Preparation method of oxygen-resistant nickel-gold alloy nano-cluster / titanium dioxide photocatalyst and application of oxygen-resistant nickel-gold alloy nano-cluster / titanium dioxide photocatalyst in carbon dioxide reduction in oxygen-containing atmosphere

Abstract

The invention belongs to the technical field of photocatalysis and carbon dioxide resource utilization, and relates to a preparation method of an oxygen-resistant NiAu alloy nano-cluster loaded titanium dioxide photocatalyst and application of the oxygen-resistant NiAu alloy nano-cluster loaded titanium dioxide photocatalyst in carbon dioxide reduction in an oxygen-containing atmosphere. The method comprises the following steps: dispersing a TiO2 carrier, adding Ni and Au precursors, and carrying out photo-reduction to form a NiAu alloy nano-cluster precursor; the precursor is placed in a Fe < 3 + > acid solution for directional etching, Ni atoms on the surface layer are selectively removed, Au sites are exposed, and the oxygen-resistant NiAu-TiO2 photocatalyst with the surface rich in Au is obtained. According to the catalyst, CO2 is activated through Ni sites, O2 adsorption is inhibited through an Au-rich surface layer, and efficient Ni-Au synergy is achieved. In an atmosphere containing 5% of O2, the CO generation rate can reach 375.5 [mu] mol.g <-1 >. H <-1 >, the selectivity is close to 100%, and high activity and stability are maintained in simulated flue gas. The process is simple, the precious metal utilization rate is high, and an effective solution is provided for direct photocatalytic conversion of CO2 in oxygen-containing industrial waste gas.

Description

Technical Field

[0001] This invention belongs to the field of photocatalysis and carbon dioxide resource utilization technology, and relates to photocatalysts. Specifically, it relates to a method for preparing an oxygen-resistant NiAu alloy nanocluster supported titanium dioxide (NiAu-TiO2) photocatalyst and its application in photocatalytic reduction of carbon dioxide under oxygen-containing atmosphere, especially under simulated industrial flue gas conditions. Technical Background

[0002] Utilizing solar energy to drive the conversion of carbon dioxide (CO2) and water (H2O) into high-value-added chemicals such as carbon monoxide (CO) and methane (CH4) is one of the important technological pathways to achieve "carbon neutrality" and sustainable energy transition. However, most existing photocatalytic CO2 reduction reactions rely on a high-purity CO2 atmosphere, which is difficult to operate in industrial environments with actual oxygen (O2) atmospheres.

[0003] Industrial flue gas is a significant source of CO2, typically composed of 72-77% nitrogen, 12-16% carbon dioxide, 3-5% oxygen, and a small amount of water vapor. Numerous studies have shown that photocatalytic CO2 reduction is severely inhibited in oxygen-containing environments. When the oxygen content reaches approximately 5%, the CO2 reduction reaction is almost completely deactivated. The fundamental reason for this is that O2 preferentially undergoes the thermodynamically and kinetically dominant oxygen reduction reaction (ORR), consuming a large number of photogenerated electrons and thus inhibiting the CO2 reduction reaction (CO2RR).

[0004] Nickel (Ni)-based catalysts are widely used in CO2 electrocatalysis and photocatalysis due to their excellent CO2 adsorption and activation capabilities. However, Ni has an extremely strong affinity for oxygen atoms, which makes it highly susceptible to oxygen-containing atmospheres and induces oxygen-free reaction (ORR), leading to a sharp decline in CO2 OR performance. Therefore, how to effectively suppress excessive O2 adsorption while retaining the strong CO2 adsorption capacity of Ni sites is a key scientific problem in constructing oxygen-resistant photocatalysts.

[0005] Alloying strategies provide an important means of controlling the local atomic environment and electronic structure of metal surfaces. By introducing gold (Au), an element with weak adsorption of oxygen atoms and good electronic control capabilities, into the Ni-based system, it is expected to significantly weaken O2 adsorption and ORR pathway while maintaining the strong interaction between Ni and CO2, thereby achieving efficient CO2 photocatalytic reduction under oxygen-resistant conditions. Summary of the Invention

[0006] This invention aims to solve the problem that existing photocatalytic carbon dioxide reduction systems are easily inhibited by oxygen reduction reactions in oxygen-containing environments. It provides a method for preparing an oxygen-resistant NiAu alloy nanoclusters / titanium dioxide (NiAu-TiO2) photocatalyst through alloy microenvironment regulation, which enables it to achieve efficient and selective CO2 reduction under oxygen-containing and simulated industrial flue gas conditions.

[0007] Technical solution

[0008] A method for preparing an oxygen-resistant nickel-gold alloy nanoclusters / titanium dioxide (NiAu-TiO2) photocatalyst includes the following steps:

[0009] (1) Photodeposition preparation of NiAu-TiO2

[0010] TiO2 is dispersed in anhydrous ethanol, and Ni and Au precursors are added in a predetermined molar ratio. The molar ratio of Ni to Au is 1:1-7:1, preferably 5:1. After removing dissolved gases by vacuuming in a closed photoreactor, an in-situ photoreduction reaction is carried out to form highly dispersed NiAu alloy nanoclusters on the TiO2 surface, thus obtaining the NiAu-TiO2 precursor.

[0011] (2) Directional etching to construct Au-rich oxygen-resistant active sites

[0012] The NiAu-TiO2 precursor was dispersed in a weakly oxidizing solution and etched at 20-60℃ for 1-30 min under an inert atmosphere. The pH of the solution was maintained at 2.0-3.0 to selectively remove Ni atoms from the alloy while inhibiting Au dissolution, thus preparing an oxygen-resistant nickel-gold alloy nanoclusters / titanium dioxide (NiAu-TiO2) photocatalyst.

[0013] In a preferred embodiment of the present invention, in step (1), the Ni precursor is at least one of nickel nitrate, nickel chloride, or nickel sulfate; and the Au precursor is chloroauric acid or gold trichloride.

[0014] In a preferred embodiment of the present invention, the conditions for the photoreduction reaction in step (1) are: a 300 W xenon lamp with an output spectrum of 320-780 nm and a light intensity of 100-300 mW / cm². 2 Irradiate continuously for 20-40 minutes, preferably 30 minutes.

[0015] In a preferred embodiment of the present invention, in step (2), the weak oxidizing solution contains Fe. 3+ An acidic aqueous solution of Fe ions 3+ The ions are derived from ferric nitrate, ferric chloride, or ferric sulfate, and their concentration is controlled between 0.5 and 2.5 mmol·L⁻¹. -1Within the specified range, the acidic environment is regulated and maintained by hydrochloric acid, nitric acid, or sulfuric acid.

[0016] The weakly oxidizing solution can selectively oxidize and dissolve metallic Ni under an inert atmosphere, while exhibiting minimal corrosivity to Au and TiO2 supports, thus enabling the selective dissolution of metallic Ni. A mild oxidant is introduced during the etching process, utilizing Fe... 3+ / Fe 2+ In redox pairs and acidic environments, Ni atoms on the surface of the alloy nanoclusters are preferentially dissolved and removed, exposing unsaturated Au active sites while retaining the synergistic active centers of the NiAu alloy.

[0017] The oxygen-resistant NiAu-TiO2 photocatalyst prepared by the method of the present invention has the following microstructure characteristics: Ni and Au are highly dispersed on the TiO2 surface in an alloy form. After directional etching, NiAu synergistic active sites with Au-rich surfaces are formed. The oxygen adsorption capacity of Au sites is significantly reduced, while Ni sites still maintain a high affinity for CO2, resulting in excellent synergistic catalytic performance between adjacent Au and Ni.

[0018] The microstructure of the Ni-Au alloy nanoclusters prepared in this invention was observed using transmission electron microscopy (TEM) and aberration-corrected annular dark-field scanning transmission electron microscopy (AC-HAADF-STEM). The composition and structure were demonstrated using X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The oxygen resistance reaction mechanism was verified using density functional theory (DFT).

[0019] This invention also provides the application of the above-mentioned oxygen-resistant NiAu alloy nanoclusters / titanium dioxide photocatalyst in the following systems.

[0020] Photocatalytic CO2 reduction and H2O oxidation performance tests:

[0021] (1) Take 2.0 mg of photocatalyst and add it to 2 mL of deionized water. Disperse the mixture by ultrasonication to form a uniform suspension. Then, drop the resulting suspension onto the surface of a microporous quartz filter membrane and dry it at 60 °C for 2 h to obtain a filter membrane loaded with the catalyst. Place the catalyst-loaded filter membrane in an intermittent flow photoreactor and distribute 0.5 mL of deionized water in an arc shape at the bottom of the reactor to ensure the uniformity of humidity in the reaction system.

[0022] (2) Before the photocatalytic reaction, the gas circulation system was evacuated for 15 min, followed by the introduction of high-purity CO2 (99.99%). Then, high-purity CO2, O2, or N2 was introduced into the reactor as needed to bring the total gas pressure in the reaction system to 100 kPa. The distance between the photocatalyst and the 300 W xenon lamp was maintained at 10 cm. The gaseous products generated by the reaction were detected using a gas chromatograph equipped with a flame ionization detector (FID) and a thermal conductivity detector (TCD). Quantitative analysis of the products was based on calibration curves established using certified standard gas mixtures, and qualitative analysis of the gas components was determined based on their retention time in the chromatographic column.

[0023] The oxygen-containing atmosphere is a mixture of carbon dioxide and oxygen with a volume content of 1-20%. Further, the oxygen-containing atmosphere is a simulated industrial flue gas with the following composition: 3-5% oxygen, 12-16% carbon dioxide, 72-77% nitrogen, and a small amount of water vapor.

[0024] Beneficial effects

[0025] The oxygen-resistant NiAu-TiO2 photocatalyst and its preparation method provided by this invention have the following outstanding advantages: This invention significantly weakens the adsorption and electron transfer of oxygen on the catalyst surface by controlling the degree of Au atom embedding and exposure, thus inhibiting the competitive oxygen reduction reaction (ORR). Density functional theory (DFT) calculations confirm that the Au-rich surface structure can significantly reduce the O2 adsorption energy from -4.35 eV in pure Ni to -1.51 eV, fundamentally inhibiting the competitive oxygen reduction reaction (ORR). Under conditions containing 5% O2, the optimal catalyst prepared by this invention exhibits near 100% selectivity for carbon monoxide (CO), with a formation rate reaching 375.5 µmol·g. -1 ·h -1 In the catalyst, Ni sites are responsible for CO2 adsorption and activation, while Au sites inhibit O2 adsorption and stabilize CO2 reduction intermediates, achieving synergistic optimization of kinetics and thermodynamics. A high CO generation rate is maintained even under simulated flue gas conditions, significantly expanding the practical application scenarios of photocatalytic CO2 reduction. The directional etching strategy significantly improves the exposure of Au active sites, reduces the amount of precious metals used, and saves material costs. Attached Figure Description

[0026] Figure 1 (a) TEM image of Ni5Au1-TiO2; (b) HAADF-STEM image of Ni5Au1-TiO2; (c) AC-HAADF-STEM image of Ni5Au1-TiO2; (d) E 1.5 TEM image of -Ni5Au1-TiO2; (e)E 1.5HAADF-STEM image of Ni5Au1-TiO2; (f) E 1.5 AC-HAADF-STEM of Ni5Au1-TiO2;

[0027] Figure 2 (a) XRD patterns of TiO2 surfaces with different Ni and Au loading ratios; (b) XRD patterns of Ni5Au1-TiO2 with different etchant concentrations;

[0028] Figure 3 .(a)Au-TiO2, Ni5Au1-TiO2 and E 1.5 (a) Au 4f XPS plot of Ni5Au1-TiO2; (b) Au-TiO2, Ni5Au1-TiO2 and E 1.5 Ni 2p XPS plot of -Ni5Au1-TiO2;

[0029] Figure 4 (a) Performance comparison of different Ni and Au loading ratios on TiO2 surface; (2) Performance comparison of Ni5Au1-TiO2 under different etchant concentrations; (3) Ni5Au1-TiO2 and E 1.5 Comparison of photocatalytic CO2 reduction performance of Ni5Au1-TiO2 under different CO2 mixed gas compositions;

[0030] Figure 5 (a) O2 molecules are adsorbed on Ni, NiAu, and etched NiAu (V) respectively. Ni (b) Optimized NiAu structure configuration and its corresponding adsorption energy; O2 molecules adsorbed on Ni, NiAu and V respectively. Ni -NiAu charge difference distribution, where Δq represents the total charge change of the O2 molecule. Detailed Implementation

[0031] The present invention will be described in detail below with reference to embodiments, so that those skilled in the art can better understand the present invention, but the present invention is not limited to the following embodiments.

[0032] Example 1

[0033] A method for preparing an unetched Ni5Au1-TiO2 catalyst includes the following steps:

[0034] 500 mg TiO2 was dispersed in 40 mL of anhydrous ethanol and sonicated for 10 min. Then, 0.175 mmol Ni(NO3)2·6H2O and 0.035 mmol HAuCl4·4H2O were added, and the mixture was irradiated under vacuum with a 300 W xenon lamp for 30 min (320-780 nm). After the reaction was completed, the sample was centrifuged, washed, and dried to obtain the Ni5Au1-TiO2 sample.

[0035] Under pure CO2 conditions, the catalyst can achieve high CO2 reduction activity, but under conditions containing 5% O2, the CO2 reduction activity decreases significantly, and the CO selectivity is about 80%.

[0036] Comparative Example 1

[0037] Single Ni composition

[0038] A method for preparing a Ni-TiO2 catalyst includes the following steps:

[0039] Using the same method as in Example 1, but with the addition of only Ni(NO3)2·6H2O and without the addition of Au precursor, Ni-TiO2 was prepared. Under conditions containing 5% O2, this catalyst produced almost no CO, indicating that the strong adsorption of O2 by Ni severely inhibited CO2 reduction.

[0040] Comparative Example 2

[0041] Single Au component

[0042] A method for preparing an Au-TiO2 catalyst includes the following steps:

[0043] Au-TiO2 was prepared using the same method as in Example 1, except that only HAuCl4·4H2O was added and no Ni precursor was added. Under conditions containing 5% O2, the CO formation rate of this catalyst was only 94.7 µmol·g. -1 ·h -1 It is significantly lower than that of the NiAu alloy sample.

[0044] Comparative Example 3

[0045] Physical mixing

[0046] Ni-TiO2 and Au-TiO2 were physically mixed at a Ni:Au atomic ratio of 5:1 without alloying or etching. Under conditions containing 5% O2, the CO formation rate of this system was 136.3 µmol·g. -1 ·h -1 This indicates that simple physical mixing cannot achieve the NiAu synergistic effect.

[0047] Comparative Example 4

[0048] Improper alloy ratio

[0049] Ni1Au1-TiO2 was used and etched. Under conditions containing 5% O2, the CO formation rate of this catalyst decreased to 105.6 µmol·g. -1 ·h -1 This indicates that excessive Au will weaken Ni's ability to adsorb and activate CO2.

[0050] Example 2

[0051] A method for preparing a lightly directionally etched Ni5Au1 alloy oxygen-resistant catalyst includes the following steps:

[0052] 50 mg Ni5Au1-TiO2 was dispersed in 10 mL of a solution containing 5 µmol FeCl3 and 0.1 mol·L⁻¹ -1 E was obtained by etching in an HCl solution at 30°C for 5 min under an Ar atmosphere, followed by washing and drying. 0.5 -Ni5Au1-TiO2.

[0053] In a CO2 atmosphere containing 5% O2, the CO formation rate of this catalyst is 203.9 µmol·g. -1 ·h -1 The CO selectivity is approximately 98.9%.

[0054] Example 3

[0055] A method for preparing a moderately directionally etched Ni5Au1 alloy oxygen-resistant catalyst includes the following steps:

[0056] 50 mg Ni5Au1-TiO2 was dispersed in 10 mL of solution containing 15 µmol FeCl3 and 0.1 mol·L⁻¹ -1 E was obtained by etching in an HCl solution at 30°C under an Ar atmosphere for 10 min, followed by washing and drying. 1.5 -Ni5Au1-TiO2.

[0057] Under conditions containing 5% O2, the catalyst achieved a CO generation rate of 375.5 µmol·g. -1 ·h -1 With a CO selectivity close to 100%, it exhibits the best oxygen-resistant photocatalytic performance.

[0058] The prepared materials were characterized, and the specific analysis is as follows:

[0059] The surface of the NiAu-loaded TiO2 sample exhibits obvious roughening characteristics, accompanied by the appearance of a large number of dark spots. Figure 1a) This phenomenon indicates the presence of extremely small metal nanoclusters on the sample surface. HAADF-STEM images show a large number of bright and uniformly distributed bright spots on the TiO2 surface. Figure 1 (b) This result is consistent with the successful loading of NiAu alloy nanoclusters with high average atomic mass onto the TiO2 surface. Further analysis of the samples using AC-HAADF-STEM with atomic number (Z) comparison can be used to resolve structural information at the atomic scale. Since the intensity of the bright spot is closely related to the atomic mass of the constituent elements, comparing the intensity of the bright spot can be an effective means of distinguishing different atomic species, especially for identifying single atoms when there are significant differences in atomic mass. Figure 1 As shown in Figure c, due to the high atomic number of NiAu species, it exhibits distinct bright regions on the surface of TiO2 nanoparticles. Within these bright regions, even brighter isolated bright spots can be observed, indicating that Au atoms are distributed within Ni nanoclusters, confirming the successful construction of the NiAu alloy structure.

[0060] Compared with TiO2 samples with rough surfaces after metal loading ( Figure 1 Compared to a), the surface of the composite material after etching treatment exhibits a relatively smooth TiO2 morphology again. Figure 1 d), while a more obvious dark depression area can be observed in the HAADF-STEM image ( Figure 1 e), indicating that the etching process effectively removed some NiAu alloy species. Nevertheless, AC-HAADF-STEM analysis showed that bright spots corresponding to some Au nanoclusters could still be observed in the sample ( Figure 1 f), further illustrating that the etching process can selectively remove Ni components and expose more Au active sites.

[0061] XRD results show that commercial titanium dioxide (TiO2) exhibits characteristic diffraction peaks of both anatase and rutile phases. Figure 2 a). After loading Ni5Au1, weak Au (111) and (200) diffraction peaks began to appear in the sample, while no obvious Ni-related diffraction peaks were observed. This phenomenon may be attributed to the low crystallinity of the Ni component and its high dispersion on the support surface. When the Ni5Au1 sample was etched to different degrees, the intensity of the characteristic diffraction peaks of Au gradually increased, indicating that some Ni was removed during the etching process, thereby exposing more Au components. This also indicates that Ni and Au coexist in the sample in an alloy form. Figure 2 (b) further confirms the successful construction of the NiAu alloy structure.

[0062] XPS was used to analyze the changes in elemental distribution of the samples before and after directional etching. Figure 3As shown, compared to Au-TiO2, the Au 4f signal intensity in the Ni5Au1-TiO2 sample is weaker, indicating that most Au atoms are embedded within the Ni component. This result is consistent with the formation of the NiAu alloy structure and also explains the overall weaker Au 4f signal on the catalyst surface. Notably, after removing part of the Ni component through directional etching, the Au 4f signal intensity in the sample significantly increased, indicating that this etching method can effectively expose Au active sites while maintaining the NiAu synergistic effect, thereby improving the utilization efficiency of noble metals. Correspondingly, the Ni 2p signal in the Ni5Au1-TiO2 sample weakened significantly after etching, indicating that the Ni component was partially removed and vacancy structures were formed in local areas, which is beneficial for exposing more metal active sites.

[0063] Example 4

[0064] A method for preparing an oxygen-resistant catalyst for excessively directional etching of NiAu alloy includes the following steps:

[0065] 50 mg Ni5Au1-TiO2 was dispersed in 10 mL of solution containing 25 µmol FeCl3 and 0.1 mol·L⁻¹ -1 E was obtained by etching in an HCl solution at 30 °C for 20 min under an Ar atmosphere, followed by washing and drying. 2.5 -Ni5Au1-TiO2.

[0066] The CO generation rate of this sample decreased to 240.7 µmol·g under conditions containing 5% O2. -1 ·h -1 This indicates that excessive removal of Ni will destroy the NiAu co-active center.

[0067] Example 5

[0068] Different alloy ratios: Ni3Au1

[0069] Using the same method as in Example 1, the molar ratio of Ni(NO3)2·6H2O and HAuCl4·4H2O was adjusted to 3:1 to prepare Ni3Au1 / TiO2, which was then etched under the conditions of Example 3 to obtain E. 1.5 -Ni3Au1 / TiO2.

[0070] Under conditions containing 5% O2, the CO generation rate of this catalyst is 298.2 µmol·g. -1 ·h -1 The CO selectivity is approximately 98%.

[0071] Example 6

[0072] Different alloy ratios: Ni7Au1

[0073] Using the same method as in Example 1, the molar ratio of Ni(NO3)2·6H2O and HAuCl4·4H2O was adjusted to 7:1 to prepare Ni7Au1 / TiO2, which was then etched under the conditions of Example 3 to obtain E. 1.5 -Ni7Au1 / TiO2.

[0074] Under conditions containing 5% O2, the CO generation rate of this catalyst is 242.6 µmol·g. -1 ·h -1 The CO selectivity was 96%.

[0075] Example 7

[0076] Simulated industrial flue gas conditions

[0077] E prepared using Example 3 1.5 The photocatalytic activity of Ni5Au1 / TiO2 was tested under simulated flue gas conditions (CO2 15%, O2 5%, N2 80%). Under these conditions, the CO formation rate was 203.5 µmol·g. -1 ·h -1 The CO selectivity remained above 99%, indicating that the catalyst has good potential for practical application.

[0078] The performance tests and oxygen resistance reaction mechanisms of the photocatalysts prepared in the above embodiments are analyzed in detail below:

[0079] Gas-solid phase photocatalytic reaction was tested under 300 W xenon lamp irradiation with CO2 and H2O as reactants. The results showed that the reaction with the unsupported metal TiO2 catalyst produced only a low CH4 formation rate (14.2 µmol·g⁻¹). -1 ·h -1 Compared to the previous method, the CH4 generation performance of TiO2 catalysts supported on Ni or Au was significantly improved, with the CH4 generation rates of Ni-TiO2 and Au-TiO2 reaching 384.1 µmol·g⁻¹, respectively. -1 ·h -1 and 590.0 µmol·g -1 ·h -1 These figures are 27.0 times and 41.5 times that of pure TiO2, respectively. Figure 4 a) These results indicate that the introduction of Ni and Au provides faster and more efficient active sites for the photocatalytic reaction and helps promote the transport of photogenerated carriers. When Ni and Au are introduced simultaneously, the CH4 generation rate is further significantly increased, with the Ni5Au1-TiO2 sample exhibiting the highest CH4 generation rate of 2779.6 µmol·g. -1 ·h -1The concentrations of Ni and Au were 7.2 times and 4.7 times that of Ni-TiO2 and Au-TiO2, respectively, and the CH4 selectivity reached 82.4%. It should be noted that when the Ni or Au content is too high, the CH4 generation performance decreases, indicating that only when the Ni:Au atomic ratio is 5:1 can Ni and Au exert the optimal synergistic effect, thereby effectively promoting the conversion of CO2 to CH4.

[0080] Existing research on photocatalytic CO2 conversion is mostly conducted under high-purity CO2 conditions. However, in practical applications, especially in environments with high CO2 emissions, the atmosphere typically contains air components, and O2 is widely present. Since O2 capture and the oxygen reduction reaction compete with the CO2 reduction process for photogenerated electrons, significantly inhibiting CO2 conversion efficiency, developing oxygen-resistant catalysts is crucial for promoting practical CO2 conversion. To more directly evaluate the oxygen resistance of the catalyst, the CO2 conversion performance of Ni5Au1 / TiO2 was tested under a total pressure of 100 kPa, with 5% CO2 replaced by O2. In the presence of O2, due to the competitive capture of photogenerated electrons and the occurrence of the ORR reaction, the overall catalytic performance significantly decreased, and the conversion of CO2 to CH4 was inhibited and maintained at a low level. At this point, the main product of Ni5Au1-TiO2 was converted to CO, with a CO formation rate of 136.3 µmol·g. -1 ·h -1 The CO selectivity was 80.2%. This result indicates that the presence of O2 preferentially consumes protons and generates H2O or H2O2, thereby thermodynamically and kinetically inhibiting the reaction of CO2 to form CH4 via the eight-electron pathway and favoring the formation of CO via the two-electron pathway.

[0081] To further investigate the effect of different elements' varying tolerance to O2 on CO2 catalytic conversion performance, Ni atoms in Ni5Au1-TiO2 were directionally etched, and their performance evolution under an oxygen-rich environment was examined. Figure 4 (b) to screen for high-performance catalysts suitable for oxygen-containing conditions. As Ni is gradually oriented etched, the CO generation rate of the sample gradually increases, where E 1.5 The CO generation rate of -Ni5Au1-TiO2 reaches 375.5 µmol·g under conditions containing 5% O2. -1 ·h -1 Furthermore, the CO selectivity was close to 100%. This result indicates that, in the presence of Ni, exposing more Au active sites is beneficial for promoting CO2 capture and conversion in an oxygen-containing environment. However, as the Ni etching depth increased, the CO generation rate decreased, suggesting that excessive removal of Ni active sites weakens the synergistic effect between Ni and Au.

[0082] Meanwhile, comparative tests were conducted on etched and unetched Ni5Au1-TiO2 catalysts under different gas composition conditions. Figure 4 c), to clarify its structure-performance relationship and practical application potential. In a pure CO2 atmosphere, E 1.5 The CO2 conversion performance of -Ni5Au1-TiO2 is slightly lower than that of unetched Ni5Au1-TiO2, which may be related to the loss of some Ni active sites and the reduced CO2 adsorption and activation capacity. However, under conditions containing 5% O2, E 1.5 The CO generation rate of -Ni5Au1-TiO2 was significantly higher than that of Ni5Au1-TiO2, and the CO selectivity was close to 100%, indicating that the numerous Ni sites in Ni5Au1 / TiO2 were more susceptible to ORR inhibition under oxygen-rich conditions, thus significantly affecting CO2 conversion efficiency. Therefore, increasing Au exposure and inhibiting ORR reactions at Ni sites is beneficial for promoting efficient CO2 conversion. Further, after replacing 80% of the CO2 with N2 to simulate flue gas conditions, although the CO2 conversion rate decreased, the system still maintained a CO2 conversion efficiency of 203.5 µmol·g. -1 ·h -1 The CO generation rate was significantly improved, with selectivity approaching 100%. This result indicates that by rationally controlling the ratio of CO2 affinity sites to oxygen-tolerant active sites, the application scope of CO2 reduction reactions in complex real-world environments can be significantly broadened.

[0083] Furthermore, the synergistic effect of Au in suppressing O2 adsorption in NiAu alloy nanoclusters was investigated using DFT calculations. Figure 5 As shown in Figure a, pure Ni exhibits an extremely strong adsorption capacity for O2, and its O2 adsorption energy (E) is very high. ad The O2 adsorption energy was -4.35 eV, indicating that Ni has poor tolerance to O2 and that the oxygen reduction reaction (ORR) inevitably occurs on the Ni surface. When Au atoms were introduced into Ni nanoclusters to form a NiAu alloy, the O2 adsorption energy significantly decreased to -2.08 eV, indicating that the introduction of Au effectively weakened the catalyst surface's ability to adsorb O2, thereby inhibiting O2 adsorption behavior. Further etching of the surface Ni atoms to expose more unsaturated Au active sites further reduced the O2 adsorption energy to -1.51 eV, indicating that with increased Au exposure, O2 adsorption and the resulting ORR process could be further suppressed. Meanwhile, Ni, NiAu, and V... Ni In the -NiAu structure, the metal-oxygen (MO) bond lengths are 1.82 Å, 1.88 Å, and 2.22 Å, respectively. Among them, V... Ni The longer O-Au bond length in the -NiAu structure indicates its weakest affinity for O2, further confirming that the introduction of Au and the increase in its exposure level are beneficial to enhancing the stability and efficiency of the CO2 reduction reaction in an oxygen-containing atmosphere.

[0084] Charge density differential distribution results ( Figure 5 b) shows that the charge transfer amount (Δq) of O2 molecules calculated using the Bader method is 1.65 e in the pure Ni system, indicating a strong interaction between O2 and Ni nanoclusters. Introducing Au into the Ni lattice significantly reduces the negative charge transfer amount of O2 to 0.88 e, demonstrating that Au effectively weakens the adsorption of O2 by Ni. Further etching of Ni atoms... Ni The Δq value of the NiAu system decreased to 0.81 e, indicating that exposing more unsaturated Au active sites can further inhibit O2 adsorption and activation. Furthermore, in Ni, NiAu, and V... Ni The O2 molecules adsorbed on the NiAu surface have O-O bond lengths of 1.56 Å, 1.48 Å, and 1.42 Å, respectively. This result indicates that the pure Ni surface induces the strongest electron transfer to O2 molecules, while the introduction of Au significantly reduces the degree of electron transfer to O2, thereby weakening the oxygen reduction reaction pathway. Therefore, by regulating the tolerance of catalytic active sites to O2, the application range of photocatalysts under various reaction atmospheres can be effectively expanded, and their operational adaptability in complex reaction environments can be improved.

[0085] Example 8

[0086] High oxygen content condition test

[0087] E prepared using Example 3 1.5 The Ni5Au1 / TiO2 catalyst was tested in a mixed atmosphere containing 20% ​​O2 and 80% CO2. The results showed that the catalyst could still maintain a viscosity of 259.3 µmol·g. -1 ·h -1 With a CO generation rate and CO selectivity approaching 100%, it exhibits excellent hyperoxia tolerance.

[0088] It should be noted that the specific parameters, proportions, and conditions given in the above embodiments and specifications are for better illustrating the technical content of the present invention and verifying its effects, and are not intended to limit the present invention. Under the guidance of the technical concept of the present invention, reasonable changes and adjustments made by those skilled in the art to the carrier type, precursor type, etching reagent, and process parameters, as long as their ultimate purpose is to achieve oxygen-resistant CO2 photocatalytic reduction by constructing Au-rich NiAu alloy nanoclusters, should be considered within the scope of protection of the present invention. For example, the TiO2 carrier can also be replaced with other semiconductor materials with matching band structures (such as zinc oxide, tungsten oxide, cadmium sulfide, carbon nitride, etc.), and the metal precursor loading method can also employ impregnation, deposition, precipitation, etc., combined with subsequent reduction and controllable etching steps, to achieve similar surface alloy structure and performance regulation, and obtain similar technical effects.

[0089] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made using the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for preparing an oxygen-resistant nickel-gold alloy nanocluster / titanium dioxide photocatalyst, characterized in that, Includes the following steps: (1) TiO2 is dispersed in anhydrous ethanol, and Ni precursor and Au precursor are added. The molar ratio of Ni precursor to Au precursor is 1:1-7:

1. After removing dissolved gas by vacuuming in a closed photoreactor, an in-situ photoreduction reaction is carried out to form highly dispersed NiAu alloy nanoclusters on the surface of TiO2 in situ, thus obtaining NiAu-TiO2 precursor; (2) The NiAu-TiO2 precursor is dispersed in a weak oxidizing solution and etched at 20-60℃ for 1-30 min under an inert atmosphere. The pH of the solution is maintained at 2.0-3.0 to achieve selective removal of Ni atoms in the alloy and suppress the dissolution of Au, thereby obtaining an oxygen-resistant nickel-gold alloy nanocluster / titanium dioxide photocatalyst.

2. The preparation method of the oxygen-resistant nickel-gold alloy nanoclusters / titanium dioxide photocatalyst according to claim 1, characterized in that: In step (1), the Ni precursor is at least one of nickel nitrate, nickel chloride, or nickel sulfate; the Au precursor is chloroauric acid or gold trichloride.

3. The preparation method of the oxygen-resistant nickel-gold alloy nanoclusters / titanium dioxide photocatalyst according to claim 1, characterized in that: In step (1), the molar ratio of the Ni precursor to the Au precursor is 5:

1.

4. The preparation method of the oxygen-resistant nickel-gold alloy nanoclusters / titanium dioxide photocatalyst according to claim 1, characterized in that: In step (1), the conditions for the photoreduction reaction are: a 300 W xenon lamp with an output spectrum of 320-780 nm and a light intensity of 100-300 mW / cm². 2 Irradiate continuously for 20-40 minutes, preferably 30 minutes.

5. The preparation method of the oxygen-resistant nickel-gold alloy nanoclusters / titanium dioxide photocatalyst according to claim 1, characterized in that: In step (2), the weak oxidizing solution contains Fe. 3+ An acidic aqueous solution of Fe ions 3+ The ions originate from ferric nitrate, ferric chloride, or ferric sulfate.

6. The preparation method of the oxygen-resistant nickel-gold alloy nanoclusters / titanium dioxide photocatalyst according to claim 1, characterized in that: In step (2), the Fe 3+ Ion concentration in the range of 0.5-2.5 mmol·L -1 Within the specified range, the acidic environment is regulated and maintained by hydrochloric acid, nitric acid, or sulfuric acid.

7. An oxygen-resistant nickel-gold alloy nanoclusters / titanium dioxide photocatalyst prepared by the method according to any one of claims 1-6.

8. The oxygen-resistant nickel-gold alloy nanoclusters / titanium dioxide photocatalyst according to claim 7, characterized in that: In the catalyst, Ni and Au are highly dispersed on the TiO2 surface in an alloy form, and after directional etching, NiAu synergistic active sites are formed on the Au-rich surface.

9. The application of the oxygen-resistant nickel-gold alloy nanoclusters / titanium dioxide photocatalyst according to claim 8 or 9 in the photocatalytic reduction of carbon dioxide to carbon monoxide in an oxygen-containing atmosphere.

10. The application according to claim 9, characterized in that: The oxygen-containing atmosphere is a mixture of carbon dioxide and oxygen with a volume content of 1-20%. Further, the oxygen-containing atmosphere is a simulated industrial flue gas with the following composition: 3-5% oxygen, 12-16% carbon dioxide, 72-77% nitrogen, and a small amount of water vapor.

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