Synthesis of cesium lead halide perovskite/zinc oxide (CsPbX3/ZnO, X= Br, I) as heterostructure photocatalyst with improved activity for heavy metal degradation

Inorganic perovskites have been recognized as highly potent materials for the display and medical industries due to their outstanding features. However, there haven’t been many reports on their implications as a photocatalyst for the removal of heavy metals. Photocatalysis has been regarded as a significant approach for the removal of pollutants because of its great sustainability, improved efficiency, and reduced energy consumption. Here, we applied inorganic cesium lead halides (Br and I) with zinc oxide heterostructure as a photocatalyst for the first time. The heterostructure has been synthesized by the traditional hot injection strategy and its photocatalytic activity was systematically investigated. Interestingly, the CsPbX₃/ZnO heterostructure as a photocatalyst has a homogeneous geometry and possesses an excellent degradation efficiency of over 50% under xenon UV-Visible light. The CsPbX₃/ZnO catalyst carries superior oxidation/reduction properties and ionic conductivity due to the synergistic photogenerated charge carrier and interaction between CsPbX₃ and ZnO. The recycling experiment showed the good stability of the catalysts. These findings suggest that inorganic lead halide heterostructure has the potential to be used for heavy metal degradation and water pollution removal catalysts.

1 Introduction

Lead tri-halide perovskites have been considered as a fascinating class of materials for next generation applications due to their remarkable characteristics, including enhanced optical features, high extinction constant, tunable bandgap, versatile surface chemistry, long-range electron-hole diffusion, and high carrier mobility (Akkerman et al., 2015; Gull et al., 2020). This class of materials possesses the general formula of ABX₃ where A is a cation (organic/inorganic), B is a divalent metal (Pb²⁺, Sn²⁺, Ge²⁺), and X is an anion (Cl^1-, Br^1-, I^1- or mixture) (Kulkarni et al., 2019; Yang et al., 2019). In recent years, semiconductor materials have been widely used as photocatalyst in the environmental and energy sectors due to their novel physiochemical features and cost-effectiveness (Batool et al., 2020; Shen et al., 2021b) Commonly used metal-based semiconducting photocatalysts include TiO₂ (Fujishima et al., 2000) (Zhang et al., 2021b), Fe₂O₃ (Hitam and Jalil, 2020), CdS (Cheng et al., 2018), MoS₂ (Shen et al., 2020), ZnS (Lee and Wu, 2017), and ZnO (Johar et al., 2015).

Zinc Oxide (ZnO) has a bandgap of 3.37 eV and can treat heavy metals due to its high photocatalytic efficiency and excitation binding energy-producing electron-hole pair (ehp) under UV or visible irradiation (Huang et al., 2015; Le et al., 2019). The electron and hole combine with the adsorbed oxygen (O^.) on the photocatalyst surface and water (H₂O) to generate O₂ and hydroxyl (OH), which help in the oxidation of organic products into end products (CO₂ and H₂O) (Senapati et al., 2012). Photocatalysis has been regarded as a significant approach for pollutant removal due to its high sustainability, improved efficiency, and low energy consumption (Shen et al., 2021a; Li et al., 2022b) The investigation of photocatalysts with remarkable features such as extraordinary sunlight absorption, significant generation, and separation of charge carriers with enhanced redox potential is quite useful for achieving efficient photocatalytic removal of pollutant (Idrees et al., 2016; Li et al., 2022c). Photocatalysts, a green technology that uses solar energy, have a significant impact on environmental restoration. Therefore, more time is required to investigate potential photocatalysts (Li et al., 2022a; Cai et al., 2022; Li et al., 2022d). In this aspect, lead tri-halide with unique properties could also be used in the photochemical conversion, if the issues of stability, inefficient photocatalytic activity, and rigorous ehp recombination rate could be optimized (Zhao et al., 2020). There have recently been a few reports on the use of inorganic lead tri-halide perovskites, their derivatives, and composites as photocatalysts. Among the cesium-based lead halides, it was observed that pristine bromide-based compounds with a wide-bandgap are difficult to photocatalyze; however, after different treatments such as making a heterostructure or changing the typical ligands are an optimal choice (Xu et al., 2017). Moreover, photoreduction of CO₂ and hydrogen evolution using a mixture of Br/Cl and Br/I has been reported (Guan et al., 2019). In comparison to these inorganic halides, cesium lead iodide (CsPbI₃) had a narrow bandgap of 1.73 eV, high emission intensity, and existed in two major phases known as alpha phase (α-CsPbI₃) and delta phase (δ-CsPbI₃) (Lai et al., 2017). Lin et al., recently reported the use of CsPbI₃ as a photocatalyst by making heterostructure with tungsten disulfide (WS₂), where they used γ-CsPbI₃ nanocrystals fabricated with several layered tungsten disulfides for the complete degradation of methylene blue (MB) into less toxic inorganic products with high photocatalytic degradation efficiency (Zhang et al., 2019). The coupling of inorganic perovskites with other compounds is considered as useful strategy for addressing the issues of instability, photocatalytic activity deficiency, and controlled ehp recombination. Ma et al. reported on the photocatalytic activity of graphitic carbon nitride (g-C₃N₄) combined with CsPbI₃ for photocatalytic degradation of the organic dye rhodamine B, and they also reported the use of Pt as a co-catalyst for hydrogen generation by water splitting (Liu and Ma, 2021). Up to now, there are no reports about the photocatalytic degradation of inorganic pollutants from water streams by the CsPbX₃/ZnO heterostructure.

Here, for the first time, we used CsPbX₃/ZnO heterostructure with ZnO as a photocatalyst to study the photocatalytic activity of CsPbX₃. (Zhang et al., 2021a). Although Xu et al., recently reported a CsPbX₃/ZnO heterostructure for light-emitting diodes. Wang et al., also used ZnO as a basis for transporting electrons to solar cells (Deng et al., 2020). To date, however, no reports have been found regarding the use of ZnO and CsPbX₃ for photocatalytic applications. This study is aimed at modifying CsPbI₃, and CsPbBr₃ using ZnO with the desired properties for the efficient photo degradation of heavy metals. We investigated the photocatalytic response in CsPbI₃, CsPbBr₃ forming heterostructures with ZnO and the results proved that δ-CsPbI₃/ZnO heterostructure is quite beneficial in the photo degradation of heavy metals under visible light with an efficiency of more than 50%, owing to its hexagonal structure.

2 Materials and method

2.1 Materials

Cesium carbonate (Cs₂CO₃, 99.99%) was bought from Macklin. Lead iodide (PbI₂, 99.99%), Lead bromide (PbBr₂, 99.99%), Octadecene (ODE, technical grade 90%), Oleic acid (OA, technical grade 90%), oleylamine (OAm, technical grade 70%), Zinc Stearate (ZnSt₂, 98%), Toluene (98%) and Hexane (99.9%) were purchased from Sigma Aldrich and used as it is received without any further modification.

2.2 Photocatalysts synthesis

2.2.1 Formation of cesium and lead halide precursors by hot injection method

Protesescu’s hot injection strategy was used for the synthesis of CsPbX₃/ZnO heterostructure, with minor modifications (Protesescu et al., 2015). The stepwise schematic presentation is shown in Figure 1. Firstly, 0.6 g of cesium carbonate (Cs₂CO₃), 2 ml OA, and 20 ml ODE were added to a 50 ml 3-neck round bottom flask and stirred continuously under vacuum for 30 min at 125°C, absolving the flask with nitrogen (N₂) for 10 min, it was placed back under vacuum. An alternative implication of vacuum and N₂ to completely remove moisture and oxygen has been applied as shown in Figure 1A. The PbI₂/Br₂ precursors were then synthesized by degassing 0.8 g of PbI₂ and 0.6 g of PbBr₂ in 20 ml ODE for 1 h under constant stirring and heating at 125°C in a 50 ml flask. The flask was then filled with a 1:1 mixture of OA and OAm (4 ml each, pre-heated at ∼70°C) and vacuumed again for 15–30 min, until the salt of lead halides was completely dissolved and the solution was no longer releasing gas (15–30 min), as shown in Figure 1B.

FIGURE 1

FIGURE 1. Schematic representation for the synthesis of the CsPbI₃/ZnO heterostructure (A) Cesium precursor (B) Lead precursor (C) formation of Cesium Lead Iodide (D) formation of Cesium Lead Iodide/Zinc Oxide heterostructure.

2.3 Formation of cesium lead halide/zinc oxide heterostructure

For the formation of cesium lead halides, the temperature of the lead halide precursor was raised to 150°C, and 4 ml cesium precursor was injected swiftly under a nitrogen environment, as shown in Figure 1C. Later, for the photocatalytic activity investigation of as synthesized CsPbX₃ with Zinc oxide, 0.4 mg ml⁻¹ zinc stearate in ODE was injected into the above mixture as a zinc source for the formation of CsPbX₃/ZnO heterostructure as shown in Figure 1D, aliquotes were taken at different times, and the reaction was quenched by dipping the flask into the ice bath. Finally, the solution was centrifuged for 3 min at 10,000 rpm, the supernatant was discarded, and precipitates were dispersed in toluene/hexane for further investigation.

2.4 Characterization techniques

X-ray diffraction patterns (XRD) spectra was collected X-ray diffractometer (Bruker D8 advance, Germany) with Cu K_α radiation (k = 1.54 nm) in the range of 2θ = 20°–70°. The valence properties of all existing elements in CsPbX₃/ZnO NPs were determined by employing X-ray photoelectron (XPS: ESCALAB 250Xi-system) Ultraviolet-visible (UV-visible) spectra were investigated by a Lambda 950 spectrophotometer in the wavelength range of 300–800 nm. Fourier Transform Infrared (FTIR) has been carried out by Shimadzu-8400S infrared spectrometer. The morphology of the material was investigated by transmission electron microscope (JEOL JSM-7800F) and energy-dispersive spectra (EDS) was obtained by using an integrated Oxford INCA X-ACT equipped with SEM. On a multi-channel battery system (LANHE-CT2001A), the electrocatalytic activity of prototype coin cells was studied in a voltage range of 0.1–3.0 V at a constant current density.

2.5 Photocatalytic activity measuring experiment

The photocatalytic activity of CsPbX₃/ZnO heterostrucutre as a photocatalyst was irradiated to a 300W xenon lamp in ambient conditions. For which ZnO (0.4 mgmL⁻¹ ZnSt₂ in ODE) was injected to CsPbX₃ solution, under constant magnetic stirring and heating to achieve equilibrium. For the photocatalytic inquiry, two different temperatures have been used i.e., 100°C and 160°C. After injecting zinc precursor into the halide perovskites, samples were prepared using 15 µL (CsPbX₃/ZnO) in 1 ml hexane at different time intervals starting from 2 min till 30min. Photocatalytic activity under UV-visible spectrophotometer in the wavelength range of 300–800 nm has been observed. To explore the photocatalytic activity of ZnO as a photocatalyst, the absorbance spectra of halide perovskites with and without zinc oxide were compared.

Degradation efficiency (%) has been calculated by using Eq. 1.

$\mathrm{D}\mathrm{e}\mathrm{g}\mathrm{r}\mathrm{a}\mathrm{d}\mathrm{a}\mathrm{t}\mathrm{i}\mathrm{o}\mathrm{n}\left(\%\right)=\left[\left({\mathrm{C}}_{\mathrm{o}}-{\mathrm{C}}_{\mathrm{t}}\right)/{\mathrm{C}}_{\mathrm{o}}\right]\ast 100,(1)$

where C_o is degradation concentration without ZnO and C_t degradation concentration with ZnO at different intervals in the above relation (Huang et al., 2015; Sajid et al., 2020).

3 Results and discussions

3.1 Characterization of CsPbX₃/ZnO heterostructure

Studies have shown that inorganic cesium lead halide perovskite is considered as a hot area for scientists and researchers due to its outstanding performance in different applications. Different reports highlight its usage as photocatalysts for CO₂ reduction (Wang et al., 2019), hydrogen evolution (Zhao et al., 2021) and degradation of different pollutants from the environment and industry (Zhao et al., 2020; Li et al., 2023). To investigate the as-synthesized system of CsPbX₃/ZnO heterostructure, different investigations have been carried out. Figure 2A is the XRD pattern of the CsPbI₃/ZnO heterostructure. The XRD pattern confirmed the presence of both CsPbI₃ and ZnO, which are highlighted with different symbols. All of the characteristic peaks correspond to JCPDS card number. 18–0376 and 36–1,451, which represent the delta and wurtzite phases, respectively. The diffraction peaks located at 21.6°, 22.7°,31.3°, and 39.3° indicate the presence of CsPbI₃ (highlighted with #), whereas the peaks at 31.8°,34.4°, 36.2°, 47.5°, 56.5°, 62.8°, 66.3°, and 67.9° correspond to the ZnO (represented with *) (Zhang et al., 2007). Figures 2B,C show the morphology of CsPbI₃ and CsPbI₃/ZnO heterostructures having the hexagonal geometry of CsPbI₃ with an average particle size of 28.3 nm that has been enlarged to 34.5 nm after the addition of photocatalyst ZnO, proving the inclusion of ZnO with the retention of the same hexagonal morphology. The dots on the surface of Figure 2C justifying the formation of the CsPbI₃/ZnO heterostructure.

FIGURE 2

FIGURE 2. (A) X-ray diffraction (XRD) pattern of CsPbI₃/ZnO heterostructure, (B,C) TEM images of CsPbI₃ and CsPbI₃/ZnO heterostructure. (D) The general XPS spectrum and (E–H) HR-XPS spectrum of CsPbI₃/ZnO heterostructure. (I) FTIR spectra of CsPbI₃/ZnO heterostructure.

XPS analysis was conducted to investigate the chemical states of elements presented in the as-synthesized CsPbI₃/ZnO heterostructure (Figure 2D). The general XPS survey spectrum proves the existence of Cs, Pb, I, Zn, and O, confirming the formation of CsPbI₃/ZnO. Figures 2E–H presents the HR-XPS deconvoluted peaks of all existing elements.

The HR-XPS Cs spectrum deconvoluted into peaks at 723.86 and 737.83 eV, ascribed to the Cs3d of Cs3d_5/2 and Cs3d_3/2, respectively (Figure 2E). The peaks at 137.96 and 142.80 eV in the core level spectrum of Pb4f are attributed to Pb4f_7/2 and Pb4f_5/2, respectively (Figure 2F). Similarly, the core-level I3d spectrum position at 618.61 eV indicated the presence of I3d_5/2 and 630 eV I3d_3/2 (Figure 2G), while the peaks at 1,021.9 and 1,044.94 eV were attributed to the formation of Zn2p_3/2 and Zn2p_1/2 (Zn-O), respectively (Figure 2H) (Lu et al., 2018; Pirhashemi et al., 2019).

The surface functionality of the materials was recorded by FTIR spectrum in the range of 650–3,500 cm⁻¹. Figure 2I shows the FTIR spectra of the CsPbI₃/ZnO heterostructure in which the peak at 716 cm⁻¹ shows the bonding between Zn-O, whereas the rest of the peaks show the presence of different ligands used for the formation of heterostructure. Generally, the peak at 1,153 cm⁻¹ represents C-N, 1,473 cm⁻¹ shows -CH₂, 1,641 cm⁻¹ to N-H, and 2,913 and 2,955 cm⁻¹ correspond to the presence of C-H attributed due to the aliphatic chains of octadecyl, oleylamine and oleic acid (An et al., 2018) (Nipane et al., 2013). EDS was used to investigate the elemental percentages in the synthesized compound, as shown in Figure 3.

FIGURE 3

FIGURE 3. EDS spectra of CsPbI₃/ZnO heterostructure and its corresponding elements’ EDS mapping.

The EDS spectrum confirms the existence and equal distribution of all the elements in the synthesized compound, and their atomic percentage is listed in Table 1.

TABLE 1

TABLE 1. Elemental percentage of as-synthesized CsPbI₃/ZnO heterostructure.

3.2 Photocatalytic activity of CsPbX₃/ZnO heterostructure

The basic photocatalytic mechanism starts with the generation of electrons and holes generated as a result of light irradiation with a wavelength greater than or equal to their bandgap; photo-induced electrons move from the valence band (VB) to the conduction band (CB), and corresponding holes move to the valence band. Hence, a redox reaction was carried out using these isolated electron-hole pairs (Ren et al., 2022). The as-synthesized product was optically characterized using UV-visible spectroscopy to analyze the behavior of inorganic halide perovskites with ZnO as a photocatalyst. The designed composite heterostructure is made up of interfaces made of various materials that are tightly bonded and have indistinguishable interface junctions (Zhao et al., 2018). The benefit of using zinc is that it has the capability to replace lead during the formation of heterostructure, indicating the potential to be used as a heavy metal degradation and water pollution removal catalyst (Kar et al., 2022).

The UV-visible absorption spectra of two different inorganic lead halide perovskite (CsPbI₃ and CsPbBr₃) with ZnO as a photocatalyst for two temperatures, low (100°C) and high (160°C), with activity times ranging from 2 to 30 min, as shown in Figures 4A–D. Figures 4A,B shows that CsPbI₃ possesses the highest photocatalytic activity, whereas Figures 4C,D represents that CsPbBr₃ has no effect on ZnO even at elevated temperatures. It was observed that pristine CsPbBr₃ has negligible photocatalytic activity due to obvious surface defects that introduce shallow transition levels and act as charge recombination sites, and also the material’s wider bandgap, which limits its use as a photocatalytic material. In comparison to CsPbBr₃, CsPbI₃ has a narrow bandgap of 1.73 eV and higher emission intensity, exhibiting the potential for excessive photo-generated ehp for photocatalysis (Tang et al., 2019; Zhang et al., 2019; Wang et al., 2021). ZnO’s good electron mobility, high absorption tendency, and cost-effectiveness make it an ideal photocatalyst. Coupling ZnO with halide perovskites enhances the generation of ehp by reducing the formation energy of the perovskites (Senapati et al., 2012; Jiang et al., 2019; Deng et al., 2020). Figures 4A,B show an absorbance peak from 370–385 nm due to zinc adsorption, confirming the presence of ZnO (Das et al., 2020; Karami et al., 2020), whereas, in Figures 4C,D show no change in the spectra, indicating that there is no zinc adsorption. Figures 5A,B depicts the obvious zinc adsorption in the CsPbI₃/ZnO heterostructure by depicting the obvious absorbance peaks from 370–385 nm at both temperatures as compared to controlled samples of CsPbI₃ and ZnO (Figure 5E), while Figures 5C,D represent no discernible change in the spectra. So, here we calculated the degradation efficiency with time in synthesized samples of CsPbI₃/ZnO heterostructure at high temperature yielding a degradation efficiency of 52% by using Eq. 1 shown in Figure 4E.

FIGURE 4

FIGURE 4. UV-visible absorbance spectra of CsPbI₃ and CsPbI₃/ZnO as a function of time at (A) 100°C and (B) 160°C. CsPbBr₃ and CsPbBr₃/ZnO at (C) 100°C and (D) 160°C. (E) Degradation efficiency with time for CsPbI₃/ZnO heterostructure.

FIGURE 5

FIGURE 5. Absorbance spectra of inorganic CsPbI₃ and CsPbI₃/ZnO heterostructures at (A) 100°C and (B) 160 C. Absorbance spectra of inorganic CsPbBr₃ and CsPbBr₃/ZnO heterostructures at (C) 100 C and (D) 160 C. (E) Absorbance spectra for the controlled samples of CsPbI₃ and ZnO. Inset shows the close view.

The cycling stability of a photocatalyst is important for practical usage. Therefore, recycling experiments are carried out for CsPbI₃/ZnO. The results are shown in Figure 5C suggested that the catalyst’s performance is negligible after four continuous cycles of photocatalyst reutilization. This study confirms that CsPbI₃/ZnO is highly stable to heavy metal phtodegradation. The post-xps analysis indicted that the peaks for all the core elements are greatly reduced with decreasing intensity, confirming the photodegradation of heavy metals (d).

3.3 Cyclic voltammograms and AC impedance analysis of the CsPbI₃/ZnO heterostructure

The electrochemical performance of CsPbI₃/ZnO was assessed to confirm its potential as a photocatalyst. In Figure 6E, the oxidative and reductive properties of the CsPbI₃/ZnO heterostructure were investigated using the characteristic cyclic voltammogram test at a scanning rate of 0.1 mV s⁻¹. The CV curve for the first cycle presented characteristic discharge peaks at 0.82 and 1.41 V, which are the reduction peaks that confirm the successful reaction of CsPbI₃/ZnO heterostructure. Moreover, cathodic peaks confirm electrolyte decomposition and the formation of an SEI passivation layer on the surface of anode material during discharge. Two oxidative peaks were observed in the anodic sweep at 1.25 V, corresponding to a gradual Zn⁺ withdrawal process in CsPbI₃/ZnO. The CV test confirms the oxidation and reduction potentials of CsPbI₃/ZnO heterostructure. The electrochemical impedance spectra with a wide-range of frequency as shown in Figure 6F. The Nyquist curve consists of a semicircle and an oblique line from high to medium-frequency and high to low-frequency regions, respectively. The semicircle in the high-frequency region defined the extent of resistance to electron transfer, confirming the negligible ion transformation and bulk polarization, while the straight line represents the high electrical conductivity of the CsPbI₃/ZnO catalyst. The result showed that the CsPbI₃/ZnO catalyst had high electrical conductivity and was conductive to zinc ion diffusion.

FIGURE 6

FIGURE 6. Adsorption of (A) CsPbI₃/ZnO and CsPbI₃, and (B) CsPbBr₃/ZnO and CsPbBr₃ heterostructure. (C) Cyclic stability of CsPbI₃/ZnO under UV light. (D) Post-XPS analysis of CsPbI₃/ZnO (E) Cyclic voltammograms of CsPbI₃/ZnO at a scanning rate of 0.1 mV s⁻¹ and (F) Nyquist plot at room temperature for CsPbI₃/ZnO heterostructure.

3.4 Photocatalytic mechanism

Figure 7 depicts the photocatalytic mechanism of CsPbX₃/ZnO heterostructure. Generally, the photocatalytic process initiates with the generation of electron hole pairs (ehp) in the presence of light with an energy greater than or equal to the bandgap (Wang et al., 2022). The electrons from the valence band (VB) are excited towards the conduction band (CB) of perovskites, thereby generating photo-active species including e⁻ and h⁺. Such photogenerated e⁻ would either combine with the h⁺ or be arbitrarily shifted to the surface of the photocatalysts, further trapped by O₂ to generate O₂^.-.for the further generation of . OH (Wei et al., 2021). The formation of heterostructure has been regarded as an effective strategy for the retardation of the e/h recombination by keeping the utmost redox potential of a photocatalyst (Shen et al., 2022). Particularly, in this case of perovskite heterostructure, the generation of ehp occurs on the surface of CsPbX₃ when an electron (eˉ) in the CsPbX₃/ZnO shifts (excites) from the valence band (VB, HOMO) to the conduction band (CB, LUMO) and leaves holes (h⁺) in the HOMO region, known as the generation of ehp. In the CsPbX₃ perovskite, these as-produced ehp react with H₂O and O₂, generating excessive hydroxyl radicals (^.OH) and oxygen molecules (O₂⁻) (Zhang et al., 2019). After the introduction of ZnO, holes can be shifted from the halide perovskite to the surface of ZnO, generating (^.OH). The overall mechanism can be summarized as follows:

$\mathrm{C}\mathrm{s}\mathrm{P}\mathrm{b}{\mathrm{X}}_3+\mathrm{h}\to {\mathrm{e}}^{-}+{\mathrm{h}}^{+},(2)$

${\mathrm{O}}_2+{\mathrm{e}}^{-}\to .{\mathrm{O}}_2^{-},(3)$

${\mathrm{H}}_2\mathrm{O}+{\mathrm{h}}^{+}\to .\mathrm{O}\mathrm{H}+{\mathrm{H}}^{+},(4)$

$\mathrm{Z}\mathrm{n}\mathrm{O}+{\mathrm{H}}^{+}\to {\mathrm{Z}\mathrm{n}}^{+}+·\mathrm{O}\mathrm{H}(5)$

FIGURE 7

FIGURE 7. Schematic representation of the photocatalytic mechanism of CsPbX₃/ZnO heterostructure.

Thus, the produced radicals help in the reduction of heavy metals into environment-friendly end products like CO₂ and H₂O (Das et al., 2020; Khan and Pathak, 2020). Hence, these synthesized CsPbX₃/ZnO heterostructures are quite useful in removing heavy metals and toxic products from the environment, soil, and different industry.

4 Conclusion

In conclusion, we have successfully synthesized the CsPbX₃/ZnO heterostructure with zinc oxide as a photocatalyst using a standard hot injection method. The as-synthesized material was characterized by using different structural characterizations to confirm the successful formation and its morphological structure. The CsPbI₃/ZnO heterostructure exhibits a degradation efficiency of 52%, which is higher than the degradation efficiency of CsPbI₃ with various other dyes. The CV and EIS analysis show high oxidation and reduction characteristics, as well as superior resistance to electron transfer, confirming the electrical conductivity. Thus, this synthesized heterostructure has the potential to be used for heavy metal degradation as well as a water cleaning catalyst.

Data availability statement

The original contributions presented in the study are included in the article/Supplementary Material, further inquiries can be directed to the corresponding author.

Author contributions

SG: Conception and design of the study, drafting of the manuscript, Acquisition of data SB: Conception and design of study, Review and edit manuscript GL: Review and editing, Supervision. MI: Review and edit manuscript.

Acknowledgments

The authors would like to acknowledge the postdoctoral research fellowship program of Shenzhen University and appreciate the technical support at the University for assistance in using the equipment.

Conflict of interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Publisher’s note

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.

References

Akkerman, Q. A., D’innocenzo, V., Accornero, S., Scarpellini, A., Petrozza, A., Prato, M., et al. (2015). Tuning the optical properties of cesium lead halide perovskite, 137, 10276–10281.Nanocrystals by anion exchange reactionsJ. Am. Chem. Soc,

CrossRef Full Text | Google Scholar

An, R., Zhang, F., Zou, X., Tang, Y., Liang, M., Oshchapovskyy, I., et al. (2018). Photostability and photodegradation processes in colloidal CsPbI₃ perovskite quantum dots. ACS Appl. Mat. Interfaces 10, 39222–39227. doi:10.1021/acsami.8b14480

PubMed Abstract | CrossRef Full Text | Google Scholar

Batool, S., Idrees, M., Javed, M. S., Saleem, M., and Kong, J. (2020). Engaging tailored capacity of layered WS₂ via sulphur bonding coupled with polyetherimide (WS₂@NC) nanocomposite for high power and improved lithium-ion storage. Mater. Chem. Phys. 246, 122832. doi:10.1016/j.matchemphys.2020.122832

CrossRef Full Text | Google Scholar

Cai, M., Wang, C., Liu, Y., Yan, R., and Li, S. (2022). Boosted photocatalytic antibiotic degradation performance of Cd_{0. 5}Zn_{0. 5}S/carbon dots/Bi₂WO₆ S-scheme heterojunction with carbon dots as the electron bridge. Sep. Purif. Technol. 300, 121892. doi:10.1016/j.seppur.2022.121892

CrossRef Full Text | Google Scholar

Cheng, L., Xiang, Q., Liao, Y., and Zhang, H. (2018). CdS-based photocatalysts. Energy Environ. Sci. 11, 1362–1391. doi:10.1039/c7ee03640j

CrossRef Full Text | Google Scholar

Das, S., Paul, T., Maiti, S., and Chattopadhyay, K. K. (2020). Ambient processed CsPbX₃ perovskite cubes for photocatalysis. Mater. Lett. 267, 127501. doi:10.1016/j.matlet.2020.127501

CrossRef Full Text | Google Scholar

Deng, W., Li, J., Jin, J., Mishra, D. D., Xin, J., Lin, L., et al. (2020). Fast and low temperature processed CsPbI₃ perovskite solar cells with ZnO as electron transport layer. J. Power Sources 480, 229134. doi:10.1016/j.jpowsour.2020.229134

CrossRef Full Text | Google Scholar

Fujishima, A., Rao, T. N., and Tryk, D. A. (2000). Titanium dioxide photocatalysis. J. Photochem. Photobiol. C Photochem. Rev. 1, 1–21. doi:10.1016/s1389-5567(00)00002-2

CrossRef Full Text | Google Scholar

Guan, Z., Wu, Y., Wang, P., Zhang, Q., Wang, Z., Zheng, Z., et al. (2019). Perovskite photocatalyst CsPbBr_3-xI_x with a bandgap funnel structure for H₂ evolution under visible light. Appl. Catal. B Environ. 245, 522–527. doi:10.1016/j.apcatb.2019.01.019

CrossRef Full Text | Google Scholar

Gull, S., Yang, Z., Wu, W., Rao, Q., Zhang, J., and Li, W. (2020). Multi-phased cesium lead iodide quantum dots with large Stokes shift. Mater. Lett. 271, 127765. doi:10.1016/j.matlet.2020.127765

CrossRef Full Text | Google Scholar

Hitam, C., and Jalil, A. (2020). A review on exploration of Fe₂O₃ photocatalyst towards degradation of dyes and organic contaminants. J. Environ. Manag. 258, 110050. doi:10.1016/j.jenvman.2019.110050

PubMed Abstract | CrossRef Full Text | Google Scholar

Huang, N., Shu, J., Wang, Z., Chen, M., Ren, C., and Zhang, W. (2015). One-step pyrolytic synthesis of ZnO nanorods with enhanced photocatalytic activity and high photostability under visible light and UV light irradiation. J. Alloys Compd. 648, 919–929. doi:10.1016/j.jallcom.2015.07.039

CrossRef Full Text | Google Scholar

Idrees, M., Batool, S., Hussain, Q., Ullah, H., Al-Wabel, M. I., Ahmad, M., et al. (2016). High-efficiency remediation of cadmium (Cd²⁺) from aqueous solution using poultry manure-and farmyard manure-derived biochars. Sep. Sci. Technol. 51, 2307–2317. doi:10.1080/01496395.2016.1205093

CrossRef Full Text | Google Scholar

Jiang, Y., Liao, J.-F., Xu, Y.-F., Chen, H.-Y., Wang, X.-D., and Kuang, D.-B. (2019). Hierarchical CsPbBr₃ nanocrystal-decorated ZnO nanowire/macroporous graphene hybrids for enhancing charge separation and photocatalytic CO₂ reduction. J. Mat. Chem. A Mat. 7, 13762–13769. doi:10.1039/c9ta03478a

CrossRef Full Text | Google Scholar

Johar, M. A., Afzal, R. A., Alazba, A. A., and Manzoor, U. (2015). Photocatalysis and bandgap engineering using ZnO nanocomposites. Adv. Mater. Sci. Eng., 1–22. 2015, doi:10.1155/2015/934587

CrossRef Full Text | Google Scholar

Kar, M., Chakraborty, R., Patel, U., Ray, S., Acharya, T., Goswami, C., et al. (2022). Impact of Zn-doping on the composition, stability, luminescence properties of silica coated all-inorganic cesium lead bromide nanocrystals and their biocompatibility. Mater. Today Chem. 23, 100753. doi:10.1016/j.mtchem.2021.100753

CrossRef Full Text | Google Scholar

Karami, M., Ghanbari, M., Amiri, O., and Salavati-Niasari, M. (2020). Enhanced antibacterial activity and photocatalytic degradation of organic dyes under visible light using cesium lead iodide perovskite nanostructures prepared by hydrothermal method. Sep. Purif. Technol. 253, 117526. doi:10.1016/j.seppur.2020.117526

CrossRef Full Text | Google Scholar

Khan, S. H., and Pathak, B. (2020). Zinc oxide based photocatalytic degradation of persistent pesticides: A comprehensive review. Environ. Nanotechnol. Monit. Manag. 13, 100290. doi:10.1016/j.enmm.2020.100290

CrossRef Full Text | Google Scholar

Kulkarni, S. A., Mhaisalkar, S. G., Mathews, N., and Boix, P. P. (2019). Perovskite nanoparticles: Synthesis, properties, and novel applications in photovoltaics and LEDs. Small Methods 3, 1800231. doi:10.1002/smtd.201800231

CrossRef Full Text | Google Scholar

Lai, M., Kong, Q., Bischak, C. G., Yu, Y., Dou, L., Eaton, S. W., et al. (2017). Structural, optical, and electrical properties of phase-controlled cesium lead iodide nanowires. Nano Res. 10, 1107–1114. doi:10.1007/s12274-016-1415-0

CrossRef Full Text | Google Scholar

Le, A. T., Pung, S.-Y., Sreekantan, S., Matsuda, A., and Huynh, D. P. (2019). Mechanisms of removal of heavy metal ions by ZnO particles. Heliyon 5, e01440. doi:10.1016/j.heliyon.2019.e01440

PubMed Abstract | CrossRef Full Text | Google Scholar

Lee, G.-J., and Wu, J. J. (2017). Recent developments in ZnS photocatalysts from synthesis to photocatalytic applications—a review. Powder Technol. 318, 8–22. doi:10.1016/j.powtec.2017.05.022

CrossRef Full Text | Google Scholar

Li, S., Cai, M., Liu, Y., Zhang, J., Wang, C., Zang, S., et al. (2022a). In situ construction of a C₃N₅ nanosheet/Bi₂WO₆ nanodot S-scheme heterojunction with enhanced structural defects for the efficient photocatalytic removal of tetracycline and Cr(vi). Inorg. Chem. Front. 9, 2479–2497. doi:10.1039/d2qi00317a

CrossRef Full Text | Google Scholar

Li, S., Cai, M., Wang, C., Liu, Y., Li, N., Zhang, P., et al. (2022b). Rationally designed Ta₃N₅/BiOCl S-scheme heterojunction with oxygen vacancies for elimination of tetracycline antibiotic and Cr(VI): Performance, toxicity evaluation and mechanism insight. J. Mater. Sci. Technol. 123, 177–190. doi:10.1016/j.jmst.2022.02.012

CrossRef Full Text | Google Scholar

Li, S., Wang, C., Cai, M., Liu, Y., Dong, K., and Zhang, J. (2022c). Designing oxygen vacancy mediated bismuth molybdate (Bi₂MoO₆)/N-rich carbon nitride (C₃N₅) S-scheme heterojunctions for boosted photocatalytic removal of tetracycline antibiotic and Cr(VI): Intermediate toxicity and mechanism insight. J. Colloid Interface Sci. 624, 219–232. doi:10.1016/j.jcis.2022.05.151

CrossRef Full Text | Google Scholar

Li, S., Wang, C., Cai, M., Yang, F., Liu, Y., Chen, J., et al. (2022d). Facile fabrication of TaON/Bi₂MoO₆ core-shell S-scheme heterojunction nanofibers for boosting visible-light catalytic levofloxacin degradation and Cr(VI) reduction. Chem. Eng. J. 428, 131158. doi:10.1016/j.cej.2021.131158

CrossRef Full Text | Google Scholar

Li, S., Cai, M., Liu, Y., Wang, C., Yan, R., and Chen, X. (2023). Constructing Cd_{0. 5}Zn_{0. 5}S/Bi2WO₆ S-scheme heterojunction for boosted photocatalytic antibiotic oxidation and Cr(VI) reduction. Adv. Powder Mater. 2, 100073. doi:10.1016/j.apmate.2022.100073

CrossRef Full Text | Google Scholar

Liu, Y., and Ma, Z. (2021). Combining g-C3N4 with CsPbI3 for efficient photocatalysis under visible light. Colloids Surfaces A Physicochem. Eng. Aspects 628, 127310. doi:10.1016/j.colsurfa.2021.127310

CrossRef Full Text | Google Scholar

Lu, C., Li, H., Kolodziejski, K., Dun, C., Huang, W., Carroll, D., et al. (2018). Enhanced stabilization of inorganic cesium lead triiodide (CsPbI₃) perovskite quantum dots with tri-octylphosphine. Nano Res. 11, 762–768. doi:10.1007/s12274-017-1685-1

CrossRef Full Text | Google Scholar

Nipane, D., Thakare, S., and Khati, N. (2013). Synthesis of novel ZnO having cauliflower morphology for photocatalytic degradation study. J. Catal., 1–8. 2013, doi:10.1155/2013/940345

CrossRef Full Text | Google Scholar

Pirhashemi, M., Elhag, S., Adam, R. E., Habibi-Yangjeh, A., Liu, X., Willander, M., et al. (2019). n–n ZnO–Ag₂CrO₄ heterojunction photoelectrodes with enhanced visible-light photoelectrochemical properties. RSC Adv. 9, 7992–8001. doi:10.1039/c9ra00639g

PubMed Abstract | CrossRef Full Text | Google Scholar

Protesescu, L., Yakunin, S., Bodnarchuk, M. I., Krieg, F., Caputo, R., Hendon, C. H., et al. (2015). Nanocrystals of cesium lead halide perovskites (CsPbX₃, X= Cl, Br, and I): Novel optoelectronic materials showing bright emission with wide color gamut. Nano Lett. 15, 3692–3696. doi:10.1021/nl5048779

PubMed Abstract | CrossRef Full Text | Google Scholar

Ren, K., Yue, S., Li, C., Fang, Z., Gasem, K. A., Leszczynski, J., et al. (2022). Metal halide perovskites for photocatalysis applications. J. Mat. Chem. A Mat. 10, 407–429. doi:10.1039/d1ta09148d

CrossRef Full Text | Google Scholar

Sajid, M. M., Shad, N. A., Javed, Y., Khan, S. B., Zhang, Z., Amin, N., et al. (2020). Preparation and characterization of Vanadium pentoxide (V₂O₅) for photocatalytic degradation of monoazo and diazo dyes. Surfaces Interfaces 19, 100502. doi:10.1016/j.surfin.2020.100502

CrossRef Full Text | Google Scholar

Senapati, S., Srivastava, S. K., and Singh, S. B. (2012). Synthesis, characterization and photocatalytic activity of magnetically separable hexagonal Ni/ZnO nanostructure. Nanoscale 4, 6604–6612. doi:10.1039/c2nr31831h

PubMed Abstract | CrossRef Full Text | Google Scholar

Shen, X., Yang, J., Zheng, T., Wang, Q., Zhuang, H., Zheng, R., et al. (2020). Plasmonic pn heterojunction of Ag/Ag₂S/Ag₂MoO₄ with enhanced Vis-NIR photocatalytic activity for purifying wastewater. Sep. Purif. Technol. 251, 117347. doi:10.1016/j.seppur.2020.117347

CrossRef Full Text | Google Scholar

Shen, X., Yang, Y., Song, B., Chen, F., Xue, Q., Shan, S., et al. (2021a). Magnetically recyclable and remarkably efficient visible-light-driven photocatalytic hexavalent chromium removal based on plasmonic biochar/bismuth/ferroferric oxide heterojunction. J. Colloid Interface Sci. 590, 424–435. doi:10.1016/j.jcis.2021.01.095

PubMed Abstract | CrossRef Full Text | Google Scholar

Shen, X., Zhang, Y., Shi, Z., Shan, S., Liu, J., and Zhang, L. (2021b). Construction of C₃N₄/CdS nanojunctions on carbon fiber cloth as a filter-membrane-shaped photocatalyst for degrading flowing wastewater. J. Alloys Compd. 851, 156743. doi:10.1016/j.jallcom.2020.156743

CrossRef Full Text | Google Scholar

Shen, X., Song, B., Shen, X., Shen, C., Shan, S., Xue, Q., et al. (2022). Rationally designed S-scheme heterojunction of C₃N₄/Bi₂MoO₆/carbon fiber cloth as a recyclable, macroscopic and efficient photocatalyst for wastewater treatment. Chem. Eng. J. 445, 136703. doi:10.1016/j.cej.2022.136703

CrossRef Full Text | Google Scholar

Tang, C., Chen, C., Xu, W., and Xu, L. (2019). Design of doped cesium lead halide perovskite as a photo-catalytic CO 2 reduction catalyst. J. Mat. Chem. A Mat. 7, 6911–6919. doi:10.1039/c9ta00550a

CrossRef Full Text | Google Scholar

Wang, Q., Tao, L., Jiang, X., Wang, M., and Shen, Y. (2019). Graphene oxide wrapped CH₃NH₃PbBr₃ perovskite quantum dots hybrid for photoelectrochemical CO₂ reduction in organic solvents. Appl. Surf. Sci. 465, 607–613. doi:10.1016/j.apsusc.2018.09.215

CrossRef Full Text | Google Scholar

Wang, J.-C., Li, N., Idris, A. M., Wang, J., Du, X., Pan, Z., et al. (2021). Surface defect engineering of CsPbBr₃ nanocrystals for high efficient photocatalytic CO₂ reduction. Sol. RRL 5, 2100154. doi:10.1002/solr.202100154

CrossRef Full Text | Google Scholar

Wang, C., Li, S., Cai, M., Yan, R., Dong, K., Zhang, J., et al. (2022). Rationally designed tetra (4-carboxyphenyl) porphyrin/graphene quantum dots/bismuth molybdate Z-scheme heterojunction for tetracycline degradation and Cr(VI) reduction: Performance, mechanism, intermediate toxicity appraisement. J. Colloid Interface Sci. 619, 307–321. doi:10.1016/j.jcis.2022.03.075

PubMed Abstract | CrossRef Full Text | Google Scholar

Wei, K., Faraj, Y., Yao, G., Xie, R., and Lai, B. (2021). Strategies for improving perovskite photocatalysts reactivity for organic pollutants degradation: A review on recent progress. Chem. Eng. J. 414, 128783. doi:10.1016/j.cej.2021.128783

CrossRef Full Text | Google Scholar

Xu, Y.-F., Yang, M.-Z., Chen, B.-X., Wang, X.-D., Chen, H.-Y., Kuang, D.-B., et al. (2017). A CsPbBr₃ perovskite quantum dot/graphene oxide composite for photocatalytic CO₂ reduction. J. Am. Chem. Soc. 139, 5660–5663. doi:10.1021/jacs.7b00489

PubMed Abstract | CrossRef Full Text | Google Scholar

Yang, D., Cao, M., Zhong, Q., Li, P., Zhang, X., and Zhang, Q. (2019). All-inorganic cesium lead halide perovskite nanocrystals: Synthesis, surface engineering and applications. J. Mat. Chem. C Mat. 7, 757–789. doi:10.1039/c8tc04381g

CrossRef Full Text | Google Scholar

Zhang, H., Feng, J., Wang, J., and Zhang, M. (2007). Preparation of ZnO nanorods through wet chemical method. Mater. Lett. 61, 5202–5205. doi:10.1016/j.matlet.2007.04.030

CrossRef Full Text | Google Scholar

Zhang, Q., Tai, M., Zhou, Y., Zhou, Y., Wei, Y., Tan, C., et al. (2019). Enhanced photocatalytic property of γ-CsPbI₃ perovskite nanocrystals with WS₂. ACS Sustain. Chem. Eng. 8, 1219–1229. doi:10.1021/acssuschemeng.9b06451

CrossRef Full Text | Google Scholar

Zhang, L., Liu, Y., He, Y., Zhang, X., Geng, C., Yang, R., et al. (2021a). Stable CsPbX₃/ZnO Heterostructure nanocrystals for light-emitting application. J. Phys. Chem. Lett. 12, 10953–10957. doi:10.1021/acs.jpclett.1c03446

PubMed Abstract | CrossRef Full Text | Google Scholar

Zhang, Y., Liu, X., Yusoff, M., and Razali, M. H. (2021b). Photocatalytic and antibacterial properties of a 3D flower-like TiO2 nanostructure photocatalyst.Scanning, 2021, 3839235, doi:10.1155/2021/3839235

PubMed Abstract | CrossRef Full Text | Google Scholar

Zhao, G., Rui, K., Dou, S. X., and Sun, W. (2018). Heterostructures for electrochemical hydrogen evolution reaction: A review. Adv. Funct. Mat. 28, 1803291. doi:10.1002/adfm.201803291

CrossRef Full Text | Google Scholar

Zhao, Y., Shi, H., Hu, X., Liu, E., and Fan, J. (2020). Fabricating CsPbX₃/CN heterostructures with enhanced photocatalytic activity for penicillins 6-APA degradation. Chem. Eng. J. 381, 122692. doi:10.1016/j.cej.2019.122692

CrossRef Full Text | Google Scholar

Zhao, Y., Wang, C., Hu, X., and Fan, J. (2021). Recent progress in CsPbX₃ perovskite nanocrystals for enhanced stability and photocatalytic applications. ChemNanoMat 7, 789–804. doi:10.1002/cnma.202100094

CrossRef Full Text | Google Scholar