CN114649538B - A kind of methanol electrolysis hydrogen production electrocatalyst and preparation method thereof - Google Patents

Abstract

The invention discloses an electrocatalyst for hydrogen production by methanol electrolysis. The electrocatalyst is molybdenum telluride doped with nitrogen and phosphorus doped with carbon as a composite carrier and platinum-based nanoparticles as a load. The catalyst formed can be used for acidic methanol electrolysis reaction; the interaction between the metal and the carrier suppresses the agglomeration of platinum-based noble metal nanoparticles and improves the utilization rate of platinum-based noble metals; the oxophilic property of molybdenum telluride can weaken the adsorption energy of carbon monoxide-like intermediates in the anode methanol oxidation process and reduce the carbon monoxide poisoning ability in the methanol oxidation reaction; nitrogen and phosphorus doping effect The electronic structure of the platinum-based noble metal can be adjusted, the electron transport of the active site and the Gibbs free energy of hydrogen adsorption can be optimized, which is beneficial to improving the efficiency of the cathode hydrogen evolution reaction; the electrocatalyst obtained by the present invention has high electrocatalytic activity and stability, and has broad application prospects in the field of methanol electrolysis hydrogen production.

Description

A kind of methanol electrolysis hydrogen production electrocatalyst and preparation method thereof

technical field

The invention relates to an electrocatalyst for hydrogen production by electrolysis of methanol, and also relates to a preparation method of the electrocatalyst for hydrogen production by electrolysis of methanol.

Background technique

With the rapid increase of global environmental problems caused by the consumption of fossil energy, the search for sustainable green energy has become an urgent need. Hydrogen is attracting attention as a promising clean, renewable energy source. At present, hydrogen is mainly derived from steam reforming of fossil fuels (methane or coal) and electrocatalytic hydrocracking in industrial production. However, the oxygen evolution reaction kinetics of electrolyzed water on the anode is slow, compared with electrolyzed water, the oxidation potential of methanol is much lower than that of water, indicating that the use of methanol oxidation as an anode reaction can significantly reduce the power consumption. Currently, platinum-based catalysts are still the most widely used catalysts for methanol oxidation and hydrogen evolution reactions. However, due to the high price and limited resources of noble metals, the use of Pt-based catalysts to enhance the catalytic activity of methanol oxidation and hydrogen evolution reactions is currently not a long-term viable solution. In addition, the carbon monoxide-like carbonaceous intermediates generated during the methanol oxidation process have strong adsorption and inhibitory catalytic effects on methanol, which easily contaminate the active sites of Pt. In the prior art, forming alloys of platinum and transition metal elements is the most common method to improve the catalytic activity of methanol oxidation reaction and hydrogen evolution reaction. Enhancing the catalytic performance of platinum-based catalysts through electronic effects, strain effects, or synergistic effects. However, there are problems such as the easy dissolution of alloys in acidic electrolytes and the strong adsorption of carbon monoxide carbonaceous intermediates on the surface of noble metals, and the prepared catalysts have poor electrocatalytic performance.

Contents of the invention

Purpose of the invention: The present invention aims at the problem of low electrocatalytic performance of methanol electrolysis hydrogen production catalysts in the prior art, and provides a nitrogen phosphorus doped carbon molybdenum telluride supported platinum-based nanoparticle methanol electrolysis hydrogen production electrocatalyst; also provides the preparation method of the above electrocatalyst.

Technical solution: The electrocatalyst for hydrogen production by electrolysis of methanol in the present invention uses molybdenum telluride doped with nitrogen and phosphorus as a composite carrier, and the carrier is platinum-based nanoparticles.

Preferably, the loading amount of the platinum-based nanoparticles is 20-60% of the mass of the entire catalyst.

Preferably, the platinum-based nanoparticles include platinum alone or an alloy of platinum and a transition metal; wherein the transition metal includes palladium, ruthenium, rhodium, silver, gold, cobalt or nickel.

Preferably, the particle diameter of the platinum-based nanoparticles is 1-10 nm.

The preparation method of the electrocatalyst for hydrogen production by electrolysis of methanol comprises the following steps:

(1) Disperse molybdenum trioxide and imidazole in water, reflux, naturally cool to room temperature after reflux, filter, wash, and vacuum-dry to obtain Mo-MOF; uniformly mix the prepared Mo-MOF and tellurium powder, and heat-treat under hydrogen-argon mixed gas to obtain nitrogen-doped carbon molybdenum telluride;

(2) heat-treating nitrogen-doped carbon molybdenum telluride and sodium hypophosphite in step (1) under nitrogen to obtain nitrogen-phosphorus-doped carbon molybdenum telluride;

(3) Add nitrogen-phosphorus-doped carbon-doped molybdenum telluride and chloroplatinic acid aqueous solution into ethylene glycol in step (2), and after stirring evenly, use microwave-assisted ethylene glycol reduction method to reduce platinum ions to platinum simple substance. After the reaction is completed, filter, wash, and vacuum-dry to obtain an electrocatalyst of nitrogen-phosphorus-doped carbon molybdenum telluride-supported platinum-based nanoparticles.

Preferably, in step (1), the mass ratio of molybdenum trioxide to imidazole is 1-3:1, the reflux temperature is 100-130° C., and the reflux time is 10-20 hours.

Preferably, in step (1), the mass ratio of Mo-MOF to tellurium powder is 1:0.5-2, the heating rate is 2-10°C/min under the hydrogen-argon mixture, the heat treatment temperature is 800-1000°C, the heat treatment time is 1-3 hours, and the volume percentage of hydrogen in the hydrogen-argon mixture is 5-10%.

Preferably, in step (2), the mass ratio of nitrogen-doped carbon molybdenum telluride to sodium hypophosphite is 1:3-8, the heating rate is 2-10°C/min under nitrogen, the heat treatment temperature is 150-350°C, and the heat treatment time is 1-3 hours.

Preferably, in step (3), the microwave power is 500-800W, and the microwave time is 2-5 minutes.

The present invention synthesizes molybdenum telluride doped with nitrogen and phosphorus as a composite carrier, and supports platinum-based nanoparticles to obtain an electrocatalyst for hydrogen production by methanol electrolysis. On the one hand, there is electron transfer between the platinum-based nanoparticles and the molybdenum telluride carrier, which causes interaction between the platinum-based nanoparticles and the carrier (interaction force is enhanced), enhances the anchoring ability between the platinum-based nanoparticles and the carrier, and can inhibit the agglomeration of the platinum-based nanoparticles (improves the dispersion), thereby improving the utilization rate of precious metals. On the other hand, the oxophilic properties of molybdenum telluride can effectively adjust the position of the d-band center of platinum-based catalysts, weaken the adsorption energy of intermediates (CO), and promote the oxidation and removal of intermediates, thereby improving the anti-poisoning ability of the catalyst (anti-poisoning ability of carbon monoxide-like intermediates), and then effectively improving the stability of the catalyst. Simultaneous doping of nitrogen and phosphorus can adjust the electronic structure of platinum, thereby optimizing the electron transport of active sites and the Gibbs free energy of hydrogen adsorption, which in turn is beneficial to improve the efficiency of hydrogen evolution reaction at the cathode and improve the electrocatalytic activity of platinum-based catalysts.

Beneficial effects: the platinum-based nanoparticles in the electrocatalyst of the present invention are evenly loaded on the molybdenum telluride doped with nitrogen and phosphorus, which can not only improve the utilization rate of the noble metal platinum, but also improve the anti-poisoning ability of the platinum-based catalyst by carbon monoxide-like intermediates, thereby improving the stability of the platinum-based catalyst, and the incorporation of nitrogen and phosphorus will provide more active sites, thereby effectively improving the catalytic activity of the platinum-based catalyst.

Description of drawings

Fig. 1 is the XRD pattern of the molybdenum telluride of nitrogen phosphorus doped carbon prepared in embodiment 1;

Fig. 2 is the XRD spectrum of the molybdenum telluride supported platinum nanoparticle of the nitrogen phosphorus doped carbon prepared in embodiment 1;

Fig. 3 is the molybdenum telluride supported platinum nanoparticle catalyst of nitrogen phosphorus doping carbon in embodiment 1, the cyclic voltammetry curve (a) and chronoamperometry curve (b) of the molybdenum telluride supported platinum nanoparticle catalyst of nitrogen doped carbon and commercial Pt/C catalyst in 0.5mol/L sulfuric acid and 1mol/L methanol mixed solution;

Fig. 4 is the molybdenum telluride supported platinum nanoparticle catalyst of nitrogen phosphorus doping carbon in embodiment 1, the linear sweep voltammetry curve (a) and chronoamperometry curve (b) of the molybdenum telluride supported platinum nanoparticle catalyst of nitrogen doped carbon and commercial Pt/C catalyst in 0.5mol/L sulfuric acid and 1mol/L methanol mixed solution;

Fig. 5 is the linear sweep voltammetry curve (a) and the chronoamperometry curve (b) of the molybdenum telluride-supported platinum nanoparticle catalyst and the commercial Pt/C catalyst in the methanol electrolysis in Example 1.

Detailed ways

The technical solution of the present invention will be further described below in conjunction with the accompanying drawings.

Example 1

a. Preparation of molybdenum telluride doped with nitrogen and phosphorus

(1) Disperse 1.4g of molybdenum trioxide and 0.664g of imidazole in 150mL of water, and reflux at 110°C for 12 hours;

(2) Cool to room temperature, filter with suction, wash with deionized water at least 3 times, and dry under vacuum at 60°C overnight;

(3) The obtained Mo-MOF and tellurium powder were uniformly mixed at a mass ratio of 1:1, and heat-treated for 2 hours under a hydrogen-argon gas mixture, the heating rate was 5°C/min, and the heat-treatment temperature was 800°C. The obtained product was named Mo ₆ Te ₈ /NC; in the hydrogen-argon gas mixture, the volume percentage of hydrogen was 5%;

(4) The obtained nitrogen-doped carbon molybdenum telluride and sodium hypophosphite were added to both ends of the porcelain boat at a mass ratio of 1:5, and heat treated under nitrogen for 2 hours at a heating rate of 5°C/min and a heat treatment temperature of 300°C. The obtained product was named Mo ₆ Te ₈ /N,PC.

The obtained nitrogen phosphorus doped carbon molybdenum telluride XRD is shown in Figure 1, Figure 1 shows that the nitrogen phosphorus doped carbon molybdenum telluride was successfully prepared.

b. Preparation of Molybdenum Telluride with Nitrogen and Phosphorus Doped Carbon Supporting Platinum Nanoparticles

(1) Disperse 80 mg of the prepared Mo ₆ Te ₈ /N,PC in 50 mL of ethylene glycol, and then add 670 μL of chloroplatinic acid aqueous solution (the content of platinum in the chloroplatinic acid aqueous solution is 30 mg/mL);

(2) Stir magnetically to form a uniform suspension, put it into a microwave reactor, microwave power 700W, microwave time 5 minutes, naturally cool to room temperature after the reaction;

(3) Suction filtration, washing with ethanol and deionized water at least 3 times, vacuum drying at 60°C overnight, and the obtained product is named PtMo ₆ Te ₈ /N,PC.

The XRD of the nitrogen-phosphorus-doped carbon molybdenum telluride loaded with platinum nanoparticles is shown in FIG. 2 . It can be seen from Fig. 2 that the diffraction peaks of Pt correspond to the standard PDF card of platinum, indicating the successful preparation of molybdenum telluride with nitrogen and phosphorus doped carbon loaded with platinum nanoparticles.

Example 2

The preparation method of PtMo ₆ Te ₈ /NC is specifically:

(1) Disperse 1.4g of molybdenum trioxide and 0.664g of imidazole in 150mL of water, and reflux at 110°C for 12 hours;

(2) Cool to room temperature, filter with suction, wash with deionized water at least 3 times, and dry under vacuum at 60°C overnight;

(3) The obtained Mo-MOF and tellurium powder were uniformly mixed at a mass ratio of 1:1, heat-treated for 2 hours under a hydrogen-argon gas mixture, the heating rate was 5°C/min, and the heat-treatment temperature was 800°C. The obtained product was named Mo ₆ Te ₈ /NC; in the hydrogen-argon gas mixture, the volume percentage of hydrogen was 5%;

(4) Disperse 80 mg of the prepared Mo ₆ Te ₈ /NC in 50 mL of ethylene glycol, and then add 670 μL of chloroplatinic acid aqueous solution (the content of platinum in the chloroplatinic acid aqueous solution is 30 mg/mL);

(5) Magnetic stirring to form a uniform suspension, put it into a microwave reactor, microwave power 700W, microwave time 5 minutes, naturally cool to room temperature after the reaction;

(6) Suction filtration, washing with ethanol and deionized water for at least 3 times, and vacuum drying at 60° C. overnight. The obtained product is named PtMo ₆ Te ₈ /NC.

Example 3

The application of the PtMo ₆ Te ₈ /N, PC prepared in Example 1, the PtMo ₆ Te ₈ /NC prepared in Example 2, and the commercial Pt/C catalyst in acidic electrolyte to catalyze methanol oxidation were tested respectively:

Get the PtMo prepared in 5mg embodiment 1₆Te₈/N, P-C, the PtMo prepared in 5mg embodiment 2₆Te₈/N-C and 5 mg commercial Pt/C catalysts were tested respectively. Three different catalysts were added to the mixture of 950 μL absolute ethanol and 50 μL Nafion, and the ultrasonic dispersion was uniform to obtain a mixed solution; 10 μL of the mixed solution was dropped onto the surface of a glassy carbon electrode as a working electrode, a carbon rod was used as a counter electrode, and a saturated calomel electrode (SCE) was used as a reference electrode. .Cyclic voltammetry scanning was performed at a scanning speed of 50mV/s between 2 and 1V, and a constant current chronograph test was performed at a potential of 0.6V for 2 hours.

Figure 3 shows the cyclic voltammetry curves and chronoamperometry curves of PtMo ₆ Te ₈ /N, PC, PtMo ₆ Te ₈ /NC and commercial Pt/C catalysts in a mixed solution of 0.5 mol/L sulfuric acid and 1 mol/L methanol. It can be seen from Figure 3a that PtMo ₆ Te ₈ /N, PC has the highest peak current density value; it can be seen from Figure 3b that after 7200s of stability testing, PtMo ₆ Te ₈ /N, PC retains the highest final current density value. Compared with PtMo ₆ Te ₈ /NC and commercial Pt/C catalysts, the PtMo ₆ Te ₈ /N, PC catalyst of the present invention has higher catalytic activity and stability when catalyzing the acidic methanol oxidation reaction.

Example 4

The application of the PtMo ₆ Te ₈ /N, PC prepared in Example 1, the PtMo ₆ Te ₈ /NC prepared in Example 2, and the commercial Pt/C catalyst to catalyze hydrogen evolution in acidic electrolytes were tested respectively:

Get the PtMo prepared in 5mg embodiment 1₆Te₈/N, P-C, the PtMo prepared in 5mg embodiment 2₆Te₈/N-C and 5 mg commercial Pt/C catalysts were tested respectively. Three different catalysts were added to the mixture of 950 μL absolute ethanol and 50 μL Nafion, and the ultrasonic dispersion was uniform to obtain a mixed solution; 10 μL of the mixed solution was dropped onto the surface of a glassy carbon electrode as a working electrode, a carbon rod as a counter electrode, and a saturated calomel electrode (SCE) as a reference electrode. Scan at a scanning speed of 5mV/s between ~-0.4V, and perform a constant current timer test for 15 hours at a potential of -0.27V.

Figure 4 shows the linear sweep voltammetry curves and chronoamperometry curves of PtMo ₆ Te ₈ /N, PC, PtMo ₆ Te ₈ /NC and commercial Pt/C catalysts in a mixed solution of 0.5 mol/L sulfuric acid and 1 mol/L methanol. It can be seen from Figure 4 that PtMo ₆ Te ₈ /N, PC requires the smallest overpotential when driving a current density of 10 mA cm ^-2 ; after 15 hours of continuous stability testing, the current density hardly changes; compared with PtMo ₆ Te ₈ /NC and commercial Pt/C catalysts, the PtMo ₆ Te ₈ /N, PC catalyst of the present invention has higher catalytic activity and stability when catalyzing the acidic hydrogen evolution reaction.

Example 5

The application of PtMo ₆ Te ₈ /N, PC and commercial Pt/C catalysts in methanol electrolysis were tested respectively:

Get the PtMo prepared in 5mg embodiment 1₆Te₈/N, P-C and 5 mg commercial Pt/C catalysts were tested respectively. Two different catalysts were added to the mixture of 950 μL absolute ethanol and 50 μL Nafion, and the ultrasonic dispersion was uniform to obtain a mixed solution; 10 μL of the mixed solution was added dropwise to the surface of the glassy carbon electrode as the cathode and anode respectively, and the electrode was placed in a mixed system of 1mol/L methanol and 0.5mol/L sulfuric acid. The speed is scanned, and the 20h constant current timer test is carried out at a voltage of 0.72V.

Figure 5 shows the linear sweep voltammetry curves and chronoamperometry curves of PtMo ₆ Te ₈ /N, PC and commercial Pt/C catalysts in methanol electrolysis. It can be seen from Figure 5a that with PtMo ₆ Te ₈ /N, PC as the cathode and anode dual-functional catalyst, the voltage required for methanol electrolysis and water electrolysis is much lower than that of commercial Pt/C catalysts; it can be seen from Figure 5b that after 20h of stability testing, the current density decay of PtMo ₆ Te ₈ /N, PC catalysts is smaller than that of commercial Pt/C catalysts. Therefore, the PtMo ₆ Te ₈ /N, PC catalyst of the present invention has higher catalytic activity and stability in methanol electrolysis.

Claims (8)

1. The preparation method of the electro-catalyst for preparing hydrogen by methanol electrolysis is characterized in that molybdenum telluride doped with carbon by nitrogen and phosphorus is used as a composite carrier, and a carrier is platinum-based nano particles, and comprises the following steps:

(1) Dispersing molybdenum trioxide and imidazole in water, refluxing, naturally cooling to room temperature after refluxing, carrying out suction filtration, washing and vacuum drying to obtain Mo-MOF; uniformly mixing the prepared Mo-MOF and tellurium powder, and performing heat treatment under hydrogen-argon mixed gas to obtain nitrogen-doped carbon molybdenum telluride;

(2) Performing heat treatment on the molybdenum telluride doped with carbon by nitrogen and sodium hypophosphite in the step (1) under nitrogen to obtain molybdenum telluride doped with carbon by nitrogen and phosphorus;

(3) Adding the molybdenum telluride doped with carbon by nitrogen and phosphorus and the chloroplatinic acid aqueous solution in the step (2) into ethylene glycol, uniformly stirring, reducing platinum ions into a platinum simple substance by utilizing a microwave-assisted ethylene glycol reduction method, and after the reaction is finished, carrying out suction filtration, washing and vacuum drying to obtain the electrocatalyst of the molybdenum telluride loaded with carbon by nitrogen and phosphorus and platinum-based nano particles.

2. The electrocatalyst according to claim 1 wherein the loading of the platinum-based nanoparticles is from 20 to 60% of the total catalyst mass.

3. The electrocatalyst according to claim 1, wherein the platinum-based nanoparticles comprise elemental platinum or an alloy of platinum and a transition metal; wherein the transition metal comprises palladium, ruthenium, rhodium, silver, gold, cobalt or nickel.

4. The electrocatalyst according to claim 1 wherein the platinum-based nanoparticles have a particle size of from 1 to 10nm.

5. The electrocatalyst according to claim 1, wherein in step (1), the mass ratio of molybdenum trioxide to imidazole is 1 to 3:1, the reflux temperature is 100 to 130 ℃, and the reflux time is 10 to 20 hours.

6. The electrocatalyst according to claim 1, wherein in step (1), the mass ratio of Mo-MOF to tellurium powder is 1:0.5 to 2, the temperature rise rate is 2 to 10 ℃/min under the hydrogen-argon mixture, the heat treatment temperature is 800 to 1000 ℃, the heat treatment time is 1 to 3 hours, and the volume percentage of hydrogen in the hydrogen-argon mixture is 5 to 10%.

7. The electrocatalyst according to claim 1, wherein in step (2), the mass ratio of the nitrogen-doped molybdenum telluride to the sodium hypophosphite is 1:3-8, the temperature rise rate is 2-10 ℃/min under nitrogen, the heat treatment temperature is 150-350 ℃, and the heat treatment time is 1-3 hours.

8. The electrocatalyst according to claim 1 wherein in step (3) the microwave power is 500 to 800W and the microwave time is 2 to 5 minutes.