Separation Efficiency Of Photogenerated Carriers Research Articles

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.

Constructing BiOBr/TiO2 heterostructure nanotubes for enhanced adsorption/photocatalytic performance

The fabrication of heterostructure materials with the synergy of adsorption and photocatalysis is an effective strategy to promote the removal of organic pollutants. In this work, BiOBr/TiO2 nanotubes were successfully obtained to enhance the removal of organic pollutants from water via the synergy of adsorption and photocatalysis. The TiO2 nanotubes were prepared using waste foam as the primary raw material by impregnation calcination, and BiOBr nanosheets were grown on their surface by a simple solvothermal method. The BiOBr/TiO2 nanotubes have significantly enhanced separation efficiency of photo-generated carriers, synergistic adsorption, and photocatalytic decomposition compared with pure TiO2 nanotubes. The enhanced activity is mainly attributed to the growth of BiOBr nanosheets leading to a substantial increase of the specific surface area and the internal electric field between the heterojunction of BiOBr/TiO2. In addition, possible degradation pathways for organic pollutants are proposed based on trapping experiments, electron spin resonance spectrometer, and density functional theory calculations. Our work provides a promising strategy for combining the advantages of adsorption and photocatalytic technologies for environmental remediation, and we anticipate it will be of significant interest to researchers in environmental science, materials science, and chemical engineering.

PVA/WO3-x/Ag2WO4 Hydrogel for Enhanced Photocatalytic Disinfection and Accelerated Wound Healing.

Bacterial wound infections are one of the growing health and safety threats to the public. In this study, WO3-x/Ag2WO4 photocatalysts were synthesized, and heterogeneous structures were constructed for non-antibiotic bactericidal use. Due to the heterostructure constructed with Ag2WO4, the photogenerated carrier separation efficiency and reactive oxygen generation capacity of WO3-x were improved, which in turn improved the inactivation rate of bacteria. Also, this photocatalyst was loaded into PVA hydrogel for photodynamic treatment of bacterial wound infections. This hydrogel dressing was demonstrated to have good biosafety by in vitro cytotoxicity tests and to have a wound healing-promoting effect by in vivo wound healing experiments. This light-driven antimicrobial hydrogel has the potential ability to treat bacterial wound infections.

The {0 1 0} and {1 1 0} facets of BiVO4 were selectively modified by Cu and g-C3N4 to enhance its visible light photocatalytic performance

The preparation of photocatalysts with high photogenerated carrier separation efficiency and excellent light absorption performance plays an important role in environmental pollution control. This paper successfully synthesised decahedral BiVO4 with co-exposed {010} and {110} facets by the hydrothermal method. Cu nanoparticles and negatively charged g-C3N4 were selectively deposited on the {010} and {110} facets of BiVO4 by photodeposition using methanol and NaIO3 as hole scavengers and electron acceptors, respectively. A Cu/BiVO4/g-C3N4 composite photocatalyst with synergistic effect of the Schottky junction, surface heterojunction and interfacial electric field was prepared. The photocatalytic performance was evaluated under visible light by degrading 2-mercaptobenzothiazole (MBT) and ciprofloxacin (CIP). Compared to pure BiVO4 and g-C3N4, Cu/BiVO4/g-C3N4-30 showed the best photocatalytic performance. The degradation efficiency of MBT was 97.9% in 60 min and the degradation efficiency of CIP was 92.8% in 120 min. The degradation of MBT was studied using high performance liquid chromatography-mass spectrometry (HPLC-MS). Therefore, this work provides a feasible strategy for designing photocatalysts that degrade organic pollutants.

In-situ construction of direct Z-scheme NiO/Bi2MoO6 heterostructure arrays with enhanced room temperature ether sensing properties under visible light irradiation

Light irradiation has emerged as a promising strategy to promote room temperature sensing of resistive-type semiconductor gas sensors recently. However, high recombination rate of photo-generated carriers and poor visible light response of conventional semiconductor sensing materials have greatly limited the further performance improvement. It is urgent to develop gas sensing materials with high photo-generated carrier separation efficiency and excellent visible light response. Herein, a novel direct Z-scheme NiO/Bi2MoO6 heterostructure arrays were designed and in-situ constructed on alumina flat substrate to form thin film sensors, which realized excellent room temperature gas response towards ether under irradiation of visible light for the first time, together with excellent stability and selectivity. Based on density functional theory calculation and experimental characterization, it was demonstrated that the construction of Z-scheme heterostructure could greatly promote the separation of photo-generated carriers and adsorption of ether. Moreover, the excellent visible light response characteristics of NiO/Bi2MoO6 could improve the utilization of visible light. In addition, the in-situ construction of array structure could avoid a series of problems caused by the conventional thick film devices. The work not only provides a promising guideline for Z-scheme heterostructure arrays in promoting the room temperature sensing performance of semiconductors gas sensors under visible light irradiation, but also clarifies the gas sensing mechanism of Z-scheme heterostructure at the atomic and electronic level.

Intramolecular built-in electric field enhanced polymerized nitrogen-carbon homojunction π*-electron delocalization enrichment promotes photocatalytic uranium (VI) reduction

The donor-acceptor (D-A) structure in conjugated systems enhances photogenerated carrier separation efficiency due to π * electron delocalization resulting from π-π interactions. This study reports a conjugated molecular carbon-nitrogen homojunction (CNH) with inherent π * electron transitions, which intrinsically enriches electron-hole pairs in the energy band region via its built-in electric field. CNH's intermolecular π-π stacking promotes efficient U(VI) reduction by boosting carrier generation and separation. Compared to CNNH, formed by temperature-controlled thermal polymerization of melamine and urea, the introduction of -NH2 disrupts the 3-s-heptazin ring in CNH's conjugated system. Heptazine integrity directly affects π-π * electron enhancement and transition, leading to a significant decrease in U(VI) reduction efficiency. Specifically, CNH exhibits optimal efficiency, reducing U(VI) by 99.6% within 60 min. This work emphasizes the significance of strong built-in electric fields generated through intramolecular π-π stacking, stimulating π-π * transitions, and enriching photogenerated π * electrons in carbon-nitrogen polymers, ultimately improving U(VI) photoreduction.

Quantum dots TiO2 loaded amorphous SiO2 composite photocatalysts: Significant performance enhancement and the effect of SiO2 surface hydroxyl groups

Using amorphous SiO2 (A-SiO2) and tetrabutyl titanate (TBOT) as raw material, a composite photocatalyst with surface loaded quantum dot size TiO2 (A-SiO2/TiO2, AST) was prepared. The degradation of tetracycline hydrochloride as well as mechanism of performance improvement by A-SiO2 were investigated. The TiO2 on the composite was anatase with a content of 9.96 wt% and a size of 7–8 nm (quantum dot level). TiO2 was uniformly distributed and was closely bonded at the interface by chemical bonds. The degradation rate of AST was 95% after 60 min UV exposure, which was comparable to pure nano-TiO2. The particle size of TiO2 in AST was reduced from 20–50 nm to 7–8 nm comparing with pure nano-TiO2 and changed from a highly agglomerated to a well-dispersed state due to abundant hydroxyl groups on A-SiO2 surface. TiO2 bandgap width increased from 3.25 eV to 3.39 eV. These led to the exposing of active sites on TiO2 and significantly increased photogenerated carrier separation efficiency. This study provides a feasible and simple method to improve TiO2 nanoparticles’ photocatalytic activity, reduce the usage and achieve recycling to cut the application cost by surface coated.

NiO co-catalyst modification ZnIn2S4 driving efficient hydrogen generation under visible light

Photocatalytic hydrogen production is considered as a good countermeasure to solve the energy crisis, but the existing photocatalysts have very slow electron-hole separation efficiency. How to design a photocatalyst with high photogenerated carrier separation efficiency has become a difficult rproblem. The efficiency of photogenerated carrier separation can significantly improve by precious metal co-catalyst, but its further development is limited by high cost. In this work, non-precious metal NiO is used as a co-catalyst and formed heterojunction with ZnIn2S4 (ZIS) as a cocatalyst, which significantly enhances the efficiencies of photogenerated carrier separation. According to the results of transient photocurrent (TPR) and Photoluminescence (PL), ZnIn2S4/NiO (ZIS/NiO) has the fastest photogenerated carrier separation rate when the mass fraction of NiO is 3%, which is about 5 times than pure ZIS. At the same time, the highest photocatalytic hydrogen production rate of 5 mmolg−1 h−1 was achieved under visible-light (λ ≥ 420 nm), which was 6.2 times more than pure ZIS (0.804 mmolg−1 h−1). This work offers a new option for low cost, high performance co-catalyst.

Enhancing photocatalytic C-O/N coupling reaction over covalent organic frameworks by pull-push electron group regulation

Covalent organic frameworks (COFs) have emerged as novel materials in photocatalytic technology for green energy and chemicals production. However, exploring highly efficient and stable COFs based materials for photocatalytic aromatic ethers and amines synthesis is still urgent. Herein, olefin-linked COFs modified with or without –F/-OCH3 groups were constructed by Knoevenagel condensation reaction. In addition, Ni active sites were embedded in the frameworks through bipyridine units to afford highly efficient and repeatable photocatalytic C-O/N coupling reaction. Through this strategy, it was found that the -F group modification greatly elevated photogenerated carriers separation efficiency attributing to its strong electronegativity and electron-withdrawing properties. Photocatalytic experiments conveyed that sp2c-F-COFdpy-Ni displayed highest photocatalytic activity and catalyzed cross-coupling of aryl C-O/N both with high yield exceeding 99 %, and exhibited excellent substrate compatibility for aryl bromides substituted with electron-withdrawing/donating groups. This investigation provides new insights into structure design of COFs for photocatalytic organic transformation.

Synergistic role of N-doped carbon quantum dots on Zn-doped cobalt ferrite (N-CQDs/ZnCF) for the enhanced photodegradation of oxytetracycline under visible light

N-doped carbon quantum dots/Zn0.4Co0.6Fe2O4(N-CQDs/ZnCF) composite was successfully synthesized by a hydrothermal method.XRD, HR-TEM, UV–Vis/DRS,PL, andXPSwere used to characterize the synthesized nanoparticles. The band gap energies of the synthesized nanomaterials were found to be less than 2 eV. PL results confirmed improved separation efficiency of photo-generated carriers on the N-CQDs/ZnCF. Additionally, HR-TEM images showed quasi-spherical and cubic morphology for both N-CQDs and ZnCF, respectively. The XPS survey spectra of 10% N-CQDs/ZnCF confirmed the presence of Zn2+, Co2+, Fe3+, N, O, and C on surfaces of N-CQDs/ZnCF. The pristine NPsand N-CQDs/ZnCF NCswere tested for the photodegradation of oxytetracycline, under visible light irradiation. The 10% N-CQDs/ZnCF nanocomposite showed the highest photocatalytic activity of up to 98% in 100 min. This enhancement was attributed to the synergistic effect of N-CQDs and ZnCF in the heterojunction, which promotes charge carrier separation and boosts photoactivity in degrading OTC.

Construction of ZnIn2S4/Bi2MoO6 heterojunction enhancement photocatalytic hydrogen evolution performance under visible light

One of the major challenges in photocatalytic hydrogen production is to improve the separation efficiency of photo-generated carriers. Therefore, we prepared ZIS/BMO heterojunctions by hydrothermal method to promote the directional separation of photogenerated carriers. A series of characterization results show that the successful preparation of heterojunctions substantially increases the separation and transfer rate of photogenerated carriers. 11% ZIS/BMO had the highest photocatalytic hydrogen production performance reached 1502.6 μmol/g/h, which is 2.78 times than ZIS monomer. Simple construction of heterojunctions but dramatic improvement of photocatalytic hydrogen production performance opens up new horizons for photocatalyst modification.

CuS@ZnIn2S4 p-n type heterojunction photocatalyst with LED visible light response

In this work, CuS@ZnIn2S4 p-n heterojunction was prepared by the ultrasonic composite method for the first time. Under LED (5 W) visible light excitation, the methylene blue (MB) degradation efficiency of CuS@ZnIn2S4-3 nanocomposite reached 95.8% in 60 min. Compared with ZnIn2S4, the spectral response range of CuS@ZnIn2S4-3 was widened, and the optical absorption capacity was increased by about 6 times. The electrochemical results revealed that CuS@ZnIn2S4-3 has good photogenerated carrier separation efficiency. Compared with ZnIn2S4, the photocurrent of CuS@ZnIn2S4-3 is increased by 2.2 times and the impedance is reduced by 4.16 times. Finally, the photocatalytic mechanism of CuS@ZnIn2S4 was explored in detail.

Synthesis of cake-like Ti-Bi bimetallic MOFs-derived OV-rich A-TiO2/β-Bi2O3 heterojunctions for photodegradation of ciprofloxacin

The cake-like Ti-Bi bimetallic MOFs and MOFs-derived oxygen vacancy-rich (OV-rich) A-TiO2/β-Bi2O3 heterojunctions were synthesized by solvothermal and high-temperature calcination techniques and applied to the degradation of ciprofloxacin (CIP). The cake-like morphology of the inherited parent MOFs allowed the A-TiO2/β-Bi2O3 heterojunctions to expose more active sites, which facilitated the enrichment of CIP. Under visible light, the synergistic effect of abundant oxygen vacancies (OV) and heterojunction results in stronger photo-responsiveness, higher photogenerated carrier separation efficiency and low recombination rate of A-TiO2/β-Bi2O3. The results of EPR as well as photodegradation CIP experiments show that heterojunction A-TiO2/β-Bi2O3 has more abundant OV and superior photocatalytic activity compared with monometallic MOFs derivatives (A/R-TiO2 and α-Bi2O3). Theoretical calculations reveal that OV can modulate the electronic and energy band structure of the material surface. In this study, new bimetallic MOFs were prepared, and OV-rich heterojunctions derived from MOFs were developed for the efficient degradation of pollutants under visible light.

Significant enhancement of photocatalytic activity of g-C3N4/vermiculite composite by the introduction of nitrogen defects

Nitrogen-defect g-C3N4/vermiculite composites (gCVx, x = 0.1, 1, 3, 4) with high efficient photocatalytic performance were constructed by a wet chemical method cooperating with the calcination process, as well as using the pre-expanded vermiculite and the melamine pre-treated by hydrochloric acid solutions of 0.1, 1, 3, 4 mol/L, respectively. Micron-sized g-C3N4 sheets with nitrogen defects were synthesized and uniformly distributed in the gCVx composites. Photocatalytic performance was evaluated by degrading Rhodamine B (RhB) aqueous solution. The results indicated that photocatalytic activities of gCVx increased firstly and then dropped down gradually with the increase of HCl concentration. gCV3 achieved the maximum degradation rate of 97.90 % for RhB after photocatalysis for 20 min, whose degradation rate constant was 14.9 times than that of bulk g-C3N4. gCV3 also exhibited the highest photocatalytic activity toward degrading the tetracycline and phenol solutions. The excellent photocatalytic performance was ascribed to the enhanced amounts of active sites, increased specific surface area, improved visible light absorption ability, accelerated charge transfer and separation efficiency of photogenerated-carriers, which resulted from the synergistic effect between vermiculite and nitrogen defects in g-C3N4, as well as the mutual electrostatic repulsion between the negative-charged vermiculite and the photo-induced electron from the nitrogen-defect g-C3N4.

Kinetically and Thermodynamically Favorable Ni–Al Layered Double Hydroxide/Ni-Doped Zn0.5Cd0.5S S-Scheme Heterojunction Triggering Photocatalytic H2 Evolution

Layered double hydroxide (LDH)-based photocatalysts have attracted more attention in photocatalysis due to their low cost, wide band gaps, and adjustable photocatalytic active sites; however, their low photogenerated carrier separation efficiency limits their photocatalytic efficiency. Herein, a NiAl-LDH/Ni-doped Zn0.5Cd0.5S (LDH/Ni-ZCS) S-scheme heterojunction is rationally designed and constructed from kinetically and thermodynamically favorable angles. The 15% LDH/1% Ni-ZCS displays comparable photocatalytic hydrogen evolution (PHE) activity with a rate of 6584.0 μmol g-1 h-1, which exceeds by ∼6.14- and ∼1.73-fold those of ZCS and 1% Ni-ZCS, respectively, and outperforms most of the previously reported LDH-based and metal sulfide-based photocatalysts. In addition, the apparent quantum yield of 15% LDH/1% Ni-ZCS reaches 12.1% at 420 nm. In situ X-ray photoelectron spectroscopy, photodeposition, and theoretical calculation reveal the specific transfer path of photogenerated carriers. On this basis, we propose the possible photocatalytic mechanism. The fabrication of the S-scheme heterojunction not only accelerates the separation of photogenerated carriers but also decreases the activation energy of H2 evolution and improves the redox capacity. Moreover, there are huge amounts of hydroxyl groups distributed on the surface of photocatalysts, which is highly polar and easy to combine with H2O with a large dielectric constant to form a hydrogen bond, which can further accelerate PHE.

W18O49/MnWO4 heterojunction for highly efficient photocatalytic reduction of CO2 under full spectrum light

Solar-energy-driven CO2 reduction for chemical reagents production, such as CH3OH, CH4 and CO, has tremendous potential for carbon neutrality in the energy industries. However, the low reduction efficiency limits its applicability. Herein, W18O49/MnWO4 (WMn) heterojunctions were prepared via one-step in-situ solvothermal process. Through this method, W18O49 tightly combined with the surface of MnWO4 nanofibers to form nanoflower heterojunction. It was found that under full spectrum light irradiation for 4 h, the yields of photoreduction of CO2 to CO, CH4 and CH3OH by 3–1 WMn heterojunction were 61.74, 71.30 and 18.98 μmol/g, respectively, which were 2.4, 1.8 and 1.1 times that of pristine W18O49, and ca.20 times that of pristine MnWO4 towards CO production. Furthermore, even in the air atmosphere, the WMn heterojunction still performed excellent photocatalytic performance. Systematic investigations demonstrated that the catalytic performance of WMn heterojunction was improved by superior light utilization and more efficient photo-generated carrier separation and migration as compared with W18O49 and MnWO4. Meanwhile, the intermediate products of the photocatalytic CO2 reduction process were also studied in detail by in-situ FTIR. Therefore, this study provides a new way for designing high efficiency of heterojunction for CO2 reduction.

Preparation of Bi2O2CO3/BiOBr0.9I0.1 photocatalyst and its degradation performance for 2,4-dichlorophenoxyacetic acid

Pesticide pollution has caused serious harm to the ecological environment and presents a major risk to human health due to drinking water resource contamination. 2,4-dichlorophenoxyacetic acid (2,4-D), as a class II toxic compound, can cause human health hazards, including neurotoxicity, hepatotoxicity, nephrotoxicity, reproductive defects and abortion. In this study, pure Bi2O2CO3/BiOBr0.9I0.1 photocatalyst material was prepared for the degradation of pesticides using a solvothermal method. The structure, morphology, and optical properties of the photocatalyst were characterized through X-ray diffraction (XRD), Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectra (DRS), Steady-state photoluminescence (PL), and Electrochemical Impedance Spectroscopy (EIS). The Bi2O2CO3/BiOBr0.9I0.1 catalyst could degrade 89.1% of 2,4-D within 120 min under visible light. After four cycles of reuse, Bi2O2CO3/BiOBr0.9I0.1 retained a high degradation performance for 2,4-D. The results of active substance capture experiments and ESR, showed that ·O2- and h+ were the main active substances. Under the synergistic effects of heterojunction and the solid solution, 10 wt%Bi2O2CO3/BiOBr0.9I0.1 was able to efficiently photocatalyze 2,4-D degradation. The use of the double modification method of solid solution and heterojunction construction regulates the band structure of BiOBr, resulting in a high photogenerated carrier separation efficiency and good light response capability. The Z-type heterojunction provides the photogenerated carriers with a high redox capacity. The synergistic effect of the two modification strategies results in the BiOBr based composite photocatalyst exhibiting excellent visible photocatalytic activity.

Construction of Y-Doped BiVO4 Photocatalysts for Efficient Two-Electron O2 Reduction to H2 O2.

Photocatalytic hydrogen peroxide (H2 O2 ) production on BiVO4 photocatalysts using water and oxygen as raw materials is a green and sustainable process. However, the photocatalytic efficiency of pristine BiVO4 is limited by severe charge recombination. In this work, rare earth element Yttrium (Y) doped BiVO4 photocatalysts were fabricated by the hydrothermal method. In the photocatalytic H2 O2 production experiment, the optimized Y-doped BiVO4 photocatalyst produced 114 μmol g-1 h-1 of H2 O2 under simulated sunlight (AM1.5) irradiation, which is four times higher than production activity of pure BiVO4 (26 μmol g-1 h-1 ). Density functional theory (DFT) calculation revealed that Y doping can enhance oxygen adsorption on the BiVO4 photocatalyst surface. Mechanistic investigations suggest that the doping process induces the in situ formation of monoclinic/tetragonal BiVO4 heterojunction, which further promotes the photogenerated carriers separation efficiency.