Separation Efficiency Of Photogenerated Carriers Research Articles

Establishing rapid charge channel via synergism of oxygen vacancy and interfacial effect to promote stable photocatalytic NO purification

Developing efficient and economical photocatalysts is critical to the practical application of nitrogen oxide (NOx) photocatalytic purification technology. At the same time, the spatial separation and migration of charges were extremely limited by the energy band mismatch and limited adaptability of the heterojunction. Herein, the interfacial effect of AgBr/Bi4O5Br2 heterojunctions with oxygen vacancies (OVs) was established to modify the interface and surface properties for enhance the photocatalytic performance. As a result, the optimal OVs-Bi4O5Br2/AgBr composite exhibited a maximum NO removal rate of 66.4 % (728 ppb → 245 ppb) and high stability for 600 min under visible light. The results show that an internal electric field could be formed by the synergism of the oxygen vacancy and interfacial effect to provide a rapid charge transport channel, which improved the separation efficiency of photo-generated carriers. It also generated abundant reactive oxygen species (ROS), which enhanced the photocatalytic NO purification performance. The present work provided a valuable design strategy for rapid charge transfer-based photocatalysts for pollutant treatment.

A construction of core–shell dual zeolite imidazole skeleton derived composite to facilitate photocarrier separation and distribution of active sites for photocatalytic water oxidation

Limited by the severe carrier recombination and insufficient active sites of the catalyst, achieving efficient photocatalytic water oxidation remains a major challenge. Herein, a core–shell zeolite imidazole skeleton (ZIF) based material with rich active sites in its interior is obtained by in-situ growth carbonization two steps method. According to characterization, performance testing and photoelectric experiments, it is confirmed that the ZIF67@ZIF8-2-800 material has good photogenerated carrier separation efficiency and surprising O2 production. The reason for the performance improved is that ZIF8 as a shell prevents the agglomeration of active sites CoO in the carbonization process of ZIF67. Theoretical calculations reveal that the core–shell structure has a favorable influence on the separation of photogenerated carriers. The N atom acts as an electron transport mediator, transferring electrons from the CoO core to the NC shell, while the holes remain in the CoO to participate in the photocatalytic water oxidation reaction.

Biomimetic photocatalyst Ce/TCPP-UiO-66-NH2 for NADH regeneration and CO2 activation

CO2 activation and conversion by enzymes to produce value-added multi-carbon compounds under mild conditions show significant impact on carbon neutrality. However, the enzyme co-factor NADH is expensive and the regeneration is still challenging for the enzyme reaction process. Inspired by natural photosynthesis, this study successfully developed a biomimetic photocatalyst Ce/TCPP-UiO-66-NH2 (TCPP: meso-tetrakis (4-carboxyphenyl) porphine) for NADH regeneration and CO2 activation. Structure analysis and spectra showed that the co-doping of Ce and TCPP reduced the band gap width of UiO-66-NH2, improved the separation efficiency of photo-generated carriers, and endowed it with excellent photocatalytic performance. The synthesized biomimetic photocatalyst Ce/TCPP-UiO-66-NH2 was then applied for NADH regeneration. The regeneration efficiency of NADH can reach up to 95 % after 3 h of light reaction, which was about 1.6 times higher than that of the control group. Ultra-fast femtosecond time-resolved transient absorption (fs-TA) showed that Ce/TCPP-UiO-66-NH2 possessed the shortest average decay time (τ¯ = 1.12 ps), indicating shorter average life-time of carriers after Ce doping, thus suppressing hole-electron recombination. Finally, the key enzyme formate dehydrogenase (FDHPa) for CO2 activation was immobilized on the membrane, combining with light regeneration of NADH for CO2 production to formate. The formate yield (3.1 mM) was 16 times higher than that of the control group (0.19 mM). This work provided an effective strategy and efficient photocatalyst for the biomimetic photocatalytic activation of CO2 to formate, which is an indispensable bridge for the further high-valuable Cn compounds production by biocatalysis.

Enhancement TiO2 photocatalytic hydrogen production via using ABO3 to construct heterojunction

The lower photogenerated carrier separation efficiency seriously hinders the photocatalytic performance of TiO2. In order to solve this problem, we utilized SrTiO3 particles with low cost, good response to visible light, tunable band structure, and type II heterojunction with TiO2 to improve the photogenerated carrier separation efficiency of TiO2 in this study. The TiO2/SrTiO3 heterojunctions have a larger specific surface area than pristine TiO2, pristine SrTiO3. The results confirmed that the formation of heterostructures reduce the interfacial resistance of charge transfer; the transient and effectively improve the electron-hole pair separation efficiency. The hydrogen production efficiency of TiO2/SrTiO3 heterojunction composite is 807.7 μmolg−1h−1, which is 26 times higher than pure TiO2 nanotubes. This work provides a new way to prepare efficient and low-cost photocatalysts using ABO3.

3D axial channels and interfacial oxygen vacancies cooperate for enhancing photo-Fenton performance of ZnO/BiOCl microsphere

Boosting photo-Fenton performance by enhancing mass transfer process of peroxy sulphate (PS) and inhibiting the recombination of photo-generation carriers is an appealing strategy. Herein, ZnO/BiOCl porous microsphere assembled by thin nanosheets was successfully fabricated via microwave-assistant method. The results discern that BOZ-30 can eliminate 75.2 % carbamazepine (CBZ, 2.5 mg L−1) in 180 min, which is 1.7 and 1.3 times folder than ZnO and BiOCl, respectively. Moreover, the catalytic mechanism revealed that 3D axial channels and interfacial oxygen vacancies (IOVs) enhance mass transfer process of PS, promote forming of BOZ-PS* complex, and boost the separation efficiency of photo-generated carriers. Therefore, myriad electrons are quickly arrived at surface active sites through thin nanosheets and trapped by BOZ-PS* composites, and then effectively transfer to CBZ. Eventually, PS was activated under the synergistic of IOVs and 3D axial channels. Furthermore, the structure-properties relationship of removal rate, specific area and total oxygen vacancies was established. This work shed a new light on to remove refractory pollution by the cooperation of defect engineering and morphology engineering.

Facile preparation of high-performance hydrochar/TiO2 heterojunction visible light photocatalyst for treating Cr(VI)-polluted water

In order to remedy the shortcomings of narrow absorption wavelength range and low photogenerated carrier separation efficiency of TiO2 photocatalyst, hydrochar (HC) was chosen to modify TiO2 by constructing HC/TiO2 heterojunction composite. HC/TiO2 composites were synthesized from glucose, tetrabutyl titanate and deionized water by a simple one-pot hydrothermal way, and their photocatalytic Cr(VI) reduction properties were studied. The results indicated that HC/TiO2 composites had tremendously improved photocatalytic Cr(VI) reduction activity, in comparison with TiO2, HC and a number of newly reported TiO2-based visible light photocatalysts. When the mass percentage of glucose to tetrabutyl titanate was 14, the obtained HC/TiO2-2 possessed the maximal photocatalytic activity, which was 19 times that of TiO2 and 14.3 times that of HC under visible light (wavelength > 420 nm) irradiation, and 3.2 times that of TiO2 under ultraviolet-visible light (Xenon lamp) irradiation. Furthermore, the photocatalytic stability of HC/TiO2-2 was also excellent. Additionally, proper choice of the photocatalysis experiment parameters could further raise the photocatalytic Cr(VI) reduction efficiency of HC/TiO2-2. The exceptionally elevated photocatalytic activity of HC/TiO2-2 was found to be due to its type-II heterojunction structure, which drastically heightened the separation and transfer efficiencies of photogenerated electrons and holes. Besides, HC/TiO2-2 also showed great potential for practical application in photocatalytic treatment of the Cr(VI) effluents discharged from freezing brine and black chromium plating industries.

Built-in electric field intensified by photothermoelectric effect drives charge separation over Z-scheme 3D/2D In2Se3/PCN heterojunction for high-efficiency photocatalytic CO2 reduction

It is a challenging issue to further drive charge separation through the oriented design of Z-scheme heterojunction in the exploitation of cost-effective photocatalytic materials. In this contribution, the unique Z-scheme 3D/2D In2Se3/PCN heterojunction is developed through implanting In2Se3 microspheres on PCN nanosheets using an in situ growth technique, which acquires the effective CO generation activity from photocatalytic CO2 reduction (CO2R). The CO yield of 4 h in the CO2R reaction over the optimal In2Se3/PCN-15 sample reaches up to 11.40 and 2.41 times higher than that of individual PCN and In2Se3, respectively. Such greatly enhanced photocatalytic performance is primarily the improvement of photogenerated carrier separation efficiency. To be more specific, the formed built-in electric field is significantly intensified by producing the temperature difference potential between In2Se3 and PCN owing to the photothermoelectric effect of In2Se3, which actuates the high-efficiency separation of photogenerated charge carriers along the Z-scheme transfer path in the In2Se3/PCN heterojunction. The effective strategy of enhancing the built-in electric field to drive photogenerated charge separation proposed in this work opens up an innovative avenue to design Z-scheme heterojunction applied to high-efficiency photocatalytic reactions, such as hydrogen generation from water splitting, CO2R, and degradation of organic pollutants.

Study of Indium Phosphide Quantum Dots/Carbon Quantum Dots System for Enhanced Photocatalytic Hydrogen Production from Hydrogen Sulfide

Quantum dots (QDs) are promising semiconductor nanocrystals in photocatalysis due to their unique properties and in contrast to bulk semiconductors. Different from the traditional modification methods of indium phosphide (InP) QDs such as metal doping, shell design, and surface ligand modification, we firstly constructed the indium phosphide quantum dot and carbon quantum dot (InP QDs/CQDs) system and used it for the study of photocatalytic hydrogen production from hydrogen sulfide (H2S) in this work. The photocatalytic performance tests show that the average rate of photocatalytic decomposition of hydrogen sulfide to produce hydrogen of the InP QDs/CQDs system increases by 2.1 times in contrast to InP QDs alone. The steady-state and time-resolved photoluminescence spectra demonstrated that the introduction of CQDs can effectively improve the separation efficiency of photo-generated carriers. In addition, the surface electronegativity of the InP QDs/CQDs system is weaker than that of InP QDs, which may reduce the repulsion between the photocatalyst and reaction substrate, promoting the surface oxidation reaction in the photocatalytic process. This work indicates that the construction of the QDs hybrid system can improve their photocatalytic performance, providing a way to optimize QDs in photocatalysis.

Dye-sensitized NH2-UiO-66 anchored with copper ions for tandem visible-light-driven hydrogen evolution

Metal-organic frameworks (MOFs) have attracted exciting application prospects in photocatalytic hydrogen (H2) evolution due to the diversity of organic ligands and metal ions. However, the inappropriate conduction band position of pristine MOFs and corresponding large overpotential for H2 evolution restrict the H2 production under visible light. Herein, a dye-sensitized NH2-UiO-66 anchored with copper ions (EY-6Cu-NU-66) was synthesized by in-situ Cu anchoring followed by Eosin Y sensitization. The H2 production activity showed that EY-6Cu-NU-66 reached 3579.82 μmol·g−1·h−1 under visible light, which was four times higher than that of dye-sensitized pristine NU-66 (EY-NU-66) and 99-fold higher than that of 6Cu-NU-66 free of dye sensitization. A series of characterizations and theoretical computations indicated that photo-generated electrons first transfer from the excited Eosin Y to the lowest unoccupied molecular orbital (LUMO) of the NU-66, then further transfer to the transition CuII/CuI metal center that is formed by Cu anchored on -NH2. This tandem mechanism not only improves the visible-light absorption ability of NU-66 but also promotes its separation efficiency of photo-generated carriers, thus greatly reducing the overpotential for H2 evolution. This work provides a new strategy for visible-light-driven H2 production by dye-sensitized MOF-based materials without noble metal loading.

Synergistic effect of photoelectrochemical aptasensor based on staggered gap ZnO/BiFeO3 heterojunction coupled with cDNA-CdS sensitizer enabling ultrasensitive assay of kanamycin

Using staggered-gap ZnO/BiFeO3 heterojunction as photoactive materials and cDNA-CdS as the sensitizer for sensitive Kanamycin (KAN) detection, we have created a unique signal-off biosensing platform. The ZnO/BiFeO3 heterojunction provides active sites for aptamer loading and enhances photocurrent responsiveness. Rapid interfacial charge transfer and the separation efficiency of photo-generated carriers are enhanced by sensitization of the ternary heterojunction ZnO/BiFeO3/CdS. Signal-amplified quenching occurs when sensitizers are replaced with sterically hindered KAN. Because of the aptamer's greater affinity for KAN, the replacement of CdS causes a decrease in photocurrent response. Additionally, the weakly conductive aptamer-KAN complex causes steric hindrance, which exacerbates the photoelectrochemical signal-damping effect even more. The photoelectrochemical aptasensor exhibits excellent selectivity and stability, detecting KAN within the range of 0.00005825–0.233 μg/mL with a detection limit of 0.0466 ng/mL (S/N = 3). This work demonstrates the potential of perovskite oxides and their heterostructures for advanced photoelectrochemical biosensing applications.

In situ synthesis of bi-functional NH2-Ti2C3Tx@COF Schottky heterojunction through interfacial electron effects for enhancing U(VI) photoreduction

Reduction of soluble U(VI) to insoluble U(IV) is considered as a promising strategy to avoid uranium contamination. Herein, a bi-functional covalent organic framework based heterojunction (NH2-Ti3C2Tx@COF) was constructed on the amino-modified Ti3C2Tx MXene for efficient photoreduction U(VI) without additional sacrificial agents. Schottky interface with electronic unidirectional channel is established by the formation of local electrophilic/nucleophilic region due to the introduction of reductive COF with alkynyl group, resulting in efficient photogenerated carrier separation and solar energy utilization. More importantly, NH2-Ti3C2Tx with negative charge served as electron collector and transfer channel can effectively surmount the low photocatalytic activity caused by high polarization of imine-linked COFs. Thus, the tailored-made design of NH2-Ti3C2Tx@COF exhibits excellent photocatalytic activity, fast reaction kinetics (removal of 97.8 % in 60 min) and high adsorptive capability (1557.2 mg/g) under the light condition. This multiple-in-one advantage makes well-designed NH2-Ti3C2Tx@COF as a promising capture platform. This work will provide some new insight and inspiration to COF based heterojunctions for enhancing U(VI) capture.

Synergistic effect of novel pyrite/N-doped reduced graphene oxide composite with heterojunction structure for enhanced photo-assisted reduction of Cr(VI) in oxic water: Specific role of molecular oxygen

To avoid severe aggregation and synergistically utilize the intrinsic and photocatalytic reducibility, pyrite (FeS2) was loaded onto N-doped reduced graphene oxides (N-rGO) to fabricate a novel FeS2/N-rGO heterojunction catalyst for enhanced chromium (Cr(VI)) reduction in oxic condition to simultaneously investigate the specific effect and role of dissolved oxygen (DO). Characterization results showed that strong interaction and combination of FeS2 and N-rGO not only achieved the uniform distribution of FeS2, but also increased the defects, and exposed more functional groups. Meanwhile, the Type II heterojunction was formed in FeS2/N-rGO, which facilitated the separation efficiency of photo-generated carriers and electrons, endowing FeS2/N-rGO a superior photocatalytic activity. Cr(VI) was almost completely reduced via FeS2/N-rGO within 60 min under irradiation (Cr(VI) = 10 mg/L, dosage = 0.2 g/L), 3 times that of pristine FeS2 (18.7 %). Trapping and Electron Spin Resonance (ESR) experiments indicated that photo-generated e− and derived O2− species from photoactivation of dioxygen (DO) were the key reactive species for the enhancement of photo-assisted Cr(VI) reduction, rather than reductive Fe2+ and S22− species. Although the photocatalysis of FeS2/N-rGO cannot directly generate hydroxyl radicals (OH), the oxidative OH ascribed to superoxide radicals (O2−), photo-induced holes and free DO preferentially consumed by Fe2+ and S22− with stronger reducibility. Hence, as compared to the anoxic condition, the reduction rate of Cr(VI) was slightly decreased, but still could be totally removed within 60 min in the oxic conditions. Due to the excessive amount of FeS2/N-rGO, Cr(III) after reduction would not be influenced by oxidative species and maintain stability under oxic condition. This study provided a facile modification strategy for FeS2 based composites and uncovered its working mechanism for Cr(VI) decontamination.

Photocatalytic removal of organic pollutants by SiO2 modified BiOCl nanosheets with abundant oxygen vacancies

In this demonstration, SiO2/BiOCl composites were fabricated by loading SiO2 nanoparticles onto the surface of BiOCl nanosheets through a conventional hydrothermal approach. SiO2/BiOCl photocatalysts were studied by specific surface area analysis, X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), UV–Vis diffuse reflection spectroscopy (UV–Vis DRS) and electron spin resonance (ESR) techniques. In light of the rich pore structures of BiOCl modified by SiO2, the photogenerated carriers separation efficiency of SiO2/BiOCl is significantly improved. Therefore, SiO2/BiOCl composite nanosheets show high efficiency towards degradation of perfluorooctanoic acid (PFOA) and rhodamine B (RhB), and the composites display exceptional stability. In comparison to the pure BiOCl, photocatalytic degradation activity of 4.4 % SiO2/BiOCl (mass ratio of SiO2/Bi(NO3)3·5H2O is 4.4 %) for RhB and PFOA increases by 100 % and 50 %, respectively. The result from the radical capture experiments suggests that holes (h+) and superoxide radicals (·O2–) play a crucial role as the primary active species in degradation of organic pollutants. The enhanced photocatalytic efficiency of the SiO2/BiOCl composites can be primarily ascribed to the construction of numerous oxygen vacancies (OVs), which effectively promote the adsorption of organic pollutants, boost light responsiveness, and expedite the separation of photoinduced e-/h+ pairs.

Construction of Low-Cost Z-Scheme Heterojunction Cu2O/PCN-250 Photocatalysts Simultaneously for the Enhanced Photoreduction of CO2 to Alcohols and Photooxidation of Water.

Solar-driven high-efficiency conversion of CO2 with water vapor into high-value-added alcohols is a promising approach for reducing CO2 emissions and achieving carbon neutrality. However, the rapid recombination of photogenerated carriers and low CO2 adsorption capacity of photocatalysts are usually the factors that limit their applicability. Herein, a series of low-cost Z-scheme heterostructures Cu2O/PCN-250-x are constructed by in situ growth of ultrasmall Cu2O nanoparticles on PCN-250. A systematic investigation revealed that there is a strong interaction between Cu2O nanoparticles and PCN-250. The resulting Cu2O/PCN-250-2 exhibits excellent photogenerated carrier separation efficiency and CO2 adsorption capacity, which dramatically promote the conversion of CO2 into alcohols. Notably, the total yield of 268 μmol gcat-1 for the production of CH3OH and CH3H2OH is superior to that of isolated PCN-250 and Cu2O. This study provides a new perspective for the design of a Cu2O nanoparticle/metal-organic framework Z-scheme heterojunction for the reduction of CO2 to alcohols with water vapor.

Bifunctional WO3/TiO2 heterojunction photocathode for high-performance photo-assisted Li–O2 battery

Photo-assisted charging is a useful method for mitigating high overpotential in Lithium–oxygen (Li–O2) batteries. Herein, WO3/TiO2 heterostructures were carefully designed on carbon-fiber fabrics and used as photocathodes in photo-assisted Li-O2 batteries. The transfer mechanism of photoexcited carriers with a strong redox ability in WO3/TiO2 heterostructures reduces the compounding of electrons (e-) and holes (h+). Accordingly, the battery’s energy can be tuned by illumination, giving an ultra-low overpotential of 0.11 V at a current density of 0.05 mA·cm-2 with excellent cycling stability (retaining a round-trip efficiency of 96.21% after 150 cycles). The cycle life can reach 1000 h due to increased photo-generated carrier separation efficiency and decreased electrochemical reaction impedance.

Synthesis of Ag3PO4/Ag/g-C3N4 Composite for Enhanced Photocatalytic Degradation of Methyl Orange.

In this study, we have successfully constructed Ag3PO4/Ag/g-C3N4 heterojunctions via the hydrothermal method, which displays a wide photo-absorption range. The higher photocurrent intensity of Ag3PO4/Ag/g-C3N4 indicates that the separation efficiency of the photogenerated electron-hole pairs is higher than that of both Ag3PO4 and Ag/g-C3N4 pure substances. It is confirmed that the efficient separation of photogenerated electron-hole pairs is attributed to the heterojunction of the material. Under visible light irradiation, Ag3PO4/Ag/g-C3N4-1.6 can remove MO (~90%) at a higher rate than Ag3PO4 or Ag/g-C3N4. Its degradation rate is 0.04126 min-1, which is 4.23 and 6.53 times that of Ag/g-C3N4 and Ag3PO4, respectively. After five cycles of testing, the Ag3PO4/Ag/g-C3N4 photocatalyst still maintained high photocatalytic activity. The excellent photocatalysis of Ag3PO4/Ag/g-C3N4-1.6 under ultraviolet-visible light is due to the efficient separation of photogenerated carriers brought about by the construction of the Ag3PO4/Ag/g-C3N4 heterostructure. Additionally, Ag3PO4/Ag/g-C3N4 specimens can be easily recycled with high stability. The effects of hydroxyl and superoxide radicals on the degradation process of organic compounds were studied using electron paramagnetic resonance spectroscopy and radical quenching experiments. Therefore, the Ag3PO4/Ag/g-C3N4 composite can be used as an efficient and recyclable UV-vis spectrum-driven photocatalyst for the purification of organic pollutants.

Preparation of Oxygen-Doping Nongraphitic Carbon Nitride via Efficiency Exfoliation for the Application of Photocatalytic Degradation.

E-OLCN photocatalyst was synthesized by oxygen doping of low molecular weight carbon nitride (LCN) with ethanol solvent stripping. The enhanced light absorption, fast electron transport rate, and photogenerated carrier separation efficiency of E-OLCN leads to the excellent photocatalytic degradation performance compared with the original materials. The synergistic effect of oxygen doping and ethanol solvent stripping plays a significant role for the modulation of electronic and structural properties of the prepared catalysts. Methyl orange (MO) and rhodamine B (RhB) are chosen as typical pollutants for the application of photocatalytic degradation. The E-OLCN sample exhibits outstanding photocatalytic degradation performance, where the rate constant k (1 × 10-2 min-1) of E-OLCN (1.68) is 2.9 times than that of O-LCN (0.58) and 8.8 times than that of pristine LCN (0.19) for MO. Moreover, modulated E-OLCN shows good stability after cycling experiments and the activity still achieved 90%. The detailed mechanism for MO degradation was proposed with the technical support of liquid chromatography-mass spectrometry (LC-MS) and electron spin resonance (EPR). The superoxide radical (·O2-) is the main active species and the MO molecule could be decomposition completely.

Preparation of TiO2/SnO2 Electron Transport Layer for Performance Enhancement of All-Inorganic Perovskite Solar Cells Using Electron Beam Evaporation at Low Temperature.

SnO2 has attracted much attention due to its low-temperature synthesis (ca. 140 °C), high electron mobility, and low-cost manufacturing. However, lattice mismatch and oxygen vacancies at the SnO2/CsPbI3-xBrx interface generally lead to undesirable nonradiative recombination in optoelectronic devices. The traditional TiO2 used as the electron transport layer (ETL) for all-inorganic perovskite solar cells (PSCs) requires high-temperature sintering and crystallization, which are not suitable for the promising flexible PSCs and tandem solar cells, raising concerns about surface defects and device uniformity. To address these challenges, we present a bilayer ETL consisting of a SnO2 layer using electron beam evaporation and a TiO2 layer through the hydrothermal method, resulting in an enhanced performance of the perovskite solar cell. The bilayer device exhibits an improved power conversion efficiency of 11.48% compared to the single-layer device (8.09%). The average fill factor of the bilayer electron transport layer is approximately 15% higher compared to the single-layer electron transport layer. Through a systematic investigation of the use of ETL for CsPb3-xBrx PSCs on optical and electronic properties, we demonstrate that the SnO2/TiO2 is an efficient bilayer ETL for PSCs as it significantly enhances the charge extraction capability, suppresses carrier recombination at the ETL/perovskite interface, facilitates efficient photogenerated carrier separation and transport, and provides high current density and reduced hysteresis.

Synthesis of novel flower-like Bi4Ti3O12/BiOCl heterojunctions with excellent piezoelectric photocatalytic performance

Photocatalysis technology can not only degrade pollutants by renewable solar energy, but also has enormous promise for resolving environmental issues. The piezoelectric field inside the piezoelectric material can be used as the driving force of charge separation to improve the photocatalytic activity. In order to study the catalytic effect of piezoelectric materials on photocatalysis, a flower-like Bi4Ti3O12/BiOCl (BTO/BOC) composite catalyst is prepared in this paper. The photogenerated carrier separation efficiency is characterized by electrochemical, PL and ESR tests. BOC's built-in electric field helps to facilitate the separation of photogenerated carrier, reducing the recombination rate and improving photocatalytic efficiency. The piezoelectric effect caused by ultrasonic vibration is coupled with the photocatalysis, which realizes the high efficiency co-catalysis of BTO/BOC piezoelectric photocatalyst. The polarized BTO/BOC heterojunction catalysts achieved a very high degradation efficiency (99.15 %) under piezo-photocatalysis. The degradation rates (k = 0.7494 min−1) are 1.74 and 8.19 times higher than photocatalysis (k = 0.4304 min−1) and piezoelectric catalysis (k = 0.0915 min−1), respectively. The investigation of the piezoelectric effect and photocatalysis's synergistic relationship is very significant.

One‐step supramolecular pre‐organizational synthesis of copper‐doped porous carbon nitride for high photocatalytic nitrogen fixation

AbstractSolar‐driven reduction of nitrogen to ammonia is a promising green approach and is considered as a sustainable alternative to the Haber–Bosch process. Carbon nitride (g‐C3N4) is an ideal non‐metallic semiconductor photocatalyst for photocatalytic N2 reduction reaction (p‐NRR). In this work, we designed a simple supramolecular self‐assembly method to prepare copper‐doped porous graphitic nitride (Cu@pg‐C3N4) photocatalysts. The synergistic semiconductor and metal interactions enabled the obtained Cu@pg‐C3N4 to achieve larger specific surface area, more efficient photogenerated carrier separation, and stronger photoreduction ability. The specific surface area of Cu@pg‐C3N4 increased from 5.69 to 75.76 μmol/L, exposing more active sites compared to bulk g‐C3N4. The NH4+ production rate of the obtained Cu@pg‐C3N4 was 150.47 μmol/L, which is 20 times higher than that of the bulk carbon nitride, exhibiting excellent N2 photofixation ability. These findings highlight the significant progress that can be achieved by metal supramolecular network modification strategies in harnessing the potential of carbon nitride for photocatalytic reduction applications.