Ni / CeOx catalyst for water gas shift reaction and preparation method of Ni / CeOx catalyst

Abstract

The invention provides a Ni / CeOx catalyst for a water gas shift reaction and a preparation method of the Ni / CeOx catalyst. The preparation method comprises the following steps: firstly, preparing a NiCe layered double hydroxide precursor through a hydrothermal synthesis method; then, the precursor is calcined, and a mixed metal oxide composed of NiO and CeO is obtained; and finally, carrying out reduction treatment on the mixed metal oxide at a specific temperature in a hydrogen / argon mixed atmosphere to obtain the Ni / CeOx catalyst which is loaded with the Ni nanoclusters and has the oxygen vacancies. A synergistic structure of an electron-rich Ni delta + active site and a high-concentration oxygen vacancy is formed in the obtained catalyst, a water gas shift reaction can be efficiently catalyzed under the illumination condition when the surface temperature of the catalyst is 77 DEG C, the CO conversion rate of the catalyst reaches 92.05% within 30 min, and the catalyst shows excellent cycle stability.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of catalysts, and particularly relates to a Ni / CeO2₋ x catalyst for a water-gas shift reaction and a preparation method thereof. BACKGROUND

[0002] The water-gas shift reaction (WGSR), CO + H2O ⇌ CO2 + H2, is a crucial catalytic process in modern chemical industry, which is the core technology for producing high-purity hydrogen from synthesis gas rich in carbon monoxide. The produced hydrogen is widely used in the ammonia synthesis industry, methanol synthesis, and as fuel for proton exchange membrane fuel cells (PEMFC). The traditional industrial WGSR process is usually divided into two stages, high-temperature shift (350-500 DEG C) and low-temperature shift (200-250 DEG C). The entire process consumes a large amount of heat energy, and the reaction temperature is significantly different from the optimal working temperature range (70-90 DEG C) of low-temperature fuel cells, resulting in low energy integration efficiency.

[0003] In order to solve the above problems, the development of a WGSR catalyst capable of operating efficiently at low temperature has become a research hotspot. Current research mainly focuses on two categories: noble metal catalysts (such as Pt, Au, Rh-based catalysts) and non-noble metal catalysts. Although noble metal catalysts exhibit certain activity at low temperature, their high cost, scarce resource reserves, and the disadvantage of being easily poisoned and deactivated in complex reaction environments greatly limit their large-scale industrial application. In contrast, non-noble metal catalysts, especially nickel-based catalysts with abundant reserves and low cost, show great application potential. However, the activity of traditional nickel-based catalysts at low temperature is generally insufficient, and the main bottlenecks are: 1) the active metal Ni nanoparticles are prone to agglomeration during preparation or reaction, resulting in a decrease in the number of active sites and a decrease in dispersion; 2) the interaction between the catalyst support (such as Al2O3, SiO2) and the metal is weak, making it difficult to effectively regulate the electronic structure of the metal; 3) the key intermediate steps of the catalytic reaction, such as the activation and dissociation of water, are limited by the properties of the catalyst surface, especially at low temperature. Technical disclosure shows that ceria (CeO2) as a functional support has attracted attention due to its excellent oxygen storage / release capacity and strong interaction with metals, but how to accurately construct a Ni / CeO2 catalyst with specific interface electronic structure and high-density active sites through a controllable synthesis method to achieve a low-temperature and high-efficiency WGSR reaction remains a technical problem to be solved. SUMMARY

[0004] The technical problem to be solved is to provide a Ni / CeO2₋ xA catalyst and its preparation method are disclosed, wherein the catalyst is supported on Ni nanoclusters and has oxygen vacancies, enabling a low-temperature and high-efficiency WGSR reaction.

[0005] Technical solution: A Ni / CeO2₋ for water-gas shift reaction x A method for preparing a catalyst, the method comprising the following steps: S1. Hydrothermal synthesis: Nickel source, cerium source, ammonium fluoride and urea are dissolved in water, hydrochloric acid is added to adjust the system, and after stirring, the resulting mixed solution is subjected to hydrothermal reaction at 90~100℃ for 20~28h. After the reaction is completed, solid-liquid separation, washing and drying are performed to obtain NiCe layered double hydroxide precursor. S2. Calcination: The NiCe layered double hydroxide precursor obtained in S1 is heated to 480~520℃ in air atmosphere at a heating rate of 1~3℃ / min and held for 3~5h to obtain a mixed metal oxide composed of NiO and CeO2. S3. Reduction: The mixed metal oxide composed of NiO and CeO2 obtained in S2 is placed in a mixed atmosphere of hydrogen and argon, heated to the reduction temperature at a heating rate of 1~3℃ / min, and subjected to reduction treatment at the reduction temperature for 3~5h to obtain Ni / CeO2₋. x catalyst.

[0006] Preferably, the nickel source in S1 is Ni(NO3)2·6H2O, and the cerium source is Ce(NO3)3·6H2O; Preferably, in the hydrogen and argon mixed atmosphere in S3, the volume fraction of hydrogen is 10-15% and the volume fraction of argon is 85-90%. The flow rate of the mixed gas is (30-120) mL / min.

[0007] Preferably, the reduction temperature in S3 is selected from 250℃, 350℃, 450℃, 550℃ or 650℃.

[0008] Preferably, the catalyst is prepared by any of the preceding methods, and the reduction temperature in step S3 is set to 450°C. The catalyst is characterized by the following: The concentration of Ce³⁺ ions on the catalyst surface accounted for 13.71% of the total concentration of cerium ions. The oxygen vacancy concentration on the catalyst surface is 52%; The coordination number of the first coordination shell Ni-Ni metallic bond in the catalyst is 6.72; The K-edge absorption position of Ni in the catalyst shifts to a lower energy end relative to the absorption edge position of the nickel foil, indicating that the Ni species is in the electron-rich Niδ state. + .

[0009] Preferably, when the catalyst is irradiated with a xenon lamp at a light power of 1.66 W / cm² and the catalyst surface temperature is stabilized at 77°C, it is used to catalyze the water-gas shift reaction for 30 min, and the CO conversion rate is 92.05% and the H2 yield is 103.24 μmol / gcat / s.

[0010] Preferably, the Ni / CeO2₋ x Application of the catalyst in the photoinduced water-gas shift reaction: The catalyst is placed in the reaction system and the surface temperature of the catalyst is maintained between 70 and 90°C under light irradiation. The reaction of carbon monoxide and water is driven by light energy to generate hydrogen and carbon dioxide.

[0011] Beneficial effects: This invention has the following advantages: 1. The Ni / CeO2 in this invention is derived from the in-situ topological transformation of the NiCe layered double hydroxide precursor. The NiCe layered double hydroxide precursor has an ultrathin nanoplate structure, which maintains nanoscale dispersion after calcination and reduction, ultimately resulting in a Ni / CeO2 nanoflower structure. This structure achieves uniform loading of Ni nanoparticles, enhances the interfacial interaction between Ni and CeO2, promotes electron transfer and reactant adsorption, thereby improving hydrogen production efficiency. In addition, the ultrathin nanoplate structure of the NiCe layered double hydroxide precursor has a geometric confinement effect, which inhibits Ni particle sintering and solves the problem of easy deactivation of traditional catalysts at high temperatures. 2. The performance of the Ni / CeO2 catalyst in the water-gas shift reaction in this invention is due to the unique photo-induced reaction pathway, rather than the traditional thermally driven mechanism. In the dark, H2O dissociates into hydroxyl groups (OH) through Ov. After illumination, Ov returns to its initial state, forming a photo-regulated oxygen cycle, which accelerates the reaction between CO and H2O (the reaction formula is: CO + H2O → CO2 + H2). Attached Figure Description

[0012] Figure 1 A comparison chart of CO conversion rates of catalysts prepared at different reduction temperatures; Figure 2 NiCe layered double hydroxide precursor, mixed metal oxide composed of NiO and CeO2, and Ni / CeO 2-x (450) SEM images and EDS maps; Figure 3 Ni / CeO 2-x(450) Comparison with current thermal catalysts (left) and photocatalysts (right); Figure 4 Ni / CeO 2-x (450) shows a positive correlation between hydrogen production rate and light power; Figure 5 Ni / CeO 2-x (450) in-situ XRD pattern; Figure 6 Ni K-edge XANES spectrum; Figure 7 To systematically reveal the effects of reduction temperature and illumination conditions on Ni / CeO using multi-scale in-situ spectroscopic techniques (quasi-in-situ XPS, in-situ EPR, and DRIFTS), 2-x The regulatory mechanisms of catalyst electronic structure, oxygen vacancy dynamics, and intermediate species in water-gas shift reaction. Detailed Implementation

[0013] The present invention will be further described below with reference to embodiments. These embodiments are illustrative of the present invention, but the present invention is not limited to these embodiments: Example 1

[0014] A Ni / CeO2₋ for water-gas shift reaction x Catalyst preparation method, the method comprising the following steps: S1: Weigh 1.62g Ni(NO3)2·6H2O (0.006 mol), 0.9876g Ce(NO3)3·6H2O (0.0023 mol), 0.074g NH4F (2 mmol), and 6.0g urea (0.1 mol), dissolve them in 100ml deionized water, and add 0.25ml concentrated hydrochloric acid. Stir vigorously with a magnetic force until all solids are completely dissolved to form a homogeneous solution. Transfer the solution to a 200ml stainless steel hydrothermal reactor lined with polytetrafluoroethylene, seal it, and place it in an electrically heated drying oven. React at 95℃ for 24 hours. S2: After the reaction is complete, allow the reactor to cool naturally to room temperature. Centrifuge the resulting suspension (8000 rpm, 10 min) and discard the supernatant. Wash and centrifuge the resulting pale green solid repeatedly with deionized water until the pH of the supernatant is close to neutral. Dry the washed solid in an oven at 60°C overnight (12 h) to obtain NiCe-LDHs precursor powder. S3: The dried NiCe-LDHs precursor powder was placed in a porcelain crucible and transferred to a muffle furnace. Under static air atmosphere, it was heated from room temperature to 500°C at a heating rate of 2°C / min and calcined at this temperature for 4 hours. After calcination, the powder was allowed to cool naturally to room temperature in the furnace to obtain a grayish-black NiCe-MMO powder. S4: The obtained NiCe-MMO powder was placed in the center of a quartz tube furnace. Reduction was carried out in a mixed gas flow of H2 / Ar (volume ratio 10:90), with the total gas flow rate controlled at 6 mL / min. The temperature was increased from room temperature to 450 °C at a heating rate of 2 °C / min, and then isothermally reduced at 450 °C for 4 hours. After reduction, the powder was cooled to room temperature under Ar atmosphere protection to obtain the final black Ni / CeO2₋. x (450) Catalyst powder. Example 2

[0015] The same steps S1, S2, and S3 as in Example 1 were used. In step S4, only the final reduction temperature was changed and set to 250°C, while other reduction conditions (heating rate, gas flow rate, and reduction time) remained unchanged. This resulted in the preparation of Ni / CeO₂₋. x (250) Catalyst. Example 3

[0016] The same steps S1, S2, and S3 as in Example 1 were used. In step S4, only the final reduction temperature was changed and set to 250°C, while other reduction conditions (heating rate, gas flow rate, and reduction time) remained unchanged. This resulted in the preparation of Ni / CeO₂₋. x (350) Catalyst. Example 4

[0017] This invention provides a Ni / CeO₂₋ for water-gas shift reaction. x A catalyst and its preparation method are disclosed. The preparation method includes the following steps: first, a NiCe layered double hydroxide precursor is prepared by hydrothermal synthesis; subsequently, the precursor is calcined to obtain a mixed metal oxide composed of NiO and CeO2; finally, the mixed metal oxide is reduced at a specific temperature in a hydrogen / argon mixed atmosphere to obtain Ni / CeO2₋ with oxygen vacancies and supported on Ni nanoclusters. x Catalyst. The catalyst obtained in this invention forms a synergistic structure of electron-rich Niδ+ active sites and high-concentration oxygen vacancies. Under light irradiation, the catalyst can efficiently catalyze the water-gas shift reaction at a surface temperature of 77°C, achieving a CO conversion rate of 92.05% within 30 minutes, and exhibiting excellent cycle stability. Example 5

[0018] The same steps S1, S2, and S3 as in Example 1 were used. In step S4, the final reduction temperature was set to 650°C, while other reduction conditions (heating rate, gas flow rate, and reduction time) remained unchanged, yielding Ni / CeO₂₋. x (650) Catalyst. Comparative Example 1

[0019] This comparative example uses a commercially available Ni / CeO2 thermal catalyst, grade Ni / CeO2-HTC90, with a Ni loading of 10 wt%. Catalyst composition: NiO (10%) / CeO2 (90%), particle size 50-100 nm, specific surface area ~45 m² / g Preparation method: Commercially available products are prepared using the traditional impregnation-calcination method without photosensitization treatment; Performance Comparison: Under the same reaction conditions (300W xenon lamp, CO / H2O mixture), the surface temperature of this thermal catalyst needs to rise above 280°C to achieve a CO conversion rate (~92%) comparable to that of the example, but it has almost no activity at a low temperature of 80°C (CO conversion rate <5%). After 24 hours of continuous operation, the activity decreased by about 35% due to carbon buildup and sintering. Comparative Example 2

[0020] The difference between this comparative example and Example 1 is that the NiCe-MMO powder was not reduced, i.e., the experimental step described in S4 was not performed. Comparative Example 3

[0021] The difference between this comparative example and Example 1 is that the NiCe-MMO powder was not calcined or reduced, i.e., the experimental steps described in S3 and S4 were not performed. Comparative Example 4

[0022] The difference between this comparative example and Example 1 is that Ni(NO3)2·6H2O was not added in S1. Comparative Example 5

[0023] The difference between this comparative example and Example 1 is that Ce(NO3)3·6H2O was not added in S1. Comparative Example 6

[0024] The difference between this comparative example and Example 1 is that no layered hydroxides were formed in S1. The same amounts of Ni(NO3)2·6H2O (1.62 g, 0.006 mol), Ce(NO3)3·6H2O (0.9876 g, 0.0023 mol), and NH4F (0.074 g, 2 mmol) as in Example 1 were weighed and dissolved in 100 mL of deionized water to form a transparent mixed salt solution. At room temperature (25°C), a 1 mol / L NaOH solution was slowly added dropwise at a rate of 5 mL / min using a peristaltic pump, while vigorous magnetic stirring (800 rpm). The pH was monitored in real time, and the addition was stopped when the solution reached 10.5 ± 0.2. During this process, a large amount of pale green flocculent precipitate was immediately formed, without an induction period for the formation of layered structures. After precipitation, stirring was continued for 2 hours for aging (without the 24-hour hydrothermal reaction with urea). The suspension was directly centrifuged (8000 rpm, 10 min), and the subsequent washing and drying steps were the same as in Example 1 to obtain a non-layered NiCe-CP precursor powder. The subsequent experimental steps were the same. Comparative Example 7

[0025] The difference between this comparative example and Example 1 is that, instead of using Ce and Ni to form a layered hydroxide, Al and Ni were used to form a layered hydroxide. The specific experimental steps are as follows: Weigh 1.62 g Ni(NO3)2·6H2O (0.006 mol), 0.938 g Al(NO3)3·9H2O (0.0025 mol), 0.074 g NH4F (2 mmol), and 6.0 g urea (0.1 mol), dissolve them in 100 ml deionized water, and add 0.25 ml concentrated hydrochloric acid. Stir vigorously with a magnetic force until all solids are completely dissolved to form a homogeneous solution. Transfer the solution to a 200 ml stainless steel hydrothermal reactor lined with polytetrafluoroethylene, seal it, and place it in an electrically heated drying oven at 95°C for 24 hours. Comparative Example 8

[0026] The difference between this comparative example and Example 1 is that nickel oxide and cerium oxide were directly mixed and then reduced with hydrogen and argon. The specific experimental steps are as follows: Weigh 0.45g NiO (Sinopharm Group, 99.9%, 30 nm) and 1.55g CeO2 (Sinopharm Group, 99.9%, 50 nm) powder, place them in an agate mortar, add 5 mL of anhydrous ethanol as a dispersant, and manually grind for 30 minutes until uniformly mixed. Dry the mixed powder in an oven at 80°C for 2 hours to obtain a NiO+CeO2-M physical mixture. S3-S4 are the same as in Example 1, calcining the mixture in air at 500°C for 4 hours (this step mainly removes potentially adsorbed organic matter), and then treating it under the same conditions (H2 / Ar 10:90, flow rate 60 mL min⁻¹, reduction at 450°C for 4 hours) to obtain the Ni / CeO2-PM(450) catalyst. Comparative Example 9

[0027] The difference between this comparative example and Example 1 is that the reduction temperature in step S4 is changed to 200°C.

[0028] Performance testing Test 1: The materials obtained in the embodiments and comparative examples of this invention were tested. All catalytic performance tests of this invention were performed in accordance with the standard method of HG / T 4675-2014, with the photothermal test part referring to ISO 10677:2011 test specification for photocatalytic materials to ensure data comparability and repeatability. The specific process is as follows: A 50 mg catalyst sample was packed into a fixed-bed quartz reactor. Pretreatment under an Ar atmosphere was performed before the reaction. Subsequently, the reactant gas (1 vol.% CO, 3 vol.% H2O, with Ar as the equilibrium gas) was introduced into the reactor. A 300 W xenon lamp was used as the light source, and the light power was controlled by adjusting the distance between the lamp and the reactor. When the light power was 1.66 W / cm², the surface temperature of the catalyst bed stabilized at 77 °C, as measured by infrared thermal imaging. The reaction products were analyzed using an online gas chromatograph (GC).

[0029] The results are as follows Figure 1 As shown, the CO conversion rate exhibits a volcano-like trend, first increasing and then decreasing with increasing reduction temperature. Ni / CeO2₋ x The (450) catalyst exhibited the highest catalytic activity, achieving a CO conversion of 92.05% after 30 minutes of reaction, corresponding to an H2 generation rate of 103.24 μmol / gcat / s and a CO2 generation rate of 174.85 mmol / gcat. Catalysts used for reduction at other temperatures showed lower activity. Furthermore, the catalyst for Ni / CeO₂₋… x (450) A 24-hour cyclic light irradiation (30 minutes of light / 30 minutes of darkness) stability test was conducted, and the results showed that its catalytic activity did not show significant attenuation. Therefore, Ni / CeO2₋x (450) The catalyst was used for subsequent experiments.

[0030] Test 2: Testing the effect of different optical powers on Ni / CeO2₋ x (450) The effect of catalyst H2 yield: All photothermal catalytic performance tests were conducted in accordance with the basic principles of national standard GB / T 23761-2009 and industry standard HG / T 4675-2014, combined with the photocatalytic testing specifications of international standard ISO 10677:2011, using a self-built fixed-bed reactor system. The light power density was calibrated using the method of national standard GB / T 26178-2010, temperature measurements conformed to ASTM E1862-14, and gaseous product analysis followed GB / T 8984-2008 gas chromatography. The specific process is as follows: Take 50mg Ni / CeO2₋ x (450) The catalyst was packed into a fixed-bed quartz reactor and pretreated in an Ar atmosphere for 30 min; Introduce the reaction raw material gas (1 vol.% CO, 3 vol.% H2O, Ar as the equilibrium gas) and control the gas flow rate at 60 mL / min; A 300W xenon lamp was used as the light source. By adjusting the distance between the light source and the reactor, the light power was set to 0.50 W / cm², 0.83 W / cm², 1.20 W / cm², and 1.66 W / cm², respectively. The reaction was carried out for 30 min under each light power condition. The H2 yield was monitored in real time by online gas chromatography, and the catalyst surface temperature was recorded (measured by infrared thermal imager), as shown in Table 1.

[0031] Table 1

[0032] As shown in Table 1, as the optical power increases from 0.50 W / cm² to 1.66 W / cm², the H₂ yield gradually increases and is positively correlated with the optical power. In addition, the temperature is 77℃ at 1.66 W / cm², which meets the integration requirements of low-temperature fuel cells (70-90℃).

[0033] Comparative examples 1-9 were tested using the same testing standards, and the results are shown in Table 2.

[0034] Table 2

[0035] In Comparative Examples 1-8, considerable activity was observed only at surface temperatures >65°C. However, even at temperatures close to Example 1 (e.g., Comparative Example 8, 70°C), the activity remained below 20% due to the lack of SMSI and photosensitized structures. Comparative Examples 6 (H2 yield 21.5%) and 7 (32.4%) demonstrate that even with disordered structures, Ce-containing systems are superior to Ce-free systems because the intrinsic photoresponse of Ce cannot be completely replaced. The activity of Comparative Example 2 (unreduced) was only 7.2 times that of Comparative Example 3 (uncalcined), indicating that the reduction step had a greater impact on activity than the calcination step, since the Ni metal sites are the core of CO activation. Comparative Example 9: At a light power density of 0.5 W / cm², the surface temperature was only 42°C, far below the activation energy requirement for the water-gas shift reaction (>60°C), demonstrating the necessity of ≥1.0 W / cm² in the claims. Test 3: Ni / CeO2₋ x (450) Cyclic stability test of the catalyst: The cyclic stability test of the catalyst was performed in accordance with the national standard GB / T 23761-2009 "Test Method for Performance of Photocatalytic Air Purification Materials". A light-dark alternating cycle mode was adopted, with each cycle consisting of 30 minutes of light and 30 minutes of darkness, for a total of 24 cycles (total duration 24 hours). After each cycle, the CO conversion rate and H2 yield were determined using an online gas chromatograph (compliant with GB / T 8984-2008). The catalyst surface temperature was monitored in real time using an infrared thermal imager (compliant with ASTM E1862). The activity decay rate was calculated using the formula [(initial activity - final activity) / initial activity] × 100%. An activity retention rate ≥ 95% was considered cyclically stable.

[0036] Take 50mg Ni / CeO2₋ x (450) The catalyst was packed into a fixed-bed quartz reactor and the feed gas was introduced according to the reaction conditions of Example 1. A 300W xenon lamp (light power 1.66 W / cm²) was used for cyclic testing: after 30 min of illumination, the illumination was stopped and kept in darkness for 30 min, which was one cycle, and a total of 24 h (24 cycles) were carried out. After each cycle, the CO conversion rate and H2 yield were measured by online gas chromatograph, and the changes in catalyst activity were recorded.

[0037] Table 3

[0038] As shown in Table 3, the catalyst activity did not decrease significantly after a 24-hour cycle test. Its CO conversion rate and H2 yield remained almost at the initial level within 24 hours, and even after 24 hours, the activity was still maintained at more than 95% of the initial value, indicating that it has excellent cycle stability.

[0039] Comparative Example 1 was tested using the same testing standards, and the results are shown in Table 4.

[0040] Table 4

[0041] As shown in Table 4, the catalyst activity in Comparative Example 1 decreased significantly after 24 hours of cycling, with its CO conversion and H2 yield decreasing by approximately 50% within 24 hours. Comparing Tables 3 and 4, it can be seen that the Ni / CeO obtained in this invention… 2-x (450) The catalyst has good catalytic performance.

[0042] Furthermore, this invention also investigates the transport mechanism of photogenerated carriers in the catalyst under illumination conditions, as detailed below: Femtosecond transient absorption spectrum (fs-TAS) was obtained under 350nm laser excitation. Figure 7 a and b show CeO 2-x and Ni / CeO 2-x (450) Differential absorption spectra with different delays. In the wavelength range of 450~750 nm, CeO2 and CeO 2-x and Ni / CeO 2-x Positive transient excited-state absorption peaks were observed in all samples. Kinetic analysis at the 650 nm absorption peak indicates that CeO₂... 2-x The excitons of Ni / CeO almost completely decay to the ground state (98%) within 1 ns, while only about 78% of the excited-state electrons decay to the ground state after Ni loading, and the absorption peak intensity increases, indicating that the excited-state electrons are transferred through different pathways. Particularly noteworthy is the Ni / CeO... 2-x (450) exhibits enhanced light absorption response across multiple wavelength bands, which is directly related to the improvement in its catalytic performance. The dynamic decay curves, fitted with a double exponential function, reveal two distinct decay processes: the rapid decay component τ1 (0.2–0.4 ps) corresponds to the rapid cooling of hot electrons through electron-phonon interactions, accompanied by electronic relaxation and the conversion of kinetic energy into thermal energy; the slow decay component τ2 (17.2–56.8 ps) reflects the lifetime of charge carriers at the interface or surface. Specific parameters indicate that CeO2… 2-x The carrier lifetimes were τ1 (0.4 ps) and τ2 (56.8 ps), respectively. The carrier lifetime at the interface was dominant, indicating that OV acts as an electron trap, directly capturing photogenerated electrons or holes and reducing the recombination probability. For Ni / CeO... 2-x (450), τ2 decreased to 17.2 ps, which is due to Ni / CeO 2-x An ultrafast electron transfer channel is formed at the interface.

[0043] Temperature-programmed desorption (TPD) was used to monitor the CO desorption behavior as a function of temperature. A CO desorption peak appeared in CeO2 at around 300°C, indicating the presence of a single Lewis acidic chemisorption site on its surface. With the increase of oxygen vacancies (O... V The introduction of CeO forms CeO 2-x A double desorption peak appears at 60°C and 390°C. This is especially true for Ni / CeO. 2-x The catalyst's chemisorption peak shifted to a higher temperature of 395℃. This indicates that oxygen vacancies created low-temperature adsorption sites, while Ni sites further enhanced the chemisorption capacity for CO.

[0044] Quasi-in-situ electron paramagnetic resonance (EPR) further revealed the influence of photogenerated carriers on active materials. Figure 7 The EPR symmetric peak at g0=2.003 in f under dark conditions can be attributed to the O of CeO2. V After H2O is introduced under light irradiation, Ce 3+ The appearance of a symmetrical peak at g2=1.966 indicates that photogenerated electrons will charge Ce. 4+ Restored to Ce 3+ Anisotropic peaks g1 (gI=2.023, gI=2.014, g...) =2.003) originates from O2 capturing photogenerated holes and Ce 4+ The O-⁻ free radical is formed through coordination. After the introduction of CO, the g1 and g2 peaks slightly decrease, indicating the formation of Ce⁻. 3+ It is promptly consumed and regenerated, followed by rapid consumption of surface O-. Furthermore, CeO... 2-x Compared to Ni / CeO 2-x (450) shows a low g1 peak, indicating a reduction in oxygen free radicals, suggesting that Ni is a key site promoting water splitting. In-situ drift characterization revealed the role of WGSR in CeO₂. 2-x and Ni / CeO 2-x The dynamic pathway in (450), such as Figure 7 As shown in b. CeO 2-x The presence of a low-intensity ·OH peak indicates that H2O has a weak ability to transform into free radicals on its surface, especially at 1053 cm⁻¹. -1 and 1317cm -1 The emergence of new peaks at these points corresponds to the ·CHO and HCOO species, respectively, indicating that CO binds to the hydroxyl hydrogen on the support surface via oxygen-bridged hydrogen transfer, ultimately forming the CHO intermediate, which further connects with OL on the surface to generate HCOO. The stability of HCOO makes it difficult for it to further convert into CO2, thus producing low-intensity CO2. δ- And CO2 peak. Ni / CeO 2-x (450) at 3644~3744cm -1The enhanced peaks at [location] confirm the dissociation of H2O into OH, while the CO peaks (2175, 2118 cm⁻¹) [are also present]. -1 The continuous decline of CO2 peaks (2361, 2334 cm⁻¹) was accompanied by the continuous decrease of CO2 peaks (2361, 2334 cm⁻¹). -1 The simultaneous growth of [the sample] demonstrates the efficient progress of the reaction. (1519~1558 cm) -1 The peak value at 1615-1650 cm⁻¹ represents the COOH intermediate, and its intensity gradually increases, indicating the reaction between CO and OH. -1 CO2 at the location δ- As time increases, it indicates that COOH is gradually dehydrogenated and converted, and the entire reaction follows the Langmuir-Hinshelwood (LH) mechanism.

[0045] In-situ X-ray photoelectron spectroscopy (XPS) further traced the valence state cycling of Ni and Ce species, directly linking the evolution of intermediates with changes in the electronic structure of active sites, thus verifying the reaction mechanism of photodriven WGSR. Ni / CeO 2-x (450) The catalyst was irradiated with light after adsorbing reactants under dark conditions for 15 min, and the surface concentration of the species was quantified by peak area integration. Under dark conditions with flowing CO and H2O, Ni... δ+ (Ni δ+ +Ni 0 +Ni 2+ Ce 3+ / (Ce 3+ +Ce 4+ The ratios of adsorbed oxygen (OS) were 11% and 23%, respectively. Simultaneously, an adsorbed oxygen (OS) peak appeared at 529.03 eV, indicating that O... V Provides coordination unsaturated sites for reactants ( Figure 7 e). After the introduction of light, Ni δ+ Increased to 33%, Ce 3+ The concentration of Ni increased to 32%, while the OS content decreased to 39%, returning to its initial value after the lamp was turned off. This phenomenon confirms that photoexcitation induced Ni... 0 The LSPR effect causes it to lose electrons and transform into Niδ + The substrate gains electrons to promote Ce 3+ -O V Regeneration.

[0046] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A Ni / CeO₂₋ for water-gas shift reaction x A method for preparing a catalyst, characterized in that: The method includes the following steps: S1. Hydrothermal synthesis: Nickel source, cerium source, ammonium fluoride and urea are dissolved in water, hydrochloric acid is added to adjust the system, and after stirring, the resulting mixed solution is subjected to hydrothermal reaction at 90~100℃ for 20~28h. After the reaction is completed, solid-liquid separation, washing and drying are performed to obtain NiCe layered double hydroxide precursor. S2. Calcination: The NiCe layered double hydroxide precursor obtained in S1 is heated to 480~520℃ in air atmosphere at a heating rate of 1~3℃ / min and held for 3~5h to obtain a mixed metal oxide composed of NiO and CeO2. S3. Reduction: The mixed metal oxide composed of NiO and CeO2 obtained in S2 is placed in a mixed atmosphere of hydrogen and argon, heated to the reduction temperature at a heating rate of 1~3℃ / min, and subjected to reduction treatment at the reduction temperature for 3~5h to obtain Ni / CeO2₋. x catalyst.

2. The Ni / CeO₂₋ for water-gas shift reaction according to claim 1 x A method for preparing a catalyst, characterized in that: In S1, the nickel source is Ni(NO3)2·6H2O, and the cerium source is Ce(NO3)3·6H2O; And / or, the molar ratio of the nickel source, cerium source, ammonium fluoride, urea and water is 1:(0.5-2):(3-5):(8-12):(800-1500).

3. The Ni / CeO₂₋ for water-gas shift reaction according to claim 1 x A method for preparing a catalyst, characterized in that: In the hydrogen and argon mixed atmosphere in S3, the volume fraction of hydrogen is 10-15% and the volume fraction of argon is 85-90%. And / or, the flow rate of the mixed gas is (30-120) mL / min.

4. The Ni / CeO₂₋ for water-gas shift reaction according to claim 1 x A method for preparing a catalyst, characterized in that: The reduction temperature in S3 is selected from 250℃, 350℃, 450℃, 550℃ or 650℃.

5. A Ni / CeO₂₋ for water-gas shift reaction x The catalyst is characterized by: The catalyst is prepared by the method described in any one of claims 1 to 4, with the reduction temperature in step S3 set to 450°C. And / or, the catalyst is characterized by the following structural features: The concentration of Ce³⁺ ions on the catalyst surface accounted for 13.71% of the total concentration of cerium ions. The oxygen vacancy concentration on the catalyst surface is 52%; The coordination number of the first coordination shell Ni-Ni metallic bond in the catalyst is 6.72; The K-edge absorption position of Ni in the catalyst shifts to a lower energy end relative to the absorption edge position of the nickel foil, indicating that the Ni species is in the electron-rich Niδ state. + .

6. The Ni / CeO2₋ for water-gas shift reaction according to claim 5 x The catalyst is characterized by: When the catalyst is irradiated with a xenon lamp at a light power of 1~2.5W / cm², the catalyst surface temperature is stabilized at 77℃. When used to catalyze the water-gas shift reaction for 30 minutes, the CO conversion rate is 92.05% and the H2 yield is 103.24μmol / gcat / s.

7. A Ni / CeO2₋ as described in claim 5 or 6 x The application of catalysts in photoinduced water-gas shift reaction is characterized by: The catalyst is placed in the reaction system, and the surface temperature of the catalyst is maintained between 70 and 90°C under light irradiation. The reaction of carbon monoxide and water is driven by light energy to produce hydrogen and carbon dioxide.

Images