Photocatalytic technology has attracted extensive attention owing to its enormous potential in splitting water into hydrogen, reducing CO₂ to solar fuels, nitrogen photo-fixation, and degrading harmful contaminants [1-6]. Efficient separation and transfer of photocatalytic charge carriers is still one of the main bottlenecks to improving the photocatalytic efficiency [7-10]. To overcome this problem, various effectual strategies have been considered, such as morphology regulation [11, 12], defect engineering [13], heteroatom doping [14-16], and fabrication of composites [17-20]. Among them, integration of two different semiconductors with well-matched energy band structures to form composites is regarded as a facile and feasible avenue toward improving the separation efficiency of photogenerated electron-hole pairs.

Recently, graphitic carbon nitride (g-C₃N₄), with a layer structure, has been receiving more interest because of its low cost, nontoxic nature, high stability, visible-light response, and possibility of large-scale preparation. Moreover, an appropriate conduction band (CB) potential (about -1.12 eV vs. NHE) endows it with a strong capability to accept photoinduced electrons [21-27]. However, the photocatalytic activity of pristine g-C₃N₄ is always low owing to the fast recombination of the photogenerated charge carriers. Inspired by the abovementioned heterostructure composites, tremendous efforts have been made to fabricate g-C₃N₄-based composites, e.g., SnS₂/g-C₃N₄ [28], TiO₂/g-C₃N₄ [29], CdS/g-C₃N₄ [30], BiOBr/g-C₃N₄ [31], Fe₂O₃/g-C₃N₄ [32], and so on [33-44]. These composites have all displayed significantly enhanced photocatalytic activities, compared with that of bare g-C₃N₄, which may be attributed to the effective transfer and separation of photoinduced charge carriers.

Cadmium molybdate (CdMoO₄) as a class of metal molybdates (MMoO₄, M = Ni, Ba, Cd, Pb, etc.) has also received considerable attention because of its promise for application in the photocatalytic field [45-47]. However, the relatively wide band gap (about 3.4 eV) restricts its photocatalytic activity, as it is only active under ultraviolet light irradiation. In this regard, some strategies have been employed to extend the light response range, such as elemental doping and engineering composites with narrow band gap semiconductors [48-50]. Since g-C₃N₄ is a visible-light-driven semiconductor, it can be considered as a candidate that couples with CdMoO₄ to enhance the light harvesting capacity. Moreover, the CB and valance band (VB) potentials of CdMoO₄ are both lower than those of g-C₃N₄, which suggest a well matched energy band structure that is favorable for the formation of a type Ⅱ heterostructure composite. To date, there are very few reports on the fabrication of CdMoO₄/g-C₃N₄ composites. Zhao et al. [51] prepared the CdMoO₄/g-C₃N₄ heterojunction via a simple mixing-calcination method. The resultant composite displays a remarkable improvement in the photocatalytic activity toward rhodamine B (RhB) degradation and CO₂ reduction. On the other hand, intimate interfacial contact between two different semiconductors is vitally important, as it will affect the transfer and separation efficiency of charge carriers. Hence, it is still a challenge to fabricate CdMoO₄/g-C₃N₄ composites with close interfacial contact by a facile approach.

Here, CdMoO₄ particles were directly deposited on the surface of g-C₃N₄ through a facile precipitation-calcination process. The CdMoO₄/g-C₃N₄ composites exhibited markedly enhanced photocatalytic activity, in contrast with those of pristine g-C₃N₄ and CdMoO₄, as demonstrated by the degradation of RhB solution under visible light irradiation. In addition, the effects of CdMoO₄ mass ratios in the composites and the active species on the photocatalytic performance were investigated. A possible mechanism for the enhancement in the photocatalytic activity was proposed based on the experimental results.

g-C₃N₄ was prepared according to our previous report [37]. Typically, 10 g of melamine was calcined at 550 ℃ for 3 h at the heating rate of 5 ℃ min^-1. The resulting powders were ground in agate mortar and collected for use without further treatment.

CdMoO₄/g-C₃N₄ composites were fabricated by in situ precipitation and calcination approach. As a representative example, 200 mg of as-prepared g-C₃N₄ was dispersed in 30 mL deionized water by ultrasonic treatment for 30 min. 18.8 mg of Cd(CH₃COO)₂·2H₂O and 19.7 mg of Na₂MoO₄·2H₂O were added to the above suspension solution with the molar ratio of 1:1. The mixture was stirred at 40 ℃ for 6 h. Then, the sediments were collected by centrifugation, washed three times using deionized water, and dried at 80 ℃ for 12 h. After that, the products were annealed at 300 ℃ for 2 h in a muffle furnace. CdMoO₄/g-C₃N₄ composites with different mass ratios were obtained through the aforesaid procedure by adjusting the amounts of Cd(CH₃COO)₂·2H₂O and Na₂MoO₄·2H₂O added. The actual contents of CdMoO₄ in the composites were determined by thermogravimetric (TG) measurements. Bare CdMoO₄ was synthesized by the same procedure, except for the addition of g-C₃N₄ at the beginning.

The crystal phases were identified with a Shimadzu XRD-7000 powder X-ray diffractometer (XRD) using Cu K_α irradiation at 40 kV and 30 mA. The morphologies, elemental maps, and microstructures were recorded on a JSM-7100F field emission scanning electronic microscope (FESEM) and a JEOL JEM 2100F high-resolution transmission electronic microscope (HRTEM). TG analysis was carried out on a Hitachi STA 7300 instrument from 50 to 800 ℃ in air flow at a heating rate of 10 ℃ min^-1. X-ray photoelectron spectroscopy (XPS) was performed on a VG Multilab 2000 instrument with Al K_α source that operated at 300 W, and all the spectra were calibrated with the C 1s peak at 284.6 eV. The ultraviolet-visible diffuse reflectance absorption spectra (UV-DRS) were recorded by using dry-pressed disk samples on a Purkinje General TU-1901 spectrophotometer with BaSO₄ as the reference sample. The fourier transform infrared (FTIR) spectra were recorded on a Thermo Nicolet Avatar 360 spectrometer using conventional KBr pellets. The Brunauer-Emmett-Teller (BET) specific surface areas were determined on a Micromeritics ASAP 2020 nitrogen adsorption apparatus. Prior to the BET analysis, the samples were degassed at 120 ℃ for 10 h to remove the adsorbed water. The photoluminescence (PL) spectra were measured at room temperature on a PerkinElmer LS55 fluorescence spectrometer with the excitation wavelength of 340 nm.

The photocatalytic activities were evaluated by degrading RhB solution under visible light irradiation on photoreactive equipment (BL-GHX-IV, Shanghai Bilang Instrument Co. Ltd, China). In each experiment, 30 mg of the photocatalyst was dispersed in 50 mL of RhB solution with the initial concentration of 1.0 × 10^-5 mol L^-1. A 300 W long-arc Xe lamp was used as the light source, and was equipped with 420 nm cutoff filters. Before the irradiation, the suspensions were stirred in the dark for 30 min to achieve adsorption-desorption equilibrium between the photocatalysts and RhB molecules. At given irradiation time intervals, 4 mL of the suspension was withdrawn and centrifuged to remove the photocatalysts. The concentration of the RhB solution in the supernatant was determined on a Purkinje General TU-1810 spectrometer.

The Mott-Schottky, EIS, and transient photocurrent response experiments were carried out on an electrochemical system (CHI 760D, Shanghai Chenhua Instruments, China) employing the standard three-electrode system. A Pt sheet and Ag/AgCl (saturated KCl) served as the counter and reference electrodes, respectively. The working electrodes were prepared as follows. 10 mg of the sample was mixed with 1 mL ethanol and 50 μL Nafion solution by using ultrasound. Then, 0.1 mL of the mixture was dropped on indium tin oxide-doped glass with the active work area of about 1 cm². A 0.1 mol L^-1 aqueous Na₂SO₄ solution was used as the electrolyte. The Mott-Schottky tests were conducted at the frequency of 1000 Hz, with the bias potential varying from -1.0 to 1.0 V. The EIS measurements were performed in darkness at the amplitude of 5 mV under open circuit potential conditions. The frequency range was 1 Hz to 100 kHz. The transient photocurrent responses were obtained at 0.5 V bias potential. A 300 W Xe lamp acted as the light source.

To probe the active species in the photocatalytic reaction, triethanolamine (TEOA), isopropanol (IPA), and p-benzoquinone (BQ) were introduced into the system as the scavengers of holes (h⁺), hydroxyl radicals (·OH), and superoxide radicals (·O₂^-), respectively. The measurements were similar to the aforementioned photocatalytic activity tests, except for the addition of scavengers into the RhB solution before visible light irradiation. The concentrations of TEOA, IPA, and BQ were 10, 10, and 1 mmol L^-1, respectively.

The actual mass ratios of CdMoO₄ in the composites were determined by TG measurements. As revealed in Fig. 1, single-phase CdMoO₄ reveals no distinct weight loss between 50 and 800 ℃ under air flow heating, which indicates that pristine CdMoO₄ is relatively stable. On the other hand, bare g-C₃N₄ displays a perceptible weight loss at about 500 ℃ and decomposes completely at around 760 ℃. Consequently, on the basis of the remaining weight, the mass ratios of CdMoO₄ in the composites can be estimated. For the CdMoO₄/g-C₃N₄ composites, the CdMoO₄ mass ratios were calculated to be 2.1, 4.8, 8.7, and 13.4 wt%. It is noteworthy that the decomposition temperatures of g-C₃N₄ decrease when coupling CdMoO₄ with g-C₃N₄, which may be because CdMoO₄ can accelerate the oxidation of g-C₃N₄ to gaseous products [51].

Fig. 2 exhibits the XRD patterns of CdMoO₄/g-C₃N₄ composites with different mass ratios, together with those of bare g-C₃N₄ and CdMoO₄. For g-C₃N₄, a weak peak located at about 13.0° and a strong peak situated at 27.2° are observed, which are ascribed to the (100) and (002) planes, respectively. These are the characteristic diffraction peaks of g-C₃N₄ that correspond to the in-planar packing motif of tri-s-triazine units and interlayer stacking of conjugated aromatic rings [32]. As for the single-phase CdMoO₄, the diffraction peaks are well matched with the tetragonal phase of CdMoO₄ (JCPDS # 85-888) [52]. Regarding the CdMoO₄/g-C₃N₄ composites, the feature peaks of both CdMoO₄ and g-C₃N₄ can be observed together, without other impurity phases. Moreover, the intensities of the diffraction peaks assigned to g-C₃N₄ gradually decrease and the peaks associated with CdMoO₄ become stronger with the increase of CdMoO₄ content in the composites. The XRD results corroborate the coexistence of CdMoO₄ and g-C₃N₄ in the composites.

The representative FESEM images of bare CdMoO₄, g-C₃N₄, and 4.8 wt% CdMoO₄/g-C₃N₄ composite are exhibited in Fig. 3a-c. As can be seen, the pristine CdMoO₄ (Fig. 3a) presents an irregular granular morphology, along with severe aggregation, while g-C₃N₄ (Fig. 3b) displays a large blocked structure with particle sizes of about 5-10 μm. The FESEM image (Fig. 3c) of 4.8 wt% CdMoO₄/g-C₃N₄ composite reveals that there are two different morphological structures in the composites. The big blocks are assigned to g-C₃N₄, whereas the small particles correspond to CdMoO₄. Energy dispersive X-ray spectrometer elemental mapping was used to further determine the distributions of different components in 4.8 wt% CdMoO₄/g-C₃N₄ composite. As illustrated in Fig. 3d-h, the composite contains C, N, Cd, Mo, and O elements. In addition, CdMoO₄ is discretely distributed on the surface of g-C₃N₄. Further investigations were performed by using the HRTEM to investigate the microstructure of the CdMoO₄/g-C₃N₄ composite. Fig. 3i also reveals that the composite comprises two different constituents. The dark sections correspond to CdMoO₄, while the grey sections are associated with g-C₃N₄. This is because electron beams can more easily pass through g-C₃N₄ than through CdMoO₄ in view of their atomic weights. The red rectangular section of the TEM image is enlarged. From the HRTEM image (inset of Fig. 3i), the interplanar spacing is measured to be 0.28 nm, which corresponds to the (112) plane of CdMoO₄. On the other hand, the lattice fringes of g-C₃N₄ are difficult to observe, which is in accordance with a previous report [36].

XPS was performed to further examine the surface chemical compositions and valence states of the various species. Fig. 4a depicts the XPS survey patterns of CdMoO₄, g-C₃N₄, and 4.8 wt% CdMoO₄/g-C₃N₄ composite. As expected, C, N, O, Cd, and Mo elements are distinctly detected in the CdMoO₄/g-C₃N₄ composite. Fig. 4b displays the high-resolution Cd 3d XPS pattern. The peaks positioned at 404.7 and 411.4 eV can be assigned to Cd 3d_5/2 and Cd 3d_3/2, respectively, which are characteristic of Cd²⁺ [51]. From the Mo 3d spectra (Fig. 4c), two peaks are observed at about 231.9 and 235.1 eV, which correspond to Mo 3d_5/2 and Mo 3d_3/2, respectively. This indicates that the oxidation state of the Mo ions is +6 [51]. The high-resolution XPS C 1s patterns are shown in Fig. 4d. For CdMoO₄, the only strong peak is found at 284.6 eV, which corresponds to the surface adventitious C. In the cases of g-C₃N₄ and 4.8 wt% CdMoO₄/g-C₃N₄ composite, two peaks at 284.6 and 287.6 eV are observed. The former is attributed to the surface adventitious C and the latter to the sp²-hybridized C of the N=C-N aromatic rings [32]. The N 1s XPS patterns (Fig. 4e) of g-C₃N₄ and CdMoO₄/g-C₃N₄ composite can be deconvoluted into three peaks at 398.0, 398.7, and 400.1 eV, which are related to the sp²-hybridized N (C=N-C) in the triazine rings, tertiary N bonded to C (N-(C)₃), and amino groups (C-N-H), respectively [32]. As demonstrated in Fig. 4f, the O 1s spectrum of CdMoO₄ can be fitted with two peaks. The peaks at 529.7 and 530.8 eV are associated with the O anions present in the lattice of CdMoO₄ and the chemisorbed O species, respectively [46]. As for g-C₃N₄, a peak at 532.3 eV is detected, which can be related to the C-O bonds stemming from the incomplete pyrolytic reaction of melamine [32, 53]. Comparing with the spectra of CdMoO₄ and g-C₃N₄, the O 1s spectrum of 4.8 wt% CdMoO₄/g-C₃N₄ composite can be deconvoluted into three peaks, which correspond to O anions, chemisorbed O species, and C-O bonds, respectively.

The molecular structures of pristine g-C₃N₄, CdMoO₄, and CdMoO₄/g-C₃N₄ with different mass ratios were investigated based on their FTIR spectra, and the relevant results are presented in Fig. 5. As for g-C₃N₄, the absorption bands in the range 1200-1650 cm^-1 correspond to the stretching vibrations of the C-N aromatic ring [32]. The peak at about 812 cm^-1 can be assigned to the characteristic breathing mode of the tri-s-triazine units [32]. In addition, the broad absorption bands centered at 3430 and 3164 cm^-1 are attributed to the stretching vibrations of the O-H bonds of adsorbed water and the terminal N-H groups, respectively. For single-phase CdMoO₄, a characteristic absorption peak appears at around 783 cm^-1, which corresponds to the stretching vibration of the O-Mo-O bonds in the [MoO₄]^2- tetrahedrons [52]. In the case of CdMoO₄/g-C₃N₄ composites, the characteristic peaks of g-C₃N₄ are clearly observed, while the peak belonging to CdMoO₄ is only found in the CdMoO₄/g-C₃N₄ composites with large mass ratios. Moreover, the feature absorption peak of CdMoO₄ in the CdMoO₄/g-C₃N₄ composites displays a slight shift from 783 to 757 cm^-1, which may be due to the strong interaction between CdMoO₄ and g-C₃N₄. This also implies that CdMoO₄ and g-C₃N₄ have formed an interface with intimate contact.

UV-DRS were used to study the optical properties of g-C₃N₄, CdMoO₄, and CdMoO₄/g-C₃N₄ composites. As revealed in Fig. 6, single-phase CdMoO₄ and g-C₃N₄ show steep absorption band edges at around 360 and 455 nm, respectively. The band gaps of CdMoO₄ and g-C₃N₄ are estimated to be 3.44 and 2.73 eV, respectively, from the equation E_g = 1240/λ_g, where E_g is the band gap and λ_g is the absorption band edge. For CdMoO₄/g-C₃N₄ composites, they exhibit similar absorption band edges to that of bare g-C₃N₄ in the visible light region. This indicates that integration of CdMoO₄ with g-C₃N₄ does not influence the structure of g-C₃N₄. It is noted that both the 8.7 wt% and 13.4 wt% CdMoO₄/g-C₃N₄ composites display another absorption edge in the ultraviolet light region, which corresponds to the intrinsic optical absorption of CdMoO₄.

The BET specific surface areas and pore size distribution curves of pristine g-C₃N₄ and 4.8 wt% CdMoO₄/g-C₃N₄ composite were obtained by nitrogen adsorption-desorption measurements, as revealed in Fig. 7. It can be seen that these two adsorption-desorption curves belong to type IV isotherm with type H3 hysteresis loops, which imply the existence of porous structures in these samples. This also indicates that introduction of CdMoO₄ in g-C₃N₄ does not significantly block or change the pore structures of g-C₃N₄. The corresponding pore size distribution curves (inset) reveal that the pore size distributions mainly range from 25 to 100 nm, which confirm the presence of porous structures in these samples. Additionally, the BET specific surface areas of g-C₃N₄ and 4.8 wt% CdMoO₄/g-C₃N₄ composite are calculated to be 27.2 and 25.6 m² g^-1, respectively, which represent a slight decrease in the specific surface area after the hybridization of CdMoO₄ and g-C₃N₄.

The photocatalytic performances of the as-prepared photocatalysts were evaluated by degrading RhB solution under visible light irradiation. As shown in Fig. 8a, the blank experiment reveals that RhB is quite stable under visible light illumination, which ruled out self-degradation of RhB. The decolorization percentage is estimated as C/C₀, where C is the concentration of RhB after adsorption and light irradiation for a certain time interval, and C₀ is the initial concentration of RhB. Single-phase CdMoO₄ reveals a very low adsorption and photocatalytic activity, with a decolorization percentage of 16.1% after 180 min visible light irradiation. Bare g-C₃N₄ displays moderate photocatalytic activity, with the decolorization percentage being 77.8% for 180 min of visible light irradiation. The CdMoO₄/g-C₃N₄ composites exhibit remarkable improvements in the photocatalytic activities. After 30 min dark adsorption and 180 min visible light illumination, the decolorization percentages are about 86.3%, 96.7%, 86.7%, and 80.1% for 2.1, 4.8, 8.7, and 13.4 wt% CdMoO₄/g-C₃N₄ composites, respectively. Obviously, the 4.8 wt% CdMoO₄/g-C₃N₄ composite exhibits the best photocatalytic activity. The degradation process could be fitted with the pseudo-first-order kinetic model, in which the value of the apparent reaction rate constant (k) is equal to the corresponding slope of the fitting curve. As depicted in Fig. 8b, the reaction rate constant of 4.8 wt% CdMoO₄/g-C₃N₄ composite is about 2.32 times higher than that of bare g-C₃N₄. The temporal UV-visible spectral changes of the RhB solution during the adsorption and photocatalytic reactions over CdMoO₄, g-C₃N₄, and 4.8 wt% CdMoO₄/g-C₃N₄ composite are displayed in Fig. 8c-e, respectively. As for g-C₃N₄ and CdMoO₄/g-C₃N₄ composite, the maximal absorbance wavelengths of RhB shift gradually from 554 to 498 nm, along with a gradual decrease in the maximal absorbance, which suggest stepwise removal of the N-ethyl groups of RhB molecules. The stability of CdMoO₄/g-C₃N₄ composite was investigated by cyclic degradation of RhB solution. After every 180 min of the photodegradation reaction, the separated photocatalysts were washed and dried. As demonstrated in Fig. 8f, the photocatalytic degradation efficiency is still 92.4% after three successive experiments.

Furthermore, XRD was also used to evaluate the stability of the photocatalysts; the results are shown in Fig. 9. The pattern of the used CdMoO₄/g-C₃N₄ composite is similar to that of the fresh one. However, the peak intensities ascribed to CdMoO₄ reduce, indicating that slight photocorrosion occurs on CdMoO₄.

To corroborate the effective transfer and separation of the photogenerated charge carriers on the CdMoO₄/g-C₃N₄ composite, EIS and transient photocurrent response measurements were employed to evaluate the interfacial charge separation efficiency. The EIS Nyquist plots of pure g-C₃N₄, CdMoO₄, and 4.8 wt% CdMoO₄/g-C₃N₄ composite are displayed in Fig. 10a. It can be observed that the diameter of the arc of CdMoO₄/g-C₃N₄ composite is smaller than those of g-C₃N₄ and CdMoO₄, which suggests a lower charge transfer resistance at the electrode surface of CdMoO₄/g-C₃N₄ composite. In addition, the transient photocurrent responses (Fig. 10b) of g-C₃N₄, CdMoO₄, and CdMoO₄/g-C₃N₄ composite under visible light irradiation were compared. Generally, photocurrent is mainly due to the transfer of photogenerated electrons to the counter electrode, and a higher photocurrent implies more efficient transfer of the photoexcited electrons. Evidently, the photocurrent response of CdMoO₄/g-C₃N₄ composite is larger than those of g-C₃N₄ and CdMoO₄. These results powerfully support the idea of improved separation and transfer efficiency of the photogenerated charge carriers in CdMoO₄/g-C₃N₄ composite. The steady-state PL spectra were also utilized to examine the separation and recombination processes of the photoinduced electron-hole pairs. As revealed in Fig. 10c, conspicuous PL quenching occurs in the 4.8 wt% CdMoO₄/g-C₃N₄ composite, compared with the case of pure g-C₃N₄, which suggests suppression of charge carrier recombination and enhancement of charge separation efficiency. To obtain deep insights into the photocatalytic mechanism, active species trapping experiments were performed under visible light irradiation. From Fig. 10d, the addition of IPA only slightly reduces the degradation of RhB, which indicates that ·OH is a minor active species in the photocatalytic process. However, the addition of TEOA and BQ greatly inhibit the degradation of RhB, which indicates that ·O₂^- and h⁺ are the main reactive species in the photocatalytic system.

To determine the band energy positions and elucidate the possible transfer pathway of the photogenerated charge carriers between g-C₃N₄ and CdMoO₄, Mott-Schottky measurements were performed to determine the conductivity types and flat-band potentials of the photocatalysts. As exhibited in Fig. 11a and 11b, the flat-band potentials of g-C₃N₄ and CdMoO₄ are estimated to be -1.34 and -0.43 V (vs. Ag/AgCl, pH = 7), which are equivalent to -1.13 and -0.22 V (vs. NHE, pH = 7), respectively. Moreover, the positive slopes reveal that g-C₃N₄ and CdMoO₄ are both n-type semiconductors. For an n-type semiconductor, the CB potential is close to the flat-band potential, and therefore, the CB potentials of g-C₃N₄ and CdMoO₄ are about -1.13 and -0.22 eV (vs. NHE, pH = 7). By considering the band gap values, the VB potentials of g-C₃N₄ and CdMoO₄ are determined to be 1.60 and 3.22 eV (vs. NHE, pH = 7), respectively.

Based on the above results, a possible mechanism for the enhanced photocatalytic activity of CdMoO₄/g-C₃N₄ composites toward the degradation of RhB under visible light illumination is proposed that is based on the improvement in the separation and transfer of the photogenerated charge carriers at the interface. As illustrated in Fig. 12, CdMoO₄ cannot be excited with visible light owing to its wider band gap, therefore, it exhibits a lower photocatalytic activity. On coupling CdMoO₄ with g-C₃N₄, the photoexcited electrons in the CB of g-C₃N₄ can easily transfer to the CB of CdMoO₄ through the contacted interface, since the CB potential of g-C₃N₄ (-1.13 eV vs. NHE) is more negative than that of CdMoO₄ (-0.22 eV vs. NHE). Meanwhile, the photogenerated holes tend to remain in the VB of g-C₃N₄. As a result, the photogenerated electrons and holes in g-C₃N₄ are effectively separated and recombination of the photoexcited charge carriers is greatly suppressed. The electrons in the CB of CdMoO₄ can reduce O₂ to generate ·O₂^- radicals, while the holes in the VB of g-C₃N₄ will directly participate in the photocatalytic reaction, because the VB potential of g-C₃N₄ is less positive than the potential of ·OH/H₂O (2.38 eV vs. NHE), and therefore g-C₃N₄ cannot oxidize H₂O to produce ·OH radicals. The EIS results, transient photocurrent response, PL spectra, and active species trapping experiments well support this mechanism.

CdMoO₄/g-C₃N₄ composites were synthesized by a facile precipitation-calcination process. Compared with those of pristine g-C₃N₄ and CdMoO₄, the photocatalytic activities of CdMoO₄/g-C₃N₄ composites toward the degradation of RhB solution were greatly enhanced, which could be ascribed to the efficient separation and transfer of the photogenerated charge carriers. EIS results, transient photocurrent response, and PL spectra confirmed the effective separation of the photoexcited electron-hole pairs. Active species trapping experiments demonstrated that h⁺ and ·O₂^- were the main active species during the photocatalytic reaction. CdMoO₄/g-C₃N₄ composites may be a promising photocatalyst for the degradation of organic pollutants.