TiO2-Ti3C2 Composites with Pt Decoration as Efficient Photocatalysts for Ethylene Oxidation under Near Infrared Light Irradiation①

ZHANG Liu-Xin PAN Xio-Yng WANG Gung-To LONG Xi YI Zhi-Guo, c

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TiO2-Ti3C2Composites with Pt Decoration as Efficient Photocatalysts for Ethylene Oxidation under Near Infrared Light Irradiation①

ZHANG Liu-Xiana, bPAN Xiao-Yangb②WANG Guang-Taoa②LONG XiabYI Zhi-Guob, c②

a(453007)b(350002)c(100049)

Efficient utilization of solar energy is highly desirable in the field of photocatalysis.However, the near-infrared part of the solar spectrum, which constitutes about 44% of sunlight, has rarely been used.Herein, we report that the TiO2coupled with MXene Ti3C2nanosheets shows promising photoactivity for ethylene oxidation under near infrared light (NIR) irradiation.Moreover, the Pt nanoparticle decoration can dramatically improve the performance of TiO2–Ti3C2nanocomposites.Within 15 minutes irradiation of the NIR light, 444 ppm of C2H4is completely removed over 1wt%Pt–TiO2–Ti3C2and the catalyst exhibits excellent stability.It is expected that our work could provide useful information for the design and synthesis of efficient and stable NIR active photocatalyst for the target applications.

MXene, layered Ti3C2, plasmonic, ethylene degradation, NIR photocatalysis;

1 INTRODUCTION

Since the discovery of water splitting on TiO2electrode by Fujishima and Honda[1], the efficient utilization of solar light for photocatalysis has gained significant interest[2].TiO2, as the most promising photocatalyst, has been widely studied in the field of photocatalysis because of its outstanding physicoche- mical properties, such as earth abundance, nontoxi- city, chemical and thermal stability, and resistance to photocorrosion[3, 4].However, due to the wide band gap of TiO2, it can only be activated under UV light irradiation[5, 6].Therefore, numerous strategies have been adopted to modify TiO2for the utilization of visible light, such as surface modification[7], doping of metal[8-10]or nonmetal elements[11-14], and combi- nation with narrow band gap semiconductors[15-17].Compared with reformative methods to activate TiO2under visible light irradiation, studies aimed at utilizing near-infrared (NIR) light for photocatalytic application, which constitutes about 44% of sunlight, are rather rare.Recently, up-conversion materials have been used to transform the NIR light into UV light to activate the TiO2under NIR light irradia- tion[18-20].However, the up-conversion photocatalysts have low photocatalytic efficiency and are difficult to prepare[18-20].In addition, carbon quantum dots[21]and Bi2WO6[22]have also been coupled with TiO2and these composite photocatalysts show promising photoactivities both under UV, visible and NIR light irradiation for dyes degradation in liquid phase.However, these catalysts still exhibit limited effi- ciency under NIR light irradiation.Therefore, it is still a challenge to prepare effective NIR photoca- talyst with high stability.

The recent and rapid development of surface plasmon resonance (SPR) mediated photocatalysis by noble metal-based composites has offered a new opportunity to overcome the limited efficiency of photocatalysts[23, 24].The SPR-induced charge transfer enables the effective harvesting of visible or even near-infrared (NIR) light to drive useful reaction processes, such as the decomposition of organic contaminants[25], and water splitting[26].Besides noble metals, it is also found that the two-dimensional Ti3C2shows strong absorption of NIR irradiation owing to the SPR effect of Ti3C2nanosheets[27-29].As the most widely studied MXene, Ti3C2has stimulated research enthusiasm because of their excellent structural stability, high electrical conductivity, and hydrophilicity[30-33], which can be obtained by selectively etching and exfoliating of Ti3AlC2powders with HF[34, 35].These fascinating properties lead to important applications, such as electrodes in lithium(Li)-ion batteries[36,37], supercapacitors[38], electrochemical biosensors[39], adsorbents[40, 41], hydrogen storage media[42, 43], catalyst supports[44-46], additives[47, 48], and many others[49-52].However, as a promising catalyst, Ti3C2has rarely been used in the field of photocatalysis.

Herein, we demonstrate that Ti3C2coupled with TiO2can be used as a promising photocatalyst for ethylene oxidation under NIR light irradiation.Moreover, Pt nanoparticles decoration on the surface of TiO2–Ti3C2nanocomposites, i.e., the resultant Pt–TiO2–Ti3C2hybrids, could further improve the photoactivities for C2H4oxidation, which is also stable under long-term operation.

2 EXPERIMENTAL

2.1 Chemicals and materials

Titanium aluminum carbide (98%, 200 mesh) was purchased from Forsman Scientific (Beijing) Co., Ltd.Hydrofluoric acid (HF, 40%), copper nitrate hydrate (Cu(NO3)2·3H2O), dibasic sodium phosphate (Na2HPO4), sodium sulfate (Na2SO4), and anhydrous ethanol (EtOH) were purchased from Sinopharm chemical regent Co., Ltd.(Shanghai, China).Deioni- zed water was supplied from local sources.All reagents and materials involved were used as received without further purification.

2.2 Synthesis of Ti3C2

The MXene-Ti3C2used in this study was synthe- sized as follows: Firstly, 0.3 g of Ti3AlC2powder was dispersed in 20 mL of 40% HF aqueous solution.Then the suspension was kept at 30 ℃under constant stirring for specific time period[35, 36].Subse- quently, the suspension was washed for several times using deionized water and centrifuged to get rid of the residual HF.After that, the products were dispersed in ethanol and subjected to strong ultro-sonication for 3 h and centrifugated at 4000 r.p.m.for 30 min.Finally, the powders were dried in an oven at 60 ℃ overnight.

2.3 Synthesis of TiO2–Ti3C2

The TiO2–Ti3C2nanocomposite was prepared by using the same procedure as the Ti3C2excepting that the reaction temperature was kept at 40 ℃ for 16 h.

2.4 Synthesis of Pt decorated TiO2–Ti3C2

Typically, 0.5 g of the as-synthesized TiO2–Ti3C2was added to 100 mL of deionized water with constant stirring to form a stable suspension.Then, the H2PtCl6(0.154 M) was added dropwise to the above suspension.Subsequently, the solution was heated to 80 ℃ in an oil bath under magnetic stirring for 7 h to achieve homogeneous dispersion of Pt ion precursors on the support.The obtained inky slurry was then dried in an oven at 80 ℃ for 24 h.Finally, the black powders were sintered at 300 ℃ for 1 h under H2atmosphere.

2.5 Synthesis of Cu2(OH)PO4

Cu2(OH)PO4microcrystals were prepared by a hydrothermal method in which stoichiometric amounts of Cu(NO3)2·3H2O and Na2HPO4were mixed into deionized water (60 mL) under constant stirring for 1 h[53].Then the suspension was trans- ferred into a 100 mL sealed Teflon-lined autoclave and followed by hydrothermal treatment at 120 ℃ for 6 h.The sample was collected by filtration, then thoroughly washed with deionized water, and finally dried in an oven at 60 ℃ for 12 h.

2.6 Sample characterization

Phase identification of the as-prepared samples was analyzed using X-ray diffraction (XRD) equip- ment (Rigaku Miniflex II) with Curadiation (= 0.154178 nm).The optical properties of the samples were characterized on a Perkin Elmer Lambda 900 UV/VIS/NIR spectrometer employing BaSO4as the internal reflectance sample.The spectra were recor- ded in the range from 200 to 1200 nm at ambient temperature in air atmosphere.A field-emission scanning electron microscopy (JSM-6700F) and transmission electron microscope (JUM-2010, FEI, Tecnia G2 F20 FEG TEM) were used to identify the morphology and microscopic structure of the as- synthesized samples.X-ray photoelectron spectro- scopy (XPS) measurements were carried out on a Phi Quantum 2000 spectrophotometer with Alradiation (1486.6 eV).

2.7 Photoelectrochemical measurements

The photoelectrochemical analysis was carried out in a conventional three-electrode cell.Ag/AgCl electrode was used as the reference electrode and Pt electrode as the counter electrode.Fluoride-tin oxide (FTO) glass was used to prepare the working electrode, which was firstly cleaned by ultrasound in ethanol for 30 min and dried at 80 ℃.The sample powders (10 mg) were ultrasonicated in 1 mL anhydrous ethanol to obtain evenly dispersed slurry.Then, the slurry was spread onto the FTO glass whose side part was protected in advance using Scotch tape.The working electrode was dried overnight under ambient conditions.A copper wire was connected to the side part of the working electrode using a conductive tape.Uncoated parts of the electrode were isolated with epoxy resin.The exposed area of the working electrode was 0.25 cm2.The photocurrent measurements were performed in a homemade three electrode quartz cell with a CHI 660D workstation under NIR light irradiation.The electrolyte was 0.2 M aqueous Na2SO4solution (pH = 6.8) without additive.

2.8 Photocatalytic activity test

The photocatalytic properties of the as-obtained samples were evaluated by measuring the degrada- tion of ethylene at atmospheric pressure in a custom- modified Pyrex reaction cell (volume: 450 mL) (Fig.S1).A 250 W infrared lamp was used as the infrared light source where the< 700 nm was filtered out during NIR light photocatalysis (Fig.S2).In a typical fixed-bed reaction: First, 0.4 g of photocatalyst was spread uniformly on the bottom of the reactor.Then, 200 μL of C2H4was injected into the reactor by micro-syringe.Prior to photo-irradiation, the reaction system was placed in the dark for 1 h to attain the adsorption-desorption equilibrium between the C2H4gas and the surface of the catalyst in the reactor.Then, the reactor was irradiated by a NIR light.At a certain time interval, 4 mL of gas was sampled from the reactor and the amount and type of gases were analyzed by a gas chromatograph (GC 9720 Fuli) equipped with a HP-plot/U capillary column, a molecular sieve 13X column, a flame ionization detector (FID) and a thermal conductivity detector (TCD).In a typical flow-bed reaction (Fig.S3), 0.6 g photocatalysts were firstly filled in the flow-bed pyrex reactor, and then the mixed gas consisting of 120 ppm C2H4, 78.9% N2and 21.1% O2was flowed through the photocatalysts and analyzed directly by the gas chromatograph (GC 9720 Fuli).The reactor was illuminated using the 250 W infrared lamp during the photoreactions.

3 RESULTS AND DISCUSSION

3.1 Characterization of photocatalysts

Fig.1a shows the formation of MXene Ti3C2.Briefly, when treating Ti3AlC2in HF aqueous solution, HF would selectively dissolve the Al species and produce exfoliated Ti3C2with an accordion-like architecture.Simultaneously, the Ti3C2layers are passivated with OH and F termi- nations.Fig.1b displays the XRD patterns of Ti3AlC2powders before and after HF treatment for different time period.The elimination of the strongest diffraction (104) peak of Ti3AlC2reveals the loss of Al element after HF treatment[34, 35, 47, 54].Simultaneously, the obvious shift of the (002) X-ray diffraction (XRD) peak at 9.8o to low angle direction indicates the occurrence of intercalation and delamination processes, as Al is replaced by OH and F elements[34].

Fig.1. (a) Schematic illustration of exfoliation process for Ti3AlC2; (b) XRD patterns of Ti3AlC2before and after being etched in HF solution for different time; (c～f) SEM images of Ti3AlC2before (c) and after HF treatment for 8 h (d), 16 h (e), and 20 h (f)

To explore the morphology changes of Ti3AlC2before and after HF treatment, SEM analysis is utilized.Fig.1c shows a typically dense layered structure of initial Ti3AlC2particle.Most of Ti3AlC2layer begins to separate after being immersed in HF solution for 8 h at 30 ℃ (Fig.1d), which is in accordance with the previously reported study[55].With the increase of treatment time, the continuous removal of Al causes further delamination, which makes the stacked sheets become thinner.As shown in Fig.1e, it can be seen that the Ti3C2is composed of lots of nanosheets and the thickness is 30 ± 10 nm.Energy dispersive spectroscopy (EDS) spectrum analysis further shows that the resultant product was composed mainly of Ti and C and a small amount of O and F (little Al) elements, which is attributed to the replacement of Al layers with OH and F (Fig.S4).These nanosheets stack together like papers with unequal spacing.At this stage, the Ti3C2layers are presumably joined together only by weak van der Waals or hydrogen forces, as demonstrated by recent study[56].However, the Ti3C2nanosheets become seriously fractured after prolonging the reaction time for 20 h, as shown in Fig.1f.Therefore, the Ti3C2obtained after HF treatment for 16 h is used for further application.Fig.S5 shows the X-ray photoelectron spectroscopy (XPS) analysis of Ti3C2.As shown in Fig.S5a, the Ti 2components of Ti3C2centered at 454.8, 455.7 and 457.2eV can be assigned as Ti–C bond, Ti–C(<1) or titanium oxycarbides, and Ti ions with reduced charge state (TiO), respectively.The C 1spectrumof the Ti3C2is fitted by five components located at 281.7, 282.2, 284.8, 286.2, and 288.6 eV, corresponding to C–Ti, C–Ti–O, C–C/C–H, C–O, and C–F bonds, respec- tively (Fig.S5b).The presence of TiOindicates that the Ti3C2is partially oxidized under this condition, although the presence of TiOcould not be detected by the XRD analysis.

The TiO2–Ti3C2nanocomposite was prepared by the same procedure as that of Ti3C2and the reaction temperature is increased to 40 ℃.The increase of reaction temperature would result in the partial dissolution of Ti3C2.As a result, the low valence state titanium ions are obtained and further oxidized by the dissolved O2to form Ti4+ions.Subsequently, the Ti4+ions are hydrolyzed in the presence of water to form TiO2.As shown in Fig.2, TiO2–Ti3C2shows new diffraction peak at 25.4o, which can be ascribed to the (101) peak of anatase TiO2.The gravimetric study shows that the formation of TiO2on Ti3C2results in the increase mass of TiO2–Ti3C2as compared to Ti3C2(Table S1).The EDS analysis shows that the atomic ratio of C to F element in TiO2–Ti3C2is obviously decreased while the atomic ratio of Ti to O content is relatively increased (Table S2).These results further confirm the formation of TiO2–Ti3C2nanocomposite.

Fig.2. XRD patterns of the as-synthesized samples

Pt–TiO2–Ti3C2nanocomposites are further pre- pared by treating the mixture of TiO2–Ti3C2and H2PtCl6under H2atmosphere.No characteristic diffraction peaks are detected for Pt species in the XRD pattern of Pt–TiO2–Ti3C2nanocomposites owing to the high dispersion and low loading amount of Pt nanoparticles (Fig.2).The X-ray photoelectron spectroscopy (XPS) analysis reveals that most of Pt in 1wt%Pt–TiO2–Ti3C2is in the metallic state (Fig.S6a).As shown in Fig.S6b, the Ti 2components of 1wt%Pt–TiO2–Ti3C2centered at 454.8, 455.7, 457.2 and 459 eV can be assigned as Ti–C bond, Ti–C(<1) or titanium oxycarbides, Ti ions with reduced charge state (TiO) and TiO2, respectively[52, 57].The C 1spectrum of 1wt%Pt– TiO2–Ti3C2is fitted by five components located at 281.7, 282.2, 284.8, 286.2, and 288.6 eV, corres- ponding to C–Ti, C–Ti–O, C–C/C–H, C–O, and C–F bonds, respectively (Fig.S6c)[52, 57].

Fig.3 shows the UV/Vis/NIR diffusive-reflectance spectra (DRS) of the as-synthesized photocatalysts.The results indicate that Ti3C2is excellent absorber over a very broad photo-irradiation range that covers ultraviolet, visible, and infrared region, consistent with the previously reported studies[27].When decorated by TiO2, the absorption in visible region decreases obviously; at the same time, the absorption in the region of 930～1200 nm increases compared to pure Ti3C2.Moreover, the Pt decoration further enhances the absorption intensity in the UV, visible and NIR region.The intense absorption implies that a high utilization efficiency of solar energy would be feasible.

Fig.3. UV-Vis/NIR diffuse reflectance spectra of the samples

The morphology of 1wt%Pt–TiO2–Ti3C2was characterized by both scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses.The SEM image shows that the Pt–TiO2– Ti3C2exhibits the similar shape as TiO2–Ti3C2(Fig.S7a).The TEM image depicted in Fig.4a, b shows that the Pt nanoparticles have an average size of ～8 nm, which are distributed uniformly on the TiO2– Ti3C2surface.This assignment is also confirmed by SEM-elemental mapping analysis (Figs.S7b～S7d).The district lattice spacing of 1.0 and 0.36 nm can also be observed on the sample, which can be ascri- bed to the (002) facets of Ti3C2and (101) planes of TiO2, respectively (Fig.4b).

3.2 Photocatalytic degradation of C2H4

The performance of the samples is investigated by photocatalytic oxidation of ethylene under near infrared (NIR) light irradiation.The blank experi- ments without photocatalyst or light irradiation show no photoactivities, suggesting that this reaction is truly driven by the photocatalytic process.For com- parison purpose, a typical NIR photocatalyst Cu2(OH)PO4[53]is prepared (Fig.S8) and its perfor- mance for C2H4oxidation is investigated.It is found that Cu2(OH)PO4is completely inactive for C2H4oxidation under NIR light irradiation (Fig.5a).In distinct contrast, the Ti3C2exhibits moderate photo- catalytic activity for C2H4oxidation under NIR light irradiation (Fig.5a).With TiO2decoration, TiO2– Ti3C2shows obviously improved photoactivity for C2H4oxidation.Dramatic activity increase was observed after the TiO2–Ti3C2sample was decorated with Pt nanoparticles.In particular, the 1wt%Pt– TiO2–Ti3C2composite shows the best photoactivity among the Pt–TiO2–Ti3C2composites (Fig.5b).Within 15 min, 444 ppm of C2H4was completely removed under NIR light irradiation.More impor- tantly, 1wt%Pt–TiO2–Ti3C2composite shows better catalytic performance than that of 1wt%Pt–Ti3C2(Fig.5b).The controlled experiment indicates that 1wt%Pt–TiO2–Ti3C2composite shows no catalytic activity when the reaction system is saturated with N2.This result indicates that the molecular oxygen is the primary oxidant for ethylene oxidation.In addition, we also found that the 1wt%Pt–TiO2–Ti3C2composite shows better catalytic performance when the water vapor is removed from the reaction system (Fig.S9).The turn over number of 1wt%Pt–TiO2– Ti3C2for photocatalytic ethylene oxidation is calculated to be 2.24 > 1 (Fig.S10), indicating that this reaction is truly driven by a catalytic process.

Fig.4. TEM image (a) and HRTEM image (b) of the 1wt%Pt–TiO2–Ti3C2

Fig.5. (a) Photocatalytic activity of Cu2(OH)PO4, Ti3C2and TiO2–Ti3C2towards the ethylene oxidation under NIR light irradiation; (b) Photocatalytic degradation of ethylene over the photocatalyst in a fixed-bed mode under NIR light irradiation

To examine the mineralization rate of ethylene oxidation, the flow mode test was further conducted as well.Before illumination, the reaction system was expelled by flowing N2.After that, the reaction gas consisting of 120 ppm ethylene, 78.9% N2and 21.1% O2was flowed through the 1wt%Pt–TiO2– Ti3C2samples and analyzed by gas chromatography (GC9720 Fuli).Fig.6 shows the time dependency of the C2H4oxidation over the 1wt%Pt–TiO2–Ti3C2catalyst under NIR light illumination in the flow mode experiment.Before turning on the light, the detected concentration of C2H4was 120 ppm and no CO2was detected.When the light was turned on, the concentration of C2H4decreased rapidly to ～4.2 ppm.Simultaneously, the concentration of CO2increased promptly to ～230.6 ppm.When the light was turned off, the amount of C2H4returned to the constant value, and in the meantime, the concen- tration of CO2rapidly decreased to zero.This result indicates that this reaction is truly driven by a photocatalytic process.The mineralization ratio of ethylene is determined to be ca.96.5% in this reaction.

Fig.6. Photocatalytic C2H4degradation and CO2generation over the 1wt%Pt–TiO2–Ti3C2under NIR light irradiation in a flow mode

The stability of the photocatalyst is also investiga- ted.As shown in Fig.7a, there is no obvious de- crease during ten successive recycling tests for the degradation of C2H4under NIR light irradiation.In addition, to learn if there is change in the crystal structure and surface composition after the photoca- talytic degradation of C2H4, we also characterized the fresh and used 1wt%Pt–TiO2–Ti3C2by XRD and XPS techniques.As shown in Fig.7b, the used 1wt%Pt–TiO2–Ti3C2has identical XRD patterns as compared to the fresh 1wt%Pt–TiO2–Ti3C2, implying no significant change occurred in the crystal structure of the sample after photocatalytic reaction.Further- more, we found that the Ti3C2is partially oxidized after NIR light irradiation at ambient temperature, which can be evidenced by XPS analysis (Fig.S11).This could be explained by the moderate activity of Ti3C2on Fig.5a.In contrast, the 1wt%Pt–TiO2–Ti3C2composite is highly stable under the reaction condition, which indicates the beneficial effect of TiO2and Pt decoration on improving the stability of photocatalyst.The contrast XPS results of typical Pt 4, C 1and Ti 2spectra, as shown in Figs.7c～7d and Fig.S12, further demonstrate that the used 1wt%Pt–TiO2–Ti3C2has a similar composition to that of the fresh 1wt%Pt–TiO2–Ti3C2.Therefore, it is concluded that the as-prepared Pt–TiO2–Ti3C2is a stable photocatalyst for the degradation of ethylene under NIR light irradiation.

To investigate the possible influence of tempera- ture on this reaction, we then conducted the C2H4oxidation over the TiO2–Ti3C2and 1wt%Pt–TiO2– Ti3C2composites under thermal condition.For TiO2–Ti3C2, the thermocatalytic reference experi- ment was carried out in the dark at 120 ℃.As shown in Fig.8a～8b, the TiO2–Ti3C2is completely inactive under this condition.This result confirms that the NIR photocatalytic property of TiO2–Ti3C2is attributed to the photocatalysis reaction rather than temperature effects.However, the 1wt%Pt–TiO2– Ti3C2shows obvious activity under thermal condition (Fig.8c～8d).The reaction rate increases with the increase of temperature.Note also 1wt%Pt–TiO2–Ti3C2exhibits weak UV light activity and strong visible light activity (Fig.S13).These results suggest that the ethylene oxidation over 1wt%Pt–TiO2–Ti3C2is driven by a photothermal catalytic process, in which photo and heat both contribute to the oxidation of C2H4.

Fig.7. (a) Recycled testing of photocatalytic activity of the 1wt%Pt–TiO2–Ti3C2toward the ethylene oxidation under NIR light irradiation; (b) XRD patterns of the fresh and used 1wt%Pt–TiO2–Ti3C2sample; X-ray photoelectron spectra of Pt 4(c) and C 1(d) of 1wt%Pt–TiO2–Ti3C2before and after photocatalytic reaction

Fig.8.(a) Temperature of the reaction system during the photoxidation of C2H4over TiO2–Ti3C2under NIR light irradiation; (b) Thermocatalytic degradation of ethylene over the TiO2–Ti3C2nanocomposite in the dark at 120 ℃; (c) Temperature of the reaction system during the photoxidation of C2H4over the 1wt%Pt–TiO2–Ti3C2under NIR light irradiation; (d) Thermocatalytic degradation of ethylene over the 1wt%Pt–TiO2–Ti3C2nanocomposite at different temperature

Fig.9. Photocurrent responses of Ti3C2under NIR light irradiation

Photoelectrochemical analysis is used to determine whether the electrons of plasmonic Ti3C2can be excited as other plasmonic materials.As shown in Fig.9, a distinct photocurrent was observed for Ti3C2under the irradiation of NIR light.This result demonstrates that the electrons of Ti3C2can be excited and applied to photocatalysis.With TiO2decoration, the photocurrent of Ti3C2decreases obviously (Fig.S14).This phenomenon has also been observed on the previous report[58].The decrease of photocurrent can be explained as follows: with the TiO2decoration, the photogenerated electrons can be preferentially transferred from Ti3C2to TiO2and then captured by O2rather than to the electrode.Therefore, the electrons are consumed and result in the decrease of photocurrent.

Based on the above results, the possible reaction mechanism has been proposed in Fig.10.As irradia- ted by the NIR light, the electrons of plasmonic Ti3C2are excited and then transferred to Pt NPs and the conduct band (CB) of TiO2owing to the matched energy band structure.Subsequently, the electrons (e-) on Pt NPs and the conduction band of TiO2would react with the adsorbed oxygen (O2) to produce superoxide radical anion (O2-).Then the O2-radicals react with C2H4to yield CO2and H2O.In addition, the NIR light irradiation also increases the reaction temperature.As a result, the ethylene oxidation can also be proceeded via a thermocatalytic process on Pt nanoparticles.That is, the efficient performance of Pt–TiO2–Ti3C2can be ascribed to the synergistic effect of light and heat.

Fig.10. Proposed reaction mechanism of C2H4oxidation over Pt–TiO2–Ti3C2under NIR light irradiation

4 CONCLUSION

In conclusion, we report that the TiO2coupled with MXene Ti3C2nanosheets shows promising photodegradation activity of ethylene under NIR light irradiation.The Pt nanoparticle decoration can greatly enhance the photocatalytic performance of TiO2–Ti3C2nanocomposite.Within 15 min, 444 ppm of ethylene was completely oxidized over 1wt%Pt– TiO2–Ti3C2under NIR light irradiation and the catalyst is stable under long-term operation.This study is expected to provide useful information for the design and synthesis of NIR active photocatalyst and extend the application of MXene.

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15 January 2018;

29 March 2018

① Financially supported by the National Natural Science Foundation of China (No.21607153, 21373224 and 21577143), the Natural Science Foundation of Fujian Province (No.2015J05044 and 2017J05031), the Strategic Priority Research Program of the Chinese Academy of Sciences (No.XDB20000000), and the Key Research Program of Frontier Sciences of the Chinese Academy of Sciences (No.QYZDB-SSW-JSC027)

Pan Xiao-Yang, E-mail: xypan@fjirsm.ac.cn; Wang Guang-Tao, E-mail: wangtao@henannu.edu.cn; Yi Zhi-Guo, E-mail: zhiguo@fjirsm.ac.cn

10.14102/j.cnki.0254-5861.2011-1950