Distorted 1T-ReS2 Nanosheets Anchored on Porous TiO2 Nanofibers

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Energy, Environmental, and Catalysis Applications 2

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Distorted 1T-ReS Nanosheets Anchored on Porous TiO Nanofibers for Highly Enhanced Photocatalytic Hydrogen Production Xinqian Wang, Biao Chen, Dedao Yan, Xinyu Zhao, Chenlu Wang, Enzuo Liu, Naiqin Zhao, and Fang He ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.9b03772 • Publication Date (Web): 06 Jun 2019 Downloaded from http://pubs.acs.org on June 6, 2019

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ACS Applied Materials & Interfaces

Distorted 1T-ReS2 Nanosheets Anchored on Porous TiO2 Nanofibers for Highly Enhanced Photocatalytic Hydrogen Production

Xinqian Wang,† Biao Chen,† Dedao Yan,† Xinyu Zhao,† Chenlu Wang,† Enzuo Liu,†, ‡ Naiqin Zhao,†, ‡, + and Fang He†, +, *

† School of Materials Science and Engineering and Tianjin Key Laboratory of Composite and Functional Materials, Tianjin University, Tianjin 300350, P.R. China. ‡ Collaborative Innovation Centre of Chemical Science and Engineering, Tianjin 300072, P.R. China. + Key Laboratory of Advanced Ceramics and Machining Technology, Ministry of Education, Tianjin University, Tianjin, 300072, China.

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Abstract: Recently, loading TiO2 with transition metal disulfides (TMDs) to construct dual functional heterostructures has been widely researched as an effective strategy to improve the photocatalytic performance of TiO2 photocatalyst. For the TMDs co-catalysts, the 2H-MoS2 and 1T-MoS2 have been widely studied and researched. However, they are suffered from poor catalytic sites/low charge transfer ability and unstable structure, respectively. In this regard, distorted 1T phase TMDs with stable structure are greatly fit for co-catalyst due to their high charge transfer ability and rich catalytic sites on both edge and basal plane. Therefore, it is highly desirable to develop distorted 1T phase TMDs/TiO2 heterostructures with well-identified interfaces for highly enhanced photocatalytic performance. Herein, we first introduce distorted 1T-ReS2 anchored on porous TiO2 nanofibers as a promising photocatalyst for achieving an exchellent photocatalytic hydrogen production. The excellent performance is attributed to the strong chemical interaction of Ti-O-Re bond between TiO2 and ReS2, the excellent electron mobility of distorted 1T-ReS2, and the abundant catalytic activity sites on both plane and edge of ReS2 co-catalyst.

Keywords: ReS2; TiO2; Ti-O-Re bond; photocatalysis; hydrogen evolution reaction

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1. Introduction Currently, the increasingly environmental pollutions and energy crisis are greatly stimulating the development of the clean and renewable energy and technologies. Among them, hydrogen energy associated with photocatalysis technology has attracted a lot of attention, owing to the advantages of low cost, vast abundance, and eco-friendliness of solar energy.1 Since Fujishima and co-workers first reported the generation of hydrogen by splitting water on titanium dioxide (TiO2) electrode,2 TiO2 has received special interest as one kind of promising photocatalysts in the past few decades with the advantages of its strong redox ability, eco-friendliness, chemical stability and low cost.3-6 However, the photocatalytic hydrogen evolution (PHE) activity of TiO2 was still restricted by its narrow spectral response range, high charge carrier recombination, and poor catalytic activity sites.7-9 In order to overcome these drawbacks, loading TiO2 with co-catalysts, especially noble metals, has been developed as an effective strategy.10, 11 The noble metals have been demonstrated significantly enhanced efficiency of charge separation and number of catalytic activity sites. However, the low reserves and high cost of noble metals restricted their practical application.12 Therefore, it is urgent to develop new co-catalysts with low-cost, earth-abundant, and many catalytic activity sites for their widespread application.13, 14 There has been an increasing interest in transition metal disulfides (TMDs) on account of their characteristic two-dimensional structure, eminent optoelectronic and catalytic properties.15,

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As a typical layered TMD, molybdenum disulfide (MoS2) has been

extensively investigated as one of alternative co-catalysts.17,

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For instance, Zhang et al.

reported that the photocatalytic hydrogen production can be efficiently enhanced by preparing 3



few-layer MoS2 coated TiO2 heterostructure by a hydrothermal method.19 It has been confirmed by Xu and co-workers that the MoS2 co-catalyst in TiO2@MoS2 composite can effectively enhance the transfer of photogenerated carriers and the number catalytic activity sites, resulting in excellent photocatalytic hydrogen evolution activity.46 Recent advancements validate that the crystal structure of MoS2 plays a crucial role in the photocatalytic hydrogen production performance.20 It is known to all that MoS2 has two phases, 2H and 1T.21 The 1T metallic phase displays greatly lower charge transfer resistance than 2H semiconducting phase.22 Moreover, the 1T phase exhibits catalytical activity on both basal plane and edge, whereas the 2H phase has catalytic activity sites only on the edge.23 Therefore, the 1T-MoS2 shows higher catalytic activity than the most common phase, 2H-MoS2.24 However, the 1T phase is metastable and tends to convert to the stable 2H phase, which is harmful to the photocatalytic performance.22 Therefore, it remains challenging to design ideal TMDs co-catalysts for boosting the hydrogen production of TiO2. Recently, distorted 1T phase TMDs have been demonstrated to be fit for photocatalytic water splitting due to their high charge transfer ability and large catalytic sites on both edge and basal plane.25, 26 Moreover, the distorted 1T phase is more thermodynamically stable than 1T phase,27 which is greatly capable of the photocatalytic application. Therefore, the distorted 1T-TMDs have been considered as promising co-catalysts. Recently, rhenium disulfide (ReS2), as an emerging member of TMDs, was discovered to have distorted 1T structure and tunable direct bandgap.28-32 In addition, the weak interlayer coupling in ReS2 makes contributions to almost layer-independent optoelectronic characters and preferably exposed of unsaturated edge sites.33-35 Therefore, the distorted 1T-ReS2 is extremely fit for photocatalytic 4


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activities as an alternative co-catalyst. However, the promising TiO2/ReS2 photocatalysts has not been reported at present. In this work, few-layer ReS2 nanosheets anchored on porous TiO2 nanofibers (TiO2@ReS2) were prepared for the first time by a hydrothermal method. The few-layer ReS2 nanosheets with distorted 1T phase exhibit large catalytic activity sites, high electron mobility, and matched band structure. Moreover, the chemical bond of Ti-O-Re between ReS2 and TiO2 can effectively accelerate the separation and transfer of the photogenerated electron-hole pairs. These unique structural advantages greatly facilitate hydrogen evolution process. As a result, the optimized TiO2@ReS2 photocatalysts with 30 wt% ReS2 exhibit a surpassing PHE activity with a rate of 1404 μmol h-1 g-1, which is nearly 34 times higher than that of pure TiO2.

2.EXPERIMENTAL SECTION 2.1 Synthesis of porous TiO2 nanofibers Porous TiO2 nanofibers were synthesized through a simple electrospinning method together with calcination.27 450 mg of polyvinyl pyrrolidone (PVP) was dissolved in 6 mL of ethanol and stirred at room temperature for 2 h. Another solution containing 3 mL of ethanol, 3 mL of acetic, and 1.62 mL of titanium tetraisopropoxide (Ti(OiPr)4) was also prepared. The above two solutions were mixed and stirred until a transparent solution was obtained. An electrical potential of 10 kV and a electrode distance of 15 cm were performed for electrospinning at a ejected rate of 0.001 mm s-1. Finally, to form porous TiO2 nanofibers, the precursor was calcined at 500 °C for 2 h with a heating rate of 5 °C/min in air. 2.2 Preparation of TiO2@ReS2 nanocomposites 5



100 mg calcined TiO2 nanofibers were dispersed into 20 mL deionized water by sonicating. Another solution containing 43 mg of ammonium perrhenate (NH4ReO4), 54.4 mg of thiourea (CH4N2S), 42 mg of hydroxylamine hydrochloride (HONH3Cl), and 10 mL deionized water was also prepared by stirring. Then, the above two solutions were mixed to get a suspension. The suspension was diverted to a Teflon-lined stainless-steel autoclave and heated at 220 °C for 24 h. When cooling down to room temperature, the solid product was repeatedly washed with deionized water and ethanol, finally dried at 80 °C overnight to obtain TiO2@ReS2 nanocomposites (containing 30 wt% of ReS2). The TiO2@ReS2 composites with 15 wt% and 60 wt% ReS2 were also prepared with half and twice mass of NH4ReO4 and CH4N2S materials, respectively. By contrast, we also prepared ReS2 nanosheets without the addition of TiO2 nanofibers. 2.3 Characterization The crystal phases of TiO2, ReS2, and TiO2@ReS2 composites were determined by X-ray diffraction (XRD, Bruke D8 advanced). Field-emission scanning electron microscopy (FE-SEM, HITACHI S4800) and transmission electron microscopy (TEM, JEOL JEM-2100f) were used to survey the core-shell structure of TiO2@ReS2. The mass ratio of ReS2 in the TiO2@ReS2 samples was analysted by thermo-gravimetric (TG, PerkinElmer) with a temperature range of 25-800 °C in air. X-ray photoelectron spectroscopy (XPS, VersaProbe PHI-5000) was measured to study the elemental states of the samples. The N2 Desorption and adsorption curves were analyzed by Brunauer−Emmett−Teller (BET, Quantachrome U.S.) method. The density functional theory (DFT) method was used to analyzed the pore size distribution. 6


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2.4 Photoelectrochemical measurements Three-electrode electrochemical workstation (GAMRY 08030) was used to measure the photoelectrochemical performances of the samples (reference electrode: saturated calomel electrode (SCE); working electrode: FTO electrode deposited with the TiO2@ReS2 nanocomposites; counter electrode: platinum foil; 2 M Na2SO3 aqueous solution was used as the electrolyte at 25 °C). The light source was a 300 W xenon arc lamp (PL-X300, Happylab, China) at the wavelength range of 320–780 nm, and the light intensity was 100 mW/cm2. Mott-Schottky plots were determined at a frequency of 5000 Hz in 0.5 M Na2SO4 aqueous solution. The voltage range of -0.5-1.2 V vs Ag/AgCl was converted to the reversible hydrogen electrode (RHE) scale by the Nernst equation: 0 E RHE  0.0592 pH  E Ag / AgCl  E Ag / AgCl

in which ERHE is the converted potential vs RHE; E0Ag/AgCl is the standard potential of Ag/AgCl filled with 0.3 M KCl solution at 25°C, and EAg/AgCl is the experimental potential vs Ag/AgCl. 2.5 Photocatalytic hydrogen production tests A slolution containing 80 mL of deionized water, 20 ml of ethanol, and 50 mg as-prepared samples were added into a quartz reactor (200 mL). The reactor was assembled on a glass automatic on-line micro gas analysis system (Labsolar 6A), and then evacuated during the stirring process to remove bubbles from the solution. 300 W xenon arc lamp (PL-X300, Happylab, China) served as the light source. The gas chromatography (GC7900, Tianmei) was used to analyzed the hydrogen delivered by nitrogen. The apparent quantum efficiency

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(AQE) was tested under a light source with a 380 nm filter. The focused intensity was ca. 1.65 mW/cm2. The AQE was measured by equation:

AQE  

NR 100% NI N H2  2 NI

100%

in which N H 2 is the number of formed H2 molecules; N R is the number of reacted electrons;

N I is the number of incident photons.

3. Results and discussion The prepared strategy of TiO2@ReS2 nanocomposites contains two steps, as illustrated in Figure 1. Porous TiO2 nanofibers was first prepared through electrospinning and calcination. As shown in the scanning electron microscopy (SEM, Figure S1, Supporting Information) images, the TiO2 nanofibers exhibit several micro-meters in length and about 150 nm in diameter. Moreover, they display rough surface with a great number of mesopores, which can provide sufficient sites for the nucleation and growth of ReS2 during the subsequent hydrothermal process.36 Figures 2a, b show the typical SEM and transmission electron microscopy (TEM) images of TiO2@ReS2 nanocomposites with 30 wt% of ReS2. It can be clearly observed that the ReS2 nanosheets coat uniformly on the surface of porous TiO2 nanofibers in TiO2@ReS2 (30%). The high-resolution TEM (HRTEM) images in Figures 2c, d further reveal that the ReS2 nanosheets with few-layers (< 5 layer) are tightly anchored on the surface of TiO2. Moreover, the lattice spacings of 0.61, 0.27 and 0.35 nm correspond to the (002) and (-220) planes of distorted 1T-ReS2 (JCPDS 89-0341) and (101) plane of anatase TiO2 (JCPDS 21-1272).37, 38 The inset fast Fourier transform (FFT) pattern further reveal the existence of (-220) plane of distorted 1T-ReS2. The energy dispersive X-ray 8


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(EDX) spectroscopy (Figure S2) demonstrated that the TiO2@ReS2 (30%) is composed of Re, S, Ti and O elements. Moreover, the element distribution of TiO2@ReS2 (30%) can be further investigated by EDX spectroscopy mapping. As shown in Figure 2e, the mappings of Ti and Re dovetail well with those of O and S, respectively. Meanwhile, the mapping areas of Ti and O are smaller than those of Re and S, demonstrating the uniformly coated ReS2 nanosheets on the TiO2 nanofibers in TiO2@ReS2 (30%). For comparison, TiO2@ReS2 composites with 15 and 60 wt% ReS2 were also prepared by adjusting the amount of Re and S sources. As shown in Figures S3 and 4, few ReS2 nanosheets and agglomerated ReS2 spheres are observed, respectively, in TiO2@ReS2 (15%) and TiO2@ReS2 (60%). Moreover, without the addition of TiO2 nanofibers in the hydrothermal process, ReS2 nanosheets will self-assemble to form ReS2 spheres (Figure S5, Supporting Information). X-ray diffraction (XRD) patterns were performed to investigate the crystal structures. It is obvious that the characteristic peaks of anatase TiO2 (JCPDS 21-1272) and rutile TiO2 (JCPDS 21-1276) can be observed in porous TiO2 nanofibers (Figure S6a, Supporting Information), and such mixed-phase TiO2 are expected to enhance charge separation, leading to significantly improve photoactivity. In addition, Figure S6b presents that the diffraction peaks located at 14.6°, 32.8°, 44.8°, and 57.1°, respectively, assign to the (002), (-220), (006), and (3-13) planes of distorted 1T-ReS2 (JCPDS 89-0341). As shown in Figure 3a, both the diffraction peaks of porous TiO2 and pure ReS2 can be detected, suggesting that the TiO2@ReS2 (30%) nanocomposites consist of anatase/rutile TiO2 and distorted 1T-ReS2. Moreover, the actual weight content of ReS2 in TiO2@ReS2 (30%) was studied by using thermogravimetric analysis (TGA). As shown in Figure 3b, a low weight loss of 2.1% below 9



150 °C is ascribed to the volatilization of water. The evident weight loss of 20.4% in the range of 150-700 °C can be attributed to the oxidation of ReS2.35 Therefore, the real weight content of ReS2 (20.8%) is smaller than the designed value (30%), due to the inadequate hydrothermal reaction. The specific surface area and pore-size distribution of the as-prepared TiO2 nanofibers and TiO2@ReS2 (30%) nanocomposites were analyzed by BET (Figures 3c and 3d). The lager specific surface area (45.5 m2/g) of TiO2 nanofibers is because their extensive mesopores around 7.0 nm. The TiO2@ReS2 (30%) composites exhibit a reduced surface area and a negative pore size shift of about 2.2 nm, suggesting the ReS2 nanosheets were tightly anchored on the surface of porous TiO2 nanofibers. The X-ray photoelectron spectroscopy (XPS) analysis was further used to examine the chemical bonding and composition of the as-prepared samples. The survey spectra (Figure 4a) reveal that the TiO2@ReS2 (30%) composites are composed of Ti, O, Re, and S elements, which originate from porous TiO2 nanofibers and ReS2 spheres. Meanwhile, the C 1s peak at 284.8 eV is ascribed to the contamination of XPS instrument.39, 40 The Re and S fine peaks of Figures 4b and 4c show that the binding energies of Re 4f7/2, Re 4f5/2, S 2p3/2 and S 2p1/2 in the pure ReS2 are located at 42.6, 45.0, 163.0 and 164.4 eV, respectively, agreeing well with the reported results in previous literature.41 For the TiO2@ReS2 (30%), all binding energies showcase a negative energy shift of 0.7 eV, implying the strong chemical coupling between ReS2 and TiO2. The Ti 2p fine peaks of TiO2 and TiO2@ReS2 (30%) are presented in Figure 4d. We can observe that the separations of binding energies of Ti 2p1/2 and Ti 2p3/2 peaks are all 5.8 eV in the two samples, further demonstrating the existence of Ti4+.42, 43 Meanwhile, the two peaks of TiO2@ReS2 (30%) shift to higher binding energy by 0.2 eV when compared 10


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with TiO2 nanofibers, further confirming the electronic interaction between ReS2 and TiO2.44, 45

The O 1s fine peaks in TiO2 and TiO2@ReS2 (30%) were also performed to reveal the

interaction between ReS2 and TiO2. As shown in Figure 4e, the O 1s spectrum of TiO2 exists three peaks, situated at 529.9, 532.1, and 533.6 eV, corresponding to the Ti-O-Ti bond, O vacancy, and hydroxyl groups, respectively. Notably, it is worth pointing out that an extra O 1s peak at 530.7 eV is observed in TiO2@ReS2 (30%), which can be attributed to the formation of Ti-O-Re bonds between ReS2 and TiO2 (illustrated in Figure 4e).46 Ultraviolet-visible (UV-vis) spectra were employed to investigate the optical absorption of TiO2 nanofibers, ReS2 spheres, and three kinds of TiO2@ReS2 composites. As shown in Figure 5a, the TiO2 nanofibers show a narrow response range of UV light, while ReS2 spheres exhibit strong absorption in both visible and UV light region. For TiO2@ReS2 composites, the absorption intensity in visible light region rises with increasing the amount of ReS2. On the other hand, excessive coating of ReS2 has a negative effect on the light absorption of TiO2 photocatalyst, which will adversely affect the PHE performance. Figure 5b presents their PHE performance under UV-vis light. It is indubitable that TiO2 nanofibers show a low hydrogen production rate of 42 μmol h-1 g-1 due to their weak absorption, massive electron–hole recombination, and poor catalytic activity sites.47 The pure ReS2 spheres also present a negligible PHE efficiency of about 0 due to their a small amount of trions and massive electron–hole recombination.48 When the ReS2 co-catalysts coating on TiO2 nanofibers, the hydrogen production rates have a great enhancement. Especially, the TiO2@ReS2 (30%) composites display the best photocatalytic activity, owing to the both enough catalytic activity sites and light absorption of TiO2.19, 11


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The TiO2@ReS2 (30%)


composites display the highest PHE rate of 1404 μmol h-1 g-1, which is nearly 34 times higher than that of TiO2. Remarkably, this is a relatively excellent PHE performance ever reported in previous works on TMDs/TiO2 for photocatalytic activity(Table S1, Supporting Information). In addition, the AQE of hydrogen production for the TiO2@ReS2 (30%) is 46.76%, which is approximately 13 times higher than pure TiO2 (3.49%), indicating that charge separation efficiency of TiO2@ReS2 (30%) is greatly improved. The smaller PHE rate of TiO2@ReS2 (15%) and TiO2@ReS2 (60%) should be, respectively, derived from the insufficient catalytic activity sites and hindered light adsorption of TiO2 and carriers transfer. More importantly, it is found that the TiO2@ReS2 (30%) composites have precise recoverability for hydrogen evolution after three recycles lasting 9 h (Figure 5c), suggesting the strong chemical stability of ReS2 and TiO2. The structural stability can be confirmed by the TEM and HRTEM images of TiO2@ReS2 (30%) nanocomposites. As shown in Figure S7, the TiO2@ReS2 (30%) composites after 9 h cycles maintain 1D core-shell structure with TiO2 nanofibers and ReS2 nanosheets. In addition, the XPS spectra further disclose that the interaction (Ti-O-Re bond) between TiO2 and ReS2 in TiO2@ReS2 (30%) after 9 h cycles keeps consistent with that of fresh TiO2@ReS2 (30%) (Figure S8, Supporting Information). In order to learn the greatly enhanced PHE rate of TiO2@ReS2 (30%), the photoluminescence (PL) spectra and photocurrent tests were performed. The PL spectra at an excitation wavelength of 245 nm were measured to evaluate the separated efficiency of photogenerated carriers. According to Figure 5d, The PL intensity of TiO2@ReS2 (30%) is weaker than that of TiO2, suggesting the more efficient separation of photogenerated carriers.17,50 Additionally, the photocurrent of TiO2@ReS2 (30%) is significantly larger than 12


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that of TiO2 (Figure 5e). The above results verify that the enhanced efficiency of charge separation originating from Ti-O-Re interaction and the distorted 1T phase of ReS2 co-catalyst is responsible for the excellent PHE performance.23 Mott-Schottky plots were measured to determine the band gap positions of ReS2 and TiO2. As shown in Figure 5f, the conduction band (CB) potential of TiO2 and ReS2 can be measured to be -0.26 and -0.14 V (vs RHE), indicating that electron transfer from TiO2 to ReS2 is feasible.51-53 It is concluded that the distorted 1T-ReS2 anchored on porous TiO2 nanofibers through Ti-O-Re bond can significantly enhance the PHE rate of TiO2. As illustrated in Figure 6, under simulated sunlight irradiation, electrons are excited to the conduction band of TiO2, with holes generated in the valance band. Owing to the chemical interaction of Ti-O-Re bond between TiO2 and ReS2 and excellent electron mobility of distorted 1T-ReS2 co-catalyst, the photoexcited electrons can rapidly transfer to ReS2 with high separated efficiency. Moreover, because the distorted 1T-ReS2 has catalytic activity sites on both plane and edge, the transferred electrons can quickly participate in the reduction reaction to get H2. Simultaneously, the holes left in the valence band (VB) of TiO2 or transferred to the VB of ReS2 are repidly consumed by the sacrificial reagents-ethnol. The large amount of hydroxyl anion present in water could easily diffuse to the surface of TiO2 or ReS2, where it is oxidized to hydroxyl radical by the holes rapidly. Then a series of oxidation reactions of ethanol would occur at a high rate.54 Therefore, the distorted 1T-ReS2 is a promising co-catalyst for enhancing the PHE performance of TiO2. The core-shell TiO2@ReS2 composites with a chemical interaction can accelerate the transport of photoexcited electrons and block the

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recombination of photogenerated carriers, bringing about the high hydrogen evolution activity.

4. Conclusions In summary, the core-shell TiO2@ReS2 nanocomposites with few-layered distorted 1T-ReS2 nanosheets were successfully prepared by a facile hydrothermal method. The optimized TiO2@ReS2 nanocomposites with 30 wt% ReS2 exhibit superior PHE activity with a rate as high as 1404 μmol h-1 g-1. It is demonstrated that the chemical interaction between TiO2 and ReS2 can greatly accelerate the separation of photoexcited electrons and holes. Additionally, the distorted 1T-ReS2 exhibits excellent electron mobility together with a lot of catalytic activity sites, thus the photoexcited electrons can rapidly transfer to ReS2 and diffuse to the active sites, leading to the high hydrogen evolution activity. This work first explores the ReS2 co-catalyst to improve the PHE activity of TiO2 photocatalyst, which provides a new avenue for the design and preparation of various photocatalysts containing distorted 1T-ReS2 co-catalyst.

ASSOCIATED CONTENT Supporting Information Available: The following files are available free of charge. XRD pattern, SEM and TEM images of TiO2, ReS2, and TiO2@ReS2 (PDF) AUTHOR INFORMATION Corresponding Author 14


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*E-mail: [email protected] (F.H.). ORCID Xinqian Wang: 0000-0003-0689-9638 Biao Chen: 0000-0002-6181-2155 Enzuo Liu: 0000-0002-3331-2532 Fang He:0000-0003-2576-9978 Notes The authors declare no competing financial interest. Acknowledgement. The authors acknowledge the fnancial support by the National Natural Science Foundation of China (Grant No. 51572189 and No. 51372169).

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Figure 1. Schematic illustration of the preparation of TiO2@ReS2 nanocomposites.

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Figure 2. (a) SEM, (b) TEM, and (c, d) HRTEM images of TiO2@ReS2 (30%). (e) Elemental mappings corresponding to the selected area by red box in (b). The insets in (c) are HRTEM image and corresponding FFT pattern.

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Figure 3. (a) XRD pattern and (b) TGA curve of TiO2@ReS2 (30%). (c) N2 adsorption/desorption isotherm curves and (d) DFT pore size distribution of TiO2 nanofibers andTiO2@ReS2 (30%).

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Figure 4. (a) XPS survey spectra of TiO2 nanofibers, ReS2 spheres, and TiO2@ReS2 (30%). (b) Re 4f and (c) S 2p peaks of pure ReS2 and TiO2@ReS2 (30%). (d) Ti 2p and (e) O 1s peaks of pure TiO2 and TiO2@ReS2 (30%). (f) The interaction between TiO2 and ReS2.

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Figure 5. (a) UV-vis absorption spectra and (b) comparison of the photocatalytic hydrogen production activities of TiO2, TiO2@ReS2 (15%), TiO2@ReS2 (30%), TiO2@ReS2 (60%), and ReS2. (c) recycling photocatalytic hydrogen evolution test of TiO2@ReS2 (30%). (d) PL spectra and (e) photocurrent density-time curves of TiO2 and TiO2@ReS2 (30%). (f) Mott-Schottky plots of pure TiO2 and ReS2.

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Figure 6. Schematic illustration of photo excited electrons transport pathway on TiO2@ReS2 (30%).

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Table of Contents

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Distorted 1T-ReS2 Nanosheets Anchored on Porous TiO2 Nanofibers

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