highest CO and H2 productions rates of 14.69 μmol mol−1 h−1 and 140 μmol mol−1 h−1 which were 2.2 times and 14.5 times than that of InGaN film photoelectrode, respectively. The enhancement of photocatalytic activity is attributed to C3N4 modification and a large electric dipole forming on the surface of InGaN QDs, which facilitate the separation and transfer of photo-generated carriers and thus promote CO2 reduction reaction. This work provides a promising strategy for the development of GaN-based photoanodes with superior stability and efficiency.

Construction of novel 2D-0D MnPS3–Cs4W11O35 composite for the improved photocatalytic hydrogen evolution activity

Photocatalytic hydrogen evolution is a prospective approach to solve the problem about energy crisis by fossil fuel combustion. As a possible novel photocatalyst for hydrogen generation, MnPS3 suffered from the lower photocatalytic activity caused by its high electron-hole recombination rate and poor oxidation capability of holes. In this paper, the MnPS3 nanosheets were exfoliated under sonication process in the solution of N-methylpyrrolidone (NMP) and 3-ethoxypropylamine, and then a series of Z-scheme 2D-0D MnPS3–Cs4W11O35 composites were prepared by a facile electrostatic assembling approach. The exfoliated MnPS3 nanosheets with the thickness of 5.4 nm present evidently increased interlayer spacing of 17.6 Å compared with 6.42 Å of bulk MnPS3. The Cs4W11O35 of 20–25 nm are uniformly immobilized on the surface of 400 nm exfoliated MnPS3 sheets with strong interfacial interaction of S–W–O bonds. The MnPS3–Cs4W11O35 composites show extended light absorption area, reduced charge recombination and significantly improved hydrogen generation activity compared with MnPS3 nanosheets. The highest hydrogen evolution rate of the MnPS3–Cs4W11O35 composites reaches 99.6 μmol g−1 h−1 with a Cs4W11O35 mass percent of 10.9, which is 2.9 times of MnPS3 nanosheets. The photocatalytic activity of MnPS3–Cs4W11O35 remains nearly unchanged after 4 cycles. As far as we are aware, there is no work carried out on the exfoliation of MnPS3 sheets in NMP and the fabrication of MnPS3–Cs4W11O35 composite for the enhanced photocatalytic hydrogen generation yet. Our work provides a new reference method for the preparation of unlaminated composite materials, and the novel MnPS3-based composite will be a useful supplement to the photocatalytic production of clean energy.

Colloidal SnO2‐Assisted CdS Electron Transport Layer Enables Efficient Electron Extraction for Planar Perovskite Solar Cells

The cadmium sulfide (CdS) is a promising electron transport layer (ETL) material for perovskite solar cells (PSCs) due to its low photocatalytic activity toward perovskite materials under UV light. The critical problem responsible for the moderate performance of CdS‐based PSCs is the parasitic light absorption of CdS, which drives researchers to deposit ultrathin ETLs. However, the ultrathin ETL often involves the undesirable shunt current leakage because of the direct contact between conducting substrate and perovskite layer. Herein, a fully low‐temperature solution‐processed colloidal SnO2‐assisted CdS (S‐CdS) ETL for planar CH3NH3PbI3 PSCs is constructed. The detailed characterizations of morphological, optical, and energy levels confirm that the assistance of colloidal SnO2 provides the ameliorated continuity, reduces surface roughness and superior wettability of ETLs for high‐quality perovskite formation as well as the favorable cascade band structure for efficient charge transfer. The study of charge transfer mechanisms reveals that the S‐CdS ETL effectively inhibits the shunt leakage, promotes the electron extraction and suppresses the charge recombination at the ETL/perovskite interface. Consequently, the S‐CdS ETL‐based PSCs deliver an appreciable efficiency of 16.26%, doubling that of conventional CdS‐based devices. To the best of our knowledge, this value is the champion efficiency reported for CdS‐based CH3NH3PbI3 PSCs.

Effects of Cu doping on the phase transition and photocatalytic activity of anatase/rutile mixed crystal TiO2 nanocomposites

Pure and Cu doped anatase/rutile mixed TiO2 nanomaterials were fabricated through sol-gel method. The obtained photocatalysts were characterized by XRD, SEM, TEM, XPS, PL and DRS, and the influences of Cu doping on the structure and photocatalytic property were studied. The results show that when the molar ratios of Cu/Ti are 1% and 2%, Cu doping promotes anatase → rutile phase transformation. When the molar ratio of Cu/Ti is 4%, the phase transformation is inhibited. Cu element coexists in the form of Cu+ and Cu2+, and Cu doping facilitates the separation of photogenerated electrons and holes. TEM image shows that copper oxides are dispersed on TiO2 particles surface, which significantly reduces the optical absorption of ultraviolet region. The photocatalytic experiment results show that the photocatalytic activity of Cu–TiO2 is lower than pure TiO2, and the higher doping concentration, the lower photocatalytic activity.

Boosting Nitrogen Activation via Bimetallic Organic Frameworks for Photocatalytic Ammonia Synthesis

Photocatalytic ammonia synthesis from N2 is a carbon-neutral strategy, although its efficiency is impeded by the activation of inert N≡N triple bonds. In N2 activation, the electron acceptance process is often strongly coupled with the electron donation process, leading to a high potential activation energy barrier and low photocatalytic activity. Herein, we proposed a strategy to decouple these two processes by bimetallic organic frameworks (BMOFs) for boosting N2 activation. The rationally designed BMOFs are composed of two functional metal nodes, in which the hard acid metal node with a high ionization potential (In) accepts the electron from N2 and the soft acid metal node with a low In donates the electron to N2. Owing to the bimetal synergistic effect, the potential activation energy barrier of N2 is reduced, as confirmed by the in situ Fourier transform infrared (FTIR) spectra and density functional theory (DFT) calculations. Via testing six kinds of bimetal combinations, it is found that, as the ionization potential difference (ΔIn) between the two metals is ≥6 eV and the proportion of high In metal reaches ∼20%, the bimetal synergistic effect becomes dominant. In all the as-prepared BMOFs, the optimal BMOF(Sr)–0.2Fe photocatalyst exhibits an NH3 evolution rate up to 780 μmol g–1 h–1. This work may unveil a corner of the hidden mechanism for the chemical bond activation in a broad range of catalytic processes.

Anatomy of a Natural Sunlight Driven CdS/CoTiO3/ZnO Ternary Photocatalyst for Efficient Optical Properties and Removal of Reactive Orange 30

ZnO as a promising photocatalyst has gained much attention for the removal of organic pollutants from water. However, the main drawbacks of the relatively low photocatalytic activity and high recombination rate of photoexcited electron-hole pairs restrict its potential applications. Promoting the spatial separation of photoexcited charge carriers is of paramount significance for photocatalysis because the difference in the band positions makes the potential gradient at the composite boundary. In this work, binary CdS/ZnO and CoTiO3/ZnO are first prepared by dispersion method and then decorated with ZnO particles to construct CdS/CoTiO3/ZnO ternary composites. For this reason, the CdS/CoTiO3/ZnO ternary composites was effectively designed and analyzed for the crystalline structure, light absorption, photoexcitation behavior and surface morphological properties by X-ray diffraction, diffuse reflectance UV/visible absorption spectroscopy, photoluminescence spectroscopy and scanning electron micrograph respectively. The photocatalytic activity was examined by degradation of the dye solution spectrophotometrically. The results of photocatalytic degradation indicated that the CdS/CoTiO3/ZnO ternary composites are much higher than those of bare CdS, CoTiO3, ZnO and any binary composites such as CoTiO3/ZnO and ZnO/CdS. The enhanced activity could be attributed to the drop electron transfer from CdS to ZnO to CoTiO3 through the interfacial potential gradient in the ternary hybrid conduction bands. The enhanced electron transfer of CdS/CoTiO3/ZnO ternary composites was also applicable to degrade other reactive dyes.

Single-atom Pt-I3 sites on all-inorganic Cs2SnI6 perovskite for efficient photocatalytic hydrogen production

Organic-inorganic lead halide perovskites are a new class of semiconductor materials with great potential in photocatalytic hydrogen production, however, their development is greatly plagued by their low photocatalytic activity, instability of organic component and lead toxicity in particular. Herein, we report an anti-dissolution environmentally friendly Cs2SnI6 perovskite anchored with a new class of atomically dispersed Pt-I3 species (PtSA/Cs2SnI6) for achieving the highly efficient photocatalytic hydrogen production in HI aqueous solution at room temperature. Particularly, we discover that Cs2SnI6 in PtSA/Cs2SnI6 has a greatly enhanced tolerance towards HI aqueous solution, which is very important for achieving excellent photocatalytic stability in perovskite-based HI splitting system. Remarkably, the PtSA/Cs2SnI6 catalyst shows a superb photocatalytic activity for hydrogen production with a record turnover frequency of 70.6 h−1per Pt, about 176.5 times greater than that of Pt nanoparticles supported Cs2SnI6 perovskite, along with superior cycling durability. Charge-carrier dynamics studies in combination with theory calculations reveal that the dramatically boosted photocatalytic performance on PtSA/Cs2SnI6 originates from both unique coordination structure and electronic property of Pt-I3 sites, and strong metal-support interaction effect that can not only greatly promote the charge separation and transfer, but also substantially reduce the energy barrier for hydrogen production. This work opens a new way for stimulating more research on perovskite composite materials for efficient hydrogen production.

Oxygen-defective MnO2/ZIF-8 nanorods with enhanced antibacterial activity under solar light

Low-cost MnO2 has been vigorously investigated in the field of catalysis. However, high amount of MnO2 usually needs to be used in the disinfection process owing to their low photocatalytic activity. In this work, modification of MnO2 with zeolitic imidazole framework-8 (ZIF-8) for improving the photocatalytic bactericidal performance was explored for the first time. Specifically, MnO2/ZIF-8 exhibited complete inactivation of multi-drug resistant Escherichia coli (E. coli) at a low concentration (3.24 μg/mL) with simulated solar irradiation. The 1O2 rather than O2− or OH was identified as the major reactive species for the bacterial inactivation. Mechanistic studies indicated that the superior bactericidal property of MnO2/ZIF-8 than the pristine material could be ascribed to the increased surface oxygen vacancies (OVs) amount and an inhibited electron and hole recombination. This study provides a novel type of photocatalyst for antibacterial application and may shed light on designing MnO2 based low-cost nanocomposites with photocatalytic bactericidal capability for the practical water disinfection treatment.

Engineering-safer-by design ZnO nanoparticles incorporated cellulose nanofiber hybrid for high UV protection and low photocatalytic activity with mechanism

Cellulose nanofiber (CNF) is a well-known biocompatible polymer with various versatile characteristics. In recent years, nano-sized materials with high flexibility and biocompatibility that exhibit ultraviolet (UV) blocking properties with maximum dispersion have attracted increasing attention, particularly, materials with photocatalytic activity. In this study, zinc oxide nanoparticle (ZnO NP) was synthesized on the surface of CNF to form a hybrid material by an environmentally friendly sol-gel reaction, and the UV blocking properties of the hybrid were systematically explored. The size of the ZnO NP on the CNF surface was optimized to improve the UV-blocking performance and the transmittance. The optimized safer-by-design structured hybrid exhibited the following features: 1) improved dispersion stability, 2) low whitening effect and 3) high UV blocking performance (i.e., 3.05 a.u. and 2.80 a.u. in UVB and UVA area, respectively). Moreover, only 8.8% rhodamine B (Rh-B) dye degraded through photocatalytic oxidation process (negligible photocatalysis activity). The synthesis strategy of the ZnO-CNF hybrid proposed in this study is a promising approach that can be implemented practically for high value-added applications in the field of cosmetics.

Building {0001} and {10[formula omitted]1} facet heterojunctions on hexagonal pyramid CdS single crystals with high photoactivity and photostability for hydrogen evolution

CdS has suitable band gap and high photoelectric conversion efficiency, which has attracted widespread attention. However, its severe photocorrosion and low photocatalytic activity limits its application. Generally, constructing heterojunction structure can effectively improve the separation efficiency of CdS photogenerated carriers, and its photocatalytic activity and stability can be further improved. Here, we prepared CdS hexagonal pyramid single crystal with co-exposed {0001} and {101¯1} crystal planes by the urothermal method. Type II heterojunction can be formed between {0001} and {101¯1} crystal planes, which can effectively improve the photocatalytic hydrogen production activity of CdS hexagonal pyramid. The photocatalytic hydrogen production activity of CdS hexagonal pyramid is 10.64 mmol·h-1·g-1 with an apparent quantum efficiency of 15.6% at 420 nm, which is 5.8 times and 13.2 times as high as CdS nanorod and CdS nanoparticles, respectively. Even after the 100 h cycle test, the CdS hexagonal pyramid shows still high photocatalytic activity. This work showed that the photocatalytic activity can be effectively improved by adjusting the crystal faces, which can further generaliza to other photocatalysts.

Development and characterization of negative air ion emitting mica- and sericite-based antimicrobial pearlescent pigments

In modern era, people are spending their time indoors around 90%. Therefore, in terms of public health, increasing indoor air quality is of great importance. In this study, it was aimed to develop pearlescent pigments that emit negative air ions in order to increase indoor air quality, and the potential of such pigments for use in composite wall paint was evaluated. For this purpose, low refractive index muscovite mica and sericite clay minerals, which were shown to emit negative ions, were combined with high refractive index TiO2. The use of two different clay minerals, different proportions of SnO2 dopant, and calcination process application were selected as experimental parameters and the effect of these parameters on the anatase-rutile phase transformation of TiO2 in the pigments was investigated. Increasing the rutile TiO2 ratio in the synthesized pigments were resulted in a better pearlescent effect and lower photocatalytic activity. In order to increase the negative air ion emitting effect of these pigments with the desired pearlescent pigment properties, these samples were also combined with extract of the Chlorophytum comosum, which also is known to emit negative air ions. As a result of the negative ion emission measurements, it was found that the samples were continued to emit negative ions without a time-dependent decrease even when not combined with the extract of C. comosum. In addition, it was showed that the prepared samples have antibacterial effect against Escherichia coli, which is abundant in indoor environments, especially in health centers such as hospitals and dispensaries, and antifungal effect against Aspergillus niger, which is known as black mold, growing on moist walls.

Photocatalytic performance of g-C3N4 based nanocomposites for effective degradation/removal of dyes from water and wastewater

The world is concerned about the hazardous effect of dyes that pose a threat to the ecosystem. It is therefore essential to remove these dyes from the aquatic system by using suitable methods. Among all the methods available, photodegradation using graphitic carbon nitride (g-C3N4) is suitable and efficient for the removal of dyes from water and wastewater. The pure g-C3N4 has low photocatalytic activity because it has a low surface area, which results in insufficient sunlight adsorption. Doping of graphitic carbon nitride was carried out to increase the photodegradation efficiency by enhancing light absorption, providing charge separation and transportation, and increasing the charge carrier lifetime. Various metals and non-metal doped g-C3N4 were found to be the most effective and privileged photocatalysts for the degradation of industrial effluents in recent times. This review highlights the heterojunction-based g-C3N4 and its enhanced photodegradation of the dyes. It also puts light on making the doped CNS (Carbon Nitride Sheets) nanocomposites through various techniques and on the dyes that are photodegraded using various catalysts. The photodegradation of dyes is mainly carried out under visible light radiation, as it is highly cost-effective. This heterojunction-based g-C3N4 shows promising results for the photocatalytic elimination of pollutants from the aqueous phase. In this review, the working principle and mechanism of the g-C3N4 photocatalysts are also discussed. Prospects and challenges faced are also discussed in this article.

Synthesis of Bi2MoO6 and Activating Peroxymonosulfate to Enhance Photocatalytic Activity under Visible Light Irradiation

AbstractBi2MoO6 nanoflakes are synthesized via a normal hydrothermal method. Bi2MoO6 photocatalysts show lower photocatalytic activity for the degradation of methylene blue under visible light irradiation. In order to further enhance the degradation efficiency, Bi2MoO6 is used to activate the peroxymonosulfate for the degradation of methylene blue under visible light. Bi2MoO6 nanoflakes show excellent degradation efficiency in the Bi2MoO6/Vis/peroxymonosulfate (PMS) system. Moreover, the influences of PMS dosage, pH value, and inorganic anions on photodegradation are evaluated. The mechanism of activating peroxymonosulfate is proved by radical quenching experiment, which reveals that sulfate radicals govern the removal of methylene blue.

The photocatalytic rate of ZnO supported onto natural zeolite nanoparticles in the photodegradation of an aromatic amine.

Aniline and its derivate are critical environmental pollutants, and thus, the introduction of an eco-friendly catalyst for removing them is an important research future. The ZnO supported on the ball-mill prepared clinoptilolite nanoparticles (CNPs) was prepared via an ion-exchange process followed by the calcination process. The amount of loaded ZnO in the ZnO-CNP (CZ) samples varied as 0.54, 0.63, 0.72, and 0.86 meq/g as the Zn(II) concentration in the ion-exchange solution varied from 0.1 to 0.5 M. The ZnO-CNP catalyst was briefly characterized by XRD, FTIR, and DRS techniques. The pHpzc value for the various ZnO-CNPs was about 7.1 that had no change with the ZnO loading. By applying the Scherrer equation on the XRD results, a nano-dimension of about 50 nm was obtained for the catalyst. Bandgap energy of the ZnO-CNP samples was estimated by applying the Kubelka-Munk equation on the DRS reflectance spectra. The value for the CZ2 catalyst was about 3.64 eV. The supported ZnO-CNP sample was then used in the photodegradation of 2,4-dichloroaniline (DCA). Raw zeolite showed a relatively low photocatalytic activity. The degradation efficiency was followed by recording the absorbance of the DCA solution by UV-Vis spectrophotometer. The effects of the essential critical operating factors on the degradation efficiency were kinetically studied by applying the Hinshelwood equation to the results. The ZnO-CNP catalyst with 2 w% ZnO showed the best photocatalytic rate in the optimal conditions of 0.75 g/L, CDCA: 15 ppm, and the initial pH: 5.8. Finally, HPLC analysis of the blank and the photodegraded DCA solutions at 180 and 300 min confirmed 74 and 87% of DCA molecules were degraded during these times. The results confirm that supported ZnO onto clinoptilolite caused enhanced photocatalytic activity because the zeolite internal electrical field prevents the e-/h+ recombination.

Highly stable halide perovskite with Na incorporation for efficient photocatalytic degradation of organic dyes in water solution.

To overcome water instability and low photocatalytic activity of lead-free halide perovskite for the degradation of organic dyes, we report a novel photocatalyst of lead-free halide perovskite with Na incorporation and employ it for the photocatalytic degradation of organic dyes in water solution under visible light irradiation. The main purpose of this work is to confirm the feasibility of lead-free halide perovskite with Na incorporation for improving the photocatalytic efficiency and recyclability in water solution and further to explore the mechanism behind the enhancement of photocatalytic performance after Na incorporation. The results show that Cs2Ag0.60Na0.40InCl6 can increase the dye degradation rate by at least 50% than the lead-free halide perovskite (Cs2AgInCl6) and the photocatalyst of Ag substituted by Na (Cs2NaInCl6). The degradation efficiency of rhodamine 6G catalyzed by Cs2Ag0.60Na0.40InCl6 reaches 94.94% over 60 min, which is 72% higher than that catalyzed by Cs2NaInCl6 and 27% higher than that catalyzed by Cs2AgInCl6. What's more, the degradation efficiency of methyl orange catalyzed by Cs2Ag0.60Na0.40InCl6 is 90.39% within 150 min, which is 66% higher than that catalyzed by Cs2NaInCl6 and 54% higher than that catalyzed by Cs2AgInCl6. Moreover, the photocatalyst of Cs2Ag0.60Na0.40InCl6 exhibits a desirable recyclability by water exposure, retaining the degradation efficiency over 90% after five cycles. The strengthened photocatalytic performance in the presence of Cs2Ag0.60Na0.40InCl6 is ascribed to an increase of radiative recombination rate and an improvement of average lifetime to 204 ns since an appropriate Na incorporation at the atomic ratio of Na/Ag=4:6 breaks the original crystal lattice and meanwhile increases the electron and hole overlap. The work proves a great potential of halide perovskite with Na incorporation for the highly efficient photocatalytic degradation of organic dyes in water solution.

A facile synthesis method of TiO2@SiO2 porous core shell structure for photocatalytic hydrogen evolution

Limited by low specific surface area and complex synthesis methods, it is laborious to realize wide utilization of photocatalytic materials. Although various photocatalytic materials have been reported constantly, as a vital prototype of photocatalytic materials with the advantages of low cost, no-toxicity, and high stability, TiO2 still reveals great research potential. Nevertheless, pure TiO2 usually present small specific surface area and low photocatalytic activity. Besides, the preparation process of composite photocatalysts based on TiO2 remain inconvenient. Hence, to enhance the photocatalytic activity of TiO2, this work proposed a facile synthesis method to fabricate a TiO2@SiO2 porous core shell structure materials based on our previous research. Specifically, silica microspheres were prepared by one-step method with atmospheric pressure drying. And TiO2@SiO2 composite gel was fabricated by a primitive liquid phase deposition. The whole process retains simple and green and the obtained porous core shell materials display extraordinary specific surface area (over 400 ​m2/g) with high photocatalytic efficiency. Under optimized conditions, the H2 production rates are roughly 3 times higher than that of P25 powder, which shows great application potential. This study confirms that the photocatalytic performance can be enhanced by improvement of active site area and provides some insights in convenient preparation of TiO2 based photocatalysts as well.

Novel NiO/RP composite with remarkably enhanced photocatalytic activity for H2 evolution from water

The low photocatalytic activity of red phosphorus (RP) for H2 production seriously restricts its wide application. In this work, we reported a facile synthesis and remarkable activity improvement of NiO/RP composite for water splitting. As a result, the 3% NiO/RP composite exhibited the highest photocatalytic activity for H2 production (57.27 μmol g−1 h−1), which is 68.56 times higher than that of pure RP (0.82 μmol g−1 h−1) under visible light (λ ≥ 420 nm) irradiation. The investigation of photocarriers separation mechanism indicated NiO/RP composite applied a Z-scheme mechanism to promote the photocarriers separation. This is a potential strategy to dramatically enhance the photocatalytic activity of RP for H2 evolution using transition metal oxide to efficiently separate the photocarriers under light irradiation.