Novel g-C3N4/CdTiO3 Heterostructures with Improved Photocatalytic Activity Under Visible Light Irradiation

Highlights

• Visible-light active g-C₃N₄CdTiO₃ heterostructure successfully synthesized

• Efficient S-scheme charge transfer enhances electron–hole separation

• Significantly improved photocatalytic degradation of RhB dye

• Generation of reactive species (•OH and OH) boosts activity

• Excellent stability and reusability for wastewater treatment applications

Introduction

Sunlight-Driven g-C₃N₄/CdTiO₃ Heterostructure Enables Efficient Charge Separation for Enhanced Photocatalytic Activity

Rapid industrialization and urbanization have resulted in severe environmental pollution and an increasing global energy crisis. The discharge of organic contaminants such as dyes, pesticides, and pharmaceutical residues into aquatic systems poses serious risks to ecosystems and human health. At the same time, the depletion of fossil fuel resources has driven intensive research toward sustainable and renewable energy technologies. In this context, semiconductor-based photocatalysis has emerged as a promising green technology for solar-driven environmental remediation and energy conversion, owing to its ability to utilize abundant solar energy under mild reaction conditions without generating secondary pollution [1-3].

Conventional photocatalysts such as TiO₂and ZnO have been extensively studied because of their strong oxidation ability, chemical stability, and low cost. However, their wide band gaps severely limit visible-light absorption, which restricts their practical application since visible light constitutes the major portion of the solar spectrum [4,5]. Therefore, the development of visible-light-active photocatalysts with efficient charge separation remains a significant research challenge.

Graphitic carbon nitride (g-C₃N₄), a metal-free polymeric semiconductor composed of carbon and nitrogen, has attracted considerable attention as a visible-light-responsive photocatalyst due to its moderate band gap (~2.7 eV), suitable band edge positions, high chemical and thermal stability, and facile synthesis from inexpensive nitrogen-rich precursors such as melamine or urea [6-8]. Consequently, g-C₃N₄ has been widely explored for photocatalytic degradation of organic pollutants, hydrogen evolution, and CO₃ reduction [9-11]. Nevertheless, pristine g-C₃N₄ suffers from low surface area, poor electrical conductivity, and rapid recombination of photogenerated charge carriers, which significantly limit its photocatalytic efficiency [12,13].

To overcome these limitations, various strategies have been devel¬oped, including heteroatom doping, morphological engineering, surface functionalization, and the construction of semiconductor heterojunctions [14-16]. Among them, heterojunction engineering has proven particularly effective in enhancing photocatalytic per¬formance by promoting interfacial charge transfer, extending light absorption, and suppressing electron–hole recombination [17,18]. In recent years, perovskite-type metal oxides have gained increasing interest in photocatalysis owing to their structural flexibility, tunable electronic properties, and excellent chemical stability [19].

Cadmium titanate (CdTiO₃), a perovskite oxide semiconductor, exhibits good crystallinity, suitable band alignment, and favorable charge transport characteristics [20,21]. These properties make CdTiO₃ a promising candidate for coupling with visible-light-active semiconductors such as g-C₃N₄. In g-C₃N₄/CdTiO₃ heterostructures, g-C₃N₄ can act as the primary visible-light absorber, while CdTiO₃ facilitates efficient charge separation and transport, thereby suppressing charge recombination through synergistic interfacial interactions.

Although numerous g-C₃N₄-based heterostructures have been reported for visible-light-driven dye degradation—particularly those coupled with metal oxides and titanates such as TiO₂, SrTiO₃, NiTiO₃, and CoTiO₃. Studies on g-C₃N₄/CdTiO₃ nanocomposites remain notably scarce. To the best of our knowledge, no systematic investigation has been reported on the synthesis, interfacial structure, and photocatalytic dye degradation performance of g-C₃N₄/CdTiO₃ composites. This clear research gap provides strong motivation for exploring g-C₃N₄/CdTiO₃ heterostructures as a new class of visible-light-responsive photocatalysts. In this work, g-C3N₄/CdTiO₃ nanocomposites were synthesized via sonication-assisted and in-situ hydrothermal routes. The influence of synthesis methodology on structural, optical, surface, and photocatalytic properties was systematically investigated using Rhodamine B as a model pollutant. The enhanced photocatalytic performance is discussed in terms of heterostructure formation, interfacial charge separation, and synergistic effects, providing valuable insights for the rational design of g-C₃N₄-based perovskite photocatalysts for wastewater treatment and environmental remediation.

Synthesis and Characterization

Materials

Melamine (Aldrich, 99.0%), Cd(NO₃)₂ (CDH, 98% metal-based), titanium isopropoxide (Aldrich, 99.0%), NaOH (CDH, 98.0%), and Rhodamine B (Aldrich, 85.0%) were used as received. All other chemicals employed in this study were of analytical grade and used without further purification.

Synthesis of CdTiO₃ Nanoparticles

CdTiO₃ nanoparticles were synthesized via a hydrothermal method from reported literature [22]. In a typical procedure, 3.43 mmol of Cd(NO₃)₂ was dissolved in 20 mL of double-distilled water, followed by the addition of 3.43 mmol of titanium isopropoxide. The resulting solution was stirred for 30 min to ensure complete mixing. Subsequently, 0.6 M NaOH (40 mL) was added dropwise, and the mixture was stirred for an additional 3 h. The resulting milky-white suspension was transferred into a Teflon-lined stainless-steel autoclave and heated at 180 °C for 16 h. After cooling to room temperature, the precipitate was collected, thoroughly washed with distilled water and ethanol, and dried for further characterization.

Scheme 1: Synthesis of CdTiO₃

Synthesis of Graphitic Carbon Nitride (g-C₃N₄)

Graphitic carbon nitride (g-C₃N₄) was synthesized via the thermal polymerization of melamine from reported literature [23,24]. In this process, melamine was placed in a covered alumina crucible and heated at 550 °C for 2 h under a nitrogen atmosphere. After cooling naturally to room temperature, a pale-yellow g-C₃N₄ powder was obtained. The as-prepared g-C₃N₄ was directly used for the subsequent nanocomposite synthesis.

Synthesis of g-C₃N₄–CdTiO₃ Nanocomposites

g-C₃N₄–CdTiO₃ nanocomposites were prepared using two different hydrothermal routes.

Sonication Route (Scheme 2): In this method, 80 mg of g-C₃N₄ was dispersed in 100 mL of deionized water and sonicated for 12 h to achieve uniform exfoliation. Subsequently, 715 mg of the as-synthesized CdTiO₃ nanoparticles was added to the dispersion. The resulting mixture was stirred and heated at 100 °C to evaporate the solvent, yielding a light-yellow g-C₃N₄–CdTiO₃ composite powder.

In-Situ Hydrothermal Route (Scheme 3): In this approach, 3.43 mmol of Cd(NO₃)₂ was dissolved in 20 mL of double-distilled water, followed by the addition of 3.43 mmol of titanium isopropoxide. The solution was stirred for 30 min, after which 0.6 mol NaOH dissolved in 40 mL of water was added, and stirring continued for 3 h to form a milky-white suspension. Then, 80 mg of g-C₃N₄ was introduced into the mixture and stirred for an additional 1 h. The resulting suspension was transferred into a Teflon-lined stainless-steel autoclave and heated at 180 °C for 16 h. After cooling to room temperature, the light-yellow g-C₃N₄–CdTiO₃ nanocomposite was collected, washed, and dried for further characterization.

Scheme 2 and 3: Synthesis of g-C₃N₄–CdTiO₃Nanocomposites by Sonication and in-Situ Route Respectively

Characterization

Powder X-ray diffraction studies (PXRD) were carried out using Ni filtered Cu-Kα radiation. Normal scans were recorded with a step size of 0.02° and step time of 1 s. The Kα2 reflections were removed to obtain accurate lattice constants. Field emission scanning electron microscopy (FESEM) was carried out by FEI quanta 3D FEG – FESEM operated at 10 kV. The pellet had been coated with gold. Transmission Electron Microscopy (TEM) studies were carried out using a Tecnai G2 20 electron microscope operated at 200 KV. TEM specimens were prepared by dispersing the sample in ethanol by ultrasonic treatment, dropping onto a porous carbon film supported on a copper grid, and then drying in air. Nitrogen adsorption–desorption isotherms were recorded at liquid nitrogen temperature (77 K) using a Nova 2000e (Quantachrome Corp.) equipment and the specific area was determined by the Brunauer–Emmett–Teller (BET) method. The powder sample was degassed at 150 ºC for 6 h prior to the surface area measurements. Diffuse-reflectance spectra (DR) spectra were recorded on Shimadzu UV-2450 spectrophotometer where the baseline was fixed using a barium sulfate reference.

Photocatalytic Activity

Rhodamine B (RhB) was selected as a model dye to evaluate the visible-light-driven photocatalytic performance of the samples. Photocatalytic experiments were performed under visible-light irradiation using a 300 W Xe lamp solar simulator (Asahi Spectra Co., Ltd.). In a typical experiment, 25 mg of photocatalyst was dispersed in 100 mL of RhB aqueous solution (5 mg L^-1) and stirred at 250 rpm at room temperature. Prior to illumination, the suspension was stirred in the dark for 30 min to establish adsorption–desorption equilibrium. During photocatalysis, aliquots of the suspension were withdrawn at regular intervals, centrifuged to remove the photocatalyst, and analyzed for RhB concentration using a UV–Vis spectrophotometer. The degradation efficiency was calculated from the change in absorbance of the RhB solution over time.

Results and Discussion

PXRD Analysis and Phase Comparison

In this study, we determine the effect of heterostructure and synthesis process effect on the photocatalytic degradation of dye molecules using ambient stable g-C₃N₄–CdTiO₃ nanocomposites. Figure 1 and 2 shows the powder X-ray diffraction patterns of pure CdTiO3 and g-C₃N₄. The PXRD pattern of the synthesized CdTiO₃ confirms the formation of a single-phase crystalline material. All the observed diffraction peaks can be well indexed to CdTiO₃ with a trigonal (hexagonal setting) structure, belonging to the space group R-3 (No. 148). No additional peaks corresponding to impurity phases such as CdO or TiO₂ are detected, indicating the high phase purity of the synthesized sample.

Figure 1: PXRD Patterns of Pure CdTiO₃

The sharp and intense diffraction peaks indicate good crystallinity of CdTiO₃. The stabilization of the R-3 symmetry suggests a distorted perovskite-type structure, where tilting and distortion of TiO6 octahedra occur due to ionic size mismatch and lattice strain. Such structural distortion is commonly observed in Cd-based titanates and is consistent with previously reported PXRD studies. Based on PXRD analysis and comparison with standard crystallographic data, the lattice parameters of CdTiO₃ in the hexagonal (trigonal) R-3 structure are 5.4432 Å and c ≈ 13.1513 Å. These lattice parameters are in good agreement with reported values for trigonal CdTiO₃, confirming the successful formation of the desired crystal structure [25]. The PXRD pattern of the synthesized g-C₃N₄ exhibits two characteristic diffraction peaks, confirming the successful formation of graphitic carbon nitride.

Figure 2: PXRD Patterns of Pure g-C3N4

The strong diffraction peak observed at 2θ ≈ 27.4° corresponds to the (002) plane, which arises from the interlayer stacking of conjugated aromatic systems within the graphitic structure. This peak reflects the periodic stacking of tri-s-triazine (heptazine) units along the c-axis. A weaker diffraction peak appearing at 2θ ≈ 13.0° is indexed to the (100) plane, which is associated with the in-plane structural packing of tri-s-triazine units within the g-C₃N₄layers. The presence of these two characteristic peaks indicates the formation of a layered, graphitic structure with moderate crystallinity. The relatively broad nature of the diffraction peaks suggests the poorly crystalline and polymeric nature of g-C₃N₄, which is typical for thermally polymerized carbon nitride. No impurity-related peaks are detected, confirming the high phase purity of the prepared g-C₃N₄. Graphitic carbon nitride crystallizes in a hexagonal structure, generally assigned to the space group P6-cm or closely related hexagonal symmetry. Based on standard PXRD analysis, the lattice parameters of g-C₃N₄ are approximately a ≈ 4.784 and c ≈ 6.792 Å. The interlayer distance (d₀₀₂) calculated from the (002) peak at ~27.4° is ~0.326 nm, which is consistent with reported values for graphitic carbon nitride [26].

The PXRD patterns of the g-C₃N₄/CdTiO₃ nanocomposites synthesized via sonication and in-situ routes are presented in the figure 3.

Figure 3: PXRD Patterns of g-C3N4/CdTiO3 Nanocomposites

In both cases, the diffraction peaks corresponding to crystalline CdTiO₃ are clearly observed, confirming that the CdTiO3 phase is well preserved after composite formation. The characteristic diffraction peak of g-C3N4 at 2θ ≈ 27.4°, assigned to the (002) plane associated with interlayer stacking of graphitic sheets, is either weak or partially overlapped by the intense CdTiO₃ reflections. This behaviour is commonly reported for CdTiO₃–g-C3N4 composites and is attributed to the low content and poor crystallinity of g-C3N4 as well as its homogeneous dispersion on the CdTiO3 surface. A comparison between the two synthesis routes reveals that the in-situ synthesized composite exhibits sharper and more intense diffraction peaks compared to the sonication-derived sample, indicating improved crystallinity and stronger interfacial interaction between CdTiO₃ and g-C₃N₄. In contrast, the sonication route shows slightly broadened peaks, suggesting smaller crystallite size and increased lattice strain due to physical mixing. Importantly, no additional impurity peaks corresponding to CdO, TiO₃, or other secondary phases are detected in either composite, confirming the phase purity and structural stability of CdTiO₃ during composite formation. Overall, the PXRD results confirm the successful formation of g-C₃N₄/CdTiO₃ nanocomposites, where CdTiO₃ retains its crystal structure while g-C3N4 is well integrated without altering the host lattice.

Morphological and Interfacial Analysis

The FESEM micrograph of CdTiO₃ (Figure 4) reveals an irregular, polycrystalline morphology composed of plate-like and block-shaped particles with non-uniform sizes consistent with reported hydrothermal CdTiO₃ morphologies [20]. The particles exhibit angular edges and faceted surfaces, indicating their crystalline nature. Lateral dimensions range from sub-micrometer to a few micrometers, as shown by the 5 μm scale bar. The particles are closely packed and moderately agglomerated, a common feature in oxide ceramics synthesized via wet-chemical or thermal methods, likely due to high surface energy and strong interparticle interactions during crystallization. The rough surface texture and fractured grain boundaries suggest that the microcrystals are aggregates of smaller primary crystallites. No spherical or fibrous structures were observed, confirming that CdTiO₃ predominantly forms irregular microcrystals rather than isotropic nanoparticles. The absence of secondary morphological features further supports the phase purity of the material, consistent with PXRD results. Overall, the FESEM analysis confirms the successful formation of crystalline CdTiO₃ with a dense, irregular microstructure, providing abundant surface sites favourable for interfacial contact in composite formation and catalytic applications.

Figure 4: FESEM Micrograph of CdTiO₃

The figure 5 and 6 shows the TEM micrograph of g-C₃N₄/ CdTiO₃ nanocomposites synthesized by sonication and in-situ methodology respectively. The low-magnification TEM images reveal large, thin sheet-like structures with lateral dimensions extending up to several hundred nanometers (≈0.5–1 µm). The high electron transparency of the sheets confirms their ultrathin, few-layer nature, distinguishing them from bulk or thick plate-like particles. The presence of partially overlapped and restacked sheets is characteristic of exfoliated two-dimensional materials formed during sample drying.

Figure 5: TEM Micrograph of g-C₃N₄/CdTiO₃ Nanocomposites Obtained by Sonication

Figure 6: TEM Micrograph of g-C₃N₄/CdTiO₃ Nanocomposites Obtained by In-situ

The intermediate-magnification inset (scale bar 0.2 µm) shows irregular polygonal nanosheets with smooth and well-defined contours, indicating that the sheets retain good structural integrity after synthesis and processing. The absence of discrete nanoparticles or large agglomerates suggests a uniform nanosheet morphology rather than particulate growth. High-magnification TEM images (scale bar 50 nm) further confirm the few-layer structure, showing clear sheet edges with slight thickness contrast. The contrast variation near the edges arises from edge folding and local thickness fluctuations, which are commonly observed in ultrathin g-C₃N₄ and oxide-based nanosheets. No phase-segregated regions or large crystalline grains are detected, implying homogeneous dispersion and intimate interfacial contact within the nanosheet framework. The high-resolution TEM (HRTEM) image exhibits distinct lattice fringes, confirming the presence of crystalline CdTiO₃ domains embedded within the nanosheet matrix. The surrounding low-contrast regions correspond to the amorphous or semicrystalline g-C₃N₄phase. The close interfacial contact between the lattice-resolved CdTiO₃ domains and the g-C₃N₄ nanosheets provides direct structural evidence for the formation of a well-coupled heterojunction, which is favourable for efficient charge transfer. TEM analysis of the composites confirms ultrathin g-C₃N₄nanosheets decorated with CdTiO₃ nanodomains. The in-situ composite exhibits more uniform dispersion and intimate interfacial contact than the sonication-derived sample, similar to trends reported for in-situ-grown g-C₃N₄ heterostructures [27,28].

Surface Area Analysis

The BET surface area of pristine CdTiO3 (95 m² g^-¹) is higher than that of bulk g-C3N4 (56 m² g^-¹), reflecting the comparatively finer oxide particles and better intrinsic porosity of CdTiO₃ and consistent with reported values [21,29]. Upon forming the g-C3N4 CdTiO₃ heterostructure, a pronounced increase in surface area is observed, confirming effective interfacial engineering between the two components. The sonication-assisted composite exhibits a surface area of 143 m² g^-¹, which is significantly higher than those of the individual constituents. This enhancement originates from ultrasonic exfoliation of g-C₃N₄ layers and the uniform anchoring of CdTiO₃ nanoparticles onto the g-C₃N₄ sheets, which suppresses restacking and creates additional exposed active sites. Notably, the in-situ synthesized g-C₃N₄/CdTiO₃ composite shows the highest surface area (187 m² g^-¹). This superior value is attributed to the simultaneous nucleation and growth of CdTiO₃ directly on the g-C₃N₄ framework, leading to a highly dispersed heterointerface, hierarchical porosity, and strong interfacial contact. The in-situ route effectively prevents particle agglomeration and maximizes pore accessibility. Overall, the progressively increased surface area from pristine materials to sonication-assisted and finally in-situ composites demonstrates that in-situ heterostructure formation is the most effective strategy for generating a high-surface-area photocatalyst, which is expected to enhance adsorption capacity, charge separation efficiency, and catalytic performance. Comparable increases have been reported in g-C₃N₄-based heterostructures and are directly correlated with enhanced photocatalytic performance [30-32].

Diffuse Reflectance Spectra Analysis

The pristine g-C₃N₄ sample exhibits an absorption edge at approximately 450 nm, corresponding to a band gap energy of 2.76 eV, confirming its effective photoactivation under visible-light irradiation. In contrast, CdTiOâ?? displays a wider band gap of 3.67 eV, indicating that it is primarily UV-active with limited visible-light absorption agree well with literature reports [6,20]. The wide band gap of CdTiO₃ complements the visible-light-responsive g-C₃N₄, facilitating the formation of a heterojunction that enhances charge separation and suppresses electron–hole recombination. Upon heterostructure formation, the band gaps of the g-C₃N₄/CdTiO₃ composites were determined to be 2.92 eV and 2.95 eV for the sonication and in-situ synthesis routes, respectively. These values confirm that the heterostructured photocatalysts retain visible-light activity, while the slight band-gap widening can be attributed to interfacial interactions and electronic structure modulation between g-C₃N₄ and CdTiO₃

In the g-C₃N₄/CdTiO₄ heterostructure, the charge-transfer behaviour is best described by an S-scheme heterojunction. g-C₃N₄, with a narrower band gap (~2.76 eV), is efficiently excited under visible-light irradiation, whereas CdTiO₃, possessing a wider band gap (~3.67 eV), is primarily UV-active and mainly functions as a charge-separation promoter under visible light. Upon intimate interfacial contact, Fermi-level equilibration between g-C₃N₄ and CdTiO₃ induces band bending and establishes an internal electric field at the heterointerface. Under light excitation, the interfacial electric field drives the recombination of photogenerated electrons in the conduction band of CdTiO₃ with holes in the valence band of g-C₃N₄, selectively removing charge carriers with weak redox ability. Consequently, highly reductive electrons remain in the conduction band of g-C₃N₄, while strongly oxidative holes accumulate in the valence band of CdTiO₃. This S-scheme charge-transfer pathway effectively suppresses electron–hole recombination while preserving strong redox potentials, thereby accounting for the enhanced photocatalytic performance of the g-C₃N₄/CdTiO₃ composite under visible-light irradiation. Slight band-gap widening in the composites has also been observed in similar heterostructures and is attributed to interfacial electronic interactions rather than quantum confinement effects [33].

Photocatalytic Performance Analysis

The photocatalytic degradation efficiency of the samples was evaluated by monitoring the normalized concentration ratio (C/ C₀) as a function of irradiation time, as shown in the figure 7. CdTiO₃ exhibits the lowest photocatalytic activity, with only a marginal decrease in C/C₀ even after prolonged irradiation, which can be attributed to its wide band gap and limited visible-light absorption, resulting in inefficient photoexcitation and rapid charge recombination. In contrast, g-C₃N₄ shows improved photocatalytic performance compared to CdTiO₃, owing to its visible-light responsiveness. However, the degradation rate remains moderate, likely due to fast recombination of photogenerated charge carriers in the absence of an efficient charge-separation pathway.

Figure 7: Comparison of Photocatalytic Activities of Pure CdTiO3, g-C3N4, g-C3N4/CdTiO3 (In-situ and Sonication) for the Degradation of RhB Under Visible Light

Both g-C₃N₄/CdTiO₃ nanocomposites demonstrate significantly enhanced photocatalytic activity, confirming the beneficial role of heterojunction formation. Among them, the in-situ synthesized composite exhibits the highest degradation efficiency, achieving a rapid and continuous decrease in C/C₀ with irradiation time. The superior performance of the in-situ composite is attributed to stronger interfacial coupling, more intimate contact between g-C₃N₄ and CdTiO₃nanosheets, and more efficient charge separation, which suppresses electron–hole recombination. The sonication- derived composite also shows enhanced activity compared to the pristine components but is slightly less effective than the in-situ sample, likely due to comparatively weaker interfacial interaction and less uniform heterojunction formation. The in-situ g-C₃N₄ CdTiO₃ composite exhibits superior RhB degradation efficiency compared to pristine g-C₃N₄ and CdTiO₃, consistent with reports on perovskite/g-C₃N₄ systems [34-36]. The enhanced performance is attributed to improved charge separation, higher surface area, and strong interfacial coupling.

Stability and Repeatability of the Photocatalyst

The reusability and stability of the g-C₃N₄CdTiO₃ photocatalyst were evaluated through consecutive photocatalytic degradation cycles, as illustrated in the figure 8. The degradation efficiency remains high and only slightly decreases over successive runs, indicating that the catalyst retains most of its photocatalytic activity even after repeated use. The marginal reduction in performance observed after multiple cycles can be attributed to minor loss of active surface sites, partial adsorption of reaction intermediates, or slight catalyst loss during recovery and washing steps, rather than structural degradation.

Figure 8: Recyclability of the g-C₃N₄/CdTiO₃ (In-situ) Photocatalyst for the Degradation of RhB Under Visible Light Irradiation (Five Successive Experimental Runs)

Importantly, no abrupt decline in activity is observed, confirming the good structural stability and repeatability of the composite photocatalyst under the applied reaction conditions. The consistent performance across cycles demonstrates that the g-C₃N₄CdTiO₃ heterostructure is robust, with strong interfacial interaction between g-C₃N₄ and CdTiO₃ effectively preventing photocorrosion and maintaining efficient charge transfer during repeated photocatalytic reactions. The composite shows excellent stability over repeated cycles better than similar g-C₃N₄-based photocatalysts reported in literature [37,38]. The absence of significant activity loss confirms structural robustness and resistance to photocorrosion.

Proposed Photocatalytic Mechanism of g-C₃N₄CdTiO₃ Heterostructure

Under light irradiation, both g-C₃N₄ and CdTiO₃ are photoexcited, generating electron–hole pairs in their respective conduction and valence bands. Due to the intimate interfacial contact formed between the g-C₃N₄ nanosheets and CdTiO₃ nanosheets, a built-in electric field develops at the heterointerface, which drives directional charge migration. Based on the relative band edge positions, photogenerated electrons in the conduction band (CB) of g-C₃N₄ transfer to the CB of CdTiO3?, while holes in the valence band (VB) of CdTiO3 migrate toward the VB of g-C₃N_4, forming an effective S-scheme heterojunction (figure 9). The photocatalytic process proceeds via an, preserving strong redox potentials while suppressing recombination. This mechanism has been widely accepted for g-C₃N₄-based heterostructures and explains the enhanced activity observed in this study [39-41]. This spatial separation of electrons and holes significantly suppresses their recombination and prolongs charge carrier lifetimes. The accumulated electrons on the CdTiO₃ surface react with dissolved oxygen to generate reactive oxygen species such as •OH radicals, while the holes retained on g-C₃N₄oxidize surface-adsorbed water molecules or organic pollutants to produce •OH radicals. These highly reactive species are primarily responsible for the degradation of organic contaminants during the photocatalytic process. Furthermore, the nanosheet-based architecture provides a large interfacial area and short charge diffusion paths, ensuring efficient charge transport and utilization. The heterostructure also stabilizes the individual components by reducing charge accumulation and photocorrosion, leading to excellent recyclability and long-term photocatalytic stability.

Figure 9: Schematic Diagram of the Mechanism for High Separation Efficiency of Photoinduced Charge Carrier and Transfer in the g-C3N4/CdTiO3 System Under Visible Light Irradiation

Conclusion

In summary, g-C₃N₄CdTiO₃ nanocomposites were successfully synthesized via sonication-assisted and in-situ hydrothermal routes, and their structural, morphological, optical, surface, and photocatalytic properties were systematically investigated. PXRD and microscopic analyses confirmed the formation of crystalline CdTiO₃ and the successful construction of intimate g-C₃N₄–CdTiO₃ heterostructures, with the synthesis route playing a crucial role in determining interfacial contact and microstructural features. The in-situ hydrothermal method produced a more homogeneous dispersion of CdTiO₃ on g-C₃N₄, resulting in enhanced interfacial interaction compared to the sonication route.

The g-C₃N₄/CdTiO₃nanocomposites exhibited significantly enhanced visible-light-driven photocatalytic degradation of Rhodamine B relative to pristine g-C₃N₄and CdTiO₃. This improvement is attributed to extended visible-light absorption, increased surface-active sites, and effective suppression of electron–hole recombination due to heterostructure formation. The photocatalytic process is governed by an S-scheme charge-transfer mechanism, which preserves the strong redox capability of photogenerated charge carriers and promotes efficient dye degradation.

Furthermore, the nanocomposite demonstrated good structural stability and repeatable photocatalytic performance over multiple degradation cycles, indicating its robustness and reusability. This study highlights the potential of CdTiO₃ as an effective perovskite partner for g-C₃N₄and provides new insight into the design of g-C₃N₄-based heterostructured photocatalysts. The findings offer a promising strategy for developing efficient visible-light-responsive photocatalysts for dye-contaminated wastewater treatment.

Acknowledgments

PKP and BK thanks ANRF for providing support through the grant no SUR/2022/004717. The authors also thank IIT Delhi and IISER Berhampur India for some of reaction and characterization facility.

Author Contributions

Pramendra Kumar Pandey and Revati Raman Chaubey: Synthesis and draft writing, Gyandeshwar Kumar Rao and Arvind Kumar Singh: Characterization, Bharat Kumar: Concept, synthesis modification, final draft writing and final submission. All the authors reviewed the manuscript.

Funding

Funding is not applicable

Declarations

Clinical Trial

Clinical trial is not applicable in the manuscript.

Consent to Publish Declaration

Not applicable

Ethics and Consent to Participate Declarations

Not applicable

Competing Interests

The authors declare no competing interests Data Availability The authors declare that the data supporting the findings of this study are available within the paper file. Should any raw data files be needed in another format they are available from the corresponding author upon reasonable request.

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