Nitrogen-doped porous carbon-coated metal nano composite catalyst and preparation method thereof

Abstract

The invention discloses a nitrogen-doped porous carbon-coated metal nano composite catalyst and a preparation method thereof. The preparation method comprises the following steps: (1) adding a fluoride into an acidic solution for reaction, then adding M<n+1>AX<n>, carrying out magnetic stirring reaction under a water bath condition, cleaning a product with deionized water, centrifuging, then sequentially carrying out ultrasonic cleaning and centrifuging with an organic solvent and deionized water, and carrying out freeze drying so as to obtain a reactant 1; 2) weighing a certain amount of thereactant 1, adding deionized water and an organic solvent, carrying out uniform ultrasonic dispersion, dissolving a transition metal salt and urea in deionized water, adding an obtained mixture in anobtained mixed solution of the reactant 1, and carrying out magnetic stirring reaction under an oil bath condition to obtain a reactant 2; 3) performing heat treatment on the reactant 2 and a nitrogen-containing compound in a high-temperature furnace to obtain a reactant 3; and 4) performing high-temperature reduction on the reactant 3 in a protective atmosphere to obtain the nitrogen-doped porouscarbon-coated metal nano composite catalyst. According to the preparation method, the problems that the oxygen reduction catalyst prepared in the prior art is easy to agglomerate and the ORR activityis reduced due to less exposure of active sites are solved.

Description

technical field [0001] The invention belongs to the technical field of nanometer materials, and in particular relates to a nitrogen-doped porous carbon-coated metal nanocomposite catalyst and a preparation method thereof. Background technique [0002] A fuel cell is a power generation device that directly converts the chemical energy of fuel into electrical energy by electrochemical reaction without combustion. Its power generation process is not limited by the Carnot cycle, and the energy conversion efficiency is high. The theoretical efficiency is as high as 85-90%, and the actual efficiency is 40-60%. It is environmentally friendly and hardly emits air pollutants such as sulfur oxides and nitrogen oxides. With low noise and easy operation, it is considered to be the preferred clean energy in the 21st century. As an efficient and clean energy conversion technology, fuel cells will definitely play an irreplaceable role in the future non-fossil energy system. The catalysts...

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Problems solved by technology

However, such coated catalysts reported in the current literature have the following problems: 1) the agglomeration of metal particles during the high-temperature pyrolysis process leads to uneven dispersion of metal particles, and the particle size is relatively large, ranging from tens to hundreds of nanometers; 2 ) The metal loading is low, usually lower than 10%; 3) Some metal particles are not completely coated, and the uneven dispersion of metal particles and low metal loading will affect the electronic interaction between the metal core and the graphitized carbon layer and The active site density of the catalyst, which leads to a decrease in catalytic activity

However, the high-temperature pyrolysis process often leads to structural collapse and agglomeration, resulting in uncontrollable subsequent growth of metal particles and thus their poor electrochemical activity.

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