Boosting Photocatalytic Efficiency of MoS2/CdS By Modulating Morphology

doi:10.21203/rs.3.rs-1041316/v1

Download PDF

Research Article

Boosting Photocatalytic Efficiency of MoS2/CdS By Modulating Morphology

https://doi.org/10.21203/rs.3.rs-1041316/v1

This work is licensed under a CC BY 4.0 License

You are reading this latest preprint version

With the rapid development of nuclear-related industries in the world, the consequent environmental pollution of radionuclides has become an increasingly serious problem due to the great harm to environmental diversity and human health. The photocatalytic removal of radionuclide on CdS-based photocatalysts has been attracted widely attentions due to the suitable band gap and high photocatalytic efficiency. In this study, approximately 97.5% of U(VI) was photo-catalytically reduced into U(IV) by 2.5 wt% MoS₂/CdS composite within 15 min. After 5 cycles, 2.5 wt% MoS₂/CdS composite still exhibited the high removal efficiency of U(VI) under 50 min irradiation, indicating the good stability. The findings indicated that CdS-based catalyst has a great potential for the photocatalytic reduction of uranyl in actual environmental remediation.

MoS2

CdS

photocatalytic reduction

U(VI)

With the development of economy and society, mankind’s demand for energy is seriously increasing year by year(Arunachalam &Fleischer 2008, Chu &Majumdar 2012, Jacobson 2009, Jacobson &Delucchi 2011). Nuclear energy as one of the most promising energy source has been widely used in countries of the world due to high energy density and clean energy(Graves et al. 2011, Jiang et al. 2018, Zhang et al. 2019). Uranium has extensively used in nuclear-related industries, which exhibits a great threat to the environmental diversity and human health(Andrews &Cahill 2013, Jiang et al. 2018, Zhang et al. 2019). Therefore, it is very important to remove these pollutants before releasing the environment. Various methods, including chemical precipitation(B. et al. 1998), ultrafiltration(Misra et al. 2009), photocatalysis(Chang et al. 2015, He et al. 2016) and adsorption(Dolatyari et al. 2016, Li et al. 2016), have been widely used to remove uranium from aqueous solutions(Xie et al. 2013b). The photocatalytic reduction of U(VI) into U(IV) by various photocatalyst is regarded as the promising method due to environmental friendly, low cost and high removal efficiency(Chang et al. 2015, Jiang et al. 2018, Qin et al. 2017, Wu et al. 2017).

CdS as a common photocatalyst has been widely investigated to photocatalytic removal of various environmental pollutants due to the feasible band gap (~2.4 eV) and high photocatalytic activity(He et al. 2016, Liu et al. 2013, Zong et al. 2010). CdS exhibits the different energy band structures due to the different crystal phases such as hexagonal and cubic structures, which determines the light absorption and redox ability of photogenerated charge carriers(Yin et al. 2016b, Zhang et al. 2014). However, the poor stability of CdS extends the light time prone to corrosion, which limits the actual environmental application(Chen et al. 2015, Li et al. 2019b, Wu et al. 2017). Various metal disulfides (e.g., MoS₂) have been extensively employed to increase electron transport, which are conducive to effectively separate electron-hole pairs and decrease band gaps(Xie et al. 2013a, Yin et al. 2016b). For instance, MoS₂/CdS composites have been widely used in energy storage (e.g., hydrogen/oxygen evolution reaction) and environmental cleanup (e.g., degradation of organics and photocatalytic removal of heavy metals and radionuclides)(Chen et al. 2015, Jiang et al. 2015, Jiang et al. 2018, Yin et al. 2016a, Zong et al. 2008). However, few investigations concerning the photocatalytic reduction of U(VI) on MoS₂/CdS composites are available.

The objectives of this study are (1) to synthesize MoS₂/CdS composites and characterize them using TEM, XRD, FTIR, UV-vis UV-visible diffuse reflectance spectroscopy (DRS), photoluminescence (PL) spectra and Electrochemical impedance spectroscopy (EIS) techniques; (2) to investigate the photocatalytic reduction of U(VI) by MoS₂/CdS under different environmental conditions; (3) to demonstrate the interaction mechanism of U(VI) on MoS₂/CdS using quenching experiments, EPR and XPS techniques. These findings are very important for environmental scientists and material engineers to design metal sulfide-containing materials with high chemical stability and excellent removal performance towards various pollutants in actual environmental remediation.

2.1 Materials

Cadmium acetate (Cd(CH₃COOH)₂·2H₂O, Aladdin, 99.99% purity), ammonium molybdate ((NH₄)₆Mo₇O₂₄·4H₂O, Aladdin, 99.99% ), thiourea ((NH₂)₂CS, Aladdin, 99% purity), N-N-dimethylformamide (DMF) and ethanol were purchased from Tianjin Damao Chemical reagent Co., Ltd. Methanol (Me), tert-butanol (TBA), p-Benzoquinone (p-BQ) were obtained from Aladdin. All the reagents used were of analytical grade and used without further purification.

2.2 Synthesis of MoS₂/CdS nanoparticles

MoS₂/CdS composites were prepared by solvothermal method(Li et al. 2019b, Wu et al. 2017, Yin et al. 2016b). CdS nanospheres were firstly prepared by hydrothermal method(Chen et al. 2015). Briefly, 0.8529 g (CH₃COO)₂H₂O and 1.2179 g (NH₂)₂CS were dissolved in 40 mL deionized water under vigorous stirring and room temperature for 30 min. The mixture was added into 50 mL Teflon-lined stainless steel autoclave and heated at 140°C for 24 h and then cooled to room temperature. The orange CdS (inset in Figure 1a) was obtained by drying it at 80 ℃ for 12 h after washing with deionized water and ethanol three times and centrifuging it at 3000 rpm for 10 min. The synthesis process of MoS₂/CdS was as follows: Typically, 0.5 g of as-prepared CdS was dispersed in the mixed solvent (16.67 mL DMF and 8.33 mL H₂O) under ultrasound treatment for 30 min, then 0.0145 g (NH₄)₆Mo₇O₂₄·4H₂O and 0.0268 g of (NH₂)₂CS were added simultaneously for 60 min. The suspension was heated at 200°C for 24 h and then cooling to room temperature under 100 mL Teflon-lined stainless steel autoclave. The MoS₂/CdS (~2.5 wt% MoS₂) composites were obtained by drying them at 60 ℃ for 12 h after washing with ethanol and deionized water several times. Additionally, 5 wt% MoS₂/CdS (Figure S1b) and 10 wt % MoS₂/CdS (Figure S1c) composites were also fabricated by adding two and four-fold amounts, respectively, of (NH₄)₆Mo₇O₂₄·4H₂O and (NH₂)₂CS.

2.3 Characterization

Transmission electron microscope (JEOL, JEM-2100F, Japan) and scanning electron microscope (Hitachi, s4800) was employed to determine morphological features. Fourier transferred infrared spectrometer (IRTracer-100 Shimadzu Corporation) were conducted using KBr disc method. Brewer-Emmett-Taylor (BET) surface area of samples was determined by TriStar II. XPS spectra were taken on an X-ray photoelectron spectroscope (Escalab 250xi instrument, Thermo ESCALAB) using monochromatic Al Kα radiation (225 W, 15 mA, 15 kV) and low-energy electron flooding for charge compensation. The crystallinity of as-prepared MoS₂/CdS was characterized using X-ray diffractometer (Rigaku Giegerflex D/Max B diffractometer with Cu-Kα radiation). EIS measurement was carried out on the CHI-660D electrochemical workstation. In the three-electrode system, Pt counter electrode in saturated Na₂SO₄ and a standard calomel reference electrode are used. PL spectra were conducted using RF-6000 photoluminescence emission spectrometer at 380 nm. The optical properties were measured by Shimadzu Corporation UV-2700 UV-Visible Light Photometer and UV-visible diffuse reflectance spectroscope (DRS, barium sulfate as the reflection standard).

2.4 Photoreduction of U(VI)

The photoreduction experiments were conducted in a photocatalytic reaction box (CEL-HXF 300, China Education Au-Light) and a Xenon lamp (150 W, as the light source) with a double-walled beaker with circulated water to keep the constant temperature. Briefly, 0.05 g of MoS₂/CdS was added 50 mL 20 mg/L UO₂²⁺ solution with a small amount of methanol. pH of the mixture was adjusted by adding small volumes of NaOH and HNO₃ solutions. The suspension was pre-introduced firstly N₂ 2h and then reacted in the dark for 30 min remove dissolved oxygen from water and to achieve the adsorption equilibrium, respectively. After adsorption equilibrium, the mixtures were exposed in a photocatalytic reaction box under different time intervals (15, 30, 60, 90 and 120 min).

In the recycle experiment, the samples after photocatalytic reaction for 60 min were washed several times with deionized water, and dried it in vacuum at 60 ºC for 12 h, and then the dried powder was collected to conduct the photocatalytic experiment again and repeated five times.

In the quenching experiment, photoreduction experiments were conducted by separately adding methanol, TBA and p-BQ solution, which were used as radical scavengers for holes, ·OH and ·O₂⁻ radical, respectively. After reaction, the suspension was centrifuged at 4000 r/min for 10 min, the concentration of uranium in supernatant was measured by UV-vis spectrophotometer at 650 nm.

3.1 Characterization

The morphology of as-prepared MoS₂/CdS was characterized by SEM and TEM images. Fig. 1a and 1b show SEM image of CdS and TEM image of 2.5 wt % MoS₂/CdS, respectively. The olive-like CdS had an irregular block-shape, rough surface and obvious aggregation(Chai et al. 2018, Chen et al. 2012). For 2.5 wt% MoS₂/CdS composite, the irregular flaky MoS₂ was anchored at the edge of CdS(Xu &Cao 2015, Zhang et al. 2018, Zong et al. 2010), As inset in Fig. 1a and 1b, the color of bright orange CdS was transformed into deep orange after adding MoS₂.

XRD analysis was used to characterize crystal structure of MoS₂/CdS (Fig. 1c). The diffraction peaks at 2θ = 24.9, 26.5, 28.3, 43.8, 48 and 52º corresponded to the (100), (002), (101), (110), (103) and (112) planes of cubic CdS, respectively(Alomar et al. 2019, Jin &Li 2020). The high diffraction peak intensity of (101) plane indicated the growth of CdS along (101) crystal plane(Wu et al. 2017). The large and sharp diffraction peak intensity of 2.5 wt% MoS₂/CdS showed the good crystallization. Compared to CdS, no obvious shift in the diffraction peak of MoS₂/CdS composites indicated the loading of MoS₂ rather than doping(He et al. 2016). However, no diffraction peak of MoS₂ may be due to the small content(Li et al. 2019b). No significant change in diffraction peaks after photocatalytic reaction indicated 2.5 wt% MoS₂/CdS composite with strong stability.

Figure 1d shows the FT-IR spectra of 2.5 wt% MoS₂/CdS nanocomposites before and after the reaction in the frequency range of 400 ~ 4000 cm⁻¹. The IR bands at 428 and 508 cm⁻¹ corresponded to the stretching vibration of Mo-S and (S-S)²⁻ bond, respectively(Habibi &Rahmati 2014). The stretching vibration of Cd-S bond and the bending vibration of H₂O were observed at 630 and 1572 cm⁻¹, respectively. The broad peak in the range of 3200 ~ 3500 cm⁻¹ was related to the vibration of O-H bond(Khawula et al. 2016). After the reaction, no new bands and little shift indicated that main interaction mechanism of U(VI) on MoS₂/CdS composite was photoreduction rather than adsorption(Yan et al. 2009, Yuan et al. 2018).

Figure S2 shows nitrogen adsorption-desorption isotherms and corresponding pore size distribution curves of CdS and 2.5 wt% MoS₂/CdS composite. The IV-type adsorption isotherms showed H₃ hysteresis loop, indicating the aggregation of plate-like particles on slit-like pores(Misra et al. 2009, Sing et al. 1985). The main size distribution (~ 2 and 85 nm) suggested the formation of mesoporous and microporous 2.5 wt% MoS₂/CdS composite. From table S1, BET specific surface area of MoS₂/CdS composite (~8.8 m²/g) was slightly higher than CdS (3.8 m²/g) due to the increase of mesopore by adding MoS₂(Yu et al. 2014), which is beneficial to improve the catalytic performance due to accommodation of more surface active sites and promotion of the transport of charge carriers (Alomar et al. 2019, Di et al. 2016).

To study the light absorption characteristics, UV-vis DRS and PL spectra (at 500-700 nm) of 2.5 wt% MoS₂/CdS composite were showed in Fig. 2a and 2b, respectively. For CdS, a strong absorption band edge at ~ 530 nm corresponded to the inherent band gap absorption of hexagonal CdS(Li et al. 2019b, Yin et al. 2016b). It is worth noting that the gradual increase of light absorption intensities in 580-800 nm with the increase of MoS₂ may be due to the color shift from bright orange into dark orange MoS₂/CdS composite(Zhang et al. 2014). According to the calculation of Tauc plots (Supporting information), the band gap of 2.5 wt% MoS₂/CdS composite (2.31 eV) was significantly lower than CdS (2.43 eV, inset of Fig. 2a) owing to charge transfer from CV of MoS₂ to CdS(Zong et al. 2010).

PL spectrum as an important tools provides important information of photo-generated electron-hole separation efficiency(Lin et al. 2017). The high PL intensity of CdS (Fig. 2b) indicated the high recombination centers due to trap-related states(Wu et al. 2017). The low PL intensity of 2.5 wt% MoS₂/CdS composite indicated low recombination of photogenerated electrons and holes(Yuan et al. 2018), which also reduce the photo-corrosion of CdS(Zong et al. 2008). The effective transfer of photogenerated electrons from CB of CdS into CB of MoS₂ indicated that the introduction of MoS₂ inhibited recombination of photogenerated electrons and holes, which significantly improved the photocatalytic activity(Yin et al. 2016a, Zhang et al. 2014).

To further understand the charge separation, the photocurrent responses of CdS and 2.5 wt% MoS₂/CdS under several intermittent full-light irradiation was showed in Figure 2c. The transient photocurrent of all samples quickly reached a constant value under continuous illumination(Jiang et al. 2015), whereas the photocurrent reached to 0 after close of irradiation. Compared to CdS (4.76 µA/cm²), the high photocurrent density of 2.5 wt% MoS₂/CdS composite (31.13 µA/cm²) indicated the effective inhibit recombination of photogenerated electrons and holes due to the formation of heterostructure(Chen et al. 2015, He et al. 2016).

As shown by Nyquist diagram of EIS spectrum in Fig. 2d, the semicircle related to charge transfer resistance (R_ct) is connected in parallel with a sub-layer capacitor (CPE)(Li et al. 2019a, Yu et al. 2014). Compared to CdS, the small semicircle of 2.5 wt% MoS₂/CdS indicated the fast electron transfer due to the excellent conductivity of the introduced MoS_{2(Qin et al. 2017)}. The characterization results reflected that the MoS₂/CdS heterojunction improved the separation and transfer efficiency of photon-generated carriers (Xu &Cao 2015, Zhang et al. 2014).

3.2 Effect of different photocatalysts and pH

As shown in Fig. 3a, the no removal of U(VI) was observed in the absence of photocatalysts and light irradiation, which ruled out the possibility of self-photolysis of U(VI) (Wang et al. 2020). Under the dark conditions, the adsorption of U(VI) on photocatalysts slightly increased (from 11.3 to 16.7%) with increasing doping amount of MoS₂, indicating no obvious difference in the adsorption capacity of photocatalysts for U(VI)(Li et al. 2019c). For CdS, the low photocatalytic efficiency of CdS (i.e., ~ 0.6% after 20 min irradiation) was mainly due to the rapid recombination of photogenerated electrons and holes(Dai et al. 2021, Qiu et al. 2021, Zhang et al. 2020b). Within 15 min irradiation, the photocatalytic efficiency of 2.5 wt% MoS₂/CdS (97.51%) was remarkably higher than 10 wt% MoS₂/CdS (65%) due to the reduction of active sites by adding aggregated MoS_{2(Chen et al. 2019, Zhang et al. 2020a)}. Fig. 3b shows the effect of pH on the photoreduction efficiency of U(VI) on 2.5 wt% MoS₂/CdS. Almost no removal of U(VI) at pH 3.0 may be due to the competing of H⁺ and U(VI)(He et al. 2017, Zhang et al. 2020b). The highest removal rate of U(VI) (99.64%) was observed at pH 7.0 due to the fast transfer of generated charges of 2.5 wt% MoS₂/CdS under neutral conditions(Dai et al. 2021), which limited the recombination of photogenerated electrons and holes (Li et al. 2019d).

3.3 Effect of U(VI) concentration and dosage

Figure 3c and 3d show the effect of U(VI) concentrations (10, 20 and 30 ppm) and dosage (0.5, 1.0 and 2.0 mg/mL) on U(VI) photoreduction, respectively. Within 5 min irradiation, the highest removal of U(VI) at 20 ppm was consistent with the previous studies(Lei et al. 2021, Zhang et al. 2020b). Similarly, the highest removal efficiency of U(VI) was observed at 1.0 g/L under light irradiation. The further increase of U(VI) concentration and photocatalyst dosage leads to the decrease of U(VI) photoreduction due to the occurrence of shielding effect after exceeding the optimal concentration and dosage(Jiang et al. 2021, Zhang et al. 2021).

3.4 Regeneration and quenching experiments

Figure 4a and 4b show the regeneration and quenching experiments of U(VI) photoreduction on 2.5 wt% MoS₂/CdS, respectively. After 5 times of recycling, 2.5 wt% MoS₂/CdS still exhibited the high photocatalytic removal efficiency (>97%, Fig. 4a). In addition, no change in microstructure and crystal structure was observed after the photocatalytic reduction process (Fig. 1c and 1d). The regeneration results indicated that 2.5 wt% MoS₂/CdS had high photoreduction efficiency, good chemical stability and excellent reusability(Yu et al. 2014). The photoreduction mechanism of U(VI) on 2.5 wt% MoS₂/CdS composites was investigated by quenching experiments. TBA, p- BQ and Me were used as electron acceptors to remove ·OH, ·O₂⁻ and holes, respectively(Jiang et al. 2018, Wang et al. 2019). As shown in Fig. 4b, only 20% of U(VI) was photo-reduced after adding p-BQ into the reaction system, indicating the significant inhibition of photocatalytic activity. The little effect of TBA and Me on U(VI) photoreduction was observed. This experiment confirmed that ·O₂⁻ radicals were responsible for U(VI) photocatalytic reduction (Yuan et al. 2018).

In order to further clarify the reaction mechanism, an electron spin resonance spin trap experiment was performed, which can detect the generation of ·OH and ·O₂⁻ in the light experimental system(Zhang et al. 2021). As displayed in Fig. 4c and Figure S3, no peak and characteristic peaks of DMPO-·OH and DMPO-·O₂⁻ were observed under the dark and light condition, respectively, indicating that ·OH and ·O₂⁻ were generated at λ > 420 nm (Gong et al. 2021). Compared to DMPO-·OH, the intensities of DMPO-·O₂⁻ were significantly weak after adding U(VI), which can be deduced that dissolved oxygen acts as an electron shuttle between 2.5 wt% MoS₂/CdS(Le et al. 2020).

3.5 XPS analysis

XPS analysis was used to determine the photocatalytic reduction of U(VI) on CdS and 2.5 wt% MoS₂/CdS composite. Apart from Cd 3d and S 2p, the appearance of low Mo 3d peak showed the success synthesis of MoS₂/CdS composite (Fig. 5a). In addition, U 4f peak was also found for 2.5 wt% MoS₂/CdS composite after reaction. As shown in Fig. 5b, the two peaks of Mo 3d at 226.0 eV and 232.5 eV corresponded to Mo⁴⁺ 3d_5/2 and Mo⁴⁺ 3d_3/2, respectively(Alomar et al. 2019, Jin &Li 2020). After the reaction, Mo⁴⁺ 3d_5/2 was shifted by +0.2eV, while Mo⁴⁺ 3d_3/2 had no obvious shift. Similarly, S 2p spectra at 161.8 and 163.0 eV corresponded to S 2p_3/2 and S 2p_1/2, respectively (Fig. 5c). Compared to CdS, the increased binding energy and slight shift (0.1-0.2 eV) of S 2p in 2.5wt% MoS₂/CdS was due to addition of MoS_{2(Wu et al. 2017)}. The slight shift of Cd 3d (i.e., Cd 3d_5/2 from 405.2 to 405.4 eV, Cd 3d_3/2 from 411.9 to 412.1 eV, Fig. S4 of SI) was due to the change of Cd 3d orbit caused by the chemical bond(Yuan et al. 2018). For 2.5wt% MoS₂/CdS, the change in binding energy of Cd 3d and S 2p may be likely to accelerate the separation of excited charges of 2.5 wt% MoS₂/CdS under the light irradiation, improving the photocatalytic activity(Yu et al. 2021). U 4f peak at 381.62 and 392.50 eV were assigned to U 4f_7/2 and U 4f_5/2 of U(VI), respectively (Fig. 5d). U 4f_7/2 can be decomposed into two peaks of 380.1 and 381.6 eV, which were attributed to U(VI) and U(IV), respectively(Zhang et al. 2020a). The similarity of U 4f_5/2 peak was also observed, indicating photoreduction of adsorbed U(VI) into U(IV) by photogenerated electrons in a short time(Li et al. 2019d, Wang et al. 2019, Zhang et al. 2020b).

3.6 Mechanism analysis

Based on the above experimental results and band structure theory, the mechanism of catalytic reduction of U(VI) with 2.5 wt% MoS₂/CdS catalyst under all-light is roughly as follows(Chang et al. 2015):

MoS₂/CdS + hν→ e⁻ + h⁺ (1)

H₂O + h⁺ → ·OH+H⁺ (2)

CH₃OH + h⁺ +·OH→ CO₂+H₂O (3)

O₂ + e⁻→ O⁻₂ (4)

U(VI)+ ·O⁻₂ → U(IV) + 2O₂ (5)

The electrons (e⁻) in the valence band (VB) are excited under light irradiation when the light energy is greater than or equal to the band gap of MoS₂/CdS (hv ≥ Eg)(Gorshkov et al. 2006). Then photogenerated electrons were jumped into the conduction band (CB), an equal number of holes (h⁺) are generated in VB (Eqn. 1). The holes of VB and electrons of CB have certain oxidation and reduction ability, respectively(Yin et al. 2016b, Zong et al. 2010). h⁺ can react with water to form ·OH radicals (Eqn. 2), and/or h⁺ can oxidize organics into CO₂ and H₂O (Eqn. 3). The ·O⁻₂ radicals were generated by reaction of e⁻ and dissolved O₂ (Eqn. 4). Therefore, the adsorbed U(VI) by the active site of catalyst can be reduced to U(IV) by ·O⁻₂ (Eqn. 5)(Jiang et al. 2018). The generated O₂ was quickly captured by e⁻ again (Eqn. 4).

In summary, 2.5 wt% MoS2/CdS composite exhibited the high photocatalytic reduction of U(VI) (97.5% within 15 min) and fast reaction equilibrium (complete removal within 30 min) due to the narrow band gap, which can effectively inhibit the recombination of photogenerated electron-hole pairs. The high photocatalytic reduction of U(VI) (~97%) after 5 recycles revealed the chemical stability of MoS₂/CdS composite. XPS analysis indicated that adsorbed U(VI) were reduced to U(IV) by photogenerated electrons. These findings are crucial for the application of CdS-based composite towards the high efficient removal of U(VI) in actual environmental cleanup.

Ethical Approval: Not applicable
Consent to Participate: Not applicable.
Consent to Publish: Not applicable.
Competing Interests: The authors declare no competing interests.

Authors Contributions: Jingting Xiao: conceptualization, methodology, investigation, writing and revising original draft. Xinshui Huang: Methodology, editing. Peng Mei: Methodology, Analysis, Editing. Huihui Wang: methodology, Analysis and editing. Yubing Sun: Conceptualization, writing-review, revising, editing, supervision.
Funding The project was financially supported by Fundamental Research Funds of the Central Universities (No. 2021MS036).
Availability of data and materials: All data generated or analyzed during this study are included in this published article.

Alomar M, Liu Y, Chen W, Fida H (2019) : Controlling the growth of ultrathin MoS₂ nanosheets/CdS nanoparticles by two-step solvothermal synthesis for enhancing photocatalytic activities under visible light.Appl. Surf. Sci.480,1078–1088
Andrews MB, Cahill CL (2013) : Uranyl bearing hybrid materials: synthesis, speciation, and solid-state structures.Chem. Rev.113,1121–1136
Arunachalam VS, Fleischer EL (2008) : The global energy landscape and materials innovation.Mrs Bull. 33,264–288
Gu B, Liang L, Dickey MJ, Yin X, S (1998) : Reductive precipitation of uranium(VI) by zero-valent iron.Environ. Sci. Technol.32,3366–3373
Chai B, Xu M, Yan J, Ren Z (2018) : Remarkably enhanced photocatalytic hydrogen evolution over MoS₂ nanosheets loaded on uniform CdS nanospheres.Appl. Surf. Sci.430,523–530
Chang K, Li M, Wang T, Ouyang S, Li P, Liu L, Ye J (2015) : Drastic layer-number-dependent activity enhancement in photocatalytic H₂ Evolution over nMoS₂/CdS (n≥1) under visible light.Adv. Energy Mater.5,1–8
Chen G, Li D, Li F, Fan Y, Zhao H, Luo Y, Yu R, Meng Q (2012) : Ball-milling combined calcination synthesis of MoS₂/CdS photocatalysts for high photocatalytic H₂ evolution activity under visible light irradiation.Appl. Catal. A-Gen.443,138–144
Chen J, Wu X-J, Yin L, Li B, Hong X, Fan Z, Chen B, Xue C, Zhang H (2015) : One-pot synthesis of CdS nanocrystals hybridized with single-layer transition-metal dichalcogenide nanosheets for efficient photocatalytic hydrogen evolution.Angew. Chem. Int. Ed.54,1210–1214
Chen K, Chen C, Ren X, Alsaedi A, Hayat T (2019) : Interaction mechanism between different facet TiO₂ and U(VI): experimental and density-functional theory investigation.Chem. Eng. J.359,944–954
Chu S, Majumdar A (2012) : Opportunities and challenges for a sustainable energy future.Nature488,294–303
Dai Z, Zhen Y, Sun Y, Li L, Ding D (2021) : ZnFe₂O₄/g-C₃N₄ S-scheme photocatalyst with enhanced adsorption and photocatalytic activity for uranium(VI) removal.Chem. Eng. J.415,129–135
Di T, Zhu B, Zhang J, Cheng B, Yu J (2016) : Enhanced photocatalytic H₂ production on CdS nanorod using cobalt-phosphate as oxidation cocatalyst.Appl. Surf. Sci.389,775–782
Dolatyari L, Yaftian MR, Rostamnia S (2016) : Removal of uranium(VI) ions from aqueous solutions using Schiff base functionalized SBA-15 mesoporous silica materials.J. Environ. Manage.169,8–17
Gong J, Xie Z, Wang B, Li Z, Zhu Y, Xue J, Le Z (2021) : Fabrication of g-C₃N₄-based conjugated copolymers for efficient photocatalytic reduction of U(VI).J. Environ. Chem. Eng.9,104–111
Gorshkov N, Izosimov I, Kolichev S, Smirnov V, Firsin N (2006) : Isotope effect in the photoreduction of UO₂F₂ enriched with O-18 in isopropanol solution.J. Nucl. Sci. Technol.43,407–410
Graves C, Ebbesen SD, Mogensen M, Lackner KS (2011) : Sustainable hydrocarbon fuels by recycling CO₂ and H₂O with renewable or nuclear energy.Renew. Sust. Energ. Rev.15,1–23
Habibi MH, Rahmati MH (2014) : Fabrication and characterization of ZnO@CdS core–shell nanostructure using acetate precursors: XRD, FESEM, DRS, FTIR studies and effects of cadmium ion concentration on band gap.Spectrochim. Acta A: Mol. Biomol. Spectrosc.133,13–18
He J, Chen L, Wang F, Liu Y, Chen P, Au C-T, Yin S-F (2016) : CdS nanowires decorated with ultrathin MoS₂ nanosheets as an rfficient photocatalyst for hydrogen evolution.Chemsuschem9,624–630
He Z, Wang D, Tang J, Song S, Chen J, Tao X (2017) : A quasi-hexagonal prism-shaped carbon nitride for photoreduction of carbon dioxide under visible light.Environ. Sci. Pollut. Res.24,8219–8229
Jacobson MZ (2009) : Review of solutions to global warming, air pollution, and energy security.Energy Environ. Sci.2,148–173
Jacobson MZ, Delucchi MA (2011) : Providing all global energy with wind, water, and solar power, part I: Technologies, energy resources, quantities and areas of infrastructure, and materials.Energ. Policy39,1154–1169
Jiang P, Yu K, Yuan H, He R, Sun M, Tao F, Wang L, Zhu W (2021) : Encapsulating Ag nanoparticles into ZIF-8 as an efficient strategy to boost uranium photoreduction without sacrificial agents dagger.J. Mater. Chem. A9,9809–9814
Jiang W, Liu Y, Zong R, Li Z, Yao W, Zhu Y (2015) : Photocatalytic hydrogen generation on bifunctional ternary heterostructured In₂S₃/MoS₂/CdS composites with high activity and stability under visible light irradiation.J. Mater. Chem. A3,18406–18412
Jiang X-H, Xing Q-J, Luo X-B, Li F, Zou J-P, Liu S-S, Li X, Wang X-K (2018) : Simultaneous photoreduction of uranium(VI) and photooxidation of arsenic (III) in aqueous solution over g-C₃N₄/TiO₂ heterostructured catalysts under simulated sunlight irradiation.Appl. Catal. B-Environ.228,29–38
Jin X, Li G (2020) : Synthesis of MoS₂/CdS nanospheres enhanced photocatalytic hydrogen evolution under visible light.J. Mater. Sci. Mater. Electron.31,9377–9384
Khawula TNY, Raju K, Franklyn PJ, Sigalas I, Ozoemena KI (2016) : Symmetric pseudocapacitors based on molybdenum disulfide (MoS₂)-modified carbon nanospheres: correlating physicochemistry and synergistic interaction on energy storage.J. Mater. Chem. A4,6411–6425
Le Z, Xiong C, Gong J, Wu X, Pan T, Chen Z, Xie Z (2020) : Self-cleaning isotype g-C₃N₄ heterojunction for efficient photocatalytic reduction of hexavalent uranium under visible light.Environ. Pollut.260,456–459
Lei J, Liu H, Yuan C, Chen Q, Liu J-A, Wen F, Jiang X, Deng W, Cui X, Duan T, Zhu W, He R (2021) : Enhanced photoreduction of U(VI) on WO₃ nanosheets by oxygen defect engineering.Chem. Eng. J.416,129–125
Li LL, Yin XL, Pang DH, Du XX, Xue H, Zhou HW, Yao QX, Wang HW, Qian JC, Yang J, Li DC, Dou JM (2019a) : One-pot synthesis of MoS₂/CdS nanosphere heterostructures for efficient H₂ evolution under visible light irradiation.Int. J. Hydrog. Energy44,31930–31939
Li LL, Yin XL, Sun YQ (2019b) : Facile synthesized low-cost MoS₂/CdS nanodots-on-nanorods heterostructures for highly efficient pollution degradation under visible-light irradiation.Sep. Purif. Technol.212,135–141
Li P, Wang J, Peng T, Wang Y, Liang J, Pan D, Fan Q (2019c) : Heterostructure of anatase-rutile aggregates boosting the photoreduction of U(VI).Appl. Surf. Sci.483,670–676
Li P, Wang J, Wang Y, Liang J, He B, Pan D, Fan Q, Wang X (2019d) : Photoconversion of U(VI) by TiO₂: An efficient strategy for seawater uranium extraction.Chem. Eng. J.365,231–241
Li Y, Wang L, Li B, Zhang M, Wen R, Guo X, Li X, Zhang J, Li S, Ma L (2016) : Pore-free matrix with cooperative chelating of hyperbranched ligands for high-performance separation of uranium.ACS Appl. Mater. Inter.,28853–28861
Lin H, Li Y, Li H, Wang X (2017) : Multi-node CdS hetero-nanowires grown with defect-rich oxygen-doped MoS₂ ultrathin nanosheets for efficient visible-light photocatalytic H₂ evolution.Nano Res.10,1377–1392
Liu Y, Yu Y-X, Zhang W-D (2013) : MoS₂/CdS heterojunction with high photoelectrochemical activity for H₂ evolution under visible Light: the role of MoS₂.J. Phys. Chem. C117,12949–12957
Misra SK, Mahatele AK, Tripathi SC, Dakshinamoorthy A (2009) : Studies on the simultaneous removal of dissolved DBP and TBP as well as uranyl ions from aqueous solutions by using micellar-enhanced ultrafiltration technique.Hydrometallurgy96,47–51
Qin N, Xiong J, Liang R, Liu Y, Zhang S, Li Y, Li Z, Wu L (2017) : Highly efficient photocatalytic H₂ evolution over MoS₂/CdS-TiO₂ nanofibers prepared by an electrospinning mediated photodeposition method.Appl. Catal. B-Environ.202,374–380
Qiu M, Liu Z, Wang S, Hu B (2021) : The photocatalytic reduction of U(VI) into U(IV) by ZIF-8/g-C₃N₄ composites at visible light.Environ. Res.196,23–30
Sing K, Everett DH, Haul R, Moscou L, Siemieniewska T (1985) : Reporting physisorption data for gas/solid system, 57.Handbook of Heterogeneous Catalysis
Wang H, Guo H, Zhang N, Chen Z, Hu B, Wang X (2019) : Enhanced photoreduction of U(VI) on C₃N₄ by Cr(VI) and bisphenol A: ESR, XPS, and EXAFS investigation.Environ. Sci. Technol.53,6454–6461
Wang Z, Xu S-M, Tan L, Liu G, Shen T, Yu C, Wang H, Tao Y, Cao X, Zhao Y, Song Y-F (2020) : 600 nm-driven photoreduction of CO₂ through the topological transformation of layered double hydroxides nanosheets.Appl. Catal. B-Environ.270,118–126
Wu A, Tian C, Jiao Y, Yan Q, Yang G, Fu H (2017) : Sequential two-step hydrothermal growth of MoS₂/CdS core-shell heterojunctions for efficient visible light-driven photocatalytic H₂ evolution.Appl. Catal. B-Environ.203,955–963
Xie J, Zhang H, Li S, Wang R, Sun X, Zhou M, Zhou J, Lou XW, Xie Y (2013a) : Defect-Rich MoS₂ ultrathin nanosheets with additional active edge sites for enhanced electrocatalytic hydrogen evolution.Adv. Mater.25,5807–5813
Xie J, Zhang J, Li S, Grote F, Zhang X, Zhang H, Wang R, Lei Y, Pan B, Xie Y (2013b) : Controllable disorder engineering in oxygen-incorporated MoS₂ ultrathin nanosheets for efficient hydrogen evolution.J. Am. Chem. Soc.135,17881–17888
Xu J, Cao X (2015) : Characterization and mechanism of MoS₂/CdS composite photocatalyst used for hydrogen production from water splitting under visible light.Chem. Eng. J.260,642–648
Yan HJ, Yang JH, Ma GJ, Wu GP, Zong X, Lei ZB, Shi JY, Li C (2009) : Visible-light-driven hydrogen production with extremely high quantum efficiency on Pt-PdS/CdS photocatalyst.J. Catal.266,165–168
Yin X-L, He G-Y, Sun B, Jiang W-J, Xue D-J, Xia A-D, Wan L-J, Hu J-S (2016a) : Rational design and electron transfer kinetics of MoS₂/CdS nanodots-on-nanorods for efficient visible-light-driven hydrogen generation.Nano Energy28,319–329
Yin X-L, Li L-L, Jiang W-J, Zhang Y, Zhang X, Wan L-J, Hu J-S (2016b) : MoS₂/CdS nanosheets-on-nanorod heterostructure for highly efficient photocatalytic H₂ generation under visible light irradiation.ACS Appl. Mater. Inter.8,15258–15266
Yu J, Jin J, Cheng B, Jaroniec M (2014) : A noble metal-free reduced graphene oxide–CdS nanorod composite for the enhanced visible-light photocatalytic reduction of CO₂ to solar fuel.J. Mater. Chem. A2,3407–3416
Yu K, Jiang P, Yuan H, He R, Zhu W, Wang L (2021) : Cu-based nanocrystals on ZnO for uranium photoreduction: plasmon-assisted activity and entropy-driven stability.Appl. Catal. B-Environ.288,119–126
Yuan Y-J, Li Z, Wu S, Chen D, Yang L-X, Cao D, Tu W-G, Yu Z-T, Zou Z-G (2018) : Role of two-dimensional nanointerfaces in enhancing the photocatalytic performance of 2D-2D MoS₂/CdS photocatalysts for H₂ production.Chem. Eng. J.350,335–343
Zhang J, Zhu Z, Feng X (2014) : Construction of two-dimensional MoS₂/CdS p-n nanohybrids for highly efficient photocatalytic hydrogen evolution.Chem. Eur. J.20,10632–10635
Zhang X-H, Li N, Wu J, Zheng Y-Z, Tao X (2018) : Defect-rich O-incorporated 1T-MoS₂ nanosheets for remarkably enhanced visible-light photocatalytic H₂ evolution over CdS: The impact of enriched defects.Appl. Catal. B-Environ.229,227–236
Zhang Y, Zhu M, Zhang S, Cai Y, Lv Z, Fang M, Tan X, Wang X (2020a) : Highly efficient removal of U(VI) by the photoreduction of SnO₂/CdCO₃/CdS nanocomposite under visible light irradiation.Appl. Catal. B-Environ.279,119–126
Zhang Z, Dong Z, Wang X, Dai Y, Cao X, Wang Y, Hua R, Feng H, Chen J, Liu Y, Hu B, Wang X (2019) : Synthesis of ultralight phosphorylated carbon aerogel for efficient removal of U(VI): Batch and fixed-bed column studies.Chem. Eng. J.370,1376–1387
Zhang Z, Liu C, Dong Z, Dai Y, Xiong G, Liu Y, Wang Y, Wang Y, Liu Y (2020b) : Synthesis of flower-like MoS₂/g-C₃N₄ nanosheet heterojunctions with enhanced photocatalytic reduction activity of uranium(VI).Appl. Surf. Sci.520,45–52
Zhang Z, Zhou R, Dong Z, Wu Y, Xu L, Xie Y, Li Z, Xiong Y, Wang Y, Liu Y (2021) : Visible-light induced photocatalytic removal of U(VI) from aqueous solution by MoS₂/g-C₃N₄ nanocomposites.J. Radioanal. Nucl. Chem.328,9–17
Zong X, Yan H, Wu G, Ma G, Wen F, Wang L, Li C (2008) : Enhancement of photocatalytic H₂ evolution on CdS by loading MoS₂ as cocatalyst under visible light irradiation.J. Am. Chem. Soc.130,7176–7181
Zong X, Wu G, Yan H, Ma G, Shi J, Wen F, Wang L, Li C (2010) : Photocatalytic H₂ Evolution on MoS₂/CdS Catalysts under Visible Light Irradiation.J. Phys. Chem. C114,1963–1968

SI20210805.docx

Download PDF

Reviews received at journal
14 Jan, 2022
Reviewers invited by journal
13 Dec, 2021
Editor invited by journal
25 Nov, 2021
Editor assigned by journal
18 Nov, 2021
First submitted to journal
01 Nov, 2021

You are reading this latest preprint version

Boosting Photocatalytic Efficiency of MoS2/CdS By Modulating Morphology

Status:

Version 1

Abstract

Figures

1. Introduction

2. Experimental

2.1 Materials

2.2 Synthesis of MoS₂/CdS nanoparticles

2.3 Characterization

2.4 Photoreduction of U(VI)

3. Results And Discussion

3.1 Characterization

3.2 Effect of different photocatalysts and pH

3.3 Effect of U(VI) concentration and dosage

3.4 Regeneration and quenching experiments

3.5 XPS analysis

3.6 Mechanism analysis

4. Conclusions

Declarations

References

Supplementary Files

Status:

Version 1

Boosting Photocatalytic Efficiency of MoS2/CdS By Modulating Morphology

Status:

Version 1

Abstract

Figures

1. Introduction

2. Experimental

2.1 Materials

2.2 Synthesis of MoS2/CdS nanoparticles

2.3 Characterization

2.4 Photoreduction of U(VI)

3. Results And Discussion

3.1 Characterization

3.2 Effect of different photocatalysts and pH

3.3 Effect of U(VI) concentration and dosage

3.4 Regeneration and quenching experiments

3.5 XPS analysis

3.6 Mechanism analysis

4. Conclusions

Declarations

References

Supplementary Files

Status:

Version 1

2.2 Synthesis of MoS₂/CdS nanoparticles