Use of a graphene derivative / titanium dioxide composite

Abstract

The application discloses a kind of graphene derivative / titanium dioxide composite material, belong to material preparation technical field.The application is: using AC-13 type asphalt mixture, by standard Marshall test determines the best oil stone ratio (OAC) is 4.8~5%, rGO-TiO2 Composite material is incorporated by the way of equal mass instead of mineral powder, incorporation ratio is 2~6%.AC-13 type asphalt mixture is composed of aggregate, asphalt and mineral powder three, the core pollutant of exhaust gas that the asphalt mixture can degrade and its concentration are HC 100~200ppm, CO 0.1~0.3%, NO 50~100ppm, applicable environmental temperature is -40~40 ℃.The asphalt mixture of the application is mixed by the way of rGO-TiO2 Composite material incorporation, can realize the sustained purification effect of automobile exhaust pollutants under different temperature environment, especially under low temperature conditions, it has certain engineering popularization potential to NO and maintain higher degradation rate.

Description

Technical Field

[0001] This invention belongs to the field of materials preparation technology, specifically relating to the application of a graphene derivative / titanium dioxide composite material (rGO-TiO2). Background Technology

[0002] In recent years, with the continuous increase in the number of motor vehicles in cities, vehicle exhaust emissions have become one of the main sources of urban air pollution, posing a serious threat to human health and the ecological environment. Nitrogen oxides (NOx) contained in exhaust gases... x Pollutants such as carbon monoxide (CO) and hydrocarbons (HC) not only easily form haze, acid rain, and photochemical smog, but can also induce respiratory diseases and cardiovascular risks, seriously affecting residents' quality of life and urban sustainable development. In cold regions, vehicle exhaust pollution is particularly prominent. Under winter conditions, frequent cold starts, prolonged idling time, and decreased efficiency of exhaust after-treatment systems lead to a significant increase in emissions per unit time. Simultaneously, the formation of temperature inversion layers compresses the near-surface atmospheric boundary layer, weakening the vertical diffusion capacity of pollutants. Under the dual effects of "high emissions" and "weak diffusion," pollutants are more likely to accumulate in the near-surface layer near roads, resulting in a significantly higher degree of air quality deterioration in winter compared to warmer regions. Therefore, vehicle exhaust pollution has become one of the core issues in environmental governance in cold-region cities.

[0003] Among numerous exhaust gas treatment technologies, semiconductor photocatalytic materials have attracted widespread attention due to their ability to be driven by light energy, mild reaction conditions, and lack of secondary pollution. Titanium dioxide (TiO2), in particular, is considered one of the most promising photocatalytic materials for engineering applications due to its high chemical stability, strong oxidizing power, non-toxicity, and low cost. Numerous studies have shown that under ultraviolet light irradiation, TiO2 can generate photogenerated electron-hole pairs, participating in various redox reactions to decompose harmful components in exhaust gases. Therefore, researchers have begun to explore the application of TiO2 photocatalysis to road engineering, investigating the construction of photocatalytic pavement materials with exhaust gas degradation capabilities to achieve in-situ reduction of pollutants at the road-vehicle interface. Current research mainly focuses on two technical approaches: one is applying TiO2 to the road surface via spraying or coating to form a surface photocatalytic coating; the other is incorporating TiO2 into asphalt binders or asphalt mixtures. Surface spraying offers advantages such as sufficient exposure of active sites and high initial efficiency, but it is susceptible to traffic wear and pollution, resulting in significant durability issues. Internal incorporation is less affected by wear, but its effectiveness is limited by the asphalt matrix encapsulation effect, leading to insufficient effective reaction interfaces. Furthermore, due to TiO2's large band gap, it can only absorb short-wavelength ultraviolet light, which accounts for less than 4% of solar radiation, leaving approximately 45% of visible light unutilized. This limitation is particularly pronounced in real-world road environments, especially in cold regions with weak winter sunlight. To enhance the photocatalytic performance of TiO2, broaden its response range to sunlight, and reduce the electron-hole recombination rate, researchers have developed various modification methods, such as nanostructure manipulation, heteroatom doping, and heterostructure construction. Among these, combining nano-TiO2 with carbon-based materials to improve photocatalytic performance has attracted widespread research attention in recent years.

[0004] Graphene and its derivatives (GO / rGO) are valued for their excellent electrical conductivity, large specific surface area, and... - The interaction ability of TiO2, which can serve as an efficient electron transport medium and effectively reduce the recombination probability of photogenerated carriers, has led to its widespread application in the composite modification research of TiO2. Huang et al. applied graphene-supported TiO2 to asphalt pavement, achieving efficient degradation of NO, CO, and HC under visible light. Nan Xiong et al. prepared a reduced graphene oxide-titanium dioxide composite photocatalyst material by combining graphene and nano-TiO2 through high-temperature vacuum annealing. The results showed that the photocatalytic performance of the composite material was significantly better than that of pure TiO2, with its band gap narrowing from 3.19 eV to 2.68 eV, and visible light absorption and activity being enhanced simultaneously. Liang et al. used a one-step hydrothermal method to achieve simultaneous reduction of GO and in-situ crystallization growth of TiO2 at 180℃, and the photocatalytic activity of the resulting composite was approximately 4.6 times that of pure TiO2. Hu et al. prepared rGO / TiO2-C composites using an improved hydrothermal route: GO and P25 TiO2 were mixed in CTAB and NaOH solution and reacted at 170℃ for 24 h, followed by annealing at 450℃ for 2 h under N2 atmosphere; during the process, GO was reduced to rGO, and TiO2 nanowires grew in situ on its surface, forming a dense interfacial bond. Tobaldi et al. constructed a composite system using a green sol-gel coupled graphene, and tested it against NO under sunlight / visible light conditions. x It exhibits higher removal efficiency and good cycle stability for VOCs (such as benzene and isopropanol). Mahmoud et al. reported that introducing about 5% rGO into the TiO2 system can significantly enhance electron transport and inhibit recombination, increasing the degradation rate of methylene blue from about 28% to about 86%. Although graphene-TiO2 composite photocatalysts have shown good potential in the laboratory, there are still some research gaps. On the one hand, existing studies are mostly focused on room temperature conditions, and research on the degradation efficiency of exhaust gases in cold regions at low temperatures is relatively lacking. On the other hand, there are few studies on adding composite materials to asphalt mixtures as internal additives and systematically evaluating their degradation performance under real vehicle exhaust conditions. Summary of the Invention

[0005] The purpose of this invention is to solve the above-mentioned problems in the background art and to provide a method for preparing graphene derivative / titanium dioxide composite material (rGO-TiO2) and its application.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] An application of a graphene derivative / titanium dioxide composite material, wherein the application is as follows: using AC-13 type asphalt mixture, the optimal asphalt-aggregate ratio (OAC) is determined to be 4.8%~5% by standard Marshall test (T 0709-2025), and the rGO-TiO2 composite material is incorporated by replacing mineral powder by equal mass, with the incorporation ratio of rGO-TiO2 being 2%~6%.

[0008] Furthermore, AC-13 asphalt mixtures consist of aggregates, asphalt, and mineral powder, with a nominal maximum aggregate size of 13.2 mm. The mix proportions for AC-13 asphalt mixtures do not have a fixed, unique value and must be determined through target mix design according to the "Technical Specification for Construction of Highway Asphalt Pavement" (JTG F40). In engineering practice, the commonly used empirical range for the mass fractions of aggregates and asphalt is: coarse aggregate 50%–60%, fine aggregate 30%–40%, mineral powder 4%–7%, and asphalt 4.5%–5.5%. The asphalt-aggregate ratio is calculated as asphalt mass / total aggregate mass (coarse aggregate + fine aggregate + mineral powder).

[0009] Furthermore, considering the dispersion state of nanomaterials in asphalt mixtures, the rGO-TiO2 composite material and mineral powder were premixed in a mixer to ensure uniform dispersion. The experiment adopted a post-filler process: the aggregate was stirred in a mixing pot at 150~160℃ for 80~100 seconds; then hot asphalt (150~160℃) was added and stirring was continued for 80~100 seconds; finally, the rGO-TiO2 composite material and mineral powder were added and stirred for 80~100 seconds.

[0010] Furthermore, the asphalt mixture can degrade the core pollutants in the exhaust gas and their concentrations are HC 100~200ppm, CO 0.1~0.3%, NO 50~100ppm, and the applicable ambient temperature is -40℃~40℃, preferably -20℃~30℃.

[0011] Further, the preparation method of rGO-TiO2 composite material is as follows: 0.15~0.25g of industrial grade rGO powder is weighed and dispersed in a mixed solution of 45~55mL of deionized water and anhydrous ethanol (volume ratio of 1:2); after ultrasonic treatment for 13~17 minutes, a uniformly dispersed black suspension is formed; then, 4.5~5.5g of nano-TiO2 particles are added to the suspension and continuously mixed under magnetic stirring for 2~3 hours to ensure that the TiO2 particles are uniformly anchored on the rGO surface; the mixed suspension is subjected to solid-liquid separation by a vacuum filtration device; the obtained filter cake is washed alternately with deionized water and anhydrous ethanol 3~4 times; the washed filter cake is placed in a 75~85℃ forced-air drying oven and dried for 22~26 hours, and ground to obtain gray precursor powder; the precursor powder is placed in a vacuum tube furnace and annealed at 580~620℃ for 2 hours, and after natural cooling, the rGO-TiO2 composite photocatalytic material is obtained.

[0012] The advantages of this invention compared to existing technologies are as follows: This invention uses a high-temperature vacuum annealing process to prepare rGO / TiO2 composite photocatalyst materials, and introduces them into asphalt mixtures as an internal additive by replacing mineral powder. Based on a self-designed exhaust gas analysis system, the changes in exhaust gas degradation efficiency and rate of asphalt mixtures with different rGO-TiO2 content under normal temperature and low temperature environments were systematically evaluated. The following conclusions were drawn:

[0013] (1) A high-temperature vacuum annealing process was used to successfully prepare rGO / TiO2 composite photocatalytic materials. The materials maintained the anatase crystal structure with high photocatalytic activity. The introduction of rGO effectively inhibited TiO2 aggregation and significantly improved the specific surface area and light absorption capacity. At the same time, Ti-OC bonds were formed at the interface and oxygen vacancies were generated, which enhanced the adsorption and activation capacity of pollutants on the surface. This is the reason why the photocatalytic efficiency of rGO-TiO2 is significantly better than that of pure TiO2.

[0014] (2) The room temperature photocatalytic degradation test showed that the comprehensive degradation performance of exhaust gas pollutants was optimal when the rGO content was 4 wt% of the mineral powder replacement amount. Compared with the pure TiO2 group, the degradation efficiency of HC, CO and NO at 60 min increased by about 8.61%, 11.85% and 43.12%, respectively.

[0015] (3) The results of the low temperature environment test showed that the degradation efficiency of the three pollutants at 0℃ was basically the same as that at room temperature. When the temperature dropped to -10℃ and -20℃, the degradation efficiency and reaction rate of HC and CO decreased significantly with the decrease of temperature. Although the degradation efficiency of NO showed a decreasing trend, it was still significantly higher than the degradation level of pure TiO2 at room temperature throughout the entire period.

[0016] (4) The rGO-TiO2 asphalt mixture constructed by internal admixture can achieve continuous purification of vehicle exhaust pollutants under different temperature conditions. It maintains a high degradation rate of NO, especially under low temperature conditions, and has certain potential for engineering promotion. Attached Figure Description

[0017] Figure 1 Here is a flowchart of the rGO-TiO2 preparation process;

[0018] Figure 2 The temperature control testing system includes (a) a gas reaction chamber; (b) a tail gas emission analyzer; and (c) a UTM 100 low-temperature testing equipment.

[0019] Figure 3 X-ray diffraction (XRD) patterns of TiO2 and rGO-TiO2 samples;

[0020] Figure 4The images show the microstructure and corresponding elemental distribution characteristics, including: (a) scanning electron microscope (SEM) image of pure TiO2 nanoparticles; (b) scanning electron microscope (SEM) image of rGO-TiO2; (c) microstructure of the surface sample of the rutted plate specimen; and (d) spatial distribution of each element.

[0021] Figure 5 The nitrogen adsorption-desorption isotherms and corresponding pore size distributions are shown, where (a) TiO2 and (b) rGO-TiO2.

[0022] Figure 6 The UV-Vis DRS and bandgap plots of TiO2 and rGO-TiO2 samples are shown.

[0023] Figure 7 The images show the full XPS spectrum and high-resolution fine spectrum of the samples, including (a) the full X-ray photoelectron energy (XPS) spectrum of rGO-TiO2; (b) the O 1s spectrum of rGO-TiO2; (c) the C 1s spectrum of rGO-TiO2; and (d) the Ti 2p spectrum of rGO-TiO2.

[0024] Figure 8 The effect of rGO-TiO2 composites with different rGO doping amounts on photocatalytic degradation of HC: (a) concentration change curves; (b) degradation efficiency; (c) degradation rate;

[0025] Figure 9 The effect of rGO-TiO2 composites with different rGO doping amounts on photocatalytic CO degradation: (a) concentration change curves; (b) degradation efficiency; (c) degradation rate;

[0026] Figure 10 The effect of rGO-TiO2 composites with different rGO doping amounts on photocatalytic degradation of NO: (a) concentration change curves; (b) degradation efficiency; (c) degradation rate;

[0027] Figure 11 The effect of low temperature environment on photocatalytic degradation of HC: (a) concentration change curve; (b) degradation efficiency; (c) degradation rate;

[0028] Figure 12 The effect of low temperature environment on photocatalytic degradation of CO: (a) concentration change curve; (b) degradation efficiency; (c) degradation rate;

[0029] Figure 13 The effect of low temperature environment on photocatalytic degradation of NO: (a) concentration change curve; (b) degradation efficiency; (c) degradation rate;

[0030] Figure 14The effect of light source on photocatalytic degradation efficiency: (a) HC degradation efficiency; (b) CO degradation efficiency; (c) NO degradation efficiency;

[0031] Figure 15 This is a schematic diagram of the photocatalytic degradation mechanism of rGO-TiO2 modified asphalt mixture pavement. Detailed Implementation

[0032] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments, but it is not limited thereto. Any modifications or equivalent substitutions to the technical solution of the present invention that do not depart from the spirit and scope of the technical solution of the present invention should be covered within the protection scope of the present invention.

[0033] This invention employs a high-temperature vacuum annealing process to prepare rGO / TiO2 composite photocatalytic materials, which are then incorporated into asphalt mixtures as a substitute for mineral powder. The microstructure, interfacial chemical bonding, and optical properties of the material are systematically characterized using XRD, SEM, BET, UV-Vis DRS, and XPS. The degradation efficiency and rate of exhaust gases from modified asphalt mixtures with different incorporation amounts are evaluated under both ambient and low-temperature conditions. By comparing and analyzing the comprehensive performance of different incorporation amounts, the optimal material ratio for cold regions is determined. This invention aims to provide a theoretical basis and engineering technical support for the design and application of air-purifying green pavement materials in cold regions.

[0034] This invention aims to improve the degradation efficiency of vehicle exhaust pollutants in road environments. A high-temperature vacuum annealing process was used to prepare an rGO / TiO2 composite photocatalytic material, which was then introduced into asphalt mixtures as an internal additive using a mineral powder substitution method. The material's structural characteristics were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), automated specific surface area and porosity analysis, UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS), and X-ray photoelectron spectroscopy (XPS). The results showed that the introduction of rGO maintained the anatase phase structure of TiO2, significantly broadened the light response range, and improved light absorption capacity. rGO also effectively inhibited TiO2 aggregation, increased the specific surface area, exposed more active sites, and significantly improved the photocatalytic degradation efficiency of exhaust gases. Under room temperature conditions, the degradation efficiency of HC, CO, and NO was best when the rGO content was 4.0 wt%, increasing by approximately 8.61%, 11.85%, and 43.12% respectively compared to the pure TiO2 group. Low-temperature test results showed that the degradation performance at 0℃ was basically consistent with that at room temperature. When the temperature dropped to -10℃ and -20℃, the degradation efficiency of HC and CO decreased significantly, while the degradation efficiency of NO, although reduced, was still higher than that of the pure TiO2 group at room temperature. Comparative tests with and without lights further confirmed that the material could still undergo effective photocatalytic reactions at -20℃. This invention demonstrates that the rGO / TiO2 composite material not only exhibits strong degradation performance for exhaust pollutants at room temperature, but also shows high degradation efficiency, especially in removing NO pollutants, under low-temperature conditions, showcasing the application potential of the rGO / TiO2 composite material in cold environments.

[0035] Example 1:

[0036] I. Materials and Methods

[0037] 1. Reagents and Instruments

[0038] Table 1 shows the materials used to prepare rGO-TiO2, along with their molecular formulas and purity information.

[0039] Table 2 shows the experimental equipment used in the preparation and characterization of rGO-TiO2, along with their models and manufacturers.

[0040] Table 1. Reagents used in the preparation of rGO-TiO2

[0041]

[0042] Table 2. Equipment used for rGO-TiO2 experiments and characterization.

[0043]

[0044] 2. Preparation of rGO-TiO2 composite materials

[0045] The raw materials used in the material preparation of this invention, including anhydrous ethanol and distilled water, are both analytical grade and have not undergone further purification. The TiO2 used is in the anatase form. See Table 1 for details.

[0046] In this invention, the mass ratio of rGO to nano-TiO2 is set to 4%. First, 0.2 g of industrial-grade rGO powder is weighed and dispersed in a 50 mL mixture of deionized water and anhydrous ethanol (volume ratio 1:2). After ultrasonic treatment for 15 minutes, a uniformly dispersed black suspension is formed. Then, 5.0 g of nano-TiO2 particles are added to the suspension and continuously mixed for 3 hours under magnetic stirring to ensure uniform anchorage of the TiO2 particles on the rGO surface. The mixed suspension is then subjected to solid-liquid separation using a vacuum filtration device. The resulting filter cake is washed three times alternately with deionized water and anhydrous ethanol. The washed filter cake is then dried in an 80°C forced-air drying oven for 24 hours and ground to obtain a gray precursor powder. Finally, the precursor powder is placed in a vacuum tube furnace and annealed at 600°C for 2 hours. After natural cooling, the rGO-TiO2 composite photocatalytic material is obtained. The experimental flowchart is shown below. Figure 1 As shown. All preparation steps and reagents were strictly performed according to laboratory standard operating procedures to ensure reproducibility and material quality stability.

[0047] 3. Preparation and characterization of rGO-TiO2 photocatalytic pavement samples

[0048] (1) This invention uses AC-13 type asphalt mixture, and rutting samples are prepared according to the Chinese standard "Test Procedure for Asphalt and Asphalt Mixtures in Highway Engineering" (JTGE 3410-2025). The optimal asphalt-aggregate ratio (OAC) is determined to be 4.9% by standard Marshall test (T 0709-2025). rGO-TiO2 composite material is incorporated by replacing mineral powder by equal mass. Three dosage gradients are set in the experiment, with replacement ratios of 2%, 4% and 6% of the total mass of mineral powder, respectively; pure asphalt mixture and pure TiO2 substitution group are set as controls. In order to optimize the dispersion state of nanomaterials in asphalt mixture, rGO-TiO2 composite material and mineral powder need to be premixed in a mixer for 3 minutes to make it uniformly dispersed. The experiment adopts the post-filler process: the aggregate is stirred in a mixing pot at 155℃ for 90 seconds; then hot asphalt is added and stirred for another 90 seconds; finally, rGO-TiO2 composite material and mineral powder are added and stirred for 90 seconds. The mixture is compacted by a rutting plate forming machine to form rutting specimens of 300mm×300mm×50mm, which are used for exhaust gas degradation testing.

[0049] (2) The surface morphology and particle packing state of the samples were observed using a TESCAN AMBER scanning electron microscope (SEM). The phase composition and crystal structure of the samples were analyzed using a Rigaku D / MAX-2600 X-ray diffractometer (XRD) under Cu Kα radiation source (λ=0.15406 Å). The surface elemental composition, chemical valence state, and interfacial bonding characteristics were characterized using a Thermo Scientific K-Alpha X-ray photoelectron spectroscopy (XPS). The specific surface area of ​​the samples was measured using a nitrogen adsorption-desorption experiment with a Micromeritics ASAP 2460. The light absorption performance of the samples was measured using a Hitachi UH4150 UV-Vis-NIR spectrophotometer with a scanning range of 200~800 nm and a band gap (E). g The results were calculated based on the Tauc Plot method. See Table 2.

[0050] (3) In order to evaluate the exhaust gas degradation efficiency of photocatalytic asphalt mixtures under real traffic environments and extreme low temperature conditions in cold regions, this invention constructs an all-weather temperature control testing system based on real exhaust gas sources (such as...). Figure 2 (As shown). The system uses a sealed box with high light transmittance as its core. Figure 2 (a) The entire experiment was conducted in the environmental chamber of the UTM-100 (Universal Testing Machine) multifunctional materials testing machine. Figure 2 (b) The UTM-100 high-precision temperature control system was used to accurately simulate temperatures from 20°C, 0°C, -10°C to -20°C. The experiment used actual exhaust gases from a medium-sized gasoline vehicle at idle as the pollution source, collected via a gas collection bag and injected into a sealed chamber until the concentrations of various gaseous pollutants within the chamber reached the preset range. The illumination system used xenon lamps to simulate natural sunlight. Considering that this invention focuses on low-temperature environments in cold regions, based on research into winter meteorological data from typical provincial capitals in northern China, the ultraviolet radiation intensity reaching the specimen surface was precisely adjusted to 27.5 W / m². 2 To accurately reflect the actual light levels in cold regions during winter. The cabin gas concentration was determined using an NHA-502 automotive exhaust gas analyzer. Figure 2 (c) Real-time monitoring and calculation of photocatalytic degradation efficiency at each time point.

[0051] 4. Results and Conclusions

[0052] (1) Sample characterization

[0053] The morphology, crystal structure, particle size, and elemental composition of pristine TiO2 and RGO-TiO2 were analyzed using XRD, SEM, XPS, BET, and UV-Vis DRS techniques.

[0054] X-ray diffraction (XRD) analysis: Figure 3 X-ray diffraction (XRD) patterns of pure TiO2 and rGO-TiO2 composite material prepared by vacuum annealing at 600℃ are shown. For the pure TiO2 sample, its XRD pattern exhibits sharp and strong diffraction peaks at 25.3°, 37.8°, 48.0°, 53.9°, 55.1°, and 62.7°. These peaks correspond to the (101), (004), (200), (105), (211), and (204) crystal planes of the anatase phase, respectively. No other impurity peaks were detected in the spectrum, indicating that the raw material is high-purity anatase titanium dioxide, which is recognized as the TiO2 crystal phase with the highest photocatalytic activity. Comparing the spectra of the rGO-TiO2 composite material and pure TiO2, it can be found that the positions and relative intensities of the diffraction peaks are basically consistent. Although the composite material underwent high-temperature vacuum annealing at 600℃, the characteristic diffraction peaks of the rutile phase did not appear in the spectrum. The addition of rGO effectively suppressed the phase transformation of TiO2 from anatase to rutile at high temperatures, ensuring that the material maintains a crystal structure with high photocatalytic activity. Furthermore, the characteristic peak 26° of the graphene (002) crystal plane was not observed in the spectrum, which may be attributed to the low rGO loading of 4% and the intensity masking of the TiO2 main peak.

[0055] Scanning electron microscopy and energy dispersive spectroscopy (SEM & EDS): In order to visually evaluate the dispersion state and surface exposure of the rGO-TiO2 composite photocatalyst in actual asphalt pavement materials, samples were randomly cut from the surface of the prepared AC-13 asphalt mixture rutting slab specimens and characterized using SEM and EDS techniques. Figure 4 The microstructure characteristics of pure TiO2 and rGO-TiO2 composite materials, as well as the microstructure and corresponding elemental distribution characteristics of asphalt mixture surfaces, are shown. Figure 4 (a) Clearly shows that pure TiO2 nanoparticles exhibit a typical spherical morphology, and no independently dispersed monomers were observed, but rather they existed in the form of tightly packed clusters. Figure 4 (b) shows the significant morphological changes after introducing rGO and annealing at 600 °C. The images show that rGO exhibits a unique two-dimensional wrinkled lamellar structure with a relatively smooth surface and good ductility. TiO2 particles are uniformly anchored on the surface and between the rGO lamellar layers.

[0056] Figure 4 (c) shows the microstructure of a sample randomly taken from the surface of the AC-13 rut plate specimen. Figure 4(d) shows the spatial distribution of each element. Compared with the global coverage of element C, element Ti shows local enrichment in the scanned area. The presence of Ti element proves that although there is a certain "encapsulation effect" in the asphalt film, under the influence of "mineral powder substitution" and "post-filler process", the rGO-TiO2 composite material is not completely submerged in the asphalt, and a part of it is effectively exposed on the surface of the asphalt concrete.

[0057] Pore ​​structure and specific surface area analysis: Figure 5 As shown, to investigate the changes in pore structure and specific surface area of ​​TiO2 and rGO-TiO2, N2 adsorption-desorption isotherms were tested at 77 K, and their specific surface area was calculated using the BET method. According to the IUPAC classification standard, pure TiO2 (… Figure 5 a) with rGO-TiO2 ( Figure 5 (b) The adsorption-desorption isotherms of the composite material exhibit typical Type IV characteristics. Within a relative pressure range (P / P0) of approximately 0.45–0.95, the adsorption capacity of the desorption branch is significantly higher than that of the adsorption branch, forming a closed hysteresis loop. Based on the shape characteristics of the loop, this hysteresis loop closely resembles Type H3, indicating the presence of slit-like mesopores formed by nanoparticle stacking or interlamellar gaps within the material. This open interlamellar mesoporous network structure is highly consistent with the lamellar loading morphology observed by SEM, which is beneficial for the rapid diffusion and transport of reactant gases within the catalyst.

[0058] Table 3 summarizes the specific surface area, pore volume, and pore size data of the two materials. The comparison reveals that the introduction of rGO comprehensively optimizes the material parameters. The specific surface area of ​​the rGO-TiO2 composite material increases to 71.29 m². 2 / g, pore volume increased to 0.1821cm³. 3 / g. This improvement indicates that rGO plays an effective skeletal support role in the composite material, suppressing excessive sintering and dense packing of TiO2 particles during high-temperature annealing. Furthermore, the pore size of the composite material increased from 20.65 nm in pure TiO2 to 22.29 nm. This confirms that the rGO sheets act as "nanospacers" in the composite material, effectively widening the gaps between particles and establishing more spacious gas transport channels.

[0059] Table 3 Specific surface area, pore volume, and pore size of TiO2 and rGO-TiO2

[0060]

[0061] Ultraviolet-Vis Diffuse Reflectance Spectroscopy (UV-Vis DRS): UV-Vis DRS reveals the photoresponse properties of materials. For example... Figure 6As shown, pure TiO2 exhibits strong intrinsic absorption only in the ultraviolet region with wavelengths less than 380 nm. In contrast, the rGO-TiO2 composite material shows a significant redshift at the absorption edge and a full-spectrum enhancement of absorption intensity in the visible light region (400~800 nm).

[0062] Tauc Plot based on Kubelka-Munk function transformation ( Figure 6 (inset) shows the bandgap width (E) of pure TiO2. g The E value is 3.18 eV. After high-temperature annealing, the E value of rGO-TiO2 is... g The value shrinks significantly to 2.66 eV. This narrowing of the band structure can be attributed to the chemical bonding effect at the Ti-OC interface, as confirmed by XPS: this bonding induces orbital hybridization of the interface atoms, effectively raising the energy level position of the valence band (VB) top. The resulting band structure optimization significantly reduces the energy threshold required for electronic transitions, giving the material a more efficient light energy utilization across the entire spectrum (especially in the visible light region).

[0063] X-ray photoelectron spectroscopy (XPS): In order to investigate the surface elemental composition and interatomic chemical state of the rGO / TiO2 composite photocatalyst, this invention performed XPS full spectrum and high-resolution fine spectrum analysis on the sample.

[0064] like Figure 7 As shown in Figure a, the XPS full spectrum of the rGO / TiO2 composite material clearly displays the characteristic peaks of Ti, O, and C, and no other obvious impurities were detected, indicating that the sample has high purity. Notably, the peak intensities of each element in the full spectrum show the order O 1s > C 1s > Ti 2p. In particular, the intensity of the C 1s peak is significantly higher than that of the Ti 2p peak, strongly demonstrating that the rGO sheets are successfully coated on the surface of the TiO2 nanoparticles. This coating structure facilitates the rapid transfer of photogenerated electrons from the internal TiO2 to the external rGO conductive network, thus enabling efficient participation in the subsequent reduction reaction. In the high-resolution C 1s spectrum (… Figure 7 b), in addition to corresponding to sp in the graphene framework 2 In addition to the characteristic peaks of hybrid carbon (CC, 284.8 eV) and oxygen-containing functional groups (CO, 286.4 eV), a new characteristic peak was detected at 283.88 eV. This peak is attributed to the chemical bonds at the Ti-OC interface, confirming that TiO2 nanoparticles are not simply physically adsorbed on the rGO surface, but are tightly anchored through chemical bonds.

[0065] O 1s spectrum ( Figure 7c) After peak fitting, two main characteristic peaks were revealed: the peak at 530.95 eV corresponds to the lattice oxygen of TiO2 (Ti-O-Ti); while the peak at 532.78 eV belongs to the Ti-CO bond and surface hydroxyl groups (Ti-OH). The abundant surface hydroxyl groups are key sites for capturing holes and generating active hydroxyl radicals (·OH) in the photocatalytic reaction. In the Ti 2p spectrum ( Figure 7 In d), two characteristic peaks were detected, located at 459.68 eV (Ti 2p). 3 / 2 ) and 465.38eV (Ti2p 1 / 2 This indicates that titanium is mainly composed of Ti. 4+ The state exists. It is similar to the Ti 2p state of standard pure TiO2. 3 / 2 Compared to the peak (typically located at 458.5~459.0 eV), the binding energy (459.68 eV) measured in this invention exhibits a significant positive shift. The increase in binding energy implies a decrease in the electron cloud density around Ti atoms, which further confirms that photogenerated electrons are transferred from the TiO2 conduction band to the rGO sheets via Ti-OC bonds, thereby effectively suppressing electron-hole recombination.

[0066] (2) Exhaust gas degradation experiment

[0067] Exhaust gas concentration: To ensure that the gas concentrations used in the study are consistent with actual conditions, a sampling survey was conducted using actual measurement methods. The intersection of Hongqi Street and Dongzhi Road in Harbin City was selected as a fixed test point. The sampling period was during peak traffic hours. The instrument used for sampling was an NHA-502 vehicle exhaust gas analyzer, which measured the vehicle exhaust gas concentration on the road surface at this intersection three times to obtain the values ​​during peak vehicle exhaust emission periods. After comprehensively considering the measurement range and accuracy of the exhaust gas concentration analyzer, the initial concentration ranges of each harmful gas are shown in Table 4.

[0068] Table 4 Initial Concentration Control Range of Test Gas

[0069]

[0070] Evaluation indicators of exhaust gas degradation performance: When conducting exhaust gas degradation experiments in a closed reaction chamber, changes in gas concentration are not only affected by the photocatalytic reaction but may also be related to non-reactive factors such as device sealing issues, adsorption on the inner wall of the chamber, and natural gas decay. To eliminate the influence of these non-photocatalytic factors on gas concentration changes, this invention uses a blank control method to calibrate the experimental system. A blank control experiment is set up without introducing photocatalytic materials, and conducted under completely identical light intensity, temperature conditions, and initial exhaust gas concentration as the formal experiment, recording NO levels. xThe concentrations of CO and HC changed over time. During data processing, the gas concentration changes of each photocatalytic experimental group were subtracted from the concentration changes of the blank group at the corresponding time on the same time scale to obtain the net degradation effect dominated by the photocatalytic reaction. For rGO-TiO2 photocatalytic materials, this invention uses photocatalytic degradation efficiency and photocatalytic degradation rate as comprehensive evaluation indicators. According to calculation formulas (1) and (2):

[0071] (1)

[0072] in, This indicates that after excluding the influence of the blank group, the components in the experimental group... Actual effective concentration degradation efficiency (unit: %) Indicates the components in the experimental group The measured rate of concentration decrease over time The situation is changing. Indicates the components in the blank test The rate of decrease in concentration over time The situation is changing.

[0073] (2)

[0074] in, The average photocatalytic degradation rate is expressed in ppm / min. The initial concentration of the gas at the start of the reaction. The gas concentration measured after the reaction is complete. This refers to the reaction time.

[0075] Photocatalytic Degradation Experiments at Room Temperature: This invention aims to screen for the optimal dosage of rGO-TiO2 composite materials suitable for the degradation of automotive exhaust pollutants. The photocatalytic degradation performance of rGO-TiO2 composite materials with different dosages for HC, CO, and NO exhaust pollutants was systematically tested to find the optimal dosage. To ensure the accuracy of the degradation effect, a blank control experiment was conducted to evaluate the natural decay of each pollutant, followed by photocatalytic degradation experiments at room temperature.

[0076] Figure 8 (a), Figure 9 (a) and Figure 10 (a) The changes in the concentrations of the three gases with reaction time under light irradiation are shown for pure TiO2 and TiO2 composites with different rGO doping amounts. It can be seen that in all experimental groups containing photocatalytic materials, the pollutant concentration gradually decreases with the extension of reaction time, indicating that the constructed photocatalytic system can effectively degrade automobile exhaust. Figure 8 (b), Figure 9 (b) and Figure 10 (b) shows that the rGO doping amount has a significant impact on the photocatalytic degradation efficiency. Compared with the pure TiO2 sample, the composite material with rGO doping showed a significant improvement in degradation efficiency, especially at an rGO doping amount of 4.0 wt%, where the degradation efficiencies of HC, CO, and NO were the best. Specifically, the degradation efficiency of HC increased by approximately 8.61% compared to pure TiO2, CO by approximately 11.85%, and NO by nearly 43.12%. This indicates that the introduction of rGO is beneficial to enhancing the overall effectiveness of the photocatalytic reaction. However, when the rGO doping amount continued to increase, the degradation efficiency decreased to some extent because excessive rGO may exacerbate the light-blocking effect, blocking some of the light from TiO2 and thus limiting the light absorption capacity of TiO2, leading to a decrease in degradation efficiency.

[0077] Figure 8 (c), Figure 9 (c) and Figure 10 (c) This section shows the degradation rate changes of each group during the reaction process. It can be observed that the degradation rate of each pollutant did not exhibit a clear regularity over time. However, the degradation rate of all three pollutants by the rGO-TiO2 composite material group was significantly higher than that of the pure TiO2 group throughout the entire reaction process, indicating that rGO doping effectively improved the kinetic rate of the catalytic reaction. Considering the degradation performance of the three pollutants, although the 6.0 wt% rGO doping group showed the fastest reaction rate in NO photocatalytic degradation, the 4.0 wt% composite material achieved a better overall balance between degradation efficiency and rate. Furthermore, excessively high rGO doping did not further improve the final degradation efficiency of HC and CO, but rather slightly decreased it; while the degradation performance improvement provided by a doping amount of 2.0 wt% was relatively limited. Therefore, it can be determined that an rGO doping amount of 4.0 wt% can achieve the best overall improvement in degradation efficiency and reaction rate for the three exhaust pollutants.

[0078] When the rGO content is 4.0 wt%, the composite material exhibits the best photocatalytic degradation performance, mainly due to the optimized balance of key factors such as carrier separation, specific surface area, and interfacial synergy. In the photocatalytic process, improved carrier dynamics are one of the key factors for performance optimization. An appropriate amount of rGO can form a conductive network on the TiO2 surface, significantly promoting the separation and migration of photogenerated electrons. This process effectively reduces electron-hole recombination, thereby enhancing the photocatalytic activity of TiO2. However, when the rGO content is too high, the layer stacking phenomenon becomes more severe, hindering the transport path of photogenerated electrons and thus limiting the efficiency of the photocatalytic reaction. Besides improved carrier separation, the increase in specific surface area also plays an important role in improving photocatalytic performance. The two-dimensional layered structure of rGO can effectively prevent the aggregation of TiO2 nanoparticles, providing more reaction sites for the composite material and significantly increasing its specific surface area and mesopore number. For the degradation of macromolecular pollutants, sufficient specific surface area and suitable pore size structure are particularly crucial. However, when the rGO doping level is too high, excessive graphene sheets may clog pores and cover active sites, affecting not only reactant adsorption but also potentially limiting the reactivity of TiO2 nanoparticles, ultimately leading to a decrease in degradation efficiency. Regarding the interfacial synergistic effect, rGO and TiO2 form a tight heterojunction interface through stable Ti-OC bonds. This interfacial structure not only promotes the efficient separation and transport of photogenerated carriers but also preserves the light absorption capacity of TiO2. Furthermore, the rGO surface is rich in oxygen functional groups, which interact with active groups such as hydroxyl groups on the TiO2 surface to form synergistic adsorption centers, enhancing the enrichment and activation of pollutant molecules. It is noteworthy that excessively low rGO content cannot fully leverage this synergistic effect, resulting in a failure to effectively improve its adsorption capacity and reaction efficiency for pollutants.

[0079] Therefore, the composite material with an rGO content of 4.0 wt% achieved the best balance in terms of degradation efficiency, reaction rate, and material stability, exhibiting the optimal photocatalytic performance. Thus, rGO-TiO2-4 with an rGO content of 4.0 wt% was selected as the optimal ratio for the rGO-TiO2 composite material.

[0080] Low-temperature photocatalytic experiments: Based on room-temperature experiments, rGO-TiO2-4 with an rGO doping content of 4.0 wt% has been determined to have the best overall degradation performance for the three exhaust gas pollutants. To further evaluate its applicability under cold operating conditions, rGO-TiO2-4 was used as the research object, and photocatalytic degradation experiments on HC, CO, and NO were conducted at RT, 0℃, -10℃, and -20℃, respectively. Figure 11 (a), Figure 12 and Figure 13(a) shows the degradation efficiency of the three gaseous pollutants over time at various temperatures. Overall, as the temperature decreases from RT to 0℃, the degradation efficiencies of HC and CO basically coincide with RT, while the degradation efficiency of NO decreases slightly, but it can still achieve near-complete removal within a 60-minute reaction time. This result is consistent with the rule in the TiO2 system that "the reaction rate near room temperature corresponds to a weaker temperature sensitivity." In the range of 0–20℃, the photogenerated carrier generation process is mainly controlled by photon flux, while the influence of adsorption on the rate is relatively limited. Therefore, the overall kinetics exhibit a quasi-isothermal characteristic.

[0081] When the temperature drops to -10℃ and -20℃, the degradation efficiency of HC and CO decreases significantly, and the degradation rates at the two temperatures are very close. Figure 11 (b) and Figure 12 (b) This indicates that the temperature is close to the low-temperature "threshold" at around -10℃, and further temperature reduction has limited inhibitory effect on HC and CO. Considering the strong adsorption behavior of asphalt materials for small organic molecules at low temperatures, it can be inferred that below -10℃, HC and CO tend to be physically adsorbed and "frozen" in the micropores of the asphalt-filler and the interlayer spaces of rGO sheets. Effective mass transfer between the gas and solid phases is significantly limited, causing the molecular flux into the photocatalytic active sites to tend towards saturation, thus resulting in no significant difference in degradation efficiency between -10℃ and -20℃.

[0082] Figure 13 (b) As the temperature decreased from room temperature to -10℃ and -20℃, the final degradation rate of NO decreased by 19.78% and 28.99% compared to RT, respectively. However, even at -20℃, its degradation rate was still significantly higher than that of the pure TiO2 control group at RT. This may be related to the strong polarity of NO molecules and the chemisorption-oxidation process that occurs on the TiO2 surface: NO first forms nitrite / nitrate species on the surface rich in hydroxyl groups and oxygen vacancies, and then... Under the influence of active species, NO is further oxidized, relying more on surface reaction barriers than on simple physical adsorption-desorption equilibrium. Therefore, it can still maintain a certain driving force at low temperatures. Studies have shown that the photocatalytic oxidation of NO can still proceed smoothly at low temperatures, as evidenced by the accumulation of nitrates on the surface. In addition, the abundant surface hydroxyl groups and defective oxygen vacancies shown by XPS analysis in this invention provide a favorable basis for the continuous generation of ·OH and the maintenance of effective electron-hole separation under low-temperature conditions, thus ensuring that the degradation efficiency of NO is still higher than that of pure TiO2 at low temperatures.

[0083] Figure 11 (c), Figure 12 (c) and Figure 13(c) The degradation rates further confirm the above analysis: Under RT and 0℃ conditions, the average degradation rates of HC and CO remained at a high level in the first 20 minutes, and then gradually decreased; while under -10℃ and -20℃ conditions, the rates of HC and CO decreased, and the two curves nearly overlapped, indicating that low-temperature adsorption and mass transfer limitation caused the reaction to change from "photogenerated carrier control" to "reactant supply limitation". Although the NO rate decreased with decreasing temperature, it was still significantly higher than the RT pure TiO2 rate level throughout the entire time period, further confirming that rGO-TiO2-4 still has a considerable photocatalytic contribution to NO at low temperatures. Considering the degradation efficiency, actual degradation rate, and rate characteristics, it can be concluded that rGO-TiO2-4 is expected to maintain effective purification capacity for NO, a key pollutant, in road surface applications in mid-to-high latitude cold regions, even when the road surface is at or below freezing point in winter.

[0084] To further distinguish the contributions of low-temperature adsorption and photocatalytic reaction, this invention conducted a comparative experiment on the rGO-TiO2-4 specimen with and without the lamp on, as shown in the figure. Figure 14 (a), Figure 14 (b) and Figure 14 (c) and corrected using the data with the lights off as the low-temperature adsorption background.

[0085] Under the same initial concentration and environmental conditions, the actual degradation efficiencies of the lamp-on group within 60 minutes were 10.14% for HC, 14.54% for CO, and 66.56% for NO. The results demonstrate that even in the frigid environment of -20℃, the photocatalytic reaction still significantly exists, and it is not merely a concentration decay caused by physical adsorption. The degradation efficiency of NO is significantly higher than that of HC and CO, which is closely related to the oxidation pathway of NO. NO on the TiO2 surface is mainly generated through oxidation reactions via photogenerated holes or ·OH radicals. / This process is highly dependent on photogenerated carriers, so the photocatalytic reaction can still proceed significantly even at low temperatures. In contrast, the oxidation reactions of HC and CO depend more on surface-active oxygen species and gas diffusion processes. At -20°C, the photocatalytic gain is relatively small due to the decrease in gas molecule kinetic energy and diffusion coefficient.

[0086] Therefore, this comparative experiment shows that the rGO-TiO2 composite photocatalyst still has considerable photocatalytic activity at -20℃, with a particularly significant degradation rate of NO. This proves that the rGO-TiO2 composite photocatalyst is especially suitable for NO removal applications in cold regions.

[0087] Figure 15This paper describes the photocatalytic mechanism of rGO-TiO2 modified asphalt pavement. Intrinsic anatase TiO2 is a typical n-type semiconductor with a band gap of approximately 3.2 eV, which limits its excitation to ultraviolet light. However, the rGO-TiO2 composite material prepared in this invention exhibits a narrowed apparent band gap of 2.67 eV. This "redshift" in optical absorption is attributed to the formation of Ti-OC chemical bonds at the TiO2-rGO interface. These chemical bonds introduce specific impurity energy levels into the band gap of TiO2. Under visible light irradiation, electrons in the valence band (VB) can be excited to these intermediate energy levels and subsequently transition to the conduction band (CB), thereby significantly improving the utilization rate of solar energy on the pavement. Under photoexcitation, electron-hole pairs (e-hole pairs) are generated within the TiO2 nanoparticles embedded in the asphalt matrix. - -h + Graphene sheets (rGO), with their excellent conductivity, act as superior electron acceptors and conductive channels, causing photogenerated electrons in the TiO2 conduction band to rapidly transfer to the rGO surface driven by the potential difference. This spatial separation effectively suppresses electron-hole recombination, prolongs the lifetime of active charge carriers, and ensures that the material maintains high quantum efficiency in the complex environment of asphalt mixtures. The separated charge carriers trigger a series of redox reactions to degrade vehicle exhaust adsorbed on the road surface: holes remaining in the TiO2 valence band have strong oxidizing capabilities. They react with adsorbed water or hydroxide ions to generate hydroxyl radicals. . OH radicals are non-selective strong oxidizing agents that can mineralize CO to CO2 and oxidize HC (hydrocarbons) to H2O and CO2. Electrons (e) accumulated on the rGO sheets... - ) reacts with adsorbed oxygen (O2) to generate superoxide radicals ( . O2). These free radicals oxidize NO to nitrate (NO3). - It exhibits high activity during the process. The chemical reaction equations for the degradation of rGO-TiO2 tail gas are shown in formulas (3) to (8):

[0088] (3)

[0089] (4)

[0090] (5)

[0091] (6)

[0092] (7)

[0093] (8).

Claims

1. An application of a graphene derivative / titanium dioxide composite material, characterized in that: The application is as follows: AC-13 type asphalt mixture is used, the asphalt-aggregate ratio is 4.8%~5%, and rGO-TiO2 composite material is added by replacing mineral powder with equal mass, with the incorporation ratio of rGO-TiO2 being 2%~6%.

2. The application of the graphene derivative / titanium dioxide composite material according to claim 1, characterized in that: AC-13 type asphalt mixture is composed of aggregate, asphalt and mineral powder. The mass fraction of aggregate and asphalt is: coarse aggregate 50% to 60%, fine aggregate 30% to 40%, mineral powder 4% to 7%, and asphalt content 4.5% to 5.5%.

3. The application of the graphene derivative / titanium dioxide composite material according to claim 1, characterized in that: Considering the dispersion state of nanomaterials in asphalt mixtures, the rGO-TiO2 composite material and mineral powder are premixed in a mixer to ensure uniform dispersion. A post-addition process is adopted: the aggregate is stirred in a mixing pot at 150~160℃ for 80~100 seconds; then hot asphalt (150~160℃) is added and stirring is continued for 80~100 seconds; finally, the rGO-TiO2 composite material and mineral powder are added and stirred for 80~100 seconds.

4. The application of the graphene derivative / titanium dioxide composite material according to claim 1, characterized in that: The asphalt mixture can degrade the core pollutants in the exhaust gas and their concentrations are HC 100~200ppm, CO 0.1%~0.3%, NO 50~100ppm, and the applicable ambient temperature is -40℃~40℃.

5. The application of the graphene derivative / titanium dioxide composite material according to claim 1, characterized in that: The preparation method of rGO-TiO2 composite material is as follows: Weigh 0.15~0.25g of industrial grade rGO powder and disperse it in a mixed solution of 45~55mL of deionized water and anhydrous ethanol (volume ratio of 1:2); after ultrasonic treatment for 13~17 minutes, a uniformly dispersed black suspension is formed; then, add 4.5~5.5g of nano-TiO2 particles to the suspension and continue mixing under magnetic stirring for 2~3 hours to ensure that the TiO2 particles are uniformly anchored on the rGO surface; the mixed suspension is subjected to solid-liquid separation by vacuum filtration device; the obtained filter cake is washed alternately with deionized water and anhydrous ethanol 3~4 times; the washed filter cake is placed in a forced-air drying oven at 75~85℃ and dried for 22~26 hours, and ground to obtain gray precursor powder; the precursor powder is placed in a vacuum tube furnace and annealed at 580~620℃ for 2 hours, and after natural cooling, the rGO-TiO2 composite photocatalytic material is obtained.

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