**4.2. Ternary composite**

BiVO4, where an significantly improved PCE activity of a near 10−fold enhancement was observe compared with pure BiVO4 under visible-light irradiation. The longer photoexcited electron lifetime of BiVO4 is mainly responsible for this improvement as the electrons are injected to RGO instantly at the site of generation, leading to a significant reduction in charge

**Figure 30.** SEM (A) and HRTEM (B) images of Bi2WO6/TiO2 [343]; SEM (C) and HRTEM (D) images of SnO2/TiO2 heter‐

A B

**Figure 31.** (A and B) TEM images of graphene decorated with Bi2WO6 composite [352].

**Figure 31.** (A and B) TEM images of graphene decorated with Bi2WO6 composite[352].

prepared a grapheneBi2WO6 composite via an in situ hydrothermal reaction (Fig. 31(A) and (B)). This grapheneBi2WO6 photocatalyst showed significantly enhanced photocatalytic activity for the degradation of RhB under visible light (*λ* > 420 nm), which was three times greater than that of the pure Bi2WO6. The enhanced photocatalytic activity could be attributed to the negative shift in the Fermi level of grapheneBi2WO6 and the high migration efficiency of photoinduced electrons; these electrons may not only be effectively involved in the oxygen reduction reaction but also suppress the charge recombination. Kudo et al.[353] reported the composite of reduced graphene oxide (RGO) with BiVO4, where an significantly improved PCE activity of a near 10fold enhancement was observe compared with pure BiVO4 under visible‐light irradiation. The longer photoexcited electron lifetime of BiVO4 is mainly responsible for this improvement as the electrons are injected to RGO instantly at the site of

A simple soft-chemical method was used to synthesize the BiOI/TiO2 heterostructures with different Bi to Ti molar ratios at low temperature of 80°C. The degradation of methyl orange under visible-light irradiation (*λ* > 420 nm) of the material revealed that the BiOI/TiO2 heterostructures exhibited much higher photocatalytic activities than pure BiOI or TiO2, where 50%BiOI/TiO2 showed the best activity among all these heterostructured photocatalysts [348]. BiOBr−Bi2WO6 mesoporous nanosheet composite enhanced photocatalytic activity is attribut‐ ed to well-matched band edge positions of BiOBr and Bi2WO6 and the large specific surface area of the mesoporous nanosheet composites in view of the incorporation of mesopores and

 A simple soft‐chemical method was used to synthesize the BiOI/TiO2 heterostructures with different Bi to Ti molar ratios at low temperature of 80°C. The degradation of methyl orange under visible‐light irradiation (*λ*  > 420 nm) of the material revealed that the BiOI/TiO2 heterostructures exhibited much higher photocatalytic activities than pure BiOI or TiO2, where 50%BiOI/TiO2 showed the best activity among all these heterostructured photocatalysts[348]. BiOBrBi2WO6 mesoporous nanosheet composite enhanced photocatalytic activity is attributed to well‐matched band edge positions of BiOBr and Bi2WO6 and the large specific surface area of the mesoporous nanosheet composites in view of the incorporation of mesopores and the highly exposed BiOBr (001) facet, compared with pure BiOBr and Bi2WO6 under

 During the past few years, another promising carbon material, graphene, which possess many unique properties, has been used for corporation with BiOX (X = Cl, Br and I) and significantly improved photocatalytic efficiencies was achieved[356‐360]. Ai and coworkers[357] have developed a facile solvothermal route tosynthesize BiOBr/graphene hybrids using graphene oxide (GO), bismuth nitrite, and CTAB as the precursors. As shown in Fig. 32, BiOBr nanoplates with hundreds nanometers in size are dispersed randomly on the 2D graphene sheet surface. Evaluated by the removal of gaseous NO under visible‐light irradiation, the as‐prepared BiOBr/graphene hybrid displays a two times higher removal rate than that of pure BiOBr. It is evidenced that the strong chemical bonding between BiOBr and graphene is mainly responsible for the fast photogenerated electrons transfer from BiOBr to

generation, leading to a significant reduction in charge recombination.

exposure to a 3W LED light[354].

heterostructured photocatalysts based on TiO2 nanofibers by combining the electrospinning technique with the hydrothermal method (Fig 30C and D). This SnO2TiO2 composite possessed a high photocatalytic activity for the degradation of rhodamine B (RhB) dye under UV light irradiation, which was almost 2.5 times higher than that of the bare TiO2. The enhanced photocatalytic efficiency was attributed to the improvement of the separation of photogenerated electrons and holes. Wang's

recombination.

206 Advanced Catalytic Materials - Photocatalysis and Other Current Trends

ostructures [351].

group[352]

To date, although a variety of approaches have been developed to prepare many kinds of visible−light−driven semiconductor heterojunction photocatalysts, many shortage is still needed to be overcomed, for example, the limited region of visible-light photo−response. To solve these problems, multi−component heterojunction systems have been developed [361,362], in which two or more visible-light active components and an electron-transfer system are spatially integrated as shown in Fig. 33 [363].

As demonstrated in Figure 33, since both semiconductor A (S-A) and semiconductor B (S-B) can be excited by UV/visible light and have different photoabsorption ranges, the conjunction of the two materials can overlap and broaden the range of UV/visible−light photoresponse. At the same time, it is well-known that the photocatalytic reaction is initiated by the incident UV/

**Figure 33.** Schematic structure of multicomponent heterojunction systems [363].

visible photons with energy equal or higher than the band-gap in both S−A and S-B, which lead to the creation of photogenerated holes in their VB and electrons in their CB. On the one hand, the electrons in the CB of S−A easily flow into metal (electron transfer I: S−A metal) through the Schottky barrier because the CB (or the Fermi level) of S−A is higher than that of the loaded metal, which is consistent with the previous study on electron transfer from the semiconductor (such as TiO2) to metal (such as Ag and Au) [361,364]. This process of electron transfer I is faster than the electron-hole recombination between the VB and the CB of S−A. Thus, plenty of electrons in the CB of S−A can be stored in the metal component. As a result, more holes with a strong oxidation power in the VB of S−A escape from the pair recombination and are available to oxidize the pollutants or OH-. On the other hand, since the energy level of metal is above the VB of S−B, holes in the VB of S−B also easily flow into metal (electron transfer II: metal S−B, see Fig. 33), which is faster than the electron-hole recombination between the VB and CB of S−B. More electrons with a strong reduction power in the CB of S−B can escape from the pair recombination and are available to reduce some absorbed compounds (such as O2 and H+ ). Therefore, simultaneous electron transfer I and II (i.e., vectorial electron transfer of S−A metal to S−B in Fig. 33) can occur as a result of UV/visible-light excitation of both S−A and S−B. In these vectorial electron−transfer processes, metal in multicomponent heterojunction systems acts as a storage and/or a recombination center for electrons in the CB of S−A and holes in the VB of S−B, and contributes to enhancing interfacial charge transfer and realizing the complete separation of holes in the VB of S−A and electrons in the CB of S−B. Therefore, the multi-component heterojunction systems can simultaneously and efficiently generate holes with a strong oxidation power in the VB of S−A and electrons with a strong reduction power in the CB of S−B, resulting in greatly enhanced photocatalytic activity, compared with the single semiconductor or semiconductor heterojunctions mentioned above.

In 2006, by using a facile photo−chemical technique, Tada et al. [361] developed a CdS−Au −TiO<sup>2</sup> ternary component nanojunction system (Fig. 34 (A) and (B)). This CdS−Au−TiO2 triple nanojunction shows significantly improved photocatalytic activity, which was far higher than that of either the single-component or two−components systems. For this photocatalytic CdS −Au−TiO2 nanojunction system, 52.2% of methylviologen (MV2+) have been reduced in 100 min, which are 1.6, 1.8 and 2.3 times higher than that of Au/TiO2, CdS/TiO2 and TiO2 [361].

**Figure 34.** TEM (A) and HRTEM (B) images of Au@CdS−TiO<sup>2</sup> [361]; SEM(C) and HRTEM (D) images of the AgBr−Ag −Bi2WO6 nanojunction system [364].

visible photons with energy equal or higher than the band-gap in both S−A and S-B, which lead to the creation of photogenerated holes in their VB and electrons in their CB. On the one hand, the electrons in the CB of S−A easily flow into metal (electron transfer I: S−A metal) through the Schottky barrier because the CB (or the Fermi level) of S−A is higher than that of the loaded metal, which is consistent with the previous study on electron transfer from the semiconductor (such as TiO2) to metal (such as Ag and Au) [361,364]. This process of electron transfer I is faster than the electron-hole recombination between the VB and the CB of S−A. Thus, plenty of electrons in the CB of S−A can be stored in the metal component. As a result, more holes with a strong oxidation power in the VB of S−A escape from the pair recombination and are available to oxidize the pollutants or OH-. On the other hand, since the energy level of metal is above the VB of S−B, holes in the VB of S−B also easily flow into metal (electron transfer II: metal S−B, see Fig. 33), which is faster than the electron-hole recombination between the VB and CB of S−B. More electrons with a strong reduction power in the CB of S−B can escape from the pair recombination and are available to reduce some absorbed compounds

**Figure 33.** Schematic structure of multicomponent heterojunction systems [363].

208 Advanced Catalytic Materials - Photocatalysis and Other Current Trends

transfer of S−A metal to S−B in Fig. 33) can occur as a result of UV/visible-light excitation of both S−A and S−B. In these vectorial electron−transfer processes, metal in multicomponent heterojunction systems acts as a storage and/or a recombination center for electrons in the CB of S−A and holes in the VB of S−B, and contributes to enhancing interfacial charge transfer and realizing the complete separation of holes in the VB of S−A and electrons in the CB of S−B. Therefore, the multi-component heterojunction systems can simultaneously and efficiently generate holes with a strong oxidation power in the VB of S−A and electrons with a strong reduction power in the CB of S−B, resulting in greatly enhanced photocatalytic activity, compared with the single semiconductor or semiconductor heterojunctions mentioned above. In 2006, by using a facile photo−chemical technique, Tada et al. [361] developed a CdS−Au −TiO<sup>2</sup> ternary component nanojunction system (Fig. 34 (A) and (B)). This CdS−Au−TiO2 triple nanojunction shows significantly improved photocatalytic activity, which was far higher than that of either the single-component or two−components systems. For this photocatalytic CdS

). Therefore, simultaneous electron transfer I and II (i.e., vectorial electron

(such as O2 and H+

Subsequently, an AgBr−Ag−Bi2WO6 nanojunction system was developed by a facile deposition −precipitation method (Fig. 34 (C) and (D)) [364]. This AgBr−Ag−Bi2WO6 nanojunction system shows much higher visible−light−driven photocatalytic activity than a photocatalyst with single visible-light response components, such as Bi2WO6 nanostructures, Ag−Bi2WO6 and AgBr−Ag−TiO2. For example, with the AgBr−Ag−Bi2WO6 nanojunction system as the photo‐ catalyst, the MX−5B could be photocatalytically degraded (42.8 mg L-1) within 60 min under visible-light irradiation, which is higher than that of Bi2WO6 nanostructures (2.0 mg L-1), Ag-Bi2WO6 (2.9 mg L-1) and AgBr−Ag−TiO<sup>2</sup> (34.1 mg L-1). Furthermore, 65% of pentachlorophenol could be mineralized within 4 h by AgBr−Ag−Bi2WO6, which is much higher than that (34.5%) of the AgBr−Ag−TiO2 composite. This excellent visible−light−driven photocatalytic perform‐ ance was mainly attributed to the vectorial interparticle electron transfer driven by the twostep excitation of both visible-light-driven components (AgBr and Bi2WO6).

A one-step low−temperature chemical bath method was developed to synthesize the flower −like Ag/AgCl/BiOCl composite [365]. The as−prepared Ag/AgCl/BiOCl composite exhibited enhanced visible−light photocatalytic activity on photodegradation of rhodamine B, which was greatly improved in comparison with either pure Ag/AgCl or BiOCl. It is evidenced that the superoxide radical, chlorine radical and the hole play a critical role in the photocatalytic degradation of RhB over the Ag/AgCl/BiOCl. Next, Ag/AgX/BiOX (X = Cl, Br) three-compo‐ nent visible-light-driven photocatalysts were synthesized by a low−temperature chemical bath method (Fig. 35) [366]. The Ag/AgX/BiOX composites showed enhanced visible−light−driven photocatalytic activity for the degradation of rhodamine B, which was much higher than Ag/ AgX and BiOX. The photocatalytic mechanisms were analyzed by active species trapping and

superoxide radical quantification experiments. The role of metallic Ag in Ag/AgCl/BiOCl and Ag/AgBr/BiOBr were analyzed, and we found that the role of metallic Ag was a surface plasmon resonance and the Z−scheme bridge for Ag/AgCl/BiOCl and Ag/AgBr/BiOBr, respectively. This results suggests that no matter in narrow band gap photocatalysts (Eg < 3.1 eV) or wide band gap photocatalysts (Eg > 3.1 eV), metallic Ag can enhance visible-light-driven photocatalytic activity though the different roles. in comparison with either pure Ag/AgCl or BiOCl. It is evidenced that the superoxide radical, chlorine radical and the hole play a critical role in the photocatalytic degradation of RhB over the Ag/AgCl/BiOCl. Next, Ag/AgX/BiOX (X = Cl, Br) three‐component visible‐light‐driven photocatalysts were synthesized by a lowtemperature chemical bath method (Fig. 35)[366]. The Ag/AgX/BiOX composites showed enhanced visiblelightdriven photocatalytic activity for the degradation of rhodamine B, which was

much higher than Ag/AgX and BiOX. The photocatalytic mechanisms were analyzed by active species

photocatalytic performance was mainly attributed to the vectorial interparticle electron transfer driven

A one‐step lowtemperature chemical bath method was developed to synthesize the flowerlike

visiblelight photocatalytic activity on photodegradation of rhodamine B, which was greatly improved

by the two‐step excitation of both visible‐light‐driven components (AgBr and Bi2WO6).

**Figure 35**. FESEM images of Ag/AgCl/BiOCl (a) and Ag/AgBr/BiOBr (b): the red arrows pointing out the Ag/AgX. TEM images of Ag/AgCl/BiOCl (c) and Ag/AgBr/BiOBr (d): blue rings show the small Ag/AgX, and the red dots point out the large Ag/AgX. HRTEM images of Ag/AgCl/BiOCl (e) and Ag/AgBr/BiOBr (f) with small Ag/AgX and HRTEM images of Ag/AgCl/BiOCl (g) and Ag/AgBr/BiOBr (h) with large **Figure 35.** FESEM images of Ag/AgCl/BiOCl (a) and Ag/AgBr/BiOBr (b): the red arrows pointing out the Ag/AgX. TEM images of Ag/AgCl/BiOCl (c) and Ag/AgBr/BiOBr (d): blue rings show the small Ag/AgX, and the red dots point out the large Ag/AgX. HRTEM images of Ag/AgCl/BiOCl (e) and Ag/AgBr/BiOBr (f) with small Ag/AgX and HRTEM images of Ag/AgCl/BiOCl (g) and Ag/AgBr/BiOBr (h) with large Ag/AgX (i)the photocatalytic degradation percentage of RhB under visible-light irradiation (*λ* ≥ 400 nm) and (k) schematic structure of multicomponent heterojunction sys‐ tems [366].

Ag/AgX (i)the photocatalytic degradation percentage of RhB under visible‐light irradiation (*λ* ≥ 400 nm) and (k) schematic structure of multicomponent heterojunction systems[366]. trapping and superoxide radical quantification experiments. The role of metallic Ag in Ag/AgCl/BiOCl and Ag/AgBr/BiOBr were analyzed, and we found that the role of metallic Ag was a surface plasmon resonance and the Zscheme bridge for Ag/AgCl/BiOCl and Ag/AgBr/BiOBr, respectively. This results suggests that no matter in narrow band gap photocatalysts (Eg < 3.1 eV) or wide band gap photocatalysts (Eg > 3.1 eV), metallic Ag can enhance visible‐light‐driven photocatalytic activity though the different roles. Recently, our group has demonstrated a simple and efficient one-pot approach to prepare Ag/ r−GO/TiO2 composites using solvothermal method under atmospheric pressures (Fig. 36) [367], where N,N−dimethylacetamide serves as the reducing agent for Ag and GO reduction. On account of the experimental result, we concluded that the introduction of Ag into classical graphene/TiO2 system (i) availably expands the absorption range, (ii) improves the photogen‐ erated electron separation and (iii)increases the photocatalysis reaction active sites. The optimized composite sample exhibits outstanding photocatalysis activity compared with pure TiO2 under simulated sunlight. We further proposed that besides the above three advantages of Ag, different sizes of Ag nanoparticles are also responsible for the improved photocatalysis ability, where small−sized Ag nanoparticles (2~5 nm) could store photoexcited electrons that

 Recently, our group has demonstrated a simple and efficient one‐pot approach to prepare Ag/rGO/TiO2 composites using solvothermal method under atmospheric pressures (Fig. 36)[367], where N,Ndimethylacetamide serves as the reducing agent for Ag and GO reduction. On account of the experimental result, we concluded that the introduction of Ag into classical graphene/TiO2 system (i) availably expands the absorption range, (ii) improves the photogenerated electron separation and

generated from TiO2, while large−sized Ag nanoparticles could utilize visible light due to their localized surface plasmon resonance (LSPR) absorption. Our work gives a new insight into the photocatalysis mechanism of noble metal/r−GO/TiO2 composites and provides a new pathway into the design of TiO2−based photocatalysts and promote their practical application in various environmental and energy issues.

superoxide radical quantification experiments. The role of metallic Ag in Ag/AgCl/BiOCl and Ag/AgBr/BiOBr were analyzed, and we found that the role of metallic Ag was a surface plasmon resonance and the Z−scheme bridge for Ag/AgCl/BiOCl and Ag/AgBr/BiOBr, respectively. This results suggests that no matter in narrow band gap photocatalysts (Eg < 3.1 eV) or wide band gap photocatalysts (Eg > 3.1 eV), metallic Ag can enhance visible-light-driven

**i** 

**k**

**Figure 35**. FESEM images of Ag/AgCl/BiOCl (a) and Ag/AgBr/BiOBr (b): the red arrows pointing out the Ag/AgX. TEM images of Ag/AgCl/BiOCl (c) and Ag/AgBr/BiOBr (d): blue rings show the small Ag/AgX, and the red dots point out the large Ag/AgX. HRTEM images of Ag/AgCl/BiOCl (e) and Ag/AgBr/BiOBr (f) with small Ag/AgX and HRTEM images of Ag/AgCl/BiOCl (g) and Ag/AgBr/BiOBr (h) with large Ag/AgX (i)the photocatalytic degradation percentage of RhB under visible‐light irradiation (*λ* ≥ 400 nm) and (k) schematic structure of multicomponent heterojunction systems[366].

**Figure 35.** FESEM images of Ag/AgCl/BiOCl (a) and Ag/AgBr/BiOBr (b): the red arrows pointing out the Ag/AgX. TEM images of Ag/AgCl/BiOCl (c) and Ag/AgBr/BiOBr (d): blue rings show the small Ag/AgX, and the red dots point out the large Ag/AgX. HRTEM images of Ag/AgCl/BiOCl (e) and Ag/AgBr/BiOBr (f) with small Ag/AgX and HRTEM images of Ag/AgCl/BiOCl (g) and Ag/AgBr/BiOBr (h) with large Ag/AgX (i)the photocatalytic degradation percentage of RhB under visible-light irradiation (*λ* ≥ 400 nm) and (k) schematic structure of multicomponent heterojunction sys‐

trapping and superoxide radical quantification experiments. The role of metallic Ag in Ag/AgCl/BiOCl and Ag/AgBr/BiOBr were analyzed, and we found that the role of metallic Ag was a surface plasmon resonance and the Zscheme bridge for Ag/AgCl/BiOCl and Ag/AgBr/BiOBr, respectively. This results suggests that no matter in narrow band gap photocatalysts (Eg < 3.1 eV) or wide band gap photocatalysts (Eg > 3.1 eV), metallic Ag can enhance visible‐light‐driven photocatalytic activity though

Recently, our group has demonstrated a simple and efficient one-pot approach to prepare Ag/ r−GO/TiO2 composites using solvothermal method under atmospheric pressures (Fig. 36) [367], where N,N−dimethylacetamide serves as the reducing agent for Ag and GO reduction. On account of the experimental result, we concluded that the introduction of Ag into classical graphene/TiO2 system (i) availably expands the absorption range, (ii) improves the photogen‐ erated electron separation and (iii)increases the photocatalysis reaction active sites. The optimized composite sample exhibits outstanding photocatalysis activity compared with pure TiO2 under simulated sunlight. We further proposed that besides the above three advantages of Ag, different sizes of Ag nanoparticles are also responsible for the improved photocatalysis ability, where small−sized Ag nanoparticles (2~5 nm) could store photoexcited electrons that

 Recently, our group has demonstrated a simple and efficient one‐pot approach to prepare Ag/rGO/TiO2 composites using solvothermal method under atmospheric pressures (Fig. 36)[367], where N,Ndimethylacetamide serves as the reducing agent for Ag and GO reduction. On account of the experimental result, we concluded that the introduction of Ag into classical graphene/TiO2 system (i) availably expands the absorption range, (ii) improves the photogenerated electron separation and

photocatalytic performance was mainly attributed to the vectorial interparticle electron transfer driven

 A one‐step lowtemperature chemical bath method was developed to synthesize the flowerlike Ag/AgCl/BiOCl composite[365]. The asprepared Ag/AgCl/BiOCl composite exhibited enhanced visiblelight photocatalytic activity on photodegradation of rhodamine B, which was greatly improved in comparison with either pure Ag/AgCl or BiOCl. It is evidenced that the superoxide radical, chlorine radical and the hole play a critical role in the photocatalytic degradation of RhB over the Ag/AgCl/BiOCl. Next, Ag/AgX/BiOX (X = Cl, Br) three‐component visible‐light‐driven photocatalysts were synthesized by a lowtemperature chemical bath method (Fig. 35)[366]. The Ag/AgX/BiOX composites showed enhanced visiblelightdriven photocatalytic activity for the degradation of rhodamine B, which was much higher than Ag/AgX and BiOX. The photocatalytic mechanisms were analyzed by active species

by the two‐step excitation of both visible‐light‐driven components (AgBr and Bi2WO6).

photocatalytic activity though the different roles.

210 Advanced Catalytic Materials - Photocatalysis and Other Current Trends

the different roles.

tems [366].

Elemental mapping of (d) Ag and (e) Ti in the same area in (c). (f)Photocatalytic degradation of Rh B under simulated sunlight irradiation over P25, Ag/rGO/TiO2 composites with different AgNO3 contents. (g) Comparison of the photocatalytic activity of rGO, P25 and Ag/rGO/TiO2 composites with **Figure 36.** (a) TEM and (b) HRTEM images of sample AGT. (c) STEM model of Ag/r−GO/TiO2. Elemental mapping of (d) Ag and (e) Ti in the same area in (c). (f)Photocatalytic degradation of Rh B under simulated sunlight irradiation over P25, Ag/r−GO/TiO2 composites with different AgNO3 contents. (g) Comparison of the photocatalytic activity of r −GO, P25 and Ag/r−GO/TiO2 composites with different AgNO3 contents for the photocatalytic H2 production under simulated sunlight irradiation [367].

**Figure 36.** (a) TEM and (b) HRTEM images of sample AGT. (c) STEM model of Ag/rGO/TiO2.

different AgNO3 contents for the photocatalytic H2 production under simulated sunlight irradiation[367]. Next, we have replaced the Ag with MoS2 quantum dots (QDs) and demonstrated a simple and an efficient onepot approach to prepare MoS2 quantum dotsgrapheneTiO2 (MGT) composites using a solvothermal method under obtained atmospheric pressures and at low temperatures (Fig. 37)[368]. The shape of MoS2 obtained using this method is quantum dot instead of a layered sheet because of the **(e)**  Next, we have replaced the Ag with MoS2 quantum dots (QDs) and demonstrated a simple and an efficient one−pot approach to prepare MoS2 quantum dots−graphene−TiO<sup>2</sup> (MGT) composites using a solvothermal method under obtained atmospheric pressures and at low temperatures (Fig. 37) [368]. The shape of MoS2 obtained using this method is quantum dot instead of a layered sheet because of the interaction between functional groups on GO sheets and Mo precursors in a suitable solvent environment. In addition, it shows significantly increased photodegradation performance even without a noble-metal cocatalyst, which is due to the increased charge separation, visible-light absorbance, specific surface area and reaction sites upon the introduction of MoS2 QDs. Besides, the enhancement mainly came from holes left in the TiO2 crystals rather than electrons transferring to reduced graphene oxide (RGO).

**Figure 37.** TEM and HRTEM images of the sample (a), (b) MGT4 and (c), (d)MoS2graphene. (e) Proposed mechanism for the photodegradation of RhB by MGT under simulated sunlight irradiation (f) Photocatalytic degradation and (g) photocatalytic degradation reaction of RhB under simulated sunlight irradiation over P25, MGT composites with different MoS2 contents[368].

**(f) (g)**

interaction between functional groups on GO sheets and Mo precursors in a suitable solvent environment. In addition, it shows significantly increased photodegradation performance even without a noble‐metal cocatalyst, which is due to the increased charge separation, visible‐light absorbance, specific surface area and reaction sites upon the introduction of MoS2 QDs. Besides, the enhancement mainly came from holes left in the TiO2 crystals rather than electrons transferring to reduced graphene

oxide (RGO).

**Figure 36.** (a) TEM and (b) HRTEM images of sample AGT. (c) STEM model of Ag/rGO/TiO2.

Elemental mapping of (d) Ag and (e) Ti in the same area in (c). (f)Photocatalytic degradation of Rh B

under simulated sunlight irradiation over P25, Ag/rGO/TiO2 composites with different AgNO3

contents. (g) Comparison of the photocatalytic activity of rGO, P25 and Ag/rGO/TiO2 composites with

different AgNO3 contents for the photocatalytic H2 production under simulated sunlight irradiation[367].

Next, we have replaced the Ag with MoS2 quantum dots (QDs) and demonstrated a simple and an

efficient onepot approach to prepare MoS2 quantum dotsgrapheneTiO2 (MGT) composites using a

shape of MoS2 obtained using this method is quantum dot instead of a layered sheet because of the

**Figure 37.** TEM and HRTEM images of the sample (a), (b) MGT4 and (c), (d)MoS2graphene. (e) Proposed mechanism for the photodegradation of RhB by MGT under simulated sunlight irradiation (f) **Figure 37.** TEM and HRTEM images of the sample (a), (b) MGT−4 and (c), (d)MoS2−graphene. (e) Proposed mechanism for the photodegradation of RhB by MGT under simulated sunlight irradiation (f) Photocatalytic degradation and (g) photocatalytic degradation reaction of RhB under simulated sunlight irradiation over P25, MGT composites with dif‐ ferent MoS2 contents [368].

Photocatalytic degradation and (g) photocatalytic degradation reaction of RhB under simulated sunlight

irradiation over P25, MGT composites with different MoS2 contents[368].

interaction between functional groups on GO sheets and Mo precursors in a suitable solvent
