Separation Efficiency Of Electron-hole Pairs Research Articles

Enhanced photoreduction of U(VI) in solution by Ti3C2Tx/g-C3N4 composites

The enhanced transfer efficiency of electron from photocatalyst to U(VI) is crucial for U(VI) photoreduction. Herein, we developed porous 2D/2D Ti3C2Tx/g-C3N4 heterojunction structure through the pyrolysis gasification of urea during direct calculation of Ti3C2 nanosheet and urea. Ti3C2Tx/g-C3N4 hybrid displayed the exceptional photocatalytic performance, high reaction rate constant (k1 = 0.0228 min−1) and rapid removal kinetics due to high photocatalytic activity, good chemical stability and highly efficient separation of photo-generated electron-hole pairs. According to quenching experiments and ESR analysis, the superoxide (.O2-) radicals played an important role in U(VI) photoreduction by Ti3C2Tx/g-C3N4. The higher efficient migration of photo-generated electrons from g-C3N4 to Ti3C2 co-catalyst was attributed to the tight interfacial interaction of –NHx of g-C3N4 with Ti3C2 via NHx-Ti chemical bonding, which increased the photoreduction of U(VI) into U(IV) by XPS analysis. The findings are crucial for designing g-C3N4-based catalysts by manipulating electronic structure for enhanced U(VI) photoreduction.

Role of Pyramidal Low-Dimensional Semiconductors in Advancing the Field of Optoelectronics

Numerous optoelectronic devices based on low-dimensional nanostructures have been developed in recent years. Among these, pyramidal low-dimensional semiconductors (zero- and one-dimensional nanomaterials) have been favored in the field of optoelectronics. In this review, we discuss in detail the structures, preparation methods, band structures, electronic properties, and optoelectronic applications (photocatalysis, photoelectric detection, solar cells, light-emitting diodes, lasers, and optical quantum information processing) of pyramidal low-dimensional semiconductors and demonstrate their excellent photoelectric performances. More specifically, pyramidal semiconductor quantum dots (PSQDs) possess higher mobilities and longer lifetimes, which would be more suitable for photovoltaic devices requiring fast carrier transport. In addition, the linear polarization direction of exciton emission is easily controlled via the direction of magnetic field in PSQDs with C3v symmetry, so that all-optical multi-qubit gates based on electron spin as a quantum bit could be realized. Therefore, the use of PSQDs (e.g., InAs, GaN, InGaAs, and InGaN) as effective candidates for constructing optical quantum devices is examined due to the growing interest in optical quantum information processing. Pyramidal semiconductor nanorods (PSNRs) and pyramidal semiconductor nanowires (PSNWRs) also exhibit the more efficient separation of electron-hole pairs and strong light absorption effects, which are expected to be widely utilized in light-receiving devices. Finally, this review concludes with a summary of the current problems and suggestions for potential future research directions in the context of pyramidal low-dimensional semiconductors.

Enhanced photocatalytic degradation performance of cornstalk templated TiO2 towards ciprofloxacin in hospital wastewater by the synergistic effect of the (101)/(001) facets coexposed and NiO cocatalyst

In this work, a novel TiO2 photocatalyst (marked as yNiO/5 F-CSTG) was designed and synthesized through a solvothermal pathway assisted with a bio-template, which prefectly combined the strategy of crystalline facet engineering and co-catalyst. The experiment and characterization results indicated that the co-exposure of {101}/{001} facets over TiO2, surface heterojunction and NiO cocatalysts jointly promote the photocatalytic performances, which can be attributed to the high separation efficiency of electron-hole pairs. Additionally, the introduction of morphology regulator (i.e., glycerinum) induced the directional growth of TiO2，being beneficial to broaden the responsive range of visible light. Consequently, compared with pristine TiO2 and CST, the photocatalytic removal rate of 1NiO/5 F-CSTG towards CIP increased ∼24.8 and ∼2.6 times. Besides, for tap-water and hospital sewage, its photocatalytic removal rate reached 89.15 % and 56.32 %, respectively. DFT calculation showed that the F- doping into TiO2 led to the formation of impurity energy level, which contributed to the electron transfer between the co-exposure facets of {101}/{001}. This work provides certain valuable hints for the development of bio-templated photocatalysts.

Internal electric field and oxygen vacancies synergistically boost S-scheme VO/BiOCl-TiO2 heterojunction film for photocatalytic degradation of norfloxacin

Sluggish interfacial dynamics and weak redox properties make the degradation of antibiotics by photocatalysts still a great challenge. Herein, constructing S-scheme heterojunction between BiOCl and TiO2 nanorod arrays (TNA) by hydrothermal method, and the synergistic effect of oxygen vacancies (VO) and Internal Electric Field (IEF) on improving the performance of the photocatalysts was revealed by adjusting the VO. The VO modified BiOCl-TiO2 (VBiTNA) exhibited excellent photocatalytic activities for norfloxacin, achieving a degradation efficiency of up to 90.2 % in just 60 min, and the rate constant was as high as 3.67 × 10-2 min−1. In addition, it also showed great photocatalytic degradation performance of NOR in a wide pH range, complex ionized water environment and real water source. The degradation intermediates and degradation pathway of NOR were predicted with LC-MS technology and Fukui function. Combined with free radical capture, electron paramagnetic resonance, relevant electrochemical testing, and DFT calculations reveals the mechanism of the enhanced photocatalytic performance of VBiTNA. The performance enhancement can be attributed to the expansion of the light absorption range, enhanced adsorption of O2 and effective activation to generate ·O2–, while improving the separation efficiency of electron-hole pairs and maintaining a strong redox capacity. This research focusing on VO and IEF mechanisms will help to advance the rational design of high-performance defective photocatalysts.

Acid modification on ZnIn2S4 with sulfur vacancy for highly efficient photocatalytic reduction of Cr(VI)

Anion vacancies caused by acid treatment over photocatalysts have significant influences on photocatalytic processes. In this study, the ZnIn2S4 (denoted as ZIS) nanoflower samples were synthesized using a one-step hydrothermal process and then impregnated with different amounts of nitric acid solutions. The gathered samples were characterized using XRD, SEM, XPS, BET, and EPR, and their photocatalytic reduction activity of Cr(VI) was also studied. Owing to defect structures, the removal of Cr(VI) of sulfur-rich vacancies ZIS-NA-3 reached nearly 100% within 90 min under simulated solar light, which was about 3 times greater than that of the original ZIS. In summary, this study confirmed that nitric acid treatment could form a defect state on the surface of catalysts, enhancing the light absorption range and improving the electron-hole pair separation efficiency. Furthermore, the stability and recycling of the ZIS-NA-3 catalysts were evaluated. This work offered a simple surface modification technique for constructing high-activity photocatalysts so as to achieve the purpose of removal from polluted wastewater containing Cr(VI).

Narrow Bandgap Schottky Heterojunction Sonosensitizer with High Electron-Hole Separation Boosted Sonodynamic Therapy in Bladder Cancer.

Sonodynamic therapy (SDT) is applied to bladder cancer (BC) given its advantages of high depth of tissue penetration and nontoxicity due to the unique anatomical location of the bladder near the abdominal surface. However, low electron-hole separation efficiency and wide bandgap of sonosensitizers limit the effectiveness of SDT. This study aims to develop a TiO2-Ru-PEG Schottky heterojunction sonosensitizer with high electron-hole separation and narrow bandgap for SDT in BC. Density functional theory (DFT) calculations and experiments collectively demonstrate that the bandgap of TiO2-Ru-PEG is reduced due to the Schottky heterojunction with the characteristic of crystalline-amorphous interface formed by the deposition of ruthenium (Ru) within the shell layer of TiO2. Thanks to the enhancement of oxygen adsorption and the efficient separation of electron-hole pairs, TiO2-Ru-PEG promotes the generation of reactive oxygen species (ROS) under ultrasound (US) irradiation, resulting in cell cycle arrest and apoptosis of bladder tumor cells. The in vivo results prove that TiO2-Ru-PEG boosted the subcutaneous and orthotopic bladder tumor models while exhibiting good safety. This study adopts the ruthenium complex for optimizing sonosensitizers, contributing to the progress of SDT improvement strategies and presenting a paradigm for BC therapy.

Layered double hydroxides derived prussian blue analogue nanocage confining NiCoP nanoparticles as efficient bifunctional electrocatalyst

Designing novel electrocatalysts with excellent catalytic activity for efficient water splitting is necessary to achieve the large-scale H2/O2 production from renewable resources. In this study, a facile hydrothermal method followed by low-temperature phosphorylation treatment was employed to fabricate a nanocage of prussian blue analogue encapsulating NiCoP nanoparticles (NiCoP@PBA), which was derived from the layered double hydroxide precursor. As a bifunctional non-precious metal electrocatalyst, NiCoP@PBA demonstrates superior performance in KOH electrolyte water splitting, with overpotentials of 59 mV for electrocatalytic hydrogen evolution reaction (HER) and 263 mV for oxygen evolution reaction (OER) at 10 mA cm−2. The catalyst also exhibits low Tafel slopes of 54 mV dec−1 for HER and 120 mV dec−1 for OER, reflecting efficient charge transfer kinetics. DFT simulations show that the Co–N moieties at the heterogeneous interface of NiCoP@PBA can optimize the surface electron distribution and energy states, thus facilitating efficient electron-hole pair separation, significantly enhancing catalytic activity for both HER and OER process, and significantly extending the electrocatalyst's service life. Our approach can be extended to more non-precious metal electrocatalysts, which is significant for the design of efficient bifunctional water splitting electrocatalysts.

S-type heterojunction enhance the photocatalytic activity of TiO2/AgBr/Ag using loofah sponge as template towards ciprofloxacin degradation

Photocatalyst TiO2/AgBr/Ag (TBA) composites using loofah sponge as a template were successfully prepared for the first time. The photocatalytic activities of the TBA composites were evaluated by removing ciprofloxacin (CIP) under visible light. The PDOS shows that the valence band edge of TBA-30 is primarily composed of Ti 3d atom states, with small contributions from O 2p atom states. The conduction band edge is dominated by Ag 4d and O 2p atom states, with minor contributions from Br 4p atom states. TBA-30 composites demonstrate outstanding photocatalytic performance, degrading 87% of the target within 180 min. The degradation rate of CIP decreased to 70.19% after five runs, Furthermore, the TOC removal efficiency of CIP reached 84.2% in the end. CIP intermediates and degradation pathway were determined by GC-MS. Three-dimensional excitation-emission matrix fluorescence spectra (3D EEM) were used to study the degradation of CIP molecules. Trapping experiments and electron paramagnetic resonance (EPR) characterisation identified superoxide (·O2-) and photogenerated holes (h+) as the primary active radicals. Furthermore, formed S-type heterojunction and Ag as the electron capture site enhanced the separation efficiency of photoinduced electron-hole pairs. The DFT calculation was used to study the electron transport performance of TBA-30 by calculating the charge density difference.

Carbon-doped Bi2MoO6 nanosheet self-assembled microspheres for photocatalytic degradation of organic dyes

Abstract In this paper, carbon-doped Bi2MoO6 (C-Bi2MoO6) nanosheet self-assembled microspheres were prepared by using the solvothermal-calcination route to improve the photocatalytic activity of Bi2MoO6. The characterization results of x-ray diffractometry, Fourier transform infrared spectrometry, Raman scattering, scanning electron microscopy, transmission electron microscopy, BET specific surface area test, and x-ray photoelectron spectrometry indicated that C replaced the O2− anion in the Bi2MoO6 lattice, thinning the nanosheets, decreasing the size of the microspheres, and increasing the specific surface area of the Bi2MoO6. Ultraviolet–visible diffuse reflectance spectroscopy, photoluminescence, electrochemical impedance spectroscopy, transient photocurrent, and linear sweep voltammetry (LSV) spectroscopy demonstrated that the carbon doping reduced the band gap energy, raised the conduction band, and enhanced the photogenerated electron–hole pairs separation efficiency of Bi2MoO6. Benefiting from these favorable changes, the C-Bi2MoO6 microspheres prepared at a molar ratio of C to Bi of 4 (4C-Bi2MoO6) exhibited the highest photocatalytic activity, and the photocatalytic degradation rate constant of rhodamine B by 4C-Bi2MoO6 microspheres was almost 2.26 times that by pristine Bi2MoO6 under simulated solar light. 4C-Bi2MoO6 microspheres (0.2 g/L) presented excellent photocatalytic performance toward RhB (20 mg/L) at pH value 1 and could remove 98.31% of the RhB within 120 min. In addition, 4C-Bi2MoO6 microspheres also possessed a high photocatalytic activity toward methylene blue and tetracycline. 4C-Bi2MoO6 microspheres assembled from thin nanosheets can be used as effective photocatalysts to degrade toxic organic molecules from wastewater.

BiOCl/BiOBr composites for efficient photocatalytic carbon dioxide reduction

BiOBr (BOB) photocatalysts have low photocatalytic CO2 reduction performance due to their low electron-hole pair separation efficiency. To improve this problem, BiOCl (BOCl) is used as a co-catalyst. BOCl is loaded into BOB to form BiOCl/BiOBr (BOCl/BOB) type Ⅰ heterojunction, which enhances the photocatalytic CO2 reduction performance of BOB by promoting the separation of photogenerated electrons and holes. The results of TPR and PL experiments show that the 20% BOCl/BOB composites have the highest photogenerated carrier separation rate, and the results of CO2 reduction experiments show that 20% BOCl/BOB composites have the best photocatalytic CO2 reduction performance of 7.353 μmolg−1h−1, which is 3.22 and 1.99 times higher than pure BOB and BOCl, respectively. This work provides an effective reference for the development of modified photocatalysts.

Indium sulfide-sensitized 2D stannum indium sulfide nanosheet arrays promoting photoelectrochemical conversion efficiency in cathodic protection

This study reports the fabrication of 2D stannum indium sulfide (SnIn4S8) nanosheet arrays sensitized with indium sulfide (In2S3) and their potential application as photoanodes in photoelectrochemical cathodic protection for 304 stainless steel. The deposition of In2S3 flakes on the surface of the SnIn4S8 nanosheet arrays induces a notable alteration in the optical absorption of the composite samples, showing a maximum redshift from 560 nm to 645 nm. The incorporation of In2S3 regulates the energy band structure of SnIn4S8 by pulling its Fermi level and valence band maximum toward a negative direction. The type II heterojunction formed by sensitization with In2S3 strengthens the separation efficiency of photoinduced carriers in SnIn4S8, inhibiting self-corrosion. The particular 5%-In2S3/SnIn4S8 composite demonstrates a notable shift in the mixed potential toward negative values, reaching a potential of −1.05 V when exposed to visible light. An excessive amount of In2S3 is not conducive to the directional flow of carriers at the heterojunction interface, preventing efficient separation of electron-hole pairs. This research highlights the advantages of the In2S3-sensitized SnIn4S8 composites for photogenerated cathodic protection.

Dynamic Ag-mediated electron transfer confined ZnO nanorods for boosted photocatalytic bacterial disinfection

Infectious diseases, particularly bacterial infections, pose a global crisis with significant impacts on public health and economic stability due to the emergence of multi-drug resistance and limitations in existing therapeutic options. The present study focused on the development of photocatalytic disinfectant and silver-decorated hexagonal zinc oxide nanorods (Ag/ZnO NRs) were fabricated through an ultrasonic-assisted solvothermal method, and investigated for the photocatalytic inactivation on E. coli. The morphological, structural, and optical characteristics of the fabricated Ag/ZnO NRs were systematically studied through various analytical techniques. Here, 3%Ag/ZnO NRs showed 96.9% inactivation of E. coli within 120 min of visible light irradiation. The excellent inactivation efficiency of the photocatalyst could be attributed to the higher charge carrier mobility, efficient electron-hole pair separation, and highvisible light harvesting ability. The Schottky heterojunction was proposed as a possible mechanism for the photoinactivation of E. coli. Further, the impacts of different dosages of nanocomposites (NCs) and varying pH on bacterial inactivation were studied under visible light exposure. The reusability and stability of the NCs were investigatedfor 6 consecutive cycles of photoinactivation and it showed excellent efficiency (91.16%) of the photocatalyst for prolonged usage. The real-time application was assessed using reclaimed wastewaterand the influence on the organic matter was determined using COD analysis. The proposed study offers a significant point reference for the practical application of photocatalysis forthe inactivation of antibiotic-resistant microbes present in water bodies and environmental wastewater.

Z-scheme heterojunction engineering and hole-extraction layer enable efficient photoelectrochemical water splitting on BiVO4 photoanode

This study presents a novel Z-scheme heterostructure that was developed by integrating three-dimensional CoFe2O4 nanospheres with Mo and W co-doped BiVO4 (MW:BVO). Subsequently, ultra-thin hydroxides (NiOOH-FeOOH) were grown on the surface of the MW:BVO@CFO photoanode in the presence of tannic acid (TA), resulting in the formation of MW:BVO@CFO/TANF photoanodes. Notably, TANF served as a hole extraction layer. Compared to pristine MW:BVO, the photocurrent density of MW:BVO@CFO/TANF photoanodes exhibited a significant enhancement from 0.96 mA/cm2 to 6.03 mA/cm2 at 1.23 VRHE with a charge separation efficiency of 90.2 % due to the synergistic effect of the Z-scheme structure and hole extraction layer. Notably, the Z-scheme architecture facilitates the effective separation and transfer of electron-hole pairs, thereby retaining electrons and holes with high redox capacity. Meanwhile, the hole extraction layer quickly exports and aggregates the photo-generated holes, thereby further improving the separation efficiency of electron-hole pairs.

Carbon quantum dots/ Cu2O S-scheme heterojunction for enhanced photocatalytic degradation of tetracycline

In this work, carbon quantum dots (CQDs) with yellow fluorescence were firstly prepared by hydrothermal method using corn stover as raw material. Then, the CQDs/Cu2O S-scheme heterojunction was obtained by combining the prepared CQDs with dodecahedral Cu2O. The catalytic performance of the prepared catalyst under visible light was studied by using tetracycline (TC) as the degradation target. The results showed that the conductivity and the active sites in Cu2O were enhanced by loading CQDs, and the 3 wt% CQDs/Cu2O heterojunction showed the highest photocatalytic performance and the most excellent stability with 92.49% of TC degradation within 100 min. It is found that the recombination rate of electron and hole was reduced by the CQDs/Cu2O heterojunction with improved separation efficiency of the photo-generated electron-hole pairs and enhanced photo-degradation efficiency.

Synthesis of novel Ag/AgBr/K0.4Y0.7Sb2O6.25 nanocomposite with enhanced photocatalytic properties

Devoloping efficient wastewater treatment photocatalysts capable of improving water quality is undoubtedly one of the main problems of present society. In recent years, novel plasmonic photocatalysts have shown new possible applications in photocatalytic wastewater treatment due to their unique properties. In this work, a novel Ag/AgBr/K0.4Y0.7Sb2O6.25 composite was successfully fabricated by photo-reduction using the pre-prepared AgBr/K0.4Y0.7Sb2O6.25 and K0.4Y0.7Sb2O6.25 (KYSbO). The AgBr/KYSbO and KYSbO were synthesized by deposition-precipitation and precipitation-heating methods. The visible-light photocatalytic performance of parent KYSbO and Ag/AgBr/KYSbO composite was evaluated using methylene blue (MB) as a model organic pollutant. The effects of catalyst dosage, pH and the initial concentration of the MB dye solution on the photocatalytic activity were also investigated in this study. Remarkably, the Ag/AgBr/KYSbO composite exhibited superior visible-light photocatalytic activity for the degradation of MB than that of parent KYSbO. MB was degraded to 91.6% in the presence of parent KYSbO after visible irradiation of 180 min, while 93.2% degraded in merely 30 min in the case of Ag/AgBr/KYSbO composite. The superior improvement in the photocatalytic activity of the Ag/AgBr/KYSbO composite can be credited to the efficient separation of photoinduced electron-hole pairs and the extended visible-light response range. Superoxide radicals are crucial for MB photocatalytic degradation in the Ag/AgBr/KYSbO composite. The possible photocatalytic mechanism was proposed.

Methane sulfonic acid-assisted synthesis of g-C3N4/Ni2P/Ni foam: Efficient, stable and recyclable for photocatalytic nitrogen fixation under visible light

Photocatalytic nitrogen fixation is of great significance for solving the energy crisis and healthy development of the environment. However, photocatalysts have problems such as low activity, poor stability and difficult recovery, which seriously limit their application. Herein, we in situ synthesized g-C3N4/Ni2P/Ni three-dimensional reticulated foam photocatalysts (CNNPF) with excellent photocatalytic nitrogen fixation performance under visible light by a two-step methane sulfonic acid-assisted carbon nitride loading-calcined phosphatisation method, using nickel foam as the carrier and raw material. The results showed that the CNNPF had a stable three-dimensional network structure, and g-C3N4 was stably immobilized to the nickel foam skeleton with Ni2P. The best performance of CNNPF with ultrasonication for 2 h and phosphatisation for 1 h showed a high photocatalytic nitrogen fixation efficiency of up to 373 μmol·h−1·g−1, which was attributed to the Ni2P co-catalyst modification of g-C3N4 that led to the improvement of photogenerated electron-hole pair separation efficiency. Meanwhile, the three-dimensional network structure is favorable to provide more active sites for N2 adsorption and activation. In addition, the prepared material also has good stability and recyclability, and its nitrogen fixation efficiency was still maintained at 350 μmol·h−1·g−1 after five cycles. The present work provides a direction for the design of efficient and recyclable photocatalytic systems that show great potential in the field of economically sustainable nitrogen fixation.

Hollow cubic TiO2 loaded with copper and gold nanoparticles for photocatalytic CO2 reduction

A simple photodeposition method is used to prepare Cu and Au nanoparticles modified TiO2 nanocomposites. The phase composition of the catalyst is determined by x-ray diffraction. The mutual synergistic effects of Cu and Au are analyzed using x-ray photoelectron spectroscopy, photoluminescence spectroscopy and UV diffuse reflectance spectroscopy. The results indicate that the TiO2 is anatase structure with hollow cubic morphology, which enhances the utilization of visible light and improves the photocatalytic performance compared with P25. The Cu0.7Au0.3/TiO2 has the highest carrier separation efficiency and the best photocatalytic performance with a CO yield of 6.08 umol g−1 h−1, which is about four times higher than that of TiO2 (1.56 umol g−1 h−1). The aforementioned results indicate that the photocatalytic activity for CO2 reduction is greatly enhanced by the addition of modest quantities of Cu and Au NPs. During the photocatalytic process, the presence of Au NPs absorbs visible light and modulates the surface structure of electrons, while Cu serves as an electron sink, hence promoting efficient separation of electron-hole pairs. Utilizing the distinct benefits of bimetal and their robust interactions is a viable and efficacious approach for boosting the photocatalytic activity.

Enhanced photocatalytic activity of SnO2/g-C3N4 nanocomposite synthesized using sonochemistry method

The SnO2/g-C3N4 nanocomposite materials were successfully synthesized via the solid reaction and sonochemistry methods. The properties of the obtained product were investigated using several methods: X-ray diffraction, UV-vis diffuse reflectance spectroscopy, and Scanning electron microscope. The photocatalytic properties of the samples were evaluated through the photodegradation of Rhodamine B solution. The results demonstrate that the SnO2/g-C3N4 prepared by the sonochemistry method exhibits higher photocatalytic activity than that prepared by the solid reaction method. This enhanced photocatalytic activity is attributed to the formation of heterostructures between SnO2 and g-C3N4 materials, resulting in the efficient separation of photo-generated electron-hole pairs. Furthermore, the nanocomposite exhibits a larger specific surface area compared to the product obtained through the solid reaction method.

Coupling Z-Scheme g-C3N4/rGO/MoS2 Ternary Heterojunction as an Efficient Visible Light Photocatalyst for Hydrogen Evolution and RhB Degradation.

Coupling heterostructures to synergistically improve the light adsorption and promote the charge carrier separation has been regarded as an operative approach to advance the photocatalytic performances. However, it is still challenging to construct heterostructures with appropriate optical properties and interfacial energy structures at the same time. In this work, a Z-scheme g-C3N4/rGO/MoS2 ternary composite photocatalyst is successfully synthesized via an effective hydrothermal method. The as-synthesized g-C3N4/rGO/MoS2 composite photocatalyst exhibited significant improvement for visible light absorption and boosted the separation efficiency of photoinduced electron-hole pairs. The g-C3N4/rGO/MoS2 system exhibited optimum visible-light-induced photocatalytic activity in hydrogen (H2) from water splitting and degrading pollutant rhodamin B (RhB), which is 22 times and 5 times higher than that of pure g-C3N4, respectively. The excellent photocatalytic activities are attributed to the synergetic effects of coupling rGO, g-C3N4, and MoS2 ternary structures to the composite photocatalyst. These combinations of intimate two-dimensional nanoconjugations can effectively inhibit charge recombination and accelerate charge transfer kinetics, forming a Z-scheme-assisted photocatalytic mechanism, thereby exhibiting superior photocatalytic activity.

Construction of P−N charge-transfer bridge in porous g-C3N4 for highly efficient visible-light-driven photocatalytic N2 fixation

Solar N2 fixation is a green and pollution-free technology to realize solar energy to chemical energy. Here, P doped g-C3N4 nanosheets (PCNx) with porous structure has been fabricated via a one-step calcination process for efficient ammonia generation. The optimal PCN0.6 catalyst provided an improved visible light photo-performance with an ammonia generation rate of 3110 µg L−1h−1g−1, 15 times higher than that for pristine g-C3N4 (CN). And the quantum efficiency at 400 nm monochromatic light reached 3.29%. Characterization results revealed that the implantation of P−N bonds in g-C3N4 resulted in expanded optical response, larger accessible active sites and efficient separation of electron-hole pairs than that of bulk counterpart. Wavefunction contour maps revealed a more localized charge density distribution upon P doping, leading to a favorable electron-rich structure. The calculated N2 adsorption energy and N2-TPD tests showed the strong capacity of nitrogen chem-adsorption by PCN0.6. Charge density differences and Bader charge demonstrated the electrons transfer from the P doping sites of g-C3N4 to adsorbed N2, thus activating N2 molecules for effective NH4+ generation. This work offered significant insights into the heteroatom doping engineering to construct active sites and steer the charge migration pathways in g-C3N4 for efficient photo-reduction of N2.