3N4 Heterojunction Photocatalysts Research Articles

Studies on ZnO/g-C3N4 Heterojunction Photocatalyst for RhB Degradation Under Vis-Light in a MNB-Agitated Pilot Reactor

Studies on ZnO/g-C3N4 Heterojunction Photocatalyst for RhB Degradation Under Vis-Light in a MNB-Agitated Pilot Reactor

Synthesis of Ag2ZnGeO4/g-C3N4 binary heterostructure: A Z-scheme heterojunction photocatalyst for enhanced tetracycline degradation under visible light

Accumulation of tetracycline was hazardous to human health and ecosystems. Ag2ZnGeO4/g-C3N4 heterojunction photocatalysts were successfully prepared by the wet impregnation method. The morphological structure and optical properties of the photocatalysts were measured by a series of characterization methods. Moreover, Ag2ZnGeO4/g-C3N4 with a loading ratio of 20 % exhibited excellent photocatalytic activity by exploring the Ag2ZnGeO4 loading, catalyst dosage, initial concentration, and initial pH of tetracycline. The degradation efficiency of 20 % Ag2ZnGeO4/g-C3N4 for 10 mg/L TC was 94.29 % at 0.2 g/L catalyst dosage, and the corresponding first-order reaction rate constant reached a maximum of 0.0199 min−1. In addition, according to the results of the trapping experiments, superoxide anion radical was the major active species. Eventually, a possible Z-scheme of the photocatalytic degradation mechanism was proposed. The heterojunction formed between Ag2ZnGeO4 and g-C3N4 could accelerate the transfer and separation of photogenerated carriers, enhancing the photocatalytic activity.

Development of 2D/2D h-MoO3/Ag/g-C3N4 heterojunction photocatalyst with enhanced photocatalytic performance for the detoxification of methylene blue and tetracycline under solar light illumination

In this study, direct thermal polycondensation, hydrothermal, and ultrasonic techniques were used to fabricate photocatalysts consisting of bare g-C3N4 (GCN), h-MoO3 (MoO3), MoO3/g-C3N4 (MGCN), and MoO3/Ag/g-C3N4 (MAGCN) composites. These methods were used to improve the photocatalytic effect, especially for environmental applications. The surface and chemical properties of the fabricated samples were investigated by XRD, FT-IR, FE-SEM, HR-TEM, UV-DRS, XPS, and PL analysis. Bare and composite photocatalysts were tested for photodegradation of the methylene blue (MB) dye and tetracycline (TC) antibiotic under solar irradiation. The MAGCN composite material exhibits remarkable efficiency in degrading 99% of MB dye and 90% of TC antibiotic within a time frame of 60 min when exposed to sunlight irradiation. The degradation rate constants (k) of MB and TC in the most active MAGCN photocatalyst were 11.02 and 7.03 times higher than those of pristine GCN, respectively. The scavenger reaction shows that the most important reactive species in the photocatalytic process are superoxide and photogenerated holes. The outstanding photocatalytic efficiency of the MAGCN catalyst was demonstrated by the fact that Ag nanoparticles act as mediators of fast charge transfer, resulting in higher absorption of sunlight, enhanced charge separation/transfer, and regeneration by MoO3 and GCN. The MAGCN photocatalyst exhibits remarkable activity, maintains its performance over six consecutive reaction cycles, and exhibits excellent stability and reusability. Intermediates were analyzed by GC-MS, and suitable degradation pathways were proposed. These results enable the development of an effective Z-scheme heterojunction photocatalyst and facilitate its wide application in the degradation of organic pollutants in wastewater.

Establishing Z-scheme Bi2WO6/g-C3N4 interfaces toward efficient photocatalytic performance of NOx under visible light

NOx gas is released from automobile emissions and fossil fuel combustion. The photocatalytic method was applied to address environmental issues, notably NOx air pollution because of environmentally friendly, low cost, and utilized solar light irradiation. In this work, a Z-scheme Bi2WO6/g-C3N4 heterojunction photocatalyst was successfully synthesized by a hydrothermal method at 180 °C for 12 h. Combining g-C3N4 with Bi2WO6 promoted two oxidation (over Bi2WO6) and reduction (over g-C3N4) sites, enhancing the photocatalytic activity of the g-C3N4 single-component system. The sample contains 20 wt% of Bi2WO6, becoming the best excellent photocatalytic activity at approximately 43.45% in 30 minutes of visible light irradiation. In addition, the photogenerated electron (e−) and hole (h+) were determined as primary agents. The high stability of Bi2WO6/g-C3N4 photocatalysts was demonstrated by little change in photocatalytic performance over five cycles of photocatalytic measurements. The NOx removal mechanism and the intermediate generation were proposed to understand the reaction process better.

Effective 1D/2D nanostructured S-scheme W18O49/g-C3N4 heterojunction photocatalyst fabrication for improved photocatalytic nitrogen fixation performance

The fundamental insights into the reaction mechanism, especially the electron transfer mechanism, are highly promising yet challenging for W18O49/g-C3N4 heterojunction catalysts during photocatalytic nitrogen fixation. Herein, the 1D/2D nanostructured S-scheme heterojunctions were designed by in situ growth of 1D W18O49 nanowires on 2D g-C3N4 nanosheets through solvothermal method using methanol as solvent. In situ XPS analysis revealed that electrons in the conduction band of W18O49 recombine with holes in the valence band of g-C3N4 under the conduction effect of internal electric field, band bending, and Coulombic attraction in the W18O49/g-C3N4 heterojunction. The photogenerated electrons are retained in g-C3N4, where the negative reduction potential of its conduction band enhances the activation of N2. As a result, the ammonia generation rate employing the optimal W18O49/g-C3N4 heterojunction is 64.8 μmol gcat−1 h−1, approximately double that of W18O49 alone and 2.3 times higher than that of g-C3N4. The enhanced activity and facile methodology make the current material exceedingly appealing for implementation in photocatalytic nitrogen fixation for the synthesis of ammonia.

Photocatalytic oxidation degradability of ammonia–nitrogen and Ni/Co ammonia complexes in ternary precursor wastewater by constructing MoS2/g-C3N4 heterojunction: Performance and mechanism

In this study, MoS2/g-C3N4 heterojunction photocatalysts were fabricated in order to treat ammonia–nitrogen wastewater resulting from the production of ternary cathode material precursors used in the manufacture of lithium-ion batteries. The catalysts were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), N2 adsorption–desorption test, UV–Vis diffuse reflectance spectra (UV–Vis DRS), Fourier-transform infrared spectroscopy (FT-IR Nicolet 6700), energy dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). The catalytic efficiency of the catalysts on ammonia–nitrogen and Ni/Co ammonia complexes in the wastewater was investigated by varying MoS2 doping, catalyst dose, adsorption duration, and photocatalysis duration. The results showed 2.0 g/L of MoS2/g-C3N4-1 wt% (photocatalyst with a content of 1 wt% MoS2) has the best photocatalytic efficiency. A degradation efficiency of 87.52 % for ammonia–nitrogen, 98.34 % for nickel and 97.80 % for cobalt was reached after one hour of dark adsorption and four hours of illumination. EDS and XPS analysis revealed that Ni2+/Ni3+ and Co2+/Co3+ were adsorbed from the solution onto the catalyst surface, and that NH4+/NH3 was converted into NO3− and N2.

Preparation of Z-type Cu2SnS3/g-C3N4 heterojunction material and its synergistic photocatalytic performance with H2O2

Due to poor visible light responsiveness and easy recombination of photo generated carriers, the photocatalytic performance of a single g-C3N4 is limited. This article presents a Z-type Cu2SnS3/g-C3N4 (CTS/CN) heterojunction photocatalyst prepared by in-situ growth of CTS on the surface of g-C3N4 using a simple solvothermal method. Through SEM results, it can be seen that as the content of g-C3N4 increases, the nanosheet gaps of flower shaped microspheres on the surface of CTS/CN increase and the size becomes thinner. The UV–vis DRS experiment showed that the introduction of CTS increased the visible light absorption range of CTS/CN composite and improved its visible light absorption ability.Under the synergistic effect of H2O2, the photocatalytic degradation efficiency of CTS/70% CN towards MO reached 99% at 50 minutes，At the same time, the degradation rate constants k of methylene blue (MB), ciprofloxacin (CIP) and levofloxacin (LEV) reached 0.06289 min−1, 0.02132 min−1 and 0.02787 min−1 respectively at 100 min.In the synergistic MO system of H2O2 for photocatalytic degradation, free radical capture experiments showed that the main active species were h+and • OH. Combined with the band structure of Cu2SnS3 and g-C3N4, a Z-type photocatalytic mechanism was proposed. Under visible light, H2O2 rapidly captured the photo generated electrons of CTS/CN, promoting the transport of photo generated carriers. This study provides theoretical guidance for the design and construction of Z-type heterojunctions with superior visible light driven photocatalytic performance.

Synthesis and characterization of Fe2SiO4/Fe2O3/g-C3N4 ternary heterojunction photocatalyst with enhanced photocatalytic activity under visible light

Ultrasonic-assisted co-precipitation is used for the first time to prepare Z-scheme Fe2SiO4/Fe2O3/g-C3N4 ternary heterojunction photocatalysts. Their morphology, crystal structure, specific surface area, optical properties, composition, and photocatalytic behavior have been thoroughly examined. When compared to single-component and binary Fe2SiO4/Fe2O3 heterojunction photocatalysts, ternary Fe2SiO4/Fe2O3/g-C3N4 heterojunction photocatalysts exhibit the most profitable performance for degradation of erythrosine under simulated light. It is likely that this is due to the high rate of separation migration of photoexcited charge carriers, the formation of Z-scheme heterojunction, and the specific surface area. Based on the results of active species trapping experiments, a possible Z-scheme mechanism could explain the significantly reduced photocatalytic rate of ternary heterojunction photocatalysts. It has been demonstrated that superoxide radicals play a significant role in the photodegradation process. A kinetic analysis revealed that the higher efficiency (97.9%) was associated with a higher rate constant (k = 0.0345 min‒1). A Fe2SiO4/Fe2O3/g-C3N4 nanocomposite is an excellent choice for large-scale applications because of its exceptional stability and recyclability.

Synthesis of S-scheme 0D/2D Co2ZrO5/g-C3N4 heterojunction photocatalyst with enhanced visible-light photocatalytic activity for tetracycline

The step-like scheme (S-scheme) heterojunction photocatalyst, which possess an improved electric field, intimate interfacial contact and reasonable energy band structure, is one of the most optimal ways to solve the wastewater problem caused by residual antibiotics. Herein, a new type of S-scheme 0D/2D Co2ZrO5/g-C3N4 (CZO/CN) heterojunction photocatalyst was prepared via an ultrasonic assisted hydrothermal method and used as photocatalyst to degrade tetracycline (TC, 20 mg/L, 100 mL). Compared to pure CN and CZO, the CZO/CN with the optimal design proportion (30CZO/CN) demonstrates the outstanding photocatalytic efficiency for TC degradation under visible-light irradiation, with the degradation rate being 94.8 % within 180 min at pH 5.0. Moreover, the 30CZO/CN exhibits superior stability, which still eliminated 90 % of TC after five times cycle runs. Furthermore, the S-scheme mechanism of photocatalytic TC removal by CZO/CN is proposed by XRD, FT-IR, XPS, UV–Vis DRS and PL analysis, which summarized that the enhanced photocatalytic activity of CZO/CN was mainly ascribed to its larger specific surface area, available light absorption region and appropriate bandgap width, dominated by the S-scheme pattern. This study presents a novel S-scheme g-C3N4-base heterojunction photocatalyst can effectively treat wastewater and provides design ideas for other heterojunctions.

Development of stable S-scheme 2D–2D g-C3N4/CdS nanoheterojunction arrays for enhanced visible light photomineralisation of nitrophenol priority water pollutants

The investigation focused on creating and studying a new 2D–2D S-scheme CdS/g-C3N4 heterojunction photocatalyst. Various techniques examined its structure, composition, and optical properties. This included XRD, XPS, EDS, SEM, TEM, HRTEM, DRS, and PL. The heterojunction showed a reduced charge recombination rate and more excellent stability, helping to lessen photocorrosion. This was due to photogenerated holes moving more quickly out of the CdS valence band. The interface between g-C3N4 and CdS favored a synergistic charge transfer. A suitable flat band potential measurement supported enhanced reactive oxygen species (ROS) generation in degrading 4-nitrophenol and 2-nitrophenol. This resulted in remarkable degradation efficiency of up to 99% and mineralization of up to 79%. The findings highlighted the practical design of the new 2D–2D S-scheme CdS/g-C3N4 heterojunction photocatalyst and its potential application in various energy and environmental settings, such as pollutant removal, hydrogen production, and CO2 conversion.

Direct Z-scheme photocatalytic removal of ammonia via the narrow band gap BiOCl/g-C3N4 hybrid catalyst upon visible light irradiation

In this study, a novel BiOCl/g-C3N4 heterojunction photocatalyst was successfully prepared. The resulting BiOCl/g-C3N4 catalyst can degrade NH3 effectively to N2 under visible-light irradiation. We used BiOCl-modified g-C3N4 nanoparticles to improve the activity of photochemically produced oxygen species. Photocurrent showed excellent photocatalysis performance of BiOCl/g-C3N4. The deposition of BiOCl resulted in a fatal decrease in the surface part and pore volume of the BiOCl/g-C3N4 samples. It was found that the photocurrent density increased with g-C3N4. Experimental results indicate that heterogeneous catalysts achieved 89.7 % degradation under visible light irradiation. The NH3 degradation product was N2 and neither NO2− nor NO3− were detected.

High proficiency Ag/β-Ag2WO4/V3O4/g-C3N4 heterojunction photocatalyst for the actuation of C(OH)–H bond

Ag/β-Ag2WO4/V3O4/g-C3N4 heterojunction photocatalyst was prepared for the actuation of the C(OH)–H bond with a mechanistic point of view.

Fabrication of NiWO4/g-C3N4 S-scheme heterojunction photocatalyst for enhanced H2 evolution

Photocatalytic H2 production is a desired route to obtain green H2 for its cleanness and sustainability properties. It is still essential to explore the highly active photocatalysts in this field. Herein, a facile solvent evaporation strategy to fabricate a NiWO4/g-C3N4 heterojunction photocatalyst was employed. The research demonstrates that NiWO4/g-C3N4 hybrids can achieve an obviously enhanced H2 evolution actively, although they have poor activity individually. The H2-releasing rate of 10 % NiWO4/g-C3N4 can reach 2546 μmol·h−1·g−1 under 300 W artificial light source illumination in 20 vol.% TEOA. Further investigations indicate that NiWO4 and g-C3N4 can form S-scheme heterojunction according to band structure analysis and photoelectrochemical tests, which leads to an effective charge separation for the energy band bending, coulomb force and interfacial electric field between g-C3N4 and NiWO4, making reserved charges with higher redox activity. In addition, NiWO4 can reduce the H2 evolution overpotential, favoring fast surface H2-releasing kinetics.

Nickel selenide/g-C3N4 heterojunction photocatalyst promotes C[sbnd]C coupling for photocatalytic CO2 reduction to ethane

Photocatalytic CO2 reduction to generate high value-added and renewable chemicals is of great potential in facilitating the realization of closed-loop and carbon–neutral hydrogen economy. Stabilizing and accelerating the formation of COCO* intermediate is crucial to achieve high-selectivity ethane production. Herein, a novel 3D/2D NiSe2/g-C3N4 heterostructure that mesoscale hedgehog nickel selenide (NiSe2) grown on the ultrathin g-C3N4 nanosheets were synthesized via a successively high temperature calcination process and in-situ thermal injection method for the first time. The optimum 2.7 % NiSe2/g-C3N4 heterostructure achieved moderate C2H6 generation rate of 46.1 μmol·g−1·h−1 and selectivity of 97.5 % without any additional photosensitizers and sacrificial agents under light illumination. Based on the results of the theoretical calculations and experiments, the improvement of photocatalytic CO2 to C2H6 production and selectivity should be ascribed to the increased visible light absorption ability, unique 3D/2D heterostructures with promoted adsorption of CO2 molecules on the Ni active sites, the type II heterojunction with improved charge transfer dynamics and lowered interfacial transfer resistance, as well as the formation of COCO* key intermediate. This work provides an inspiration to construct efficient photocatalysts for the direct transformation of CO2 to multicarbon products (C2+).

In situ solid-state fabrication of Z-Scheme BiVO4/g-C3N4 heterojunction photocatalyst with highly efficient-light visible activity and their antibacterial properties against bacterial pathogens

Here, BiVO4/g-C3N4 composite photocatalyst with various weight percent of BiVO4 were synthesized by in-situ solid-state fabrication via calcination process. Photocatalyst was characterized by various analytical techniques (XRD, SEM, TEM, UV–vis-DRS, and TGA). The SEM and TEM results showed that composites materials BiVO4 dispersed uniformly on the surface of g-C3N4 sheets, revealing that g-C3N4 sheets was probably a promising support for in-situ growth of nano-size materials. The achieved intimate interfacial contact between BiVO4 and g-C3N4 promoted the charge transfer and inhibited recombination rate of photogenerated electron-hole pairs, which significantly improved the photocatalytic activity. Remarkably, catalytic efficiency of BiVO4/g-C3N4 composites has been demonstrated, via photodegradation of organic pollutants such as rhodamine-B (RhB) and ciprofloxacin (CIP). The 5 wt.% BiVO4/g-C3N4 showed excellent photocatalyst activity and potentially degraded RbB (98 %) and CIP (95 %) in 75 min of irradiation time in the presence of visible light. Moreover, radical trap experiment indicated that the –•O2 and •OH acted as main reactive species for photocatalytic degradation. In addition, BiVO4/g-C3N4 nanocomposite showed strong antibacterial potential against bacterial pathogens; E. coli ATCC-15224, Staphylococcus aureus MTCC-3160 and Pseudomonas aeruginosa PAO1. Studies revealed that depended on time and BiVO4/g-C3N4 concentration, bacterial growth, and viability (CFU count) was consistently declined. The increasing doses of BiVO4/g-C3N4 significantly (p ≤ 0.05) inhibited the virulence factors like pyoverdin, pyocyanin, elastase, exoprotease, rhamnolipid, and swimming motility of P. aeruginosa PAO1 by 76.9, 49.0, 71.1, 53.3, 89.5, and 60 %, respectively. Furthermore, biofilms formed by E. coli, S. aureus and P. aeruginosa PAO1 were maximally inhibited at 10 µgmL−1 BiVO4/g-C3N4 to a maximum of 67, 56 and 56 %, respectively. Also, exopolysaccharide (EPS) releasing ability of isolates were suppressed by BiVO4/g-C3N4. The fluorescently labelled probe DCFH-DA staining of bacterial isolates showed nanocomposite-dependent increase in ROS production and superoxide radicals. The photodegradation of RhB and (CIP) recommends that synthesized BiVO4/g-C3N4 nanocomposite have strong photocatalytic properties. Summarily, newly synthesized BiVO4/g-C3N4 photocatalyst can be employed as an alternative to remediate the environmental pollution as well as a therapeutic agent for topical administration in controlling the pathogenic infections.

Recent Advances in LDH/g-C3N4 Heterojunction Photocatalysts for Organic Pollutant Removal

Environmental pollution has been decreased by using photocatalytic technology in conjunction with solar energy. An efficient method to obtain highly efficient photocatalysts is to build heterojunction photocatalysts by combining graphitic carbon nitride (g-C3N4) with layered double hydroxides (LDHs). In this review, recent developments in LDH/g-C3N4 heterojunctions and their applications for organic pollutant removal are systematically exhibited. The advantages of LDH/g-C3N4 heterojunction are first summarized to provide some overall understanding of them. Then, a variety of approaches to successfully assembling LDH and g-C3N4 are simply illustrated. Last but not least, certain unmet research needs for the LDH/g-C3N4 heterojunction are suggested. This review can provide some new insights for the development of high-performance LDH/g-C3N4 heterojunction photocatalysts. It is indisputable that the LDH/g-C3N4 heterojunctions can serve as high-performance photocatalysts to make new progress in organic pollutant removal.

Synthesis of a double type-II CdS/Zn2In2S5/g-C3N4 heterojunction photocatalyst for the photodegradation of tetracycline under visible light

Herein, the ternary CdS/Zn2In2S5/g-C3N4 (CdS/ZIS/CN) heterojunction photocatalyst was successfully prepared via a one-pot method for photodegradation of tetracycline (TC) under visible light irradiation. The surface morphology, structure and optical properties of the prepared photocatalytic material were analyzed by XRD, SEM, TEM, UV–vis DRS, FT-IR and PL. Moreover, the experimental results exhibited that the ternary CdS/ZIS/CN photocatalyst revealed excellent photocatalytic activity compared with g-C3N4. In this work, 94.73% of TC (20 mg/L, pH=11) was degraded by 0.5 g/L 30CdS/ZIS/CN within 60 min of visible light irradiation. Additionally, the degradation rate of the photocatalyst decreased by about 9.41% after the fourth cycle, indicating its high stability and reusability. Subsequently, a possible double type-II mechanism of photodegradation was eventually provided based on active radical capture experiments. The current investigation provided a promising strategy to construct the high-efficiency heterojunction photocatalyst to degrade antibiotic contaminants.

Recyclable and flexible Bi(Ho3+-Yb3+)OBr/g-C3N4 composite porous fiber for efficient water purification and real-time temperature sensing.

Herein, an electrospinning porous nanofiber with large specific surface area, excellent flexibility, remarkable tensile strength, and high stability of thermal degradation has been developed by loading Ho3+/Yb3+ co-doped BiOBr/g-C3N4 (BHY/CN) heterojunction photocatalysts on polyacrylonitrile (PAN) nanofibers. The optimized BHY/CN-2 nanofiber demonstrates outstanding photocatalytic activity for the degradation of 98.83% tetracycline (TC, 60min) and 99.06% rhodamine B (RhB, 90min) under simulated sunlight irradiation, and maintains a high level of reusability and recycling stability in three cycles. In addition, temperature monitoring of the catalytic degradation process can be feedback by (5F4, 5S2) → 5I8 and 5F5 → 5I8 radiation transitions of Ho3+ with excellent sensitivity. More importantly, the nanofiber luminescence performance is enhanced by the doping of g-C3N4, which maintain the effective upconversion luminescence properties even in water, providing a reliable reference for real-time monitoring and feedback of the operating temperature, and further expanding the application fields of photocatalysts.

Synthesis and characterization of enhanced visible light-driven C-doped ZnO-2D GO/g-C3N4 heterojunction photocatalyst

Well-designed 2D graphene oxide-modified polymeric graphitic carbon nitride composite nanosheets (GO/g-C3N4) as desirable sensitizers and catalytic substrates for optimising the visible light-driven photocatalytic performance of ZnO-based photocatalysts have been investigated. Herein, 2D GO/g-C3N4 composite nanosheets are first developed by ultrasonic and hydrothermal methods, and then coupled with ZnO nanoparticles to prepare a series of ternary GO/g-C3N4-ZnO heterojunction composites with vary GO loading concentrations. Characterization of the photocatalysts was carried out by SEM, TEM, XPS, XRD, DRS, photoluminescence (PL) spectroscopy; evaluation of the visible light photocatalytic activity was performed by degrading an aqueous methylene blue (MB) solution. XPS studies showed that the formation of a ZnC bond in 15 % GO/g-C3N4-ZnO is due to the replacement of oxygen by carbon, indicating the construction of a hybrid heterojunction composed of C-doped ZnO and visible light sensitive GO/g-C3N4 composite nanosheets. The photodegradation performance of 15 % GO/g-C3N4-ZnO is 5.3, 2.9, and 2.2 times higher than that of pure ZnO, g-C3N4, and g-C3N4-ZnO, respectively. Due to the increase of GO loading in GO/g-C3N4 composite nanosheets, some characteristics of efficient visible light photocatalysis, such as a wider light absorption range, fluorescence quenching in the PL spectrum, excellent optical response in photocurrent measurement, and good stability，were confirmed and can be attributed to the electronic interaction between heterostructures and the effective transfer of photogenerated electrons in these ternary nanocomposites. This work may provide a new promising pathway for the construction of easily prepared 2D GO/g-C3N4 hybrid-modified nanocomposites, which is a hopeful material for wastewater control.

Phosphate ester functionalized fluorene-benzothiadiazole alternating copolymer/hydroxylated g-C3N4 heterojunctions for efficient hydrogen evolution under visible-light irradiation

It is highly desirable to explore functionalized polymer semiconductor/g-C3N4 heterojunction photocatalysts with the tight interfacial connection for promoting the photogenerated electron-hole pair separation, improving the hydrophilicity, extending the visible light response and achieving the efficient visible light-driven H2 evolution. Herein, we synthesized novel poly[9,9-bis(3-ethyl phosphate propyl)fluorene-alt-benzothiadiazole] (PPFBT) with a phosphate ester on every repeating unit by the Suzuki polymerization and then fabricated PPFBT/hydroxylated g-C3N4 (PPFBT/CN-OH) heterojunctions via a surface hydroxyl-induced assembly process. The ratio-optimized 5PPFBT/CN-OH shows the hydrogen evolution activity of 2662.4 μmol·g−1·h−1, an 11.1-time enhancement compared to CN-OH. The improved photocatalytic activity is mainly attributed to the enhanced electron-hole pair separation due to the tight interfacial connection by hydrogen bond (P=O…H-O) and N…S interactions between PPFBT and CN-OH. It is verified that abundant phosphate ester groups of PPFBT improve the hydrophilicity and form coordination bonds with platinum (P=O:Pt) as a cocatalyst to facilitate water splitting for H2 evolution. It is also confirmed that the enhanced electron-hole pair separation is mainly dependent on the excited high-energy level electron transfer from CN-OH to PPFBT. This work provides a rational molecular design strategy for constructing efficient functionalized polymer semiconductor/g-C3N4 heterojunctions for sunlight-driven H2 evolution.