CN110444772A - A kind of bimetallic base Fe-Co-N-S codope C catalyst and the preparation method and application thereof - Google Patents

Abstract

The invention discloses a preparation method of a bimetallic-based Fe-Co-N-S co-doped carbon catalyst, which is characterized in that it comprises the following steps: 1) adding 40 mg of ZIF-67 to a container containing 20 mL of ethanol , after ultrasonic dispersion was uniform, 2 mL of FeTsPc aqueous solution was quickly added, and the mass ratio of ZIF‑67/FeTsPc was controlled to be 1/0.25‑2, magnetically stirred for 24 h and then centrifuged to dry to obtain FeTsPc/ZIF‑67 composite material; 2) Weigh Take 120 mg of the composite material sample obtained in step 1), place it in a quartz tube furnace and heat-treat at 500‑1000 °C for 3 h in an Ar atmosphere to obtain a bimetallic Fe‑Co‑N‑S co-doped carbon catalyst, namely Fe ‑Co‑N‑S‑C. This method has simple process, mild and controllable operating conditions, and the obtained material has excellent electrochemical performance and low cost, and has good application prospects.

Description

A kind of bimetallic base Fe-Co-N-S co-doped carbon catalyst and its preparation method and application

technical field

The invention relates to the field of electrocatalysis and fuel cells, in particular to the preparation of a novel bimetallic-based Fe-Co-N-S co-doped carbon catalyst and its application in fuel cell cathode oxygen reduction reactions, especially a bimetallic Fe-Co-N-S co-doped carbon catalyst and its preparation method and application.

Background technique

As an environmentally friendly and efficient technology, fuel cells can be applied as electrochemical energy conversion devices for various transportation and portable electronic devices. However, the slow kinetics of the cathode oxygen reduction reaction, or ORR, severely hinders the development of fuel cell technology. To date, noble metal-based materials such as Pt, Pd, or Ir have been considered as the most efficient ORR electrocatalysts. However, the disadvantages of such materials, such as high cost, scarcity of raw materials, and poor stability, greatly limit the large-scale commercial application of fuel cells. Therefore, it is crucial to develop cost-effective and high-performance metal-free ORR electrocatalysts.

Currently, the non-noble metal ORR electrocatalyst that has received the most attention is the transition metal-doped MNC (M = Fe, Co) system, which can exhibit performance comparable to that of Pt-based catalysts through rational design and construction of its active site structure. Recent studies have found that the structure of the precursor used to prepare MNC-type catalysts is closely related to its ORR performance. Metal-organic frameworks (MOFs), a novel porous material composed of metals and organic ligands, are ideal precursors for the preparation of MNC-type ORR catalysts. In order to improve the ORR activity of porous carbon catalysts derived from metal-organic frameworks (MOFs), the introduction of external secondary heteroatom sources on the basis of metal-organic frameworks (MOFs) has attracted widespread interest. The introduced external secondary heteroatoms include N, P and Non-metal heteroatoms such as S and metal heteroatoms such as Fe and Co mainly involve the following documents: (1) "Applied Catalysis B" in 2019 reported ZIF doped with tris-1,10-phenanthroline nickel nitrate -67 Co/Ni/N triple-doped carbon catalyst performance research on oxygen reduction reaction under acidic and basic conditions; (2) In 2019, ACSSustainable Chemistry & Engineering reported the electrospinning Co-Fe Prussian Nitrogen-doped carbon nanofiber-coated Fe-Co alloy nanoparticle composites prepared by adding blue analogues to polyacrylonitrile fibers and further heat treatment and their electrocatalytic performance for oxygen reduction reaction in alkaline media; (3 ) "Journal of the Electrochemical Society" in 2018 reported the Fe/Co/P co-doped porous carbon catalyst prepared with FeCl ₃ , CoCl ₂ and phytic acid as precursors and its oxygen reduction reaction in alkaline media Electrocatalytic performance; (4) "ACS Applied Materials &Interfaces" in 2017 reported Fe/Ni/P co-doped reduction using metalloporphyrin-based MOFs, PCN-600-Ni and graphene oxide as precursors and templates Graphene oxide catalysts and their electrocatalytic performance for oxygen evolution reactions. However, it has been reported that using sulfonated iron phthalocyanine (FeTsPc) as a foreign heteroatom source, introducing Fe and S simultaneously on the basis of ZIF-67 to design and synthesize Fe, Co, N, and S co-doped carbon composite catalysts and their There are no literature and patent reports on the application of electrocatalytic oxygen reduction reaction.

purpose of invention

The object of the present invention is to provide a bimetallic-based Fe-Co-N-S co-doped carbon catalyst and its preparation method and application in view of the deficiencies of the prior art. This method has simple process, mild and controllable operating conditions, and the obtained material has excellent electrochemical performance and low cost, and has good application prospects.

The technical scheme that realizes the object of the present invention is:

A method for preparing a bimetallic-based Fe-Co-N-S co-doped carbon catalyst, which is different from the prior art, comprises the following steps:

1) Add 40 mg ZIF-67 into a container containing 20 mL of ethanol, and after ultrasonic dispersion, quickly add 2 mL of FeTsPc aqueous solution, control the mass ratio of ZIF-67/FeTsPc to 1/0.25-2, and magnetically stir for 24 h After centrifugal drying, FeTsPc/ZIF-67 composite material is obtained;

2) Weigh 120 mg of the composite material sample obtained in step 1), and place it in a quartz tube furnace for heat treatment at 500-1000 °C for 3 h in an Ar atmosphere to obtain a bimetallic Fe-Co-N-S co-doped carbon catalyst that is Fe-Co-N-S-C.

The bimetallic Fe-Co-N-S co-doped carbon catalyst prepared by the above preparation method is Fe-Co-N-S-C.

Application of the bimetallic-based Fe-Co-N-S co-doped carbon catalyst, ie, Fe-Co-N-S-C prepared by the above preparation method, in the fuel cell cathode oxygen reduction reaction.

In the M-N-C (M = Fe, Co) catalyst system, by rationally designing and constructing its active site structure, it can exhibit performance comparable to that of Pt-based catalysts, and the structure of the precursor is very critical to the ORR performance of the prepared catalyst.

In this technical solution, ZIF-67 and sulfonated iron phthalocyanine (FeTsPc) are used as heteroatom precursors, and a bimetallic Fe-Co-N-S co-doped carbon catalyst is prepared by a simple heat treatment method, and the addition of FeTsPc significantly improves The thermal stability of MOFs is improved, the dispersion and uniformity of each component in the prepared catalyst are good, and there is a strong electron transfer interaction between each dopant atom, which greatly enhances the electrocatalysis of the catalyst for the oxygen reduction reaction. active. In addition, the Fe-Co-N-S co-doped carbon catalyst also exhibits better electrochemical stability and methanol resistance than commercial Pt/C.

This method has simple process, mild and controllable operating conditions, and the obtained material has excellent electrochemical performance and low cost, and has good application prospects.

Description of drawings

Fig. 1 is the schematic flow sheet that prepares Fe-Co-N-S co-doped carbon catalyst in the embodiment;

Fig. 2 is the SEM figure of the Fe-Co-N-S co-doped carbon catalyst prepared in the embodiment;

Fig. 3 is the TEM figure of the Fe-Co-N-S co-doped carbon catalyst prepared in the embodiment;

Fig. 4 is the Co-NC prepared in the embodiment, Fe-Co-NC, Fe-Co-NSC and commercial Pt/C catalyst in O Saturated 0.1 M _KOH solution linear sweep voltammetry curve;

Figure 5 is a chronoamperometry curve of the Fe-Co-NSC and commercial Pt/C catalysts prepared in Example for the methanol resistance test in _O2 -saturated 0.1 M KOH solution at 0.3 V _RHE .

Detailed ways

The content of the present invention will be further described below in conjunction with the accompanying drawings and embodiments, but the present invention is not limited.

Example:

Referring to Fig. 1, a kind of preparation method of bimetallic base Fe-Co-N-S co-doped carbon catalyst comprises the steps:

1) Add 40 mg ZIF-67 into a container containing 20 mL of ethanol, and after ultrasonic dispersion, quickly add 2 mL of FeTsPc aqueous solution, control the mass ratio of ZIF-67/FeTsPc to 1/0.25-2, and magnetically stir for 24 h After centrifugal drying, FeTsPc/ZIF-67 composite material is obtained;

2) Weigh 120 mg of the composite material sample obtained in step 1), and place it in a quartz tube furnace for heat treatment at 500-1000 °C for 3 h in an Ar atmosphere to obtain a bimetallic Fe-Co-N-S co-doped carbon catalyst that is Fe-Co-N-S-C.

The bimetallic Fe-Co-N-S co-doped carbon catalyst prepared by the above preparation method is Fe-Co-N-S-C.

Application of the bimetallic-based Fe-Co-N-S co-doped carbon catalyst, ie, Fe-Co-N-S-C prepared by the above preparation method, in the fuel cell cathode oxygen reduction reaction.

According to SEM and TEM analysis, the structure of MOFs in this case did not show obvious damage and agglomeration after heat treatment, indicating that the addition of FeTsPc improved the thermal stability of MOFs, and the dispersion and uniformity of the components in the prepared catalyst were good. , uniformly distributed black particles can also be observed on the surface of the bimetallic-based Fe-Co-N-S co-doped carbon catalyst prepared by the preparation method of this example. STEM results show that they are mainly metal Co and Co oxides, with a particle size of about 25 nm or so, as shown in Figure 2 and Figure 3.

XPS analysis pointed out that the N 1s and Co 2p peak positions of Fe-Co-N-S-C in the double metal-based Fe-Co-N-S co-doped carbon catalyst prepared by the preparation method of this example were negatively shifted respectively compared with the corresponding values of Co-N-C 0.2 eV and a positive shift of 1.1 eV, indicating that there is a strong electron transfer interaction between dopant atoms in the Fe-Co-N-S-C catalyst, which is beneficial to enhance the electrocatalytic performance of this catalyst for oxygen reduction reaction.

The bimetallic-based Fe-Co-N-S co-doped carbon, Fe-Co-N-C, Co-N-C and commercial Pt/C catalysts prepared by the preparation method in this example were compared to oxygen in alkaline medium by linear sweep voltammetry. Electrocatalytic properties for reduction reactions. The results show that the limiting current density of the bimetallic-based Fe-Co-N-S co-doped carbon catalyst prepared by the preparation method in this example is 6.46 mA cm-2 for the oxygen reduction reaction, which is significantly higher than the 5.39 mA of Fe-Co-N-C cm-2, 5.25 mA cm-2 of Co-N-C and 5.32 mA cm-2 of commercial Pt/C catalyst. In addition, half of the bimetallic Fe-Co-N-S co-doped carbon catalyst prepared by this example The wave potential is 0.856 V, which is almost comparable to the half-wave potential of 0.866 V of the commercial Pt/C catalyst. These results indicate that the bimetallic-based Fe-Co-N-S co-doped carbon catalyst prepared by the preparation method in this example exhibits excellent electrocatalytic activity for the oxygen reduction reaction in alkaline media, as shown in Figure 4.

The methanol resistance performance was compared by chronoamperometry. As shown in Figure 5, the current density of the commercial Pt/C catalyst dropped sharply after the rapid addition of 2 M methanol solution at about 250 s, while the bimetallic catalyst prepared by the preparation method in this example The current density of the Fe-Co-N-S co-doped carbon catalyst based on Fe-Co-N-S did not change significantly, indicating that the bimetallic Fe-Co-N-S co-doped carbon catalyst prepared by the preparation method in this example has excellent methanol resistance.

Claims (3)

1. a kind of preparation method of bimetallic base Fe-Co-N-S co-doped carbon catalyst is characterized in that, comprises the steps: 1) Add 40 mg ZIF-67 into a container containing 20 mL of ethanol, and after ultrasonic dispersion, quickly add 2 mL of FeTsPc aqueous solution, control the mass ratio of ZIF-67/FeTsPc to 1/0.25-2, and magnetically stir for 24 h After centrifugal drying, FeTsPc/ZIF-67 composite material is obtained; 2) Weigh 120 mg of the composite material sample obtained in step 1), and place it in a quartz tube furnace for heat treatment at 500-1000 °C for 3 h in an Ar atmosphere to obtain a bimetallic Fe-Co-N-S co-doped carbon catalyst that is Fe-Co-N-S-C. 2. the bimetallic base Fe-Co-N-S co-doped carbon catalyst that makes with the described preparation method of claim 1 is Fe-Co-N-S-C. 3. The application of the bimetallic-based Fe-Co-N-S co-doped carbon catalyst of claim 2, namely Fe-Co-N-S-C, in the fuel cell cathode oxygen reduction reaction.