CN114182280B - MEC hydrogen evolution cathode electrode based on Ni-SAPO-34 composite material - Google Patents

Abstract

The invention relates to a MEC hydrogen evolution cathode electrode based on Ni-SAPO-34 composite material, which is prepared by adding the Ni-SAPO-34 composite material into absolute ethyl alcohol containing Nafion solution to form suspension, dripping the suspension on carbon paper, and drying to form Ni-SAPO-34 load of 1-5 mg/cm ² Is provided. The cathode electrode is used in the MEC device, reduces the cost of cathode materials of the MEC device, improves the hydrogen evolution catalytic efficiency of the cathode electrode, has electrochemical performance and hydrogen production efficiency similar to those of Pt/C electrodes, and is obviously superior to other cathode materials.

Description

MEC hydrogen evolution cathode electrode based on Ni-SAPO-34 composite material

Technical Field

The invention belongs to the technical field of microbial electrolytic cells, relates to a cathode material for a microbial electrolytic cell, and particularly relates to a cathode electrode prepared from a Ni-SAPO-34 composite material.

Background

Microbial electrolysis cells (Microbial Electrolysis Cell, MEC) are the reverse process of Microbial Fuel Cells (MFC), a technique that produces hydrogen by microbial oxidation of organic substrates.

The MEC device mainly comprises a power supply, an external circuit, a cathode, an anode and an electrolyte solution. The MEC degrades the organic matters in the solution through the action of the anode microorganisms, hydrogen ions and electrons are generated at the same time, the electrons are transferred to the anode, then reach the cathode through an external circuit, the hydrogen ions are released into the solution through proton exchange, and then transferred to the cathode area through the electrolyte, and hydrogen is generated by combining with the electrons under the action of an external voltage. Compared with other hydrogen production systems, MEC can efficiently produce hydrogen while treating wastewater, has the characteristics of green, energy conservation and environmental protection, and has wide prospects in the aspects of solving energy and environmental problems and the like.

The cathode is the place where MEC produces hydrogen, so the cathode material is a key factor affecting MEC hydrogen evolution performance. Reducing the cost of cathode materials and improving the catalytic efficiency of cathode hydrogen evolution remain the major problems currently faced by MECs. To increase hydrogen evolution efficiency, MEC cathodes require a supported metal catalyst to reduce hydrogen evolution overpotential. The hydrogen evolution catalytic activity of the hydrogen evolution reaction is related to the strength of the adsorption of hydrogen atoms by metal atoms.

Pt has moderate free energy of adsorption to hydrogen atoms, and has very low overpotential (about 25 mV), and is the hydrogen evolution material with the best performance in MEC application. Lu et al (Hydrogen production with effluent from an ethanol-H) ₂ -coproducing fermentation reactor using a single-chamber microbial electrolysis cell[J]. Biosensors and Bioelectronics2009, 24:3055-3060.) Pt-loaded carbon cloth was used as cathode, and (1.41.+ -. 0.08) m was obtained at a voltage of 0.6V ³ /(m ³ Hydrogen production rate of d); after being combined with a fermentation system, the hydrogen production rate reaches 2.11m ³ /(m ³ D), the total recovery rate of the hydrogen reaches 96 percent, and the power energy efficiency reaches 287 percent.

Pt has excellent electrocatalytic performance, but it is expensive, has poor stability, and causes serious environmental pollution during development. In addition, some substances in the wastewater may also cause deactivation of the Pt catalyst. Therefore, it becomes important to find a cleaner, cheaper, more efficient cathode catalyst that can replace Pt.

Liu et al (P Dopants Triggered New Basal Plane Active Sites and Enlarged Interlayer Spacing in MoS) ₂ Nanosheets toward Electrocatalytic Hydrogen Evolution[J]. Energy Letters2017, 2 (4): 745-752.) MoS doping by non-metallic P ₂ The nano-sheet proves that the P doping increases the active center on the original basal plane, increases the interlayer spacing of the nano-sheet and improves MoS ₂ Electrocatalytic efficiency in hydrogen evolution reactions.

Li et al (Synergistic Tuning of the Electronic Structure of Mo) ₂ C by P and Ni Codoping for Optimizing Electrocatalytic Hydrogen Evolution. Inorganic Chemistry2020, 59:13741-13748.) by a method of forming a new pattern in N ₂ Is directly carbonized, and cation Ni and anion P are introduced into Mo ₂ In C-based materials. Proved that P and Ni respectively serve as anions and cations to cooperatively regulate Mo ₂ The electrochemical performance of C reduces the activation energy and endows the catalyst with good catalytic performance.

Ghasem et al (Pulse Electrodeposition of a Superhydrophilic and Binder-Free Ni-Fe-P Nanostructure as Highly Active and Durable Electrocatalyst for Both Hydrogen and Oxygen Evolution Reactions [ J)]. Applied Materials & Interfaces2020, 12:53719-53730.) a three-dimensional electrocatalyst of nickel-iron-phosphorus nanostructures with good intrinsic electrocatalytic activity was synthesized at different frequencies and durations using a pulsed electrodeposition process. By changing parameters such as coating frequency, coating time and the like, the electrocatalytic performance of the coating is found to be optimal at 1Hz and 1200 s.

The above experimental results demonstrate that the increase in active surface area, the synergistic effect of nickel, iron, phosphorus, is an important factor in producing excellent stability and electrocatalytic activity.

SAPO-34 molecular sieves are one of the series of silicoaluminophosphate molecular sieves developed by United states United Carbide Corporation (UCC) and have a unit cell chemical composition of (Al _16.5 P _14.1 Si _5.4 )O ₇₂ Belonging to a trigonal system, which is composed of SiO ₄ ，AlO ₄ ^- , PO ₄ ⁺ Three tetrahedra are formed, the pore size is between 0.43 and 0.50nm, and the specific surface area is large. The crystal framework of the SAPO-34 molecular sieve is similar to that of the chabazite molecular sieve, is of a chabazite-like structure, and has a special CHA framework and eight-membered ring pore channels. This structure results in greater diffusion resistance to the isomeric or heavier hydrocarbons and less diffusion resistance to the lower hydrocarbons. In addition, the SAPO-34 molecular sieve has both B-type and L-type acid centers, and the strength of the B-type acid centers is higher and the number is more compared with the L-type acid centers, and the acidity is mainly derived from bridge hydroxyl groups (Si-OH-Al). The SAPO-34 molecular sieve also has excellent heat stability and hydrothermal stability, and the framework collapse temperature is 1000 ℃.

The SAPO-34 molecular sieve is prepared by a hydrothermal synthesis method, water is used as a reaction medium, a silicon source, an aluminum source, a phosphorus source and a template agent are mixed according to a certain molar ratio to form gel, and the SAPO-34 molecular sieve is obtained after aging, crystallization, washing, suction filtration, drying and roasting.

The SAPO-34 molecular sieve is widely applied to the catalytic application fields of Methanol To Olefin (MTO), ammonia selective catalytic reduction of NOx and the like due to the excellent catalytic performance, but has limitation in practical application. A large number of research results show that the performance of the molecular sieve can be optimized by carrying out metal modification on the molecular sieve.

Li Duichun et al (theoretical study of MTO reaction on Fe, co, ni modified SAPO-34 molecular sieves [ J)]. Clean coal technology Surgery (operation)2018, 24 (05): 103-112.) examined the MTO catalytic performance of SAPO-34 molecular sieves modified with Fe, co and Ni, respectively, and found that the introduction of Ni atoms had a greater impact on ethylene selectivity than the other two metals.

Maede et al (Improvement of light olefins selectivity and catalyst lifetime in MTO reaction; using Ni and Mg-modified SAPO-34 synthesized by combination of two templates[J)]. Journal of Industrial and Engineering Chemistry2011, 17 (4), 755-761)) to the SAPO-34 are respectively subjected to Ni modification and Mg modification, and the results prove that the catalyst modified by the two metals has higher selectivity and longer service life to the low-carbon olefin, wherein the Ni-SAPO-34 has better catalytic performance and service life than the Mg-SAPO-34.

Li Jingjing et al (removal of dichloroethane from model oil by modified SAPO-34 molecular sieves [ J)]. Chemical progress2017, 36 (10): 3730-3736.) the molecular sieves modified with Ni, cu, mg, zn were prepared, respectively, using an isovolumetric impregnation method, and it was found that Ni-SAPO-34 had stronger dechlorination and regeneration than other metal-modified SAPO-34.

Disclosure of Invention

The invention aims to provide an MEC hydrogen evolution cathode electrode based on a Ni-SAPO-34 composite material, so that the cost of the cathode material of an MEC device is reduced, and the hydrogen evolution catalytic efficiency of the cathode electrode is improved.

The MEC hydrogen evolution cathode electrode based on the Ni-SAPO-34 composite material is prepared by adding the Ni-SAPO-34 composite material into absolute ethyl alcohol containing Nafion solution to form suspension, and dripping the suspensionNi-SAPO-34 loading capacity formed by drying on carbon paper is 1-5 mg/cm ² Is provided.

Wherein, the Ni-SAPO-34 composite material is prepared according to a fixed molar ratio n (Al ₂ O ₃ )∶n(SiO ₂ )∶n(P ₂ O ₅ ) N is the template agent and n is the H ₂ O) =1:0.7-1.3:0.8-1.2:1.8-2.3:50-90, adding an aluminum source, a silicon source, a phosphorus source and a template agent into deionized water, uniformly mixing, adding a nickel precursor according to the molar ratio of n (Si) to n (Ni) =5-40:1, carrying out static hydrothermal crystallization reaction for 12-72 h at 150-230 ℃ in a sealed state, and roasting the reaction product at 450-600 ℃ for 6-24 h.

Specifically, the template may be diethylamine, triethylamine, tetramethylammonium hydroxide, tetraethylammonium hydroxide or tetrapropylammonium hydroxide, and tetraethylammonium hydroxide (TEAOH) is preferably used as the template in the present invention.

Furthermore, the types and sources of the aluminum source, the silicon source and the phosphorus source are not particularly limited, and can be various conventional aluminum sources, silicon sources and phosphorus sources used for preparing various molecular sieves. More specifically, the aluminum sources of the present invention include, but are not limited to, pseudo-boehmite, sodium metaaluminate, aluminum sulfate, or aluminum isopropoxide; the silicon source includes, but is not limited to, white carbon black, silica sol or ethyl orthosilicate; the phosphorus source includes, but is not limited to, phosphoric acid, phosphorous acid, polyphosphoric acid, or phosphate.

Specifically, the nickel precursor is a water-soluble salt of metallic nickel, and nickel nitrate is preferably used in the invention.

Further, the molar ratio of n (Si) to n (Ni) is preferably 10:1.

Wherein the concentration of the Nafion solution is preferably 2wt%.

The invention is based on the unique CHA framework and eight-membered ring pore canal of the SAPO-34 molecular sieve, takes the CHA framework and eight-membered ring pore canal as a carrier to load nickel oxide, synthesizes the Ni-SAPO-34 composite material by adopting an in-situ method, can fully disperse the nickel oxide on the pore canal and the surface of the molecular sieve, and exposes more contactable active sites. Meanwhile, the added Ni and P in the SAPO-34 can generate electronic interaction to generate synergistic effect, so that the electrocatalytic activity of the catalyst is improved, and the hydrogen evolution reaction rate is accelerated.

The invention is preferably carried out with Ni (NO) ₃ ) ₂ ·6H ₂ O is used as a nickel precursor, and the addition of the O has a certain influence on the synthesis of the SAPO-34 molecular sieve. This is due to the added NO ^3- The negative charge can be selectively adsorbed with the negative charge of a synthetic sol system, so that the negative charge property and stability of the sol are improved, more small grains are easy to generate in the synthesis process, the morphology of part of crystals is changed from cube to loose elliptic sphere with nano grains aggregated, and the specific surface area is increased compared with SAPO-34. Meanwhile, the introduction of the Ni source can promote the growth of the crystal of the SAPO-34 molecular sieve, so that the crystallinity of the Ni-SAPO-34 molecular sieve is increased.

Meanwhile, the SAPO-34 is used as a carrier of Ni, and P in the carrier can also interact with Ni to endow the molecular sieve with excellent electrochemical performance. Ni 2p of Ni-SAPO-34 _3/2 XPS spectrum shows that Ni compared with NiO ³⁺ The corresponding characteristic peak moves to the high-energy direction, the area proportion of the occupied peak increases, and Ni does not appear ²⁺ The main peak, which illustrates that nickel in Ni-SAPO-34 exists primarily in trivalent form and has an electronic interaction with phosphorus species in the molecular sieve framework. In addition, compared with pure NiO, the proportion of the surface oxygen corresponding peak area in the O1 s XPS spectrum of the Ni-SAPO-34 is obviously increased, which indicates that the number of oxygen vacancies is increased, and the existence of a large number of oxygen vacancies accelerates the conversion and migration of active substances, thereby being beneficial to the electrocatalytic hydrogen evolution reaction.

By linear voltammetric scanning and Taffel slope analysis comparison of different cathode materials Ni-SAPO-34, SAPO-34 and NiO, CP, pt/C, the electrochemical performance of the Ni-SAPO-34 is found to be similar to that of Pt/C, and is obviously superior to other cathode materials. Compared with MEC hydrogen production data of three cathode materials, namely Ni-SAPO-34 and Pt/C, CP, the Ni-SAPO-34 composite material has good hydrogen evolution performance.

Drawings

FIG. 1 is an XRD spectrum of a SAPO-34 molecular sieve and Ni-SAPO-34 composite.

FIG. 2 is an SEM and TEM image of SAPO-34 molecular sieves and Ni-SAPO-34 composites.

FIG. 3 is N of a SAPO-34 molecular sieve and Ni-SAPO-34 composite ₂ Adsorption-desorption curves and pore size distribution plots.

FIG. 4 is an XPS spectrum of Ni-SAPO-34 composite and NiO.

FIG. 5 is a linear scan of three cathode electrodes of Ni-SAPO-34 composite, CP and Pt/C.

FIG. 6 shows the Taphillips slope of three cathode electrodes, ni-SAPO-34 composite, CP and Pt/C.

FIG. 7 is a graph of gas yield and gas composition of three cathode electrodes, ni-SAPO-34 composite, CP and Pt/C, at each cycle of the MEC.

Detailed Description

The following describes in further detail the embodiments of the present invention with reference to the drawings and examples. The following examples are presented only to more clearly illustrate the technical aspects of the present invention so that those skilled in the art can better understand and utilize the present invention without limiting the scope of the present invention.

The experimental methods, production processes, apparatuses and devices involved in the embodiments and application examples of the present invention all belong to the names conventional in the art, and the names and abbreviations thereof are all well-known and clear in the relevant application fields, and those skilled in the art can understand the conventional process steps according to the names and apply the corresponding devices, and implement the methods according to the conventional conditions or the conditions suggested by the manufacturer.

The various raw materials or reagents used in the examples and application examples of the present invention are not particularly limited in source, and are conventional products commercially available. The preparation may also be carried out according to conventional methods known to the person skilled in the art.

Example 1.

5mL of deionized water, 4.53g of phosphoric acid and 2.90g of pseudo-boehmite are sequentially added into a polytetrafluoroethylene lining, stirring is carried out for 2 hours at room temperature, 22.76g of tetraethylammonium hydroxide (TEAOH) is added, stirring is carried out for 2 hours, 1.30g of white carbon black is added, stirring is carried out for 1 hour, then the mixture is sealed in a stainless steel reaction kettle, and static crystallization reaction is carried out for 24 hours at 200 ℃. Taking out, cooling, filtering with distilled water, washing to neutrality, oven drying at 80deg.C, grinding, and calcining at 550deg.C in a muffle furnace for 6 hr to obtain SAPO-34 molecular sieve.

Sequentially adding 5mL of deionized water, 4.53g of phosphoric acid and 2.90g of pseudo-boehmite into a polytetrafluoroethylene lining, stirring at room temperature for 2h, adding 22.76g of tetraethylammonium hydroxide (TEAOH), stirring for 2h, adding 1.30g of white carbon black, stirring for 1h, and adding 0.60g of Ni (NO) ₃ ) ₂ ·6H ₂ O, stirring for 1h, sealing in a stainless steel reaction kettle, and carrying out static crystallization reaction at 200 ℃ for 24h. Taking out, cooling, filtering with distilled water, washing to neutrality, oven drying at 80deg.C, grinding, and calcining at 550deg.C in a muffle furnace for 6 hr to obtain Ni-SAPO-34 composite material.

XRD spectra of the SAPO-34 molecular sieve and the Ni-SAPO-34 composite material are shown in FIG. 1, characteristic diffraction peaks of the SAPO-34 molecular sieve appear at the angles of theta=9.7 degrees, 13.1 degrees, 16.3 degrees, 21.0 degrees, 26.3 degrees and 31.0 degrees, the characteristic diffraction peaks respectively correspond to (101), (110), (021), (211), (220) and (214) crystal faces (PDF#47-0429) of the SAPO-34, and other impurity peaks are not found in the figures, so that the synthesized SAPO-34 and Ni-SAPO-34 are both pure phases. The characteristic diffraction peak intensity of Ni-SAPO-34 is enhanced compared with that of the SAPO-34 molecular sieve, which shows that the addition of Ni can promote the growth of the SAPO-34 molecular sieve crystal.

FIG. 2 is an SEM and TEM image of SAPO-34 molecular sieves and Ni-SAPO-34 composites. In the SEM image of SAPO-34 of FIG. 2 (A), the morphology of SAPO-34 is in a tetragonal structure, and the particle size is about 1-2 μm. However, as shown in the SEM images of Ni-SAPO-34 shown in FIGS. 2 (B) and 2 (C), the morphology of SAPO-34 is significantly changed after Ni is introduced, wherein the morphology of part of crystals is changed into loose ellipsoids formed by aggregation of nano-sized small grains. FIGS. 2 (D) and 2 (E) are TEM images of Ni-SAPO-34, and black spots are observed in the molecular sieve, which is proved to contain nickel oxide. In addition, the simultaneous presence of micropores and mesopores can also be observed from the Ni-SAPO-34 TEM map of FIG. 2 (F) with a smaller field of view.

N from the SAPO-34 molecular sieve and Ni-SAPO-34 composite of FIG. 3 ₂ The adsorption-desorption curves and pore size distribution diagrams can show that the SAPO-34 and the Ni-SAPO-34 belong to IV type adsorption curves. When the relative pressure of the curve is low, the adsorption capacity of the molecular sieve is rapidly increased, which indicates that more micropores exist in the molecular sieve; when P/P ₀ =0.2, the adsorption amount shows a gentle trend, and as the relative pressure continues to increase, a larger hysteresis loop appears on the Ni-SAPO-34 curve, which indicates that the Ni-SAPO-34 curve has a micro-mesoporous multi-stage pore structure, and is consistent with the result observed by a transmission electron microscope.

As can be seen from the interpolated pore size distribution plot of FIG. 3, the pore sizes of both SAPO-34 and Ni-SAPO-34 are centered around 3.5 nm. The specific surface area, pore volume and pore diameter of the catalyst are important parameters of the catalytic activity of the reaction. The larger the specific surface area of the catalyst and Kong Rongyue, the more advantageous is the dispersion of the active components, the exposure of the active sites and the rapid diffusion of the reactive species. Among the pore structure parameters of Table 1, ni-SAPO-34 has a larger total specific surface area and a microporous surface area, the large specific surface area being H ⁺ The reaction of the catalyst provides more active sites, and the large total pore volume and mesoporous pore volume are favorable for rapid diffusion of reaction species and are more favorable for catalyzing hydrogen evolution reaction.

The surface element composition and valence state of the composite material have direct influence on the electrocatalytic performance of the composite material, so XPS is utilized to analyze the valence state and existence state of Ni and O elements in the Ni-SAPO-34 composite material, and the Ni-SAPO-34 composite material has the same effect as Ni (NO ₃ ) ₂ ·6H ₂ The pure NiO obtained by O calcination was compared.

FIG. 4 (A) shows Ni 2p XPS spectra of Ni-SAPO-34 and NiO, with peaks at 856.8eV and 862.54eV respectively attributed to Ni ³⁺ And Ni ²⁺ . Ni in Ni-SAPO-34 compared with NiO ³⁺ The characteristic peak area of (2) is obviously increased, and the characteristic peak area is shifted to a high binding energy direction by 1.2eV, which indicates that nickel in Ni-SAPO-34 exists mainly in trivalent state and has electronic interaction with phosphorus species in a molecular sieve framework.

FIG. 4 (B) is an O1 s XPS spectrum of Ni-SAPO-34 and NiO, with peaks of binding energy 530.4eV and 532.4eV respectively assigned to lattice oxygen and surface oxygen. Compared with NiO, the peak area of surface oxygen in Ni-SAPO-34 is obviously increased, which indicates that the number of oxygen vacancies is increased, and the existence of a large number of oxygen vacancies accelerates the conversion and migration of active substances, thereby being beneficial to the electrocatalytic hydrogen evolution reaction.

4mg of the Ni-SAPO-34 composite material prepared above was weighed, and 0.5mL of absolute ethyl alcohol and 10. Mu.L of 2wt% Nafion solution were added thereto, followed by ultrasonic treatment for 0.5h, thereby forming a uniform suspension.

Cutting carbon paper into 1cm×1cm size, sequentially using 0.5mol/L H ₂ SO ₄ The solution and 0.5mol/L NaOH solution are soaked for 2 hours respectively, and impurities on the surface of the carbon paper are removed. Then soaking for 5 hours by using distilled water, removing acid and alkali on the surface of the carbon paper, and airing for standby.

Sucking the suspension by a pipetting gun, uniformly dripping the suspension on two sides of the treated carbon paper, and naturally drying at room temperature to obtain the Ni-SAPO-34 composite material with the loading capacity of 2mg/cm ² Is provided.

The electrochemical properties of the composite material have a significant impact on its hydrogen-generating activity in MEC. At room temperature, a three-electrode system is adopted, an Ag/AgCl electrode is used as a reference electrode, a platinum net is used as a counter electrode, a cathode electrode loaded with the Ni-SAPO-34 composite material is used as a working electrode, and linear scanning and Tafel test analysis are carried out on the cathode electrode through a CHI660E electrochemical workstation of Cinnamomum, so that the electrochemical performance of the Ni-SAPO-34 composite material is inspected.

Linear voltammetric sweep curves (LSVs) are used to analyze the overpotential of a cathode material by analyzing the change between measured current and potential. LSV linear scanning range-1.5-0V, scanning speed 10mV/s; the scanning range of the Tafil curve is-1.2-0V, and the scanning speed is 2mV/s.

Meanwhile, blank Carbon Paper (CP) and Pt/C were used as cathode electrodes, respectively, and their electrochemical properties were tested under the same conditions for comparison.

FIG. 5 shows a linear scan of Ni-SAPO-34 composite, CP, and Pt/C electrodes. In the graph, the current density of the cathode of the Ni-SAPO-34 composite material can reach 8.44mA/cm under the overpotential of 0.89V ² The current density is far higher than that of the CP cathode by-5.89 mA/cm ² -8.76mA/cm substantially close to Pt/C electrode ² The Ni-SAPO-34 composite electrode has higher hydrogen evolution catalytic capability.

The tafel slope is an important parameter for the kinetics of the electrocatalytic hydrogen evolution reaction. The difficulty of one electrode reaction can be measured by fitting the linear region of the polarization curve to obtain the equilibrium potential and the exchange current density. Wherein, the reaction is easier to occur when the equilibrium potential is smaller, the reaction is easier to occur when the exchange current density is larger, and the hydrogen evolution reaction rate is faster.

FIG. 6 shows the Taphillips slope of three cathode electrodes, ni-SAPO-34 composite, CP and Pt/C. As can be seen from the graph, the Taphil slopes of the Ni-SAPO-34 composite electrode and the Pt/C electrode are close to each other, are 53.84mV/dec and 47.31mV/dec respectively, and are far lower than 132.51mV/dec of the CP electrode, which shows that the hydrogen evolution catalytic activity of the Ni-SAPO-34 composite electrode is similar to that of the Pt/C electrode, and a conclusion consistent with the linear scanning result is obtained.

Example 2.

Preparation of Ni-SAPO-34 composite Material with a loading of 1mg/cm according to the method of example 1 ² Is provided.

Example 3.

Preparation of Ni-SAPO-34 composite Material with a loading of 4mg/cm according to the method of example 1 ² Is provided.

Example 4.

5mL of deionized water, 4.53g of phosphoric acid and 2.90g of pseudo-boehmite are sequentially added into a polytetrafluoroethylene lining, and stirred at room temperature for 2 hours, 22.76g of tetraethylammonium hydroxide (TEAOH) is added, stirred for 2 hours, 1.30g of white carbon black is added, stirred for 1 hour, and 0.30g of Ni (NO) ₃ ) ₂ ·6H ₂ O, stirring for 1h, sealing in a stainless steel reaction kettle, and carrying out static crystallization reaction at 200 ℃ for 24h. Taking out, cooling, filtering with distilled water, washing to neutrality, oven drying at 80deg.C, grinding, and calcining at 550deg.C in a muffle furnace for 6 hr to obtain Ni-SAPO-34 composite material.

According to the method of example 1, the Ni-SAPO-34 composite material prepared by the method is used for preparing the Ni-SAPO-34 composite material with the loading capacity of 2mg/cm ² Is provided.

Example 5.

5mL of deionized water, 4.53g of phosphoric acid and 2.90g of pseudo-boehmite were sequentially added into a polytetrafluoroethylene lining, and stirred at room temperature for 2h, adding 22.76g tetraethylammonium hydroxide (TEAOH), stirring for 2h, adding 1.30g white carbon black, stirring for 1h, and adding 1.20g Ni (NO) ₃ ) ₂ ·6H ₂ O, stirring for 1h, sealing in a stainless steel reaction kettle, and carrying out static crystallization reaction at 200 ℃ for 24h. Taking out, cooling, filtering with distilled water, washing to neutrality, oven drying at 80deg.C, grinding, and calcining at 550deg.C in a muffle furnace for 6 hr to obtain Ni-SAPO-34 composite material.

According to the method of example 1, the Ni-SAPO-34 composite material prepared by the method is used for preparing the Ni-SAPO-34 composite material with the loading capacity of 2mg/cm ² Is provided.

Application example 1.

In order to examine the hydrogen evolution catalytic activity of the cathode electrode, the electrode loaded with the Ni-SAPO-34 composite material prepared in each example was used as a hydrogen evolution cathode electrode to run in a MEC device for treating coking wastewater and catalyzing hydrogen production.

The MEC device adopts a 100mL single-chamber reactor, and 20mL activated bacterial sludge and 80mL nutrient solution are added. Wherein the activated sludge is obtained from a coking wastewater treatment plant, and the nutrient solution consists of a substrate (1 g/L glucose), a phosphate buffer solution with a pH value of 7 and trace element solutions containing trace elements such as calcium, magnesium, manganese and the like.

And (3) carrying out hydrogen production test by taking the carbon felt attached with the domesticated electrogenerated bacteria as an anode, ag/AgCl as a reference electrode and taking the electrode loaded with the Ni-SAPO-34 composite material as a cathode.

Meanwhile, blank Carbon Paper (CP) and Pt/C are respectively used as hydrogen evolution cathodes, and the hydrogen evolution performance of the hydrogen evolution cathodes is tested and compared under the same conditions.

MEC is operated under the conditions of 0.7V of external voltage and 30 ℃, the hydrogen production current is monitored by using a universal meter, and the gas production rate is recorded every 0.5 h. The gas generated by the device is collected by a drainage and gas collection method, and the composition of the gas is detected by a gas chromatograph.

The hydrogen evolution properties of the Ni-SAPO-34 composite electrodes prepared in the examples are shown in Table 2.

FIG. 7 provides a graph of gas yield and gas composition of the Ni-SAPO-34 composite prepared in example 1, and of the Pt/C and CP cathode materials at each cycle of the MEC.

In each operation period, the gas yield of the cathode MEC of the Ni-SAPO-34 composite material is 12.8+/-0.84 mL, the gas yield of the cathode MEC of the Pt/C composite material is 14.1+/-0.67 mL, and the gas yield of the cathode MEC of the Pt/C composite material is close to and is far higher than 6.7+/-0.31 mL of the gas yield of the cathode MEC of the CP composite material.

Further analyzing the gas components to find H in the total gas production amount of the Ni-SAPO-34 composite electrode ₂ The content of the catalyst is 69.13 percent, and the catalyst is H in Pt/C ₂ The content of 72.66% also shows high hydrogen selectivity. In addition, the methane selectivity (14.45%) of the Ni-SAPO-34 composite is also close to and lower than the methane selectivity (14.59%) of Pt/C.

The results show that the Ni-SAPO-34 composite material has high electrocatalytic activity when used as a cathode of a Microbial Electrolytic Cell (MEC).

The above embodiments of the invention are not intended to be exhaustive or to limit the invention to the precise forms disclosed. Various changes, modifications, substitutions and alterations may be made by those skilled in the art without departing from the principles and spirit of the invention, and it is intended that the invention encompass all such changes, modifications and alterations as fall within the scope of the invention.

Claims (6)

1. Application of Ni-SAPO-34 composite material in preparing MEC hydrogen evolution cathode electrode, wherein the MEC hydrogen evolution cathode electrode is prepared by adding the Ni-SAPO-34 composite material into absolute ethyl alcohol containing Nafion solution to form suspension, dripping the suspension on carbon paper, and drying to form Ni-SAPO-34 with a load of 1-5 mg/cm ² Wherein:

the Ni-SAPO-34 composite material is prepared according to a fixed molar ratio n (Al ₂ O ₃ )∶n(SiO ₂ )∶n(P ₂ O ₅ ) N is the template agent and n is the H ₂ O) =1:0.7-1.3:0.8-1.2:1.8-2.3:50-90, adding aluminum source, silicon source, phosphorus source and template agent into deionized water, mixing uniformly, then adding nickel precursor according to the mole ratio of n (Si) to n (Ni) =5-40:1The solid nickel nitrate is subjected to static hydrothermal crystallization reaction for 12-72 h at 150-230 ℃ in a sealing state, and the reaction product is baked for 6-24 h at 450-600 ℃ to obtain the product.

2. The use according to claim 1, wherein the template is diethylamine, triethylamine, tetramethylammonium hydroxide, tetraethylammonium hydroxide or tetrapropylammonium hydroxide.

3. The use according to claim 1 or 2, characterized in that the templating agent is tetraethylammonium hydroxide.

4. Use according to claim 1, characterized in that the aluminium source is pseudo-boehmite, sodium metaaluminate, aluminium sulphate or aluminium isopropoxide, the silicon source is white carbon black, silica sol or ethyl orthosilicate, and the phosphorus source is phosphoric acid, phosphorous acid, polyphosphoric acid or a phosphate.

5. Use according to claim 1, characterized in that the molar ratio n (Si) to n (Ni) is 10:1.

6. The use according to claim 1, characterized in that the concentration of the Nafion solution is 2wt%.