CN114524489A - Co with 2D/3D hybrid structure2P-CeOxPreparation method and application of integrated electrode - Google Patents

Abstract

The invention relates to Co with a 2D/3D hybrid structure₂P‑CeO_xA preparation method and application of an integrated electrode belong to the technical field of catalysis. The preparation method comprises the following steps: soaking foam Nickel (NF) in Co (NO) solution₃)₂6H₂O、Ce(NO₃)₃6H₂Performing multi-potential deposition reaction in a mixed solution of O and NaCl, repeatedly washing with deionized water after reaction, and dryingDrying to obtain Co (OH)₂‑CeO_xa/NF electrode; mixing Co (OH)₂‑CeO_x/NF electrode in NaH₂PO₂Phosphorization under existence to obtain a target product Co₂P‑CeO_xa/NF electrode. The method has the characteristics of simplicity, convenience, high efficiency, low cost and low decomposition voltage required by electrocatalysis, and can be applied to the fields of electrocatalysis hydrogen production, urea degradation, small molecule catalytic oxidation and the like.

Description

Co with 2D/3D hybrid structure2P-CeOxPreparation method and application of integrated electrode

Technical Field

The invention relates to Co with a 2D/3D hybrid structure₂P-CeO_xA preparation method and application of an integrated electrode belong to the technical field of catalysis.

Background

Along with the social development and the improvement of the industrialization degree, the accompanying environmental pollution and the energy crisis are increasingly intensified, and researchers are promoted to explore and develop a high-efficiency sustainable green energy system. As a green and sustainable 'carbon-free' energy source, the hydrogen energy source has the characteristics of high energy, no pollution, good combustion performance and the like. The hydrogen production by electrocatalysis water splitting has the advantages of high product purity, zero emission and the like, and is considered to be an attractive hydrogen production technology. The urea is an ideal hydrogen storage material with application prospect due to low price, stability, relative innocuity, easy storage and transportation and higher energy density (16.9MJ/L) than liquid hydrogen. Electrocatalytic Urea Oxidation (UOR) is also recognized as an effective way to produce hydrogen from urea-rich wastewater. Compared with anodic oxidation reaction (OER, 1.23V vs standard hydrogen electrode potential (RHE)) for water decomposition, the theoretical potential (0.37V vs RHE) required by the UOR is lower, and the potential is greater to replace the OER to realize high-efficiency hydrogen production. However, UOR is essentially a slow kinetic process involving six electron transfer, requiring a suitable electrocatalyst to accelerate the slow reaction process of UOR, lowering the reaction energy barrier and thus achieving efficient urea electrolysis. To date, precious metal materials (such as platinum, rhodium, etc.) have outstanding electrocatalytic activity on UOR, but their rarity, high price, etc. limit their development in practical large-scale applications. Therefore, the research and development of the non-noble metal-based electrocatalyst with high efficiency, energy conservation and environmental protection, particularly the application of the bifunctional electrocatalyst in Hydrogen Evolution Reaction (HER) and UOR, has more important practical significance.

The transition metal phosphide is used as a novel bifunctional electrocatalyst, has the advantages of high conductivity of metalloid, low preparation cost, controllable central metal valence state and the like, and is widely applied in the fields of electrocatalysis of HER, UOR and the like. The cobalt phosphide has good corrosion resistance and good electrocatalytic activity in both acidic and alkaline systems. But business of businessThe industrialized cobalt phosphide is limited in wide application in the field of electrocatalysis due to the characteristics of high overpotential, low oxidation efficiency and the like. Recent researches show that the electronic structure of the transition metal phosphide can be effectively adjusted by introducing other metal elements or constructing a unique heterostructure, so that the conductivity of the transition metal phosphide is improved, and the intrinsic catalytic activity of the catalyst is further improved. Since CeO_xHaving two stable and reversible oxidation states (Ce)⁴⁺/Ce³⁺) The reversible surface oxygen ion exchange capacity, good electron/ion conduction efficiency and excellent oxygen storage/release capacity, and oxygen vacancies are easily generated on a heterogeneous interface to improve the ionic conductivity, so the method has wide application prospect in the energy-related field. In view of cobalt phosphide and CeO_xExcellent physical and chemical properties by constructing cobalt phosphide and CeO_xThe heterostructure not only can form an optimized electronic structure on the surface of the catalyst by utilizing metal-phosphorus and metal-oxygen bonds, but also can adjust the proportion of metals with different valence states in the catalytic material to generate more vacancies or defects so as to promote the catalytic reaction.

Disclosure of Invention

One of the purposes of the invention is to provide Co with a 2D/3D hybrid structure₂P-CeO_xA preparation method of an integrated electrode.

Another object of the present invention is to provide a Co utilizing 2D/3D hybrid structure₂P-CeO_xAn application method for electrocatalytic hydrogen production by an integrated electrode and urea degradation.

In order to achieve the purpose, the invention adopts the technical scheme that:

co with 2D/3D hybrid structure₂P-CeO_xThe preparation method of the integrated electrode comprises the following steps: soaking foam Nickel (NF) in Co (NO) solution₃)₂ 6H₂O、Ce(NO₃)₃ 6H₂Performing multi-potential deposition reaction in a mixed solution of O and NaCl, repeatedly washing with deionized water after the reaction, and drying to obtain Co (OH)₂-CeO_xa/NF electrode; mixing Co (OH)₂-CeO_x/NF electrode in NaH₂PO₂Phosphating the mixture in the presence of oxygen to obtain a target product Co₂P-CeO_xa/NF electrode.

Further, in the above preparation method, the mixed solution contains 0.9mol/L Co (NO)₃)₂ 6H₂O、0.09mol/L Ce(NO₃)₃ 6H₂A mixed solution of O and 0.1mol/L NaCl in a volume of 70 mL.

Further, in the preparation method, the multi-potential deposition reaction takes a platinum wire as a counter electrode, an Ag/AgCl electrode as a reference electrode and NF as a working electrode.

Furthermore, in the above preparation method, the multi-potential deposition reaction is performed by depositing the Ag/AgCl material at-1.2V vs. 400s, then depositing the Ag/AgCl material at 0.5V vs. 50s, and the electrodeposition area is 10X 10mm²。

Further, in the preparation method, the drying condition is drying at 60 ℃ for 12 hours.

Further, in the preparation method, the phosphorization is to prepare Co (OH)₂-CeO_xthe/NF electrode was placed in an alumina porcelain boat and placed in the middle of a tube furnace while the other was charged with 0.6g NaH₂PO₂The porcelain boat is placed in a pot containing Co (OH)₂-CeO_xThe porcelain boat of the/NF electrode keeps a distance of 10cm and is positioned at the upstream position of the gas path at N₂The temperature was raised to 350 ℃ under the atmosphere and maintained for 2 hours.

Furthermore, in the preparation method, the temperature rise rate is 2 ℃/min.

The Co with 2D/3D hybrid structure prepared by the preparation method provided by the invention₂P-CeO_xThe integrated electrode is applied to electrocatalytic hydrogen production and urea degradation.

Further, the application and the method are as follows: co of 2D/3D hybrid structure₂P-CeO_xAn integrated electrode as a working electrode, a platinum wire as a counter electrode and Hg/HgO as a reference electrode are placed in a quartz reaction container to form a three-electrode system, and N is introduced into a KOH solution containing urea₂And (3) the reaction is carried out for 20min until the reaction is saturated, and the rotating speed of 1600rpm is always kept in the process.

Further, in the above application, the KOH solution containing urea is a KOH solution containing 0.33mol/L urea and 1mol/L with pH of 13.7.

The invention has the beneficial effects that:

1. the Co2P-CeOx integrated electrode with a 2D/3D hybrid structure is constructed in a multi-potential deposition and low-temperature phosphorization mode, so that the conductivity is further improved, more active sites are exposed, the mass/charge transmission is promoted, the electronic structure is optimized, and the electrocatalytic activity and stability are improved.

2. By adopting the method of the invention, the urea is degraded while the electrocatalytic hydrogen production is carried out by adopting a two-electrode system in the alkaline medium containing the urea, and the potential of only 1.42V can reach 30mA/cm²The current density is reduced by 0.17V compared with the potential required by full water decomposition, the degradation efficiency of the electro-catalysis urea after 10 hours reaches 76.4 percent, and a new thought is provided for designing a novel multi-level hybrid structure integrated electrode.

3. The method has the characteristics of simplicity, convenience, high efficiency, low cost and low decomposition voltage required by electrocatalysis, and can be applied to the fields of electrocatalysis hydrogen production, urea degradation, small molecule catalytic oxidation and the like.

Drawings

FIG. 1 is Co₂P-CeO_xScanning Electron Micrograph (SEM) of/NF electrode.

FIG. 2 is Co₂P-CeO_x/NF、Co₂P/NF and CeO_xX-ray diffraction (XRD) spectrum of/NF electrode.

FIG. 3 is a graph showing the performance of electrocatalytic hydrogen evolution of different catalytic electrodes, wherein (a) is a polarization curve and (b) is a Tafel curve.

FIG. 4 is a graph of the performance of different catalytic electrodes for electrocatalytic urea oxidation, where (a) is the polarization curve and (b) is the Tafel curve.

FIG. 5 shows Co under a two-electrode system₂P-CeO_xA polarization curve diagram of the NF electrocatalytic hydrogen production and urea degradation.

FIG. 6 is a graph of urea degradation efficiency for a two-electrode system.

Detailed Description

Example 1

1) Foamed nickel (N)F，10×20×1mm³) The pretreatment of (1): sequentially performing ultrasonic treatment in 3mol/L HCl, ethanol and water for 15min to clean the surface, and drying for later use;

2) soaking NF in 70mL of 0.9mol/L Co (NO)₃)₂ 6H₂O、0.09mol/L Ce(NO₃)₃ 6H₂In the mixed solution of O and 0.1mol/L NaCl, a platinum wire is taken as a counter electrode, an Ag/AgCl electrode is taken as a reference electrode, NF is taken as a working electrode, a multi-potential step method is adopted to deposit for 400s by-1.2V vs. Ag/AgCl, then 0.5V vs. Ag/AgCl is adopted to deposit for 50s, and the electrodeposition area is 10 multiplied by 10mm²Repeatedly washing with deionized water, drying at 60 deg.C for 12h to obtain Co (OH)₂-CeO_xa/NF electrode;

3) mixing the prepared Co (OH)₂-CeO_xthe/NF electrode was placed in an alumina porcelain boat and placed in the middle of a tube furnace while the other was charged with 0.6g NaH₂PO₂The porcelain boat is placed in a pot containing Co (OH)₂-CeO_xThe porcelain boat of the/NF electrode keeps a distance of 10cm and is positioned at the upstream position of the gas path at N₂Heating to 350 ℃ at the heating rate of 2 ℃/min in the atmosphere, and keeping for 2h to obtain the target product Co₂P-CeO_xa/NF electrode.

4) For comparison, Co (OH)₂/NF electrode and CeO_xthe/NF electrode was placed in an alumina porcelain boat and placed in the middle of a tube furnace while the other was charged with 0.6g NaH₂PO₂Is placed at a distance of 10cm from the porcelain boat and is located at the upstream position of the gas path at N₂Raising the temperature to 350 ℃ at the temperature rise rate of 2 ℃/min in the atmosphere, and keeping the temperature for 2 hours to respectively obtain Co₂P/NF electrode and CeO_xa/NF electrode.

As can be seen from FIG. 1, the composite Co₂P-CeO_xIs a hybrid structure of a 2D nano sheet and a 3D nano flower. The XRD spectrum of figure 2 confirms that the composite material is Co₂P and CeO_xThe complex of (1).

Example 2

In a standard three-electrode system, a platinum wire is taken as a counter electrode, Hg/HgO is taken as a reference electrode, and the synthesized composite electrode is taken as a working electrodeIn a 1mol/L KOH solution (pH 13.7), according to E_RHE＝E_Hg/HgO+0.098+0.059pH converts the potential vs. hg/HgO to a potential vs. standard hydrogen electrode (RHE). Before each test, N is₂The solution was pumped in for at least 20min until saturation and the rotation speed of 1600rpm was maintained throughout the test to facilitate surface bubble release. The overpotential (η) is based on η ═ E_RHE-0. The test for Linear Sweep Voltammograms (LSV) (97% iR correction) was performed at a sweep rate of 5mV/s over a potential interval of 0 to-0.4V vs. RHE. Tafel slopes are obtained from η ═ a + blogJ, where η is the overpotential, b is the tafel slope, and J is the current density. The results are shown in FIG. 3.

As shown in FIG. 3 (a), Co₂P-CeO_xthe/NF electrode shows higher electrocatalytic HER performance and the current density is 10mA/cm²Only needs lower over potential 84mV which is lower than that of other electrode materials Co₂P/NF(106mV)、CeO_xNF (203mV) and NF (268 mV). The slope of the Tafel plot is shown in FIG. 3 (b), Co₂P-CeO_x/NF、Co₂P/NF、CeO_xTafel slopes of/NF and NF were 53.2, 55.5, 127.2 and 151.8mV/dec, Co₂P-CeO_xThe Tafel slope of/NF is minimum, which shows that the electrode has faster electron transfer efficiency and is more beneficial to electrocatalysis of HER.

Example 3

In a standard three-electrode system, a platinum wire is used as a counter electrode, Hg/HgO is used as a reference electrode, and the synthesized composite electrode is used as a working electrode. In a 1mol/L KOH solution (pH 13.7) containing 0.33mol/L urea, according to E_RHE＝E_Hg/HgO+0.098+0.059pH converts the potential vs. hg/HgO to a potential vs. standard hydrogen electrode (RHE). Before each test, N is₂The solution was pumped in for at least 20min until saturation and the rotation speed of 1600rpm was maintained throughout the test to facilitate surface bubble release. And carrying out LSV test at a scanning speed of 5mV/s within a potential interval of 1.2-1.6V vs. Tafel slopes are obtained from E ═ a + blogJ, where E is the potential, b is the tafel slope, and J is the current density. The results are shown in FIG. 4.

As shown in FIG. 4 (a), Co₂P-CeO_xthe/NF shows the highest electrocatalytic activity, and the current density reaches 30mA/cm²The time overpotential only needs 1.37V, and Co₂P/NF(1.38V)、CeO_xThe potentials required by/NF (1.40V) and NF (1.48V) are both larger than that of Co₂P-CeO_xof/NF and with increasing current density, Co₂P-CeO_xThe performance of the/NF catalytic UOR is obviously superior to that of other materials. FIG. 4 (b) shows Tafel curves for different catalysts, Co₂P-CeO_xTaffel slopes of/NF (106mV/dec) are all lower than Co₂P/NF(138mV/dec)、CeO_xNF (162mV/dec) and NF (158mV/dec) indicate that they have more favorable UOR catalytic kinetics.

Example 4

A standard two-electrode system is adopted, and Co is used in an electrolytic cell containing 0.33mol/L urea and 1mol/L KOH solution respectively₂P-CeO_xThe results of the full hydrolysis test conducted with/NF as both cathode and anode are shown in FIG. 5.

The current density reaches 30mA/cm²The hydrogen production process only needs 1.42V potential for driving, and the full water decomposition (HER II OER) needs 1.59V for reaching the current intensity and is 0.17V higher than the HER II UOR, so that the high-efficiency energy-saving hydrogen production is realized. Cathode (H) in the electrolytic process₂) And an anode (O)₂) A large amount of bubbles are generated.

The two-electrode system is adopted to maintain the current density at 70mA/cm²Continuously electro-catalyzing urea oxidation, and monitoring the degradation content of urea in real time by adopting a dimethylaminobenzaldehyde-assisted ultraviolet-visible spectrum detection method. As shown in FIG. 6, after 10h of continuous electrolysis, the degradation efficiency of urea reaches 76.4%, and finally, the urea is degraded while the hydrogen is produced by electrocatalysis.

Claims (10)

1. Co with 2D/3D hybrid structure₂P-CeO_xThe preparation method of the integrated electrode is characterized by comprising the following steps of: soaking foam Nickel (NF) in Co (NO) solution₃)₂ 6H₂O、Ce(NO₃)₃ 6H₂Performing multi-potential deposition reaction in a mixed solution of O and NaCl, and repeatedly washing with deionized water after reactionDrying to obtain Co (OH)₂-CeO_xa/NF electrode; mixing Co (OH)₂-CeO_x/NF electrode in NaH₂PO₂Phosphorization under existence to obtain a target product Co₂P-CeO_xa/NF electrode.

2. The method according to claim 1, wherein the mixed solution contains 0.9mol/LCo (NO)₃)₂ 6H₂O、0.09mol/L Ce(NO₃)₃ 6H₂A mixed solution of O and 0.1mol/L NaCl in a volume of 70 mL.

3. The method according to claim 1, wherein the multi-potential deposition reaction is carried out by using a platinum wire as a counter electrode, an Ag/AgCl electrode as a reference electrode, and NF as a working electrode.

4. The method of claim 3, wherein the multi-potential deposition reaction is performed by depositing the alloy at-1.2V vs. Ag/AgCl for 400s and then at 0.5V vs. Ag/AgCl for 50s, and the electrodeposition area is 10 x 10mm²。

5. The method according to claim 1, wherein the drying condition is drying at 60 ℃ for 12 hours.

6. The method of claim 1, wherein said phosphating is performed using prepared Co (OH)₂-CeO_xthe/NF electrode was placed in an alumina porcelain boat and placed in the middle of a tube furnace while the other was charged with 0.6g of NaH₂PO₂The porcelain boat is placed in a pot containing Co (OH)₂-CeO_xThe porcelain boat of the/NF electrode keeps a distance of 10cm and is positioned at the upstream position of the gas path at N₂Raising the temperature to 350 ℃ under the atmosphere, and keeping the temperature for 2 h.

7. The method according to claim 6, wherein the temperature is raised at a rate of 2 ℃/min.

8. Co of 2D/3D hybrid structure prepared by the preparation method of claim 1₂P-CeO_xThe integrated electrode is applied to electrocatalytic hydrogen production and urea degradation.

9. Use according to claim 8, characterized in that the method is as follows: co of 2D/3D hybrid structure₂P-CeO_xAn integrated electrode as a working electrode, a platinum wire as a counter electrode and Hg/HgO as a reference electrode are placed in a quartz reaction container to form a three-electrode system, and N is introduced into a KOH solution containing urea₂And the rotating speed of 1600rpm is always kept in the process until the saturation.

10. The use according to claim 9, wherein the KOH solution containing urea is a 1mol/L KOH solution containing 0.33mol/L urea and having a pH of 13.7.

Images