阅读说明：本技术 一种用于电催化产氢的中空氧化物/磷化物碳包覆复合材料的合成方法及应用 (Synthesis method and application of hollow oxide/phosphide carbon-coated composite material for electrocatalytic hydrogen production ) 是由 张彪 何春年 赵乃勤 师春生 刘恩佐 于 2019-09-12 设计创作，主要内容包括：本发明属于电催化技术领域,公开一种用于电催化产氢的中空氧化物/磷化物碳包覆复合材料的合成方法,主要步骤包括:合成纳米二氧化硅颗粒；合成中空纳米二氧化铈；合成H-CeO<Sub>2</Sub>/Ni@NC；合成目标产物H-CeO<Sub>2</Sub>/Ni@NC。本发明利用过渡金属氧化物对过渡金属进行调控,实现了快速的水分子解离以及氢气脱出反应,实现了高效催化水解产氢反应。中空二氧化铈纳米球是由八面体亚纳米二氧化铈颗粒组成,所以具有多孔的特性即使得电解液和气体传输更加快速；中空结构可以暴露更大的比表面积使得活性位点的利用率得到提升。(The invention belongs to the technical field of electrocatalysis, and discloses hollow oxygen for electrocatalysis hydrogen productionThe synthesis process of composite material with carbide/phosphide as main material includes the main steps of synthesizing nanometer silica particle; synthesizing hollow nano cerium dioxide; synthesis of H-CeO 2 /Ni @ NC; synthesis of target product H-CeO 2 /Ni @ NC. The invention utilizes the transition metal oxide to regulate and control the transition metal, realizes rapid dissociation of water molecules and hydrogen removal reaction, and realizes high-efficiency catalytic hydrolysis hydrogen production reaction. The hollow cerium dioxide nanospheres are composed of octahedral sub-nano cerium dioxide particles, so that the hollow cerium dioxide nanospheres have the characteristic of being porous, namely electrolyte and gas are transported more rapidly; the hollow structure can expose larger specific surface area, so that the utilization rate of active sites is improved.)

1. A synthetic method of a hollow oxide/phosphide carbon-coated composite material for electrocatalytic hydrogen production is characterized by comprising the following steps:

(1) synthesizing nano-silica particles: 4mL of tetraethyl silicate (25%) was added rapidly to a mixed solution of 60mL of ethanol and 25mL of deionized water with moderate stirring. Stirring the mixed solution for one hour at room temperature, centrifuging, washing with water and ethanol for three times, and finally evaporating to dryness under the vacuum condition at 60 ℃;

(2) synthesizing hollow nano cerium dioxide: 0.15g of silicon dioxide powder was dispersed in a solution of ethanol/deionized water (40mL/20mL) and sonicated for half an hour to form a homogeneous suspension;

then 3.5g of cerous nitrate hexahydrate and 0.5g of urea are sequentially added into the solution and stirred for 30 minutes, and finally uniform white solution is formed;

transferring the solution to a 100mL high-temperature-resistant stainless steel reaction kettle, and sealing;

placing the hydrothermal kettle in a hydrothermal box at 160 ℃ for heat preservation for 8 hours, and naturally cooling to room temperature to obtain a product;

washing with water for three times, and evaporating to dryness at 50 ℃;

finally, putting the obtained white powder into 1MKOH solution, keeping the temperature at 50 ℃ for 12 hours, washing and drying to obtain hollow cerium dioxide nanospheres;

(3) synthesis of H-CeO₂/Ni @ NC: firstly, 0.15g of hollow cerium dioxide is dispersed into an ethanol/deionized water (30/30mL) solution, ultrasonic treatment is carried out for 0.5 hour, and then 1mL of ammonia water (25%) is injected and stirred;

after ten minutes, sequentially adding 0.8g of nickel nitrate hexahydrate and 0.25g of dopamine hydrochloride powder, stirring the mixed solution at room temperature for 6 hours, centrifugally washing for three times, and drying at 60 ℃ in vacuum;

then the obtained brown black powder is subjected to heat preservation for 2 hours in argon atmosphere at the temperature of 750 ℃, and finally a precursor H-CeO is obtained₂(ii)/Ni @ NC powder.

(4) Synthesis of target product H-CeO₂/[email protected]：H-CeO₂Respectively placing 0.1g of/Ni @ NC powder and 0.1g of sodium hypophosphite in a square boat, wherein the sodium hypophosphite is placed at the upstream of the tube furnace, then preserving the heat at 300 ℃ for 2H, and naturally cooling to room temperature to obtain a target product H-CeO₂a/Ni @ NC black powder.

2. Use of the synthesis method according to claim 1 to obtain a hollow oxide/phosphide carbon-coated composite material for electrocatalytic hydrogen production, characterized in that the H-CeO₂/Ni₂P @ NC is applied to HER electrocatalyst.

Technical Field

The invention belongs to the technical field of electrocatalysis, and particularly relates to synthesis of a ternary heterostructure catalyst material with a carbon nano-layer coated hollow cerium dioxide nano-sphere surface loaded with nickel phosphide nano-particles and application of the ternary heterostructure catalyst material in hydrolysis hydrogen production.

Background

The hydrogen is an energy carrier with high energy density and clean combustion without pollution, and the electrocatalytic hydrolysis is a mode capable of producing hydrogen in a large scale and sustainable manner. However, the main reason for hindering the large-scale application of the electrocatalytic hydrolysis hydrogen production is that the commercial electrocatalysts are expensive, low in catalytic activity and not satisfactory in stability to meet industrial requirements, which severely restricts the development of the water electrolysis hydrogen production technology, so that the development of materials with low cost, low synthesis method threshold, high activity and high stability is urgently needed to solve the above-mentioned problems.

Transition metals and their compounds are important candidates because of their abundant earth reserves and low prices. Among many transition metal compounds, transition metal phosphide has shown its potential application value, and has been extensively studied since the fact that phosphide was discovered in 2005 to have catalytic activity similar to noble metals. Although many years of research have shown that the HER catalytic activity of transition metal phosphides for acidic conditions is greatly improved, the catalytic activity under alkaline conditions is still poor, in contrast to the more mature commercial electrolytic cell development under alkaline conditions and the higher catalytic activity exhibited by the other half reaction (OER) under alkaline conditions. Thus, alkaline conditions were controlledThe catalytic activity of medium transition metal phosphides is very valuable but challenging. Nickel (Ni) phosphide₂P) as one of the transition metal phosphorus group compounds, attention of a wide range of researchers has recently been paid, and the catalytic activity under acidic conditions has platinum-like catalytic activity thanks to its excellent electrical conductivity and suitable hydrogen proton adsorption energy. However, due to the slow water molecule splitting capacity (volmerstein), the catalytic activity under alkaline conditions is 2-3 times smaller than that under acidic conditions, so how to accelerate the hydrogen proton supply rate of water molecules under alkaline conditions is very critical. In addition, the structural design of the catalyst is also very important, and the porous hollow structure can shorten the space transmission distance of the electrolyte to enable the electrolyte to be rapidly transmitted to active sites and expose more specific surface area to enable the utilization rate of the active sites to be more efficient.

Based on the above analysis, we designed a universal method to load nickel phosphide nanoparticles on the surface of hollow ceria, wherein the porous hollow ceria not only provides nucleation sites and large specific surface area, but also can effectively capture water molecules and activate them to generate hydrogen protons required for the next reaction. The nickel phosphide nano-particles are uniformly dispersed on the surface of the cerium dioxide nanospheres and form a heterojunction with the cerium dioxide. Due to the strong interaction influence of the heterojunction, the electronic structure of the nickel phosphide is changed, and then the adsorption strength of the nickel phosphide on hydrogen protons is regulated and controlled, so that the nickel phosphide is easier to desorb from the surface of the catalyst to generate hydrogen. The carbon nano-layer coating structure can inhibit the falling off or the partial aggregation growth of the catalyst, and can also accelerate the transmission of electrons to active sites, thereby improving the conductivity of the catalyst.

Therefore, the invention firstly uses silicon dioxide as a hard template to prepare hollow porous cerium dioxide nanospheres (H-CeO) by a hydrothermal method₂) Then coating a poly-dopamine chelated nickel ion layer (H-CeO) on the surface of the nanosphere₂～Ni²⁺@ PDA), then high temperature CVD calcining is carried out to obtain a hollow cerium dioxide surface loaded elemental nickel particle externally coated nitrogen-doped carbon layer (H-CeO)₂/Ni @ NC), and finally carrying out phosphating treatment to obtain a target product H-CeO₂/Ni₂P @ NC. Through electrochemical test, H-CeO₂/Ni₂The HER activity of P @ NC under alkaline condition is greatly improved, and the current density of 10mA cm in 1M KOH electrolyte is calculated based on the geometric area of a glassy carbon electrode^-2The HER over-potential is only 123mV, and the Tafel slope is reduced to 60mV dec^-1。

Disclosure of Invention

The invention aims to synthesize H-CeO by a universal hydrothermal and CVD method₂/Ni₂The P @ NC heterostructure realizes efficient hydrolysis hydrogen production reaction under alkaline conditions.

The technical scheme of the invention is realized by the following steps:

(1) synthesizing nano-silica particles: 4mL of tetraethyl silicate (25%) was added rapidly to a mixed solution of 60mL of ethanol and 25mL of deionized water with moderate stirring. The mixed solution was stirred at room temperature for one hour, centrifuged, washed three times with water and ethanol, and finally evaporated to dryness in vacuo at 60 ℃.

(2) Synthesizing hollow nano cerium dioxide: 0.15g of silica powder was dispersed in a solution of ethanol/deionized water (40mL/20mL) and sonicated for half an hour to form a uniform suspension. Then 3.5g of cerium nitrate hexahydrate and 0.5g of urea were added to the above solution in this order and stirred for 30 minutes to finally form a uniform white solution. The solution was transferred to a 100mL high temperature resistant stainless steel autoclave and sealed. And (3) placing the hydrothermal kettle in a hydrothermal box at 160 ℃ for heat preservation for 8 hours, and naturally cooling to room temperature to obtain a product. Washed with water three times and evaporated to dryness at 50 ℃. And finally, putting the obtained white powder into 1MKOH solution, keeping the temperature at 50 ℃ for 12 hours, washing and drying to obtain the hollow cerium dioxide nanosphere.

(3) Synthesis of H-CeO₂/Ni @ NC: first, 0.15g of hollow ceria was dispersed in an ethanol/deionized water (30/30mL) solution, sonicated for 0.5 hour, and then 1mL of ammonia (25%) was injected and stirred. After ten minutes, 0.8g of nickel nitrate hexahydrate and 0.25g of dopamine hydrochloride powder were sequentially added, and the mixed solution was stirred at room temperature for 6 hours, then centrifuged and washed three times, and dried at 60 ℃ under vacuum. Then the obtained brown black powder is kept warm for 2 hours at 750 ℃ in argon atmosphere to finally obtainTo precursor H-CeO₂(ii)/Ni @ NC powder.

(4) Synthesis of target product H-CeO₂/[email protected]：H-CeO₂Respectively placing 0.1g of/Ni @ NC powder and 0.1g of sodium hypophosphite in a square boat, wherein the sodium hypophosphite is placed at the upstream of the tube furnace, then preserving the heat at 300 ℃ for 2H, and naturally cooling to room temperature to obtain a target product H-CeO₂a/Ni @ NC black powder.

The H-CeO₂/Ni₂P @ NC is applied to HER electrocatalyst.

Compared with the prior art, the invention has the advantages that:

(1) the hollow cerium dioxide surface-loaded nickel phosphide nanoparticles synthesized by the silica hard template method can be popularized to other transition metal phosphide such as cobalt phosphide, copper phosphide and the like, and have good universality.

(2) The invention utilizes the transition metal oxide to regulate and control the transition metal, realizes rapid dissociation of water molecules and hydrogen removal reaction, and realizes high-efficiency catalytic hydrolysis hydrogen production reaction.

(3) The hollow cerium dioxide nanospheres are composed of octahedral sub-nano cerium dioxide particles, so that the hollow cerium dioxide nanospheres have the characteristic of being porous, namely, electrolyte and gas transmission is faster; the hollow structure can expose larger specific surface area, so that the utilization rate of the active sites is improved; the carbon coating layer structure can effectively inhibit the segregation growth and the falling deactivation of the active substances on one hand, and can be used as an electron transport carrier to accelerate the electron transport to the active sites on the other hand.

Drawings

FIG. 1 is an SEM photograph of the hollow cerium oxide obtained in example 1 of the present invention. From the figure, spherical morphology and surface prominence are evident, and further amplification can find the configuration composed of sub-nanoparticles with octahedral structure.

FIG. 2 shows H-CeO obtained in example 1 of the present invention₂SEM photograph of/Ni @ NC. From the figure, it is apparent that the nano hollow ceria surface supports many nano metallic nickel particles.

FIG. 3 shows H-CeO obtained in example 1 of the present invention₂/Ni₂TEM image of P @ NC. The carbon-coated hollow structure is evident from the figure.

FIG. 4 shows H-CeO obtained in example 1 of the present invention₂/Ni₂LSV curve measured in alkaline electrolyte of P @ NC, normalized by electrochemical surface area (ECSA). The excellent intrinsic electrocatalytic activity of the electrocatalyst is evident from the figure.

Detailed Description

Specific examples of the preparation process according to the invention are given below, the only variable in these cases being the amount of nickel nitrate added, the rest remaining unchanged. These examples are only intended to illustrate the preparation process of the present invention in detail and do not limit the scope of protection of the claims of the present application. Nothing in this specification is said to apply to the prior art.