Introduction

Increasing number of contaminants such as heavy metal ions, dyes, and organic chemicals in natural water is dangerous to environment and humans. Cr(VI) and dyes are common contaminants which are discharged from industries to water bodies. They are highly dissolvable in water and can cause lung cancer, intestine cancer, kidney damage, asthma, etc. (Ashraf et al. 2019) (Shrivastava 2012; Singh et al. 2017; Toor and Jin 2012). Photocatalysis has been proved to be a capable method to remove water contaminants due to low cost, low energy consumption, and regenerable solution (Bhuyan et al. 2015; Salem et al. 2009; Sharma et al. 2017; Singh et al. 2018). Transition metal dichalcogenides (MoS2, MoSe2, WS2, WSe2) have enticed great attention due to special-layered stable structure, high carrier mobility, direct bandgap, large surface area, and controllable interfaces (Andoshe et al. 2015; Saha et al. 2019; Wang et al. 2018). Among TMD’s, MoSe2 has been proved to be an efficient photocatalyst due to high surface activity, enormous surface area, good chemical stability, and visible-NIR region bandgap (Chu et al. 2016; Narang et al. 2018a; Siddiqui et al. 2018).

There are various methods to synthesize MoSe2 nanostructures (in synthesis section—Table 1, various MoSe2 synthesis methods are summarized) such as solvothermal, molecular beam epitaxy, electrochemical deposition, and chemical vapor deposition (Chu et al. 2016; Jia et al. 2015; Roy et al. 2016; Wang et al. 2016). These methods are complicated or require high temperatures to operate. Hydrothermal is a simple, environmentally friendly, and effective method to synthesize MoSe2 nanostructures. Hydrothermal method provides controlled growth rate and nucleation uniformity, and it is suitable for large scale production (Chaudhary et al. 2018; Narang et al. 2018b). MoSe2 exists in several crystal structures depending on the composition and temperature of the system; these structures exhibit diverse chemical and catalytic properties (Chu et al. 2016; Liu et al. 2015; Siddiqui et al. 2018; Fan et al. 2014).

Table 1 Synthesis methods of MoSe2 and comparison with respect to different parameters
Full size table

Photocatalytic degradation process takes place at the interface between photocatalyst surface and pollutant; therefore, it is expected that the photocatalytic activity is correlated with crystalline planes and surface structures. •OH radical is a major reactant responsible for the photocatalytic degradation of pollutants. •OH radicals are formed on MoSe2 surface when holes react with adsorbed water, and electrons react with oxygen-forming superoxide radical which further react and form •OH radicals. Researchers reported that there is a direct correlation between the amount of •OH generation and photocatalytic efficiency (Gągol et al. 2018). Acidic conditions promote the generation of hydroxyl radicals by lowering the recombination reaction of hydroxyl radicals.

It was observed from previously reported results, MoSe2 is a good photocatalyst for cationic dyes such as methylene blue (MB) and rhodamine B (RhB) (Wu et al. 2016). For degradation of anionic dye, surface modification of MoSe2 is required which is possible via doping, synthesizing composite with other suitable materials, and varying pH (Zhou et al. 2018). In this study, nanosheets and nanourchins of MoSe2 were hydrothermally synthesized by varying the pH and comparative photocatalytic study on organic dyes (MB, MO) and heavy metal Cr(VI) were performed. Enhanced photocatalytic efficiency of nanosheets over nanourchins is observed and is correlated with crystallinity, enhanced surface area, and hydroxyl ion concentration. Adsorption studies, role of reactive species, intermediate products using HPLC, and regenerable properties of catalysts were also studied.

Materials

MilliQ deionized water (DI) was used as base-liquid. Selenium Se (99.99%), Central Drug House Pvt. Ltd., sodium molybdate, Na2MoO4 (99.99%), Thermo Fisher Scientific India Pvt. Ltd., hydrazine hydrate, N2H4.H2O (80%), Central Drug House Pvt. Ltd. and acetic acid, CH3COOH (99.5%) from High Purity Laboratory Chemicals Pvt. Ltd. solutions were used in synthesis. Methylene blue (C16H18ClN3S, Fisher scientific), methyl orange (C14H14N3NaO3S, Fisher scientific), potassium iodide (KI, Pallav chemicals and solvents Pvt. Ltd.), and tert-butyl alcohol ((CH3)3COH, Central Drug House Pvt. Ltd.) have been used for photocatalysis.

Synthesis process

Schematic of synthesis process for MoSe2 nanostructures (nanosheets and nanourchins) is shown in Fig. 1. Two solutions are prepared, in the first solution, 0.02 mol of sodium molybdate is dissolved in 50 ml of deionized water (DI) at room temperature and stirred until clear solution is obtained. Separately, second solution is prepared by dissolving 0.04 mol of selenium powder in 10 ml of hydrazine hydrate at room temperature and stirred, to give complete black suspension. Selenium reacts with hydrazine hydrate to yield selenium ions (Se2−) as shown in Eq. (i). Second solution is added dropwise to the first solution and stirred for 20 min. Hydrazine hydrate reduces MoO42− anions from sodium molybdate and produce Mo4+ cations, as shown in Eq. (ii). The resultant dark brown color solution is obtained with pH 12.

Fig. 1
figure 1

Schematic of MoSe2 (nanosheets and nanourchins) synthesis process

Full size image

MoSe2 nanostructure at pH 5 and pH 8

Acetic acid is added to the as-prepared solution of pure MoSe2 (before transferring to autoclave) to change the pH value of the solution. Solutions at pH 5 and pH 8 were obtained by adding 13 ml and 6 ml of acetic acid, respectively. Finally, dark brown color solutions were transferred to autoclave and placed in furnace at 200 °C for 24 h. In autoclave, reaction between Se2− and Mo4+ takes place to form MoSe2 as shown in Eq. (iii) (Mittal et al. 2019). After 24 h, the autoclaves are allowed to cool till room temperature. Subsequently, obtained solutions were sequentially washed with DI water and acetone, followed by drying at 50 °C for 2 h. Samples prepared at pH 5 and pH 8 are labelled as MSE5 and MSE8, respectively.

$$ 5{\mathrm{N}}_2{\mathrm{H}}_4+2\mathrm{Se}\to {\mathrm{N}}_2+4{\mathrm{N}}_2{\mathrm{H}}_5++2{\mathrm{Se}}^{2-} $$
(i)
$$ 2\mathrm{Mo}{\mathrm{O}}_4^{2-}+{\mathrm{N}}_2{\mathrm{H}}_2+4{\mathrm{H}}_2\mathrm{O}\to 2{\mathrm{Mo}}^{4+}+{\mathrm{N}}_2+12{\mathrm{O}\mathrm{H}}^{-} $$
(ii)
$$ {\mathrm{Mo}}^{4+}+2{\mathrm{Se}}^{2-}\to \mathrm{Mo}{\mathrm{Se}}_2 $$
(iii)

Relevant synthesis condition, raw materials, size, and morphology of Mose2 are summarized in Table 1. In the present study, we have reported synthesis of nanosheets and nanourchins morphology of MoSe2 using simple and economic hydrothermal method.

Characterizations

FESEM (Quanta 3D FEG) analysed the morphology of the powdered MoSe2. Crystal structure was analysed using XRD (Rigaku Smart Lab) with Cu Kα radiation of 1.540 Å in the range of 10–80°. UV-Vis spectrophotometer (Cary 100 series, Agilent Technologies) was used to analyse the band gap of the synthesized materials. Raman spectroscopy (HR800 JY, Lab RAM HR) was carried out in the range of 220 to 300 cm−1. XPS (Multiprobe Surface analysis system, Omicron) was used to determine the hydroxyl ion concentration. The surface areas and pore diameter of the materials were analyzed using multipoint BET and Barrett-Joyner-Halenda (BJH) method by nitrogen adsorption–desorption isotherm measurements at 77.4 K using Quantachrome Instruments (version 3.0). The degradation products of MB were analysed by HPLC (Agilent technologies (1260- ∞ series)) using Hiplex X Column with temperature of detector and column at 35 °C and 65 °C, respectively. Deionized water was used as mobile phase with flow rate of 0.6 ml/min.

Results and discussion

Morphology of as synthesized materials was studied using FESEM as shown in Fig. 2. Figure 2a–d showed the SEM images of MSE5 and MSE8 at magnification of 1 μm and 100 nm. MSE5 showed clusters of nanosheets, the pattern is irregular, inner surface is dense, and smooth while the outer surface is composed of multiple folds nanosheets. MSE8 consists of evenly circulated microsphere of diameter ~ 150 nm. The nanourchins were made by the accumulation of several nanospheres which were gathered at one place and giving realization of nanourchins. Thus, significant change in morphology was observed by changing synthesis conditions.

Fig. 2
figure 2

FESEM images of MoSe2 of a, b nanosheets and c, d nanourchins at 1 μm and 100 nm

Full size image

Crystal structure and orientation of MSE5 and MSE8 were observed by XRD diffractograms as shown in Fig. 3a and b, respectively. XRD peaks for MSE5 and MSE8 were observed at 2θ 13.6°, 13.4°; 26.3°, 26.1°; 31.3°, 31.5°; 37.8°, 37.7°; 46.8°,47.1°; 55.8°,55.9°, and 64.5°, 64.3° corresponds to (002), (100), (004), (102), (200), (211), and (204) hkl planes, respectively as confirmed by the JCPDS file no. 77-1715 (Roy et al. 2016; Saha et al. 2019; Tang et al. 2016). As observed from XRD, MSE5 has sharp and intense peaks as compared with MSE8, implying higher crystallinity in MSE5 sample as compared with MSE8. The calculated lattice constants a and c were 3.3 Å and 12.56 Å for MSE5 and 3.3 Å and 12.9 Å for MSE8, which are in good agreement with the earlier results (Zhang et al. 2018).

Fig. 3
figure 3

XRD Diffractograms of a MSE5 and b MSE8

Full size image

To further confirm the crystallinity and phase components of MSE5 and MSE8, Raman spectra were recorded as shown in Fig 4a and b, respectively. In the Raman spectrum of MSE5, the peaks were positioned at 239.6 cm−1 and 284.8 cm−1 and of MSE8, peaks positioned at 240.2 cm−1 and 284.9 cm−1, corresponded to A1g and E2g phonon modes of MoSe2, respectively (Ghosh et al. 2016; Kirubasankar et al. 2019). A1g mode is assigned to out of plane and E2g is assigned to in plane optical branch. The Δω between E2g and A1g mode was 45.2 cm−1 and 44.8 cm−1 for MSE5 and MSE8, respectively. It was observed that MSE5 has high intensity as compared with MSE8 which implies more defects in MSE8 than in MSE5.

Fig. 4
figure 4

Raman spectra of a MSE5 and b MSE8

Full size image

Band gap of MSE5 and MSE8 was calculated using Tauc’c plot as shown in Fig. 5a and b, respectively. Absorption spectra of MSE5 and MSE8 lie in the visible and IR region. Band gap energies were calculated from plot of (αhʋ)1/2 vs hʋ and found to be 2.0 eV for MSE5 and MSE8, where α is absorption coefficient, defined as a = 2.303 A/t, where “A” is absorbance and t is the thickness of cuvette. It was observed that there is no effect of pH on band gap of MoSe2.

Fig. 5
figure 5

Tauc’s plot of a MSE5 and b MSE8

Full size image

The measurements of N2 adsorption–desorption was performed to calculate the pore diameter, specific surface area, and the pore volume. One hundred milligram of MSE5 and MSE8 were degassed for 6 h at 150 °C before measurement and outgassed for 1 h at 100 °C. The nitrogen adsorption–desorption isotherms and pore size distribution obtained for MSE5 and MSE8 are shown in Fig. 6a and b, respectively. Table 2 represented the BET surface area and pore diameter of MSE5 and MSE8. MSE5 and MSE8 exhibit isotherm of type IV which is characteristic of mesoporous material. MSE8 has narrow pore size distributions than MSE5 and possessed a single peak which confirms uniform size distribution. BET surface area for MSE5 and MSE8 were 78.633 m2 g−1 and 72.978 m2 g−1, respectively. The maximum pore size of MSE5 is 1.6 nm and of MSE8 is 3.5 nm which further confirms the mesoporous nature of MSE5 and MSE8.

Fig. 6
figure 6

a Plot of N2 adsorption–desorption isotherm and b pore-size distribution curves for MSE5 and MSE8

Full size image
Table 2 BET pore volume, pore diameter, and surface area for MoSe2 nanostructures
Full size table

XPS study was performed to confirm the oxidation state and calculate the hydroxyl ion concentration of synthesized materials (Khanuja et al. 2007; Khanuja et al. 2008). The general scan as shown in Fig. 7a and b indicated the elemental peaks of Mo, Se, C, and O. The HR-XPS of the Mo 3d core level of MoSe2 are shown in Fig 7c and d, peak at 228.4 eV in MSE5 and 232.4 eV in MSE8 corresponded to Mo 3d5/2 and peak at 231.6 eV in MSE5 and 235.5 eV in MSE8 corresponded to Mo 3d3/2, suggesting Mo4+ characteristics (Zhao et al. 2016). As shown in Fig. 7e and f, Se 3d5/2 and Se 3d3/2 components located at binding energies of 54.2 and 54.7 eV, respectively in MSE5 and 54.8 and 55.3 eV in MSE8, representing an oxidation state of − 2 for Se, thus confirmed the formation of MoSe2 (Bi et al. 2015). The difference in binding energy because of the spin orbital coupling, ∆Eb = Eb (Se 3d3/2) − Eb (Se 3d5/2) was 0.5 eV. The O 1 s spectra are as shown in Fig. 7g and h, peaks at binding energy of 530.1 eV in MSE5 and 530.5 eV in MSE8 corresponded to C=O of MoSe2, peak at 531.8 eV in MSE5 and 531.7 eV in MSE8 corresponded to the C–O–Mo and peak at 533.27 eV in MSE5 and 533.2 eV in MSE8 corresponded to O–OH (Azeez et al. 2018). Effect of pH was observed on surface hydroxyl concentration; percentage of hydroxyl oxygen concentration was 31.3% and 28.2% for MSE5 and MSE8, respectively. Hydroxyl radicals are responsible for degradation of pollutants, and increase in hydroxyl concentration was observed with decrease in pH value. Thus, acidic conditions promote generation of hydroxyl radicals and degradation efficiency by lowering recombination reaction (Zhang et al. 2014).

Fig. 7
figure 7

XPS Spectra of a, b general scan; c, d Mo 3d; e, f Se 3d; and g, h O 1 s of MSE5 and MSE8

Full size image

Figure 8a and b showed the self-photodegradation of MB and MO, respectively. MB and MO was irradiated under xenon arc lamp for 30 min and analyzed using UV-vis spectroscopy at 664 nm and 464 nm for MB and MO, respectively. It was observed that there is no significant change in the MB and MO concentration. This showed that the direct photocatalysis or self-photodegradation was insignificant in the absence of the photocatalyst.

Fig. 8
figure 8

Self- photodegradation of a MB and b MO using xenon lamp

Full size image

Figure 9 showed degradation efficiency vs time plot for degradation of MB, MO, and reduction of Cr(VI) in the presence of MSE5 and MSE8. Solutions of 1 mg/100 ml of each MB, MO, and Cr(VI) were prepared, and 20 mg of MSE5 and MSE8 were added to each solution and stirred under AM (air mass) 1.5 solar illuminations 100 mW/cm2 from xenon arc lamp under same conditions. One milliliter of solution was taken out from each solution in some interval of time and analyzed using UV-visible spectroscopy. Degradation of MB, MO, and reduction of Cr(VI) into Cr(III) was observed by UV-Vis spectroscopy at characteristic absorbance peak at 664 nm, 464 nm, and 350 nm, respectively. η = 1- [C/C0] * 100 was used to calculate degradation efficiency (η), where C0 denotes absorption of pollutant before irradiation and C denotes adsorption after irradiation at time t. MSE5 degraded 94.7% of MB, ~ 92.6% of MO and ~ 90.7% of Cr(VI) in 45 min of irradiation. MSE8 degraded 78% of MB, 77.8% of MO, and 66.7% of Cr(VI) in Cr(III) in 45 min of irradiation. As evident from the results (Fig. 9), MSE5 showed high photocatalytic efficiency as compared with MSE8 due to (i) enhanced surface area, (ii) high crystallinity, and (iii) large concentration of hydroxyl radicals. Enhanced surface area and large pore size in MSE5 as compared with MSE8 (Table 3) lead to increase in number of active sites, thus slower recombination rate and thereby producing more holes and electrons that help in degradation of adsorbed contaminants present on the surface of photocatalyst (Ashraf et al. 2019). Sample MSE5 has higher crystallinity as compared with MSE8 as evident through sharp and intense peaks observed in MSE5 through XRD and Raman studies (Figs. 3 and 4), resulting in higher degradation efficiency of MSE5 due to favorable charge transport properties. MSE5 has higher concentration of hydroxyl radicals as compared with MSE8 (Fig. 7g, h) which is a major reactant responsible for the degradation of pollutants.

Fig. 9
figure 9

Degradation efficiency vs time plot of MB, MO, and Cr(VI) in the presence of MSE5 and MSE8

Full size image
Table 3 Comparison of the photocatalytic degradation efficiency of MoSe2 for different water pollutants
Full size table

Some of the earlier reported results of photodegradation of pollutants using MoSe2, and its composites are summarized in Table 3. As observed from results, it can be seen that the degradation efficiency of MSE5 and MSE8 are higher for cationic dye, anionic dye as well as organic pollutant than those of other photocatalysts. Hence, MSE5 and MSE8 acted as an excellent photocatalyst.

Figure 10a and b showed C/C0 vs time plot for degradation of MB, MO, and reduction of Cr(VI) in the presence of MSE5 and MSE8. Kinetics of adsorption on MSE5 and MSE8 were investigated by pseudo first order and pseudo second order as shown in Fig. 10.

Fig. 10
figure 10

a, bC/C0 vs time plot c, d pseudo first order adsorption model and e, f pseudo second-order adsorption model of MB, MO, and Cr(VI)

Full size image

The pseudo first-order adsorption, pseudo second-order adsorption and intra-particle diffusion model are given by the Eqs. (xiii) and (xiv), respectively.

$$ {Q}_t={Q}_e\left(1-{e}^{-{k}_1t}\right) $$
(xiii)
$$ \frac{\mathrm{t}}{Q\mathrm{t}}=\frac{1}{k_2{\left(Q\mathrm{e}\right)}^2}+\frac{\mathrm{t}}{\mathrm{Qe}} $$
(xiv)

where Qt and Qe denotes the adsorbed amount at time t and amount adsorbed at equilibrium. k1 and k2 are the rate constant for pseudo first order and pseudo second order, respectively. Values of k1 and k2 were evaluated from the slope of plot ln (Qe − Qt) vs time and plot of t/Qt vs time, respectively.

Kinetic study for MSE5 and MSE8 were found to follow pseudo first and second order adsorption model for MB, which suggested that adsorption process was initially controlled by physisorption followed by chemisorption. For MO and Cr(VI), MSE5 and MSE8 were found to follow pseudo first order adsorption model for MO and Cr(VI), which suggested that adsorption process was controlled by physisorption. In physisorption process, molecules form monolayer adsorption when adsorbed on the surface by valence bond. In chemisorption process, reaction between the surface and the adsorbate takes place. On interaction between the adsorbate molecule and surface of catalyst, in chemisorption process, new interacting electronic bonds, whereas in physisorption process no bond formation take place.

In order to evaluate the reusability of MSE5 and MSE8, reduction of Cr(VI) into Cr(III) was checked for five cycles as shown in Fig. 11. In the first cycle, 92% and 67% of Cr(VI) was reduced using MSE5 and MSE8, respectively. The solutions resultant from the photocatalytic reduction was filtered washed and dried. The dried samples were used for the reduction of new solution of Cr(VI). After 5th cycle, degradation efficiency changed from 92 to 87% in case of MSE5 and 67 to 62% in case of MSE8. Such decrease was due to wastage of photocatalyst during each cycle and can be concluded that both photocatalyst acted as perfect candidate for environment remediation.

Fig. 11
figure 11

Recyclability test of a MSE5 and b MSE8 for Cr(VI) reduction

Full size image

Photocatalytic degradation mechanism of MoSe2 is shown in Fig. 12. Photocatalytic reaction initiated when irradiation light has energy equal to or greater than band gap of MoSe2. Electrons from valence band moved to conduction band by absorbing energy from irradiation light, leaving behind a hole and resulting in formation of electron-hole pair. Holes reacts with water to yield hydroxyl radical, and electrons reacts with oxygen to yield superoxide radical which further produce hydroxyl radicals. These radicals react with contaminants and degrade them into harmless or less toxic substances.

Fig. 12
figure 12

Photocatalytic mechanism of MoSe2 nanostructures

Full size image

Photocatalytic mechanism can be summarized as follows.

  1. (a)

    Adsorption of photon- and electron-hole pair generation:

$$ \mathrm{Mo}{\mathrm{Se}}_2+\mathrm{h}\nu \to {e}^{-}+{h}^{+}\left(\mathrm{Mo}{\mathrm{Se}}_2-\mathrm{PANI}\right) $$
(iv)
  1. (b)

    Neutralization of OH− groups to produce •OH radicals:

$$ {\mathrm{H}}_2\mathrm{O}\to {\mathrm{OH}}^{-}+{\mathrm{H}}^{+} $$
(v)
$$ {h}^{+}+{\mathrm{OH}}^{-}\to {}^{\bullet}\mathrm{OH} $$
(vi)
  1. (c)

    Oxygen ionosorption:

$$ {e}^{-}+{\mathrm{O}}_2\to \cdotp {\mathrm{O}}_2^{-} $$
(vii)
  1. (d)

    Neutralization of \( \cdotp {O}_2^{-} \) by protons:

$$ \cdotp {O}_2^{-}+{\mathrm{H}}^{+}\to \mathrm{H}{\mathrm{O}}_2^{-} $$
(viii)
  1. (e)

    Transient hydrogen peroxide formation:

$$ 2\mathrm{H}{\mathrm{O}}_2^{-}\to {\mathrm{O}}_2+{\mathrm{H}}_2{\mathrm{O}}_2 $$
(ix)
  1. (f)

    Second reduction of oxygen by H2O2

$$ {\mathrm{H}}_2{\mathrm{O}}_2+{\mathrm{e}}^{-}\to {\mathrm{O}\mathrm{H}}^{-}+{}^{\bullet}\mathrm{OH} $$
(x)
  1. (g)

    Decomposition of contaminant by •OH radical

$$ \mathrm{Contaminant}+{}^{\bullet}\mathrm{OH}+{\mathrm{O}}_2\to {\mathrm{CO}}_2+{\mathrm{H}}_2\mathrm{O}+\mathrm{other}\ \mathrm{products} $$
(xi)
  1. (h)

    Direct oxidation by holes

$$ \mathrm{contaminant}+{\mathrm{h}}^{+}\to \mathrm{less}\ \mathrm{toxic}\ \mathrm{products} $$
(xii)

In order to investigate the role of the reactive species in photocatalytic degradation mechanism, photocatalytic degradation of MB and reduction of Cr(VI) was performed in the presence of trappers such as t-BuOH for \( {}{}^{\bullet}\mathrm{OH} \)and KI for holes and \( {}{}^{\bullet}\mathrm{OH} \). 1mM in 100ml of t-BuOH and KI were used in the photocatalysis process (Mavinakere Ramesh and Shivanna 2018; Mittal et al. 2019). Effect of radical trappers on the photodegradation efficiency of MSE5 and MSE8 is shown in Fig. 13. Reduction in photocatalytic activity was observed in the presence of trappers, implying the role of \( {}{}^{\bullet}\mathrm{OH} \) in the photodegradation process.

Fig. 13
figure 13

Trapping experiment for MB degradation and Cr(VI) reduction using t-BuOH and KI as scavengers in the presence of a MSE5 and b MSE8

Full size image

To investigate the degradation products of MB, HPLC was performed at 0 min and 30 min as shown in Fig. 14a and b, respectively. It was indicated from the results that photocatalytic degradation of dye not only caused its decoloration but also degraded the dye molecules. As shown in Fig. 14, intensity of MB peak was decreased, and new peaks appeared which corresponded to degraded products of the dye. Area of MB peak at 5.7 min decreased after 30 min, and new peaks at lower retention time were observed. Intermediates were observed at 2.0, 2.9, 3.2, and 3.5 min were assigned to thionin, azure C (AC), azure A (AA), and azure B (AB), respectively (Alamo-Nole et al. 2013; Ullah et al. 2017). These intermediates were further degraded and finally converted to CO2 and H2O.

Fig. 14
figure 14

HPLC analysis of degraded products of MB at a 0 min and b 30 min using MSE5

Full size image

Conclusion

Nanosheets and nanourchins morphology of MoSe2 were successfully obtained via hydrothermal method. During the synthesis process, acetic acid plays an important role in modification of the inherent negatively charged MoSe2 surface. The photocatalytic degradation of cationic dye (MB), anionic dye (MO), and reduction of (Cr(VI)) using different morphologies of MoSe2 (nanosheets and nanourchins) were performed and found to have good photocatalytic performance for cationic as well as anionic dye. The superior degradation efficiency of MSE5 (nanosheets) and MSE8 (nanourchins) is due to (i) high crystallinity of material (as observed by XRD and Raman studies), (ii) large pore size (as observed in BET analysis), and (iii) higher concentration of •OH radicals (as observed by XPS studies). The degraded products of MB were examined by high-performance liquid chromatography (HPLC) which confirms the complete degradation of dye. Photocatalysis mechanism along with trapping experiment was explained. Reaction kinetics were studied and found to follow pseudo first- and second-order model. Repeatability of the materials were also studied and found to have reusable properties.