Facile one-step synthesis of pellet-press-assisted saddle-curl-edge-like g-C3N4 nanosheets for improved visible-light photocatalytic activity

Graphitic carbon nitride (g-C₃N₄) has attracted increasing interest as a visible-light-active photocatalyst. In this study, saddle-curl-edge-like g-C₃N₄ nanosheets were prepared using a pellet presser (referred to as g-CN P nanosheets). Urea was used as the precursor for the preparation of g-C₃N₄. Thermal polymerization of urea in a pellet form significantly affected the properties of g-C₃N₄. Systematic investigations were performed, and the results for the modified g-C₃N₄ nanosheets are presented herein. These results were compared with those for pristine g-C₃N₄ to identify the factors that affected the fundamental properties. X-ray diffraction analysis and high-resolution transmission electron microscopy revealed a crystallinity improvement in the g-CN P nanosheets. Fourier-transform infrared spectroscopy provided clear information regarding the fundamental modes of g-C₃N₄, and X-ray photoelectron spectroscopy (XPS) peak-fitting investigations revealed the variations of C and N in detail. The light-harvesting property and separation efficiency of the photogenerated charge carriers were examined via optical absorption and photoluminescence studies. The valence band edge and conduction band edge potentials were calculated using XPS, and the results indicated a significant reduction in the bandgap for the g-CN P nanosheets. The Brunauer–Emmett–Teller surface area increased for the g-CN P nanosheets. The photocatalytic degradation performance of the g-CN P nanosheets was tested by applying a potential and using the classical dye Rhodamine B (RhB). The RhB dye solution was almost completely degraded within 28 min. The rate constant of the g-CN P nanosheets was increased by a factor of 3.8 compared with the pristine g-C₃N₄ nanosheets. The high crystallinity, enhanced light absorption, reduced bandgap, and increased surface area of the saddle-curl-edge-like morphology boosted the photocatalytic performance of the g-CN P nanosheets.     

Amino group-rich porous g-C3N4 nanosheet photocatalyst: Facile oxalic acid-induced synthesis and improved H2-evolution activity

The reasonable modulation of tri-s-triazine structure units of g-C₃N₄ is an effective method to optimize its intrinsic electronic and optical properties, thus boosting its photocatalytic hydrogen-evolution activity. Herein, amino groups are successfully introduced into the tri-s-triazine structure units of g-C₃N₄ nanosheets to improve their H₂-evolution activity via a facile oxalic acid-induced supramolecular assembly strategy. In this case, the resulting amino group-rich porous g-C₃N₄ nanosheets display a loose and fluffy structure with a large specific surface area (70.41 m² g^?1) and pore volume (0.50 cm³? g^??1), and enhanced visible-light absorption (450–800 nm). Photocatalytic tests reveal that the amino group-rich porous g-C₃N₄ nanosheets (AP-CN1.0 nanosheets) exhibit a significantly elevated photocatalytic H₂-production activity (130.7 μmol h^?1, AQE = 5.58%), which is much greater than that of bulk g-C₃N₄ by a factor of 4.9 times. The enhanced hydrogen-generation performance of amino group-rich porous g-C₃N₄ nanosheets can be mainly attributed to the introduction of more amino groups, which can reinforce the visible-light absorption and work as the interfacial hydrogen-generation active centers to boost the photocatalytic hydrogen production. The present facile and effective regulation of tri-s-triazine structure units may provide an ideal route for the exploitation of novel and highly efficient g-C₃N₄ photocatalysts.     

Z-scheme g-C3N4 nanosheet photocatalyst decorated with mesoporous CdS for the photoreduction of carbon dioxide

Herein, novel mesoporous CdS nanoparticle (NP)-incorporated porous g-C₃N₄ nanosheets with large surface areas and varying CdS NP percentages were constructed for the first time. The synergistic effect of mesoporous CdS NPs and porous g-C₃N₄ nanosheets indicated effective charge carrier separation and promoted CO₂ photoreduction to form CH₃OH upon illumination. The highest yield of CH₃OH over 3% CdS-g-C₃N₄ heterostructures was determined to be approximately 1735 μmol g^?1, which was 3.8- and 5.50 times greater than those of mesoporous CdS NPs and pristine g-C₃N₄ nanosheets, respectively. In addition, the mesoporous 3%CdS-g-C₃N₄ heterostructure showed an outstandingly enhanced CO₂ photoreduction rate of 192.7 μmol g^?1 h^?1, which was estimated to be ~4.1 and 5.9- times better than CdS (47.1 μmol g^?1 h^?1) and pristine g-C₃N₄ (32.6 μmol g^?1 h^?1), respectively. The photoreduction performance was retained at approximately 94.7% after five cycles of illumination for 45 h. The remarkable synthesized mesoporous CdS-g-C₃N₄ heterostructure played an essential role, with its narrow bandgap and high surface area enabling improved photoinduced carrier separation and a widened range of light absorption. A plausible mechanism for CO₂ photoreduction by the mesoporous CdS-g-C₃N₄ heterostructure was proposed and verified by photoelectrochemical and photoluminescence measurements.     

One-Step Synthesis of g-C3N4 Nanosheets with Enhanced Photocatalytic Performance for Organic Pollutants Degradation Under Visible Light Irradiation

Graphitic carbon nitride (g-C₃N₄) has received much interest as a visible-light-driven photocatalyst for degrading pollutants such as organic dyes and antibiotics. However, g-C₃N₄ bulk activity could not meet expectations due to its rapid recombination of photogenerated electron–hole pairs and low specific surface area. In our study, melamine was thermally treated one-step in the presence of NH₄Cl to produce g-C₃N₄ nanosheets. The characterizations of surface morphology and optical properties of all g-C₃N₄ samples were investigated by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectrum (XPS), transmission electron microscopy (TEM), and UV–visible diffuse reflectance spectroscopy. Compared to bulk g-C₃N₄, g-C₃N₄ nanosheets demonstrated excellent photocatalytic activities, with approximately 98% RhB removal after 210 min of visible light irradiation. Furthermore, the effect of catalyst dosage, pH, and RhB concentration on the removal percentage dye of g-C₃N₄ nanosheets was also investigated. h⁺ and ^?O₂^? species were demonstrated as the key reactive species for the RhB. Besides, ECN exposed a tetracycline degradation efficiency of 80.5% under visible-light irradiation for 210 min, which is higher than BCN (60.8%). The improved photocatalytic activity of g-C₃N₄ nanosheets is due to the restriction of the recombination of photogenerated electrons/hole pairs, as provided by photoluminescence spectra and Nyquist plot. As a result, our research may offer an effective approach to fabricating g-C₃N₄ nanosheets with high photocatalytic activity and high stability for environmental decontamination.

     

0D CoP cocatalyst/ 2D g-C3N4 nanosheets: An efficient photocatalyst for promoting photocatalytic hydrogen evolution

In this work, cobalt phosphide (CoP) nanoparticles were successfully decorated on an ultrathin g-C₃N₄ nanosheet photocatalysts by in situ chemical deposition. The built-in electric field formed by heterojunction interface of the CoP/g-C₃N₄ composite semiconductor can accelerate the transmission and separation of photogenerated charge-hole pairs and effectively improve the photocatalytic performance. TEM, HRTEM, XPS, and SPV analysis showed that CoP/g-C₃N₄ formed a stable heterogeneous interface and effectively enhanced photogenerated electron-hole separation. UV-vis DRS analysis showed that the composite had enhanced visible light absorption than pure g-C₃N₄ and was a visible light driven photocatalyst. In this process, NaH₂PO₂ and CoCl₂ are used as the source of P and Co, and typical preparation of CoP can be completed within 3 hours. Under visible light irradiation, the optimal H₂ evolution rate of 3.0 mol% CoP/g-C₃N₄ is about 15.1 μmol h⁻¹. The photocatalytic activity and stability of the CoP/g-C₃N₄ materials were evaluated by photocatalytic decomposition of water. The intrinsic relationship between the microstructure of the composite catalyst and the photocatalytic performance was analyzed to reveal the photocatalytic reaction mechanism.     

Visible light-activated degradation of microcystin-LR by ultrathin g-C3N4 nanosheets-based heterojunction photocatalyst

Microcystins (MCs) is a harmful toxin generated by blue-green algae in water, which has seriously threatened the ecological safety of water and human body. It is urgent to develop new catalysts and techniques for the degradation of MCs. A feasible electrostatic self-assembly method was carried out to synthesize BiVO₄/g-C₃N₄ heterojunction photocatalyst with highly efficient photocatalytic ability, where BiVO₄ nanoplates with exposed {010} facets anchored to the g-C₃N₄ ultrathin nanosheets. The morphology and microstructure of the heterojunction photocatalysts were identified by XRD, SEM, TEM, XPS, and BET. The g-C₃N₄ nanosheets have huge surface area over 200 m²/g and abundant mesoporous ranging from 2-20 nm, which provides tremendous contact area for BiVO₄ nanoplates. Meanwhile, the introduction of BiVO₄ led to red-shift of the absorption spectrum of photocatalyst, which was characterized by UV-vis diffuse reflection spectroscopy (DRS). Compared with pure BiVO₄ and g-C₃N₄, the BiVO₄/g-C₃N₄ heterojunction shows a drastically enhanced photocatalytic activity in degradation of microcystin-LR (MC-LR) in water. The MC-LR could be removed within 15 minutes under the optimal ratio of BiVO₄/g-C₃N₄. The outstanding performance of the photocatalyst is attributed to synergetic effect of interface Z-scheme heterojunction and high active facets {010} of BiVO₄ nanoplates, which provides an efficient transfer pathway to separate photoinduced carriers meanwhile endows the photocatalysts with strong redox ability.     

Development of mesoporous Bi2WO6/g-C3N4 heterojunctions via soft- and hard-template-assisted procedures for accelerated and reinforced photocatalytic reduction of mercuric cations under vis light irradiation

In this study, mesoporous Bi₂WO₆/g-C₃N₄ heterojunctions were developed using soft and hard templates [triblock copolymer surfactant (F127) and mesoporous silica (MCM-41), respectively]. The performance of the developed heterojunctions was assessed through the photocatalytic reduction of mercuric cations under Vis light illumination, with HCOOH being adopted to provide sacrificial holes agent. Surface measurements demonstrated that the fabricated specimens acquired large specific surface areas when compared with the neat ingredient. Furthermore, a transmission electron microscopy (TEM) analysis of the developed heterojunctions showed the homogeneous distribution of the spherical Bi₂WO₆ nanoparticles (NPs) on the surface of g-C₃N₄ nanosheets. Meanwhile, an accelerated rate (700 μ·mol·g^?1·h^?1) of photocatalytic mercuric cation reduction with improved efficiency (approximately 100%), compared with those of the pure ingredients [rate of 55 μ·mol·g^?1·h^?1 and efficiency of 13% for g-C₃N₄ nanosheets; rate of 95 μ·mol·g^?1·h^?1 and efficiency of 20% for mesoporous Bi₂WO₆ NPs], was accomplished via testing of the Bi₂WO₆/g-C₃N₄ heterojunction comprising 4 wt% Bi₂WO₆ after 40 min of illumination. Evidently, the efficiency of the photocatalytic reduction of mercuric cations endorsing the Bi₂WO₆/g-C₃N₄ heterojunction comprising 4 wt% Bi₂WO₆ NPs is 7.7 and 5 times more when compared with those of the neat g-C₃N₄ nanosheets and mesoporous Bi₂WO₆ NPs, respectively. The improved performance of the fabricated heterojunctions in the photocatalytic reduction of mercuric cations could be ascribed to i) fast diffusion of the mercuric cations through the mesoporous texture to the active ensembles, ii) greater specific surface area, iii) limited bandgap magnitude, iv) homogenous dispersion of the Bi₂WO₆ NPs on the surface of the nanosheets, and v) finite particle dimension of the mesoporous Bi₂WO₆ NPs. The durability and stability of the Bi₂WO₆/g-C₃N₄ heterojunctions were confirmed via their recyclability, which was maintained for up to five runs without pronounced activity loss.     

Fabrication of CuFe2O4@g-C3N4@GNPs nanocomposites as anode material for supercapacitor applications

The aim of this study was to synthesize CuFe₂O₄ together with g-C₃N₄ and GNPs in various combinations on the surface of Ni foam for use as anode materials in supercapacitors. The fabricated electrodes were investigated by XRD, FTIR, XPS, BET, SEM and TEM for content and by CV, GCD and EIS analysis for electrochemistry. The characterization results showed that CuFe₂O₄ was successfully synthesized together with g-C₃N₄ and GNPs in a nanosponge-like geometry. The highest value of specific capacitance was found to be 989 mF/cm² at 2 mA measurement in the triple combination. Moreover, the stability of this electrode was measured to be 70% after 1500 cycles at 16 mA, while the energy and power densities were calculated to be 27.8 mWh/cm² and 300 mW/cm², respectively. The EIS results show that the carbon-based component increased the Cs value by decreasing the charge transfer and diffusion resistances of the electrodes. Compared to its counterparts in the literature, its Cs value is quite high, but its stability is low, so it can be used in low-cycle applications.     

Hydrothermal deposition of AgCl/AgBr co-sensitizers to modify TiO2 NTs for enhanced photocatalytic performance

AgCl/AgBr co-sensitizers were prepared on TiO₂ nanotube arrays (TiO₂ NTs/AgCl/AgBr) by the hydrothermal method. The composition, morphology, optical absorption, photoelectric and photoelectrocatalytic (PEC) performances of TiO₂ NTs/AgCl/AgBr were influenced by the concentration ratio of KCl/KBr. The investigation results revealed that the TiO₂ NTs/AgCl/AgBr photocatalyst exhibited dramatically strong visible light absorption and outstanding photoelectrochemical capacity. The photoelectrode produced high visible light surface photovoltage (-0.43 V), transient photocurrent (0.47 mA/cm²) and carrier concentration (4.39 × 10²⁰ cm^-3). The sample also showed high PEC activity in the organic dye and Cr(VI) removal, and the photocatalytic mechanism and charge carrier transfer path were described based on PEC results. The investigation would offer prospective insight to the sensitization of TiO₂ NTs, which would result in extensive attraction in the preparation and application of semiconductor materials as photoelectrodes and photocatalysts with superior photoelectrochemical performances.     

Coupling TiO2 nanorods with g-CN using modified physical vapor deposition for efficient photoelectrochemical water oxidation

The core-shell TiO₂@g-CN nanorods arrays were constructed directly on fluorine-doped tin oxide grass using vacuum magnetic filtered arc ion plating. The unique structure combines both advantages from TiO₂ as an effective electron-transfer layer and graphic carbon nitride (g-CN) with a proper band gap serving as visible light absorption layer. Under 100 mW/cm² (AM 1.5G) light illumination, the optimal TiO₂@g-CN produces a photocurrent density of 0.91 mA/cm² at 1.23 V vs reversible hydrogen electrode, which is 2.1 times of the bare TiO₂ (0.43 mA/cm²) obtained at the same potential. The improved photoelectrochemical performance is mainly attributed from the improved charge separation and transport within the heterojunction as well as the enhanced light absorption.     

Mesoporous BiVO4/2D-g-C3N4 heterostructures for superior visible light-driven photocatalytic reduction of Hg(II) ions

In this contribution, a Z-scheme mesoporous BiVO₄/g-C₃N₄ nanocomposite heterojunction with a considerable surface area and high crystallinity was synthesized by a simple soft and hard template-assisted approach. This material demonstrates superior visible light-driven photocatalysis for the photoreduction of Hg(II) ions. TEM and XRD results show that the mesoporous BiVO₄ NPs, with a monoclinic phase and an ellipsoid-like shape, are highly dispersed onto the porous 2D surfaces of g-C₃N₄ nanosheets with a particle size of 5–10 nm. The obtained BiVO₄/g-C₃N₄ nanocomposites with a p-n heterojunction show significantly enhanced Hg(II) photoreduction efficiency compared to the mesoporous BiVO₄ NPs and pristine g-C₃N₄. Among all synthesized photocatalysts, the 1.2% BiVO₄/g-C₃N₄ nanocomposite indicated the highest photoreduction of Hg(II) performance, reaching ~ 100% within 60 min; this result is 3.9 and 4.5 –fold larger than that of the BiVO₄ NPs and pristine g-C₃N₄. The Hg(II) photoreduction rates highly increase to 208.90, 314.95, 411.23 and 418.68 μmol g⁻¹min⁻¹ for the mesoporous 0.4, 0.8, 1.2 and 1.6% BiVO₄/g-C₃N₄ nanocomposites, respectively. The reduction rate of the mesoporous 1.2% BiVO₄/g-C₃N₄ nanocomposite demonstrated a 5.2 and 3.8 times larger increase than that of the pristine g-C₃N₄ nanosheets and pure BiVO₄ NPs. The superior Hg(II) photoreduction efficiency was ascribed to decreased carrier recombination and the improved utilization of visible light by constructing BiVO₄/g-C₃N₄ nanocomposites with a p-n junction. Transient photocurrent measurement and photoluminescence spectra were employed to confirm the possible Hg(II) photoreduction mechanism over these BiVO₄/g-C₃N₄ photocatalysts. This research provides an accessible route for the nanoengineered design of mesoporous BiVO₄/g-C₃N₄ heterostructures that demonstrated unique photocatalytic performance.     

Enhancement of photocatalytic and photoelectrochemical properties of BiOI nanosheets and silver quantum dots co-modified TiO2 nanorod arrays

In this study, TiO₂ nanorod arrays (TNR), Ag quantum dots (QDs) sensitized with TNR TiO₂/Ag, bismuth oxyhalide (BiOI) nanosheets, and Ag QDs co-modified with TNR and TiO₂/BiOI/Ag (TBA) were prepared by a stepwise process. The morphological, structural, compositional, optical, photocatalytic (PC), and photoelectrochemical (PEC) properties of the samples were investigated. The TBA-2 sample exhibited the highest photocurrent density (281.8 μA/cm²) and photodegradation efficiency (93.3%), with values 9.7 times and 2.25 times higher than those for TNR, respectively. The improvement in sample performance can be attributed to the formation of a heterojunction between BiOI and TiO₂, thereby enhancing the absorption of visible light and improving the charge separation efficiency; Ag QDs limit interfacial electron-hole pair recombination. The experimental results show that TBA can effectively promote light-induced carrier transport and visible light absorption, while inhibiting the recombination rate of the electron-hole pairs, PEC, and PC.     

Visible-light-driven Ni3FeN/g-C3N4 Z-scheme heterostructure for remarkable photocatalytic water splitting

It is very essential to grow efficient and abundant photocatalysts for overall water cracking to produce hydrogen. Ni₃FeN nanosheets were synthesized by combining simple sol–gel and calcining methods using urea as nitrogen source. A heterostructure was constructed between Ni₃FeN and g-C₃N₄ to enhance the absorption capacity of visible light. The reformed Z-scheme Ni₃FeN/g-C₃N₄ heterojunction exhibited an excellent visible-light photocatalytic activity. The average hydrogen evolution rate of 5 wt% Ni₃FeN/g-C₃N₄ composite is 528.7 μmol h⁻¹ g⁻¹ due to the Z-scheme Ni₃FeN/g-C₃N₄ junction, which promotes the separation of photogenerated e⁻/h⁺. Interestingly, the average H₂ production of Ni₃FeN/g-C₃N₄ is nearly 8.3 and 3.6 times higher than that of Fe₄N/g-C₃N₄ and Ni₄N/g-C₃N₄, respectively, indicating that bimetallic nitrides as cocatalysts are more conducive to enhancing the performance of photocatalysts. Importantly, the Ni₃FeN/g-C₃N₄ composite exhibited good cycle stability, and the hydrogen production performance hardly changed after four cycle experiments. Furthermore, photoluminescence, electrochemical impedance spectroscopy, and transient photocurrent response show that Ni₃FeN/g-C₃N₄ heterojunction improves the separation efficiency of photoinduced e⁻/h⁺. This work provides a feasibility of the cocatalyst Ni₃FeN for use in photocatalytic hydrogen production.     

Structure and magnetic properties of Cr-Doped tin monoxide prepared by hydrothermal method

Ball- and sheet-like Sn_1-xCr_xO were successfully prepared by one-step hydrothermal method. The SEM and TEM results show that the diameter of ball-like unit is about 15 μm and the unit was assembled by several nanosheets with a thickness of about 0.5 μm. Raman pattern displays that there are two intense Raman mode E_g (~114 cm⁻¹) and A_1g (~211 cm⁻¹) in the SnO, and the A_1g peak shifted significantly. UV–Visible spectrum illustrates that the bandgap of the Cr-doped SnO firstly decreases and then increases as the Cr concentration increases, which is attributed to the sp-d exchange interactions and Burstein-Moss theory. The analysis of XPS also provides evidence for the incorporation of Cr into the system. Furthermore, it is found that oxygen vacancy (V_O) decreases with the increase of Cr content. Based on Krӧger-Vink notation system, the competition mechanism between V_O and V_Sn could explain the origin and variation of magnetism of Sn_1-xCr_xO from structural defects.     

Mixed 3D/2D dimensional TiO2 nanoflowers/MoSe2 nanosheets for enhanced photoelectrochemical hydrogen generation

Recently, v arious kinds of methods have been implemented to broaden the visible light response and fasten the carrier's separation of TiO₂-based photoanodes. As a promising hydrogen evolution reaction catalyst, MoSe₂ is rarely investigated especially combined with TiO₂ photoanode. In this study, we report a composite photoanode of MoSe₂ nanosheets (with 1T and 2H phase)-modified 3D TiO₂ nanoflowers (NFs).The hybrid of 3D TiO₂ NFs/2D MoSe₂ holds great promise in boosting the PEC water splitting performance. TiO₂ NFs/MoSe₂-15 showed the largest photocurrent density of 1.40 mA/cm², which was five times higher than that of pure TiO₂ NFs under AM1.5G illumination. Moreover 10 times improvement in current density was observed for the TiO₂ NFs/MoSe₂-15 under visible light. This increase could be ascribed to synergistic effects of light absorption enhancement and more efficient carrier separation after MoSe₂ modification. This study not only provides a reference to boost the photoelectrochemical performance of photoelectrodes but also renders a perspective on the potential applications of MoSe₂ nanosheets.     

Decontamination of radioactive concrete using electrokinetic technology

The experimental results of the electrokinetic decontamination with 0.01 M of nitric acid were that the cesium ions were removed by up to 52% from the concrete after 15 days, also the cobalt ions were only removed by up to 0.7%. The concrete should be washed with H₂SO₄ as a pretreatment before electrokintic decontamination to lower its pH below 4.0. The removal efficiencies of ⁶⁰Co and ¹³⁷Cs by nitric acid were increased by 3.1 and 2.5% more than those by acetic acid. The larger the particle size of the concrete, the more the removal efficiencies of ⁶⁰Co and ¹³⁷Cs were increased. Also, the removal efficiencies of ⁶⁰Co and ¹³⁷Cs by the application of an electric current of 20 mA/cm² were increased by 1.6 and 3.9% more than those by the application of 10 mA/cm². The removal efficiencies of ⁶⁰Co and ¹³⁷Cs from the radioactive concrete of 1,940 Bq/kg were 99.8 and 92.3% by electrokinetic decontamination after pretreatment by the application of an electric current of 20 mA/cm² for 25 days.     

Surface characterization and photocatalytic reactivity of innovative Ti/TiO2 and Ti/Pt−TiO2 mesh photoelectrodes

Novel Ti/TiO₂ and Ti/Pt–TiO₂ mesh photoelectrodes were produced by anodizing titanium mesh in H₂SO₄ solution. Their structural and surface morphology were examined by X-ray diffraction (XRD), scanning electronic microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The analytical results indicated that the crystal structure, morphology and pore size were affected significantly by the voltage and current density applied in anodization and the percentage platinum content. The results of XPS measurement showed that the binding energy of O 1s and Ti 2p increased slightly owing to platinum deposition (Pt⁰, Pt²⁺ and Pt⁴⁺) onto the TiO₂ surface. The photoelectrocatalytic (PEC) oxidation of methyl orange in aqueous solution using the Ti/TiO₂ and Ti/Pt–TiO₂ meshes was investigated. The experimental results demonstrated that Ti/TiO₂ mesh prepared at 160 V and 110 mA cm^–2 achieved the best PEC oxidation. The efficiency of PEC oxidation could be further enhanced by applying an electrical bias between the working electrode and counter electrode. An optimal electrical bias voltage was found to be 0.6 V, while an optimal platinum content was 3.37%.     

Photoelectrochemical properties of iron (III)-doped TiO2 nanorods

Fe (iron)-doped TiO₂ nanorods were grown on fluorine doped tin oxide (FTO) substrates with various Fe doping concentrations using modified chemical bath deposition (M-CBD). We investigated the effects of Fe doping concentration on the morphological, structural, optical, and photoelectrochemical (PEC) properties of the TiO₂ nanorods. From this study, it was found that the PEC properties were mainly dependent on the morphological and optical properties of the Fe-doped TiO₂ nanorods. At low Fe doping concentration, the PEC properties were highly affected by the optical properties. On the other hand, the PEC properties were significantly affected by the morphological properties at high doping concentration. We observed a maximum photocurrent density of 0.48 mA/cm² at a Fe doping concentration of 2 at% from this study. In addition, the donor density and flat-band potential of the Fe doping concentration from the Mott–Schottky plot were analyzed.     

Controlled preparation of P-doped g-C3N4 nanosheets for efficient photocatalytic hydrogen production

Hydrogen production by photolysis of water by sunlight is an environmentally-friendly preparation technology for renewable energy. Graphitic carbon nitride (g-C₃N₄), despite with obvious catalytic effect, is still unsatisfactory for hydrogen production. In this work, phosphorus element is incorporated to tune g-C₃N₄'s property through calcinating the mixture of g-C₃N₄ and NaH₂PO_2, sacrificial agent and co-catalyst also been supplied to help efficient photocatalytic hydrogen production. Phosphorus (P) doped g-C₃N₄ samples (PCN-S) were prepared, and their catalytic properties were studied. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and ultraviolet diffuse reflection (UV-DRS) were used to study their structures and morphologies. The results show that the reaction rate of PCN-S is 318 μmol h⁻¹ g⁻¹, which is 2.98 times as high as pure carbon nitride nanosheets (CN) can do. Our study paves a new avenue, which is simple, environment-friendly and sustainable, to synthesize highly efficient P doping g-C₃N₄ nanosheets for solar energy conversion.     

Construction,structure and photocatalysis of janus nanofiber modified by g-C3N4 nanosheets heterostructure photocatalysts

The construction of photocatalyst with gradient band structure is guided by the principle of band gap engineering. Rational structural design is advanced and applied to construct a new-typed peculiarly structural and functional carbon-based [TiO₂/C]//[Bi₂WO₆/C] Janus nanofiber modified by g-C₃N₄ nanosheets heterostructure photocatalyst (denoted as TB-JgHP). The flexible carbon-based [TiO₂/C]//[Bi₂WO₆/C] Janus nanofiber with one side responding to ultraviolet light and the other capturing visible light is fabricated by conjugate electrospinning, and then g-C₃N₄ nanosheets are uniformly grown in-situ on the surface of the Janus nanofibers by using gas-solid reaction via gasification of urea. The optimized TB-JgHP possesses remarkable hydrogen evolution efficiency (17.48 mmol h⁻¹ g⁻¹) and methylene blue degradation rate (99.2%) under simulated sunlight illumination for 100 min, demonstrating prominent dual-functional characteristics. The enhanced photocatalytic performance benefits from the unique Janus structure as well as the synergistic effects among the triple heterostructures of TiO₂ and Bi₂WO₆, g-C₃N₄ and TiO₂, g-C₃N₄ and Bi₂WO₆. The formation of gradient band structure among heterostructures is more conducive to the multi-step separation of photo-induced electron-hole pairs and more effective absorption of light. Further, flexible self-standing carbon-based photocatalysts not only have outstanding electron transport performance, but also are easy to separate from solution with preeminent recyclable stability. Based on a series of characterization techniques, it is further proved that TB-JgHP has higher carrier separation efficiency than the counterpart contrast samples. The formation mechanism of TB-JgHP is proposed, and the construction technique is established. The design philosophy and construction technique presented in this work pave a new avenue for research and development of other heterostructure photocatalysts.