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CN-121988364-A - For CO2Photo-reduced cobalt monoatomic/carbon nitride catalyst and preparation and application thereof

CN121988364ACN 121988364 ACN121988364 ACN 121988364ACN-121988364-A

Abstract

The invention discloses a cobalt single-atom/carbon nitride catalyst for high-efficiency photocatalytic CO 2 reduction, and a preparation method and application thereof, wherein a strong electron coupling effect is formed between a single-atom cobalt center and a modified carbon nitride carrier in the catalyst, so that the separation efficiency of photo-generated electron-hole pairs is remarkably improved, the interfacial charge transfer is accelerated, and the chemisorption and activation capability of CO 2 molecules are enhanced. Under the irradiation of simulated sunlight, the catalyst shows excellent CO 2 photo-reduction performance, the CO generation rate can reach 327.8 mu mol g ‑1 ·h ‑1 , and the catalyst has good circulation stability. The invention effectively solves the problems of low utilization rate of active sites and serious charge recombination of the traditional catalyst through the synergistic effect of carrier surface engineering and monoatomic site construction under the condition of no noble metal. The catalyst prepared by the preparation method provided by the invention has a wide application prospect in the resource utilization of CO 2 driven by solar energy.

Inventors

  • WANG WEI
  • CHENG WENXUAN

Assignees

  • 宁夏大学

Dates

Publication Date
20260508
Application Date
20260115

Claims (9)

  1. 1. A method for preparing a cobalt monoatomic/carbon nitride catalyst for CO 2 photo-reduction, comprising the steps of: (1) Preparing graphite phase Carbon Nitride (CN) carrier, namely heating urea to 400-700 ℃ in a crucible at a heating rate of 1-10 ℃ per minute, and preserving heat at the temperature of 0.5-5 h to obtain a CN material; (2) Preparing an oxygen doped carbon nitride (OCN) carrier, namely dispersing the CN material obtained in the step (1) in deionized water, adding concentrated nitric acid with the mass concentration of 20% -80% (the preferred range is 25% -75%, more preferred 30% -70%), stirring at 10-200 ℃ for 1-10 h, cooling, standing at low temperature, centrifugally washing and vacuum freeze-drying after the treatment is finished to obtain the OCN material; (3) Dispersing the OCN material obtained in the step (2) in an aqueous solution containing polyethylene glycol, stirring under the protection of inert atmosphere, then adding cobalt chloride, citric acid and 2-mercaptopyridine, and continuing stirring under the inert atmosphere for reaction for 10-50 h; (4) And (3) heat treatment, namely heating the precursor obtained in the step (3) to 100-500 ℃ at a heating rate of 1-10 ℃ per minute under the protection of inert atmosphere, preserving heat at the temperature of 1-6 h, and cooling to obtain the cobalt monoatom/carbon nitride catalyst.
  2. 2. The method according to claim 1, wherein in step (1), the temperature increase rate is 1 to 10 ℃ per minute (preferably in the range of 2 to 8 ℃ per minute, more preferably 4 to 6 ℃ per minute), the holding temperature is 400 to 700 ℃ per minute (preferably in the range of 450 to 650 ℃ and more preferably 500 to 600 ℃) and the holding time is 0.5 to 5 h (preferably in the range of 1 to 4 h, more preferably 1.5 to 3 h).
  3. 3. The method according to claim 1, wherein in the step (2), the amount of the CN material is 0.1-5 g (preferably in the range of 0.2-4 g, more preferably 0.5-3 g), the amount of the concentrated nitric acid is 1-20 ml (preferably in the range of 2-15 ml, more preferably 4-10 ml), the temperature of the stirring treatment is 10-200 ℃ (preferably in the range of 20-150 ℃, more preferably 40-100 ℃), the time of the stirring treatment is 1-10 h (preferably in the range of 1-8 h, more preferably 2-5 h), the temperature of the low-temperature standing is 0-5 ℃, the standing time is 1-5 h, and then vacuum freeze-drying is performed to obtain the Co/OCN material.
  4. 4. The method according to claim 1, wherein in step (3), the OCN material is used in an amount of 0.01-1 g (preferred range: 0.02-0.6 g, more preferred 0.05-0.3 g); the dosage of the aqueous solution of polyethylene glycol is 1-20 to ml (the preferred range is 2-15 to ml, more preferred 4-10 to 3836), the mass concentration of the aqueous solution of polyethylene glycol is 1-15% (the preferred range is 1-10%, more preferred 3-7%), the dosage of cobalt chloride hexahydrate is 0.1-1 mmol (the preferred range is 0.2-0.8mmol, more preferred 0.3-0.6 to mmol), the dosage of citric acid monohydrate is 0.1-1 mmol (the preferred range is 0.15-0.8mmol, more preferred 0.2-0.6 to mmol) and the dosage of 2-mercaptopyridine is 0.1-2 mmol (the preferred range is 0.2-1.5mmol, more preferred 0.5-1 mmol), the stirring time before adding the cobalt source is 1-9 to h (the preferred range is 2-7 to h, more preferred 3-5 to h), the stirring reaction time after adding the cobalt source is 10-50 (the preferred range is 0.15-0.8mmol, more preferred range is 0.2-0.6 to mmol ℃, the preferred range is 0.2-20 to 6524 ℃ and the preferred range is 0.20-30 ℃ and the preferred range is 3-30 ℃ to 3637 ℃ and the stirring time is 0.1-2 mmol (the preferred range is 20-20 to 60 ℃ and the preferred range is 20-30 ℃ and the preferred range is 3-30 ℃ to be dried).
  5. 5. The method according to claim 1, wherein in step (4), the temperature increase rate is 1-10 ℃ min -1 (preferably range: 2-8 ℃ min -1 , more preferably 4-6 ℃ min -1 ), the holding temperature is 100-500 ℃ preferably range: 200-400 ℃, more preferably 250-350 ℃) and the holding time is 1-6 h (preferably range: 2-5 h, more preferably 3-5 h).
  6. 6. A cobalt monoatomic/carbon nitride catalyst, characterized in that it is obtainable by the process according to any one of claims 1 to 5.
  7. 7. The catalyst of claim 6, wherein the catalyst comprises a carbon nitride support and cobalt monoatoms stably anchored to the support in an atomically dispersed form, wherein Co-N and Co-O coordination structures are formed between the cobalt monoatoms and the support atoms; The carbon nitride carrier is oxygen doped carbon nitride (OCN) modified by acid treatment.
  8. 8. Use of a cobalt monoatomic/carbon nitride catalyst according to claim 6 or 7 for the photocatalytic reduction of carbon dioxide.
  9. 9. The use according to claim 8, characterized in that the catalytic reduction of CO 2 to CO is carried out under 300W xenon lamp full spectrum irradiation, in particular after adding 1-7 mL water, 1-3mg tris (2, 2' -bipyridine) ruthenium (II) dichloride hexahydrate and 4-6mL triethanolamine to a glass reactor.

Description

Cobalt monoatomic/carbon nitride catalyst for CO 2 photo-reduction and preparation and application thereof Technical Field The invention belongs to the technical field of photocatalytic materials, and particularly relates to a cobalt monoatomic/carbon nitride catalyst for high-efficiency photocatalytic reduction of carbon dioxide (CO 2), a preparation method thereof and application thereof in solar-driven CO 2 resource conversion. Background With the rapid development of industrialization, the concentration of CO 2 in the atmosphere is continuously increased due to the massive consumption of fossil energy, and global climate warming and ecological environment problems are caused. Under the background, the utilization of inexhaustible solar energy to convert CO 2 into high-added-value chemicals such as carbon monoxide (CO), methane (CH 4) or methanol (CH 3 OH) through a photocatalysis technology is regarded as a green sustainable way for achieving the aim of double carbon. However, a key challenge in achieving large-scale application of this technology is the development of non-noble metal photocatalysts that combine high activity and high stability. In recent years, single-atom catalysts have shown great potential in the heterogeneous catalysis field because of their maximum utilization of metal atoms and unique and uniform active centers. The anchoring of the monoatoms to a suitable support is critical for their successful use. The graphite phase carbon nitride (g-C 3N4, CN) is used as a nonmetallic polymer semiconductor, has a proper energy band structure, good chemical stability and rich nitrogen sites, and is one of ideal candidate carriers for loading single atoms. However, the catalyst also has inherent defects of narrow visible light absorption range, high photon-generated carrier recombination rate and the like, and further improvement of the catalytic performance is limited. To overcome the above-mentioned bottleneck, it is particularly important to modify CN. Research shows that the electron energy band structure of the carbon nitride can be effectively regulated by doping oxygen (forming OCN), the light response range of the carbon nitride is widened, and abundant surface defects are introduced as additional metal anchoring sites, so that the performance of the carbon nitride as a carrier is enhanced. In the selection of active metals, cobalt (Co) is used as non-noble metal, so that the cost is low, and the cobalt (Co) often shows high activity on CO products in the CO 2 reduction reaction and is an active center metal with great potential. However, in the conventional preparation method, co species are very easy to agglomerate on the surface of the g-C 3N4 carrier to form low-activity nano particles or clusters, so that the atom utilization efficiency and the catalytic performance are seriously reduced. Therefore, a synthetic strategy capable of realizing highly uniform and stable dispersion of Co atoms on the modified carbon nitride carrier is developed, and the synergistic catalytic effect between the Co monoatoms and the OCN carrier is fully exerted, so that the method has important scientific value and application prospect in constructing an efficient and stable CO 2 photo-reduction catalyst. At present, how to achieve this objective through a simple and controllable process is still a technical problem to be solved in the art. Disclosure of Invention The invention aims to provide a high-performance cobalt single atom/carbon nitride catalyst and a simple and efficient preparation method thereof, aiming at solving the problems of few active sites, fast carrier recombination, easy agglomeration of metals, insufficient CO 2 activation capability and the like in the CO 2 reduction reaction of the traditional photocatalyst. The catalyst remarkably improves the separation and transmission efficiency of photo-generated charges and enhances the adsorption and activation capacity of CO 2 molecules by constructing strong electron interaction between Co monoatoms and an oxygen doped carbon nitride (OCN) carrier. In order to achieve the above purpose, the invention adopts the following technical scheme: In a first aspect, the present invention provides a cobalt monoatomic/carbon nitride catalyst for CO 2 photoreduction. The catalyst takes OCN modified by acid treatment as a carrier, cobalt is stably anchored on the carrier in an atomically dispersed form, and a definite Co-N and Co-O double coordination structure is formed in the carrier. In a second aspect, the invention provides a preparation method of the cobalt monoatomic/carbon nitride catalyst, which comprises the following steps: (1) The preparation of the carrier precursor, namely, taking urea as a precursor, carrying out high-temperature pyrolysis to obtain a block CN, and grinding for later use. (2) And (3) modifying the carrier, namely dispersing the CN powder obtained in the step (1) into deionized water, and adding 65% -68% of concentrated