AU2021100865A4

AU2021100865A4 - Preparation and application of a series non-copper catalyst for preparing methane by electrocatalytic carbon dioxide

Info

Publication number: AU2021100865A4
Application number: AU2021100865A
Authority: AU
Inventors: Ge DU; Yanxiong Fang; Chengchao Li; Baoyu Liu; Dalei Sun; Yuying ZHENG
Original assignee: Guangdong University of Technology
Current assignee: Guangdong University of Technology
Priority date: 2021-02-12
Filing date: 2021-02-12
Publication date: 2021-04-22
Anticipated expiration: 2029-02-12

Abstract

The invention discloses the preparation and application of a non-copper-based electrocatalyst for catalyzing the electrochemical reduction of carbon dioxide to produce methane. The catalyst is a sulfide-metal element/oxide composite catalyst. The sulfides include ZnIn2S 4 , ZnS2, SnS2, SnSe2, MoS2, MoSe2, Ag2S, PbS, NiS, FeS2 and Co3S4. Metal simple substance/oxide includes rare earth Y/Y 20 3, La/La203, Ce/CeO2 and transition Fe/Fe203, Ni/NiO, Co/Co203, Mn/MnO2, and the molar ratio of sulfide to metal simple substance/oxide is 1:1-10:1. The preparation process of the catalyst includes sol-gel, hydrothermal crystallization, centrifugal washing, and drying. The electrochemical reduction of carbon dioxide to methane applies an H-type three-electrode reaction system, and the electrolyte solution adopts alkaline aqueous electrolyte. The catalyst preparation has a wide range of raw materials, simple preparation methods, easy operation, which is suitable for large scale production with broad industrial application prospects.

Description

Preparation and application of a series non-copper catalyst for preparing methane by

electrocatalytic carbon dioxide

TECHNICAL FIELD

The invention relates to the field of carbon dioxide electrochemical reduction reaction

(CO2RR), in particular to the preparation and application of a sulfide-metal simple

substance/oxide composite electrocatalyst for electrochemically reducing carbon dioxide to

prepare methane.

BACKGROUND

The electrochemical C02 reduction reaction (CO 2 RR) can convert the greenhouse gas

CO2 into higher value-added chemicals and fuels with the use of regenerative electricity. It

is considered to be a combination of carbon resource recycling and renewable energy storage

as a very promising method. The CO 2 RR to methane is even better because the product

methane, as a clean, high-quality, and efficient hydrocarbon resource, it not only has a high

energy density (-55.5MJ kg- 1), but also many important fine chemicals/drugs (such as

ethylene, acetylene, tetrachloride, etc.) are important synthetic raw materials, so it is favored

by the scientific and industrial circles. However, due to the inherent chemical inertness and

thermodynamic stability of CO2 molecules, the bottleneck and breakthrough that CO 2 RR

faces lies in the development of high-performance electrocatalysts. So far, the published

literature reports on the research and development of high-efficiency catalysts from CO 2 RR

to methane mainly focus on copper-based electrocatalysts. On the one hand, the

disadvantages are that the scarcity of precious metal copper leads to higher prices; On the

other hand, univalent copper in copper-based catalysts is easy to be reduced in the reaction

process, which leads to the rapid deactivation of the whole catalyst. However, there are few

reports about non-copper-based catalysts catalyzing CO2 RR to methane. In 2020, Wang

Guoxiong, a researcher at the State Key Laboratory of Catalytic Basis, Dalian Institute of

Physicochemical Sciences, Chinese Academy of Sciences, and Academician Bao Xinhe

reported that the composite catalyst of phthalocyanine cobalt-zinc-nitrogen-carbon, which

is a non-copper-based catalyst, can effectively electrocatalyze CO 2 RR to methane, but the

preparation process of the catalyst is complicated and difficult for large-scale production.

The sulfide-metal simple substance/oxide composite electrocatalyst described in this patent

can be completed by a simple one-step solvothermal method including water, and the

preparation process is simple and environment-friendly; besides the target product methane,

the product is H 2 and a small amount of CO, which shows good electrocatalytic activity for

preparing methane from CO 2 RR and has broad industrial application prospects.

SUMMARY

The technical problem to be solved by the invention is that by the development of high

performance carbon dioxide electrochemical reduction catalyst, hydrogen is replaced by

water, and the one-step electrochemical reduction of C02 in aqueous electrolytic solution is

realized to prepare methane.

The efficient catalyst is a sulfide-metal simple substance/oxide composite

electrocatalyst. The sulfide comprises one or a mixture of several of ZnIn2S4, ZnS2, SnS2,

SnSe2, MoS2, MoSe2, Ag2S, PbS, NiS, FeS2 and Co3S4; The metal in the metal simple

substance/oxide includes one or a mixture of transition metals and rare earth metals, such as

Y/Y 2 0 3 , La/La203, Ce/CeO2, Fe/Fe203,, Ni/NiO, Co/Co20 and Mn/MnO2. In terms of metal

elements, the molar ratio of sulfide-metal simple substance/oxide is 1:1-9:1. Its preparation

method adopts solvothermal method including water. The specific synthesis steps are as

follows:

Adding one or more of zinc salt such as Zn(N03)2-6H20, tin salt such as SnC1 4 -5H20,

molybdenum salt such as Na2MoO 4 , silver salt such as AgNO3, lead salt such as Pb(OAC) 4 , nickel salt such as NiCl 2 , iron salt such as FeCl3 and cobalt salt such as CH 4 6CO04 into solvent to obtain solution A. The solvent R is one or more of deionized water, alcohol, ketone, halogenated hydrocarbon or aromatic hydrocarbon and nitrogen-containing organic solvent.

Dissolving one or more of yttrium salt such as yttrium nitrate, lanthanum salt such as

lanthanum nitrate, cerium salt such as cerium nitrate, iron salt such as ferric sulfate, nickel

salt such as nickel nitrate, cobalt salt such as cobalt acetate and manganese salt such as

manganese chloride in solvent R to obtain solution B; Mixing the solution A and the solution

B according to the metal atom molar ratio of 1: 1-20: 1 to obtain a solution C.

Thiourea, N'N- diphenyl thiourea (DPTU), one or more of methionine, cysteine and

cystine are dissolved in solvent r to obtain solution D. Then adding solution D into solution

C by titration according to the molar ratio of 1: 1-1: 5 between solution D and metal elements

in solution A, adding one or a mixture of several suitable structure directing agents such as

cetyltrimethylammonium bromide, polyvinylpyrrolidone, sodium dodecyl benzene

sulfonate, polyethylene glycol and amine oleate according to the molar ratio of 1: 1-1: 60

between solution D and metal elements in solution A, the pH value of the solution is adjusted

to 2-10 by ammonia water solution with a concentration of 2.0 mol/L. Finally, the obtained

mixed solution is transferred to a polytetrafluoroethylene kettle, and is placed in an electric

blast drying box for hydrothermal reaction for 2-48 hours at a temperature of 50-250C.

Finally, the precipitate is centrifugally washed and placed in a vacuum drying box for drying

at the temperature of 50-120'C for 6-24 hours to obtain sulfide-metal. Then, the sulfide

metal simple substance/oxide composite catalyst prepared above is applied to prepare

methane by electrochemical reduction of carbon dioxide with aqueous electrolyte. The

specific operation is as follows:

Firstly, the prepared sulfide-metal simple substance/oxide composite catalyst is placed

in a solution containing water, ethanol and perfluorosulfonic acid resin Nafion, and the

loading amount of the catalytic material is 0.5-100 mg/cm 2 . Then, the solution is evenly

dripped on the gas diffusion electrode body, such as carbon paper, carbon fiber cloth, carbon

felt, carbon brush or graphite felt, and then dried naturally to serve as the working electrode.

Then, a three-electrode sealing H-type electrocatalytic chemical reaction device

including a working electrode, a Pt auxiliary electrode, and an Ag/AgC1 reference electrode

is adopted. In the alkaline ionic liquid containing KHC0 3 , K 2 C0 3 , KOH, potassium iodide,

potassium bromide and other inorganic alkaline salts and cations such as guanidine ions,

imidazole ions, pyrrole ions, quaternary amine ions, piperidinium ions, quaternary ions,

amino acid ester ions, etc. In the aqueous alkaline electrolyte solution, the electrolyte

concentration is 0.1-2.0M. At room temperature, under the set voltage and magnetic stirring,

continuously pass C02 at the set flow rate, and detect gas products by GC, and liquid

products by nuclear magnetism.

The present invention enables the one-step electrocatalytic chemical reduction of

carbon dioxide to methane in an alkaline electrolyte containing water by developing a high

performance carbon dioxide electrocatalyst sulfide-metal monomer/oxide composite

catalyst with water instead of hydrogen. Moreover, the above high-performance catalyst

preparation materials developed are widely sourced, and the synthesis method is mature and

easy to promote, which has a broad industrial application prospect.

DESCRIPTION OF THE INVENTION

The application of the present invention in electrochemical C02 reduction will be

further explained with specific examples, which are used to illustrate the present invention,

but are not limited to the scope of the present invention. In addition, it should be understood

that after reading the teaching of this invention, those skilled in the art can make various changes or modifications to this invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

Example 1

1.Preparation of Ce-doped SnS2

Here, SnC14-5H2O(0.97mmol) and Ce(N03)2-3H2O(0.03mmol) were mixed in 15mL

of deionized water and stirred for 30min, which is marked as solution A, while 4mmol of L

cysteine was dissolved in 15 mL of deionized water and stirred for 30min, which is marked

as solution B. Then adding B dropwise to A under the condition of strong stirring. Continue

stirring for a certain time of 60min, then transfer the solution to a polytetrafluoroethylene

kettle, put it into an oven for hydrothermal reaction, while the hydrothermal temperature

range is 180°C, the reaction time is 12h. Then centrifugally wash the precipitate, and dry it

to prepare Sno.97Ceo.o3S2 nanoparticles.

2.Electrochemical test conditions and results

The carrying capacity of the catalyst material on the glass carbon electrode is 0.5

mg/cm 2, the electrolyte of each chamber is 25 mL, KHCO 3 (pH = 7.2) of 0.5 M, the

concentration of C02 is 99. 99%, the flow rate is 30 cm 3/min, the room temperature, the test

voltage is -0.8 V- -1.2 V (VS.RHE).The electrolytic products include CH 4 , H 2 and a small

amount of CO, and the faraday efficiency of CH 4 is 12.6% at -1.2V(vs.RHE). Nuclear

magnetic testing liquid-free products. The products without liquid phase were tested by

NMR(Nuclear magnetic testing).

Comparative example 2

1.Preparation of undoped tin disulfide material

1 mmol of 1mmolSnCl4-5H20 was dissolved in 15 mL of deionized water and stirred

thoroughly that is marked as solution A. 4 mmol of L-cysteine was dissolved in 15 mL of

deionized water and stirred thoroughly to mark solution B. Subsequently, B was added to A drop by drop under strong stirring conditions and continued to be stirred for a certain time.

The reaction time was 12h. The solution was washed by centrifugation and dried, and finally

the SnS2 nanoparticles were obtained.

2.Electrochemical test conditions

The load of catalyst material on the glassy carbon electrode is 0.5mg/cm2 , the

electrolyte in each chamber is 25 mL, the concentration of C02 is 99.99%, the flow rate is

cm 3/min, the test voltage is -0.8 V ~ -1.2 V (vs. RHE) at room temperature. Electrolytic

products include CH 4 , H2 and a small amount of CO. The Faraday efficiency of CH 4 is 9.5%

at -1.2v(vs.RHE). The products without liquid phase were tested by NMR.

Example 3

1.Preparation of Co doped SnS2

In this example, SnC14-5H2O(0.97mmol) and Co(N0 3)2 -6H 20 (0.03mmol) in l5mL of

deionized water and stir thoroughly for 30min to be marked as solution A. Take another

4mmol of L-cysteine and dissolve it in l5mL of deionized water and stir thoroughly for

min to be marked as solution B. Then add B under strong stirring condition. B was added

drop by drop to A and stirred for 60 min, then the solution was transferred to a PTFE kettle

and put into an oven for hydrothermal reaction at 180°C for 12 h. The precipitate was then

washed by centrifugation and dried to produce Sno.9 7 Coo.o3S2 nanoparticles.

2.Electrochemical test conditions and results

The load of catalyst material on the glassy carbon electrode is 0.5Mmg/cm 2 , the

electrolyte in each chamber is 25ml, the concentration of C02 is 99.99%, the flow rate is

cm 3/min, the test voltage is-0.8 V-1.2 V (vs. RHE) at room temperature. Electrolytic

products include CH4 , H2 and a small amount of CO. The Faraday efficiency of CH 4 is 16.7%

at -1.2v(vs.RHE). The products without liquid phase were tested by NMR.

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1.The electrocatalyst for preparing methane by electrochemical reduction of carbon

dioxide is characterized in that the catalyst is composed of sulfide-metal simple

substance/oxide in series, and the molar ratio of sulfide-metal simple substance/oxide is 1:

1-9: 1 in terms of metal elements.

The sulfide includes one or a mixture of several of ZnIn2S4, ZnS2, SnS2, SnSe2, MoS2,

MoSe2, Ag2S, PbS, NiS, FeS2 and Co3S4.

The metal in the metal simple substance/oxide includes one or a mixture of transition

metals and rare earth metals, such as Y/Y 2 0 3 , La/La203, Ce/CeO2, Fe/Fe203, Ni/NiO,

Co/Co203 and Mn/MnO2.

2.The electrocatalytic chemical reduction of carbon dioxide to methane catalyst

according to claim 1, characterized in that its preparation process comprises the following

steps:

(1) One or more of zinc salt such as Zn(NO3)2-6H20, tin salt such as SnC4-5H20,

molybdenum salt such as Na2MoO 4 , silver salt such as AgNO3, lead salt such as Pb (OAC) 4

, nickel salt such as NiCl 2 , iron salt such as FeCl3, cobalt salt such as CH 4 6 CO4 are dissolved

in solvent R to obtain solution A. The solvent R is one or more of deionized water, alcohol,

ketone, haloalkane or aromatic hydrocarbon and nitrogenous organic solvent.

(2) One or more of yttrium salts such as yttrium nitrate, lanthanum salts such as

lanthanum nitrate, cerium salts such as cerium nitrate, iron salts such as ferric sulfate, nickel

salts such as nickel nitrate, cobalt salts such as cobalt acetate, and manganese salts such as

manganese chloride are dissolved in solvent r to obtain solution B. The solvent R is as

described in claim 1.

(3) One or more of thiourea, NN-diphenylthiourea (DPTU), methionine, cysteine and

cystine, is dissolved in solvent R to obtain solution C. Solvent R is as described in claim 1.

(4) Mix the above solution A and solution B according to the metal atom molar ratio of

1:1 to 20:1, preferably 5:1 to 10:1 to obtain solution D; then mix solution C with the metal

element molar ratio of solution A to 1 :1-1:5, preferably 1:1-1:3. Under vigorous stirring,

titrate C into solution D, after the dropwise addition is completed. Then add a suitable

structure directing agent at a molar ratio of 1:1-1:60 to the metal element in solution A,

preferably 1:10-1:20, and adjust the pH value of the solution with an aqueous ammonia

solution with a concentration of 2.Omol/L It is 2-10, preferably 6-8. Finally, the obtained

mixed liquid is transferred to a polytetrafluoroethylene kettle and placed in an electric

heating blast drying box at a temperature of 50-250°C, preferably 80-180°C. Hydrothermal

reaction is 2-48h, preferably 6-24h, and finally the precipitate is washed by centrifugation

and placed in a vacuum drying cabinet at a temperature of 50120°C, preferably 80100°C,

for 6-24h, preferably 10-18h. Afterwards, a sulfide-metal element/oxide composite catalyst

is obtained.

The structure directing agent mentioned in (4) above includes one or more of

cetyltrimethylammonium bromide, polyvinylpyrrolidone, sodium dodecylbenzene

sulfonate, polyethylene glycol, and amine oleate mixture.

3.The electro-catalytic chemical reduction of C02 to produce methane as claimed in

claim 1 is characterized by adopting an H-type electro-catalytic chemical reaction device

sealed by three electrodes. With gas diffusion electrode as working electrode, Pt electrode

as auxiliary electrode, Ag/AgC1 as reference electrode and alkaline aqueous solution as

electrolyte, CO2 was continuously introduced at a set flow rate at room temperature under

set voltage and magnetic stirring, and gas products were detected by GC and liquid products

were monitored by NMR.

4.The working electrode according to claim 3 is characterized in that it comprises a gas

diffusion electrode body such as carbon paper, carbon fiber cloth, carbon felt, carbon brush or graphite felt, and a sulfide-metal simple substance/oxide series composite carbon dioxide electrochemical reduction catalyst loaded on the gas diffusion electrode body. The loading process is as follows: the catalytic material according to claims 1 and 2 is placed in a solution containing water, ethanol and perfluorosulfonic acid resin Nafion, and the loading amount of the catalytic material is 0.5-100mg/cm 2 , preferably 10-50mg/cm 2 . Then, the solution is evenly dripped on the gas diffusion electrode body, which is naturally dried and used as the working electrode.

5.The alkaline aqueous electrolyte according to claim 3, which is characterized in that

the electrolyte comprises inorganic alkaline salts such as KHCO 3 , K2 C0 3 , KOH, potassium

iodide and potassium bromide, and cationic alkaline ionic liquids such as guanidine ions,

imidazole ions, pyrrole ions, quaternary ammonium ions, piperidine ions, quaternary

ammonium ions and amino acid ester ions, and the electrolyte concentration is 0.1-2.M,

preferably 0.3-1.0M.