Research On Large-scale Preparation Of Self-supported Electrocatalysts And The Corresponding Electrochemical Properties

Electrolytic water hydrogen production technology has the advantages of high purity of hydrogen,pollution-free reaction process,huge reserves of raw materials and so on.It is a promising mainstream hydrogen production technology in the future.At present,the main difficulty lies in the need to overcome the high energy barrier in the electrolysis of water.In order to reduce the energy barrier,the development and preparation of high-efficiency electrocatalyst has become a key link.In industry,the size of the electrode pieces needed in the electrolytic cell of the hydrogen production equipment is often large,and the replacement cycle of the electrode pieces is also relatively short,which puts forward high requirements for the production speed of the electrocatalytic electrode materials.At present,the preparation methods of selfsupporting structure are mainly hydrothermal method and chemical vapor deposition method.On the one hand,the size of the substrate is limited by the reaction vessel,so it is difficult to achieve the preparation of large-area structure;on the other hand,the preparation cycle is generally long,which often varies from several hours to tens of hours,and the preparation speed is difficult to meet the requirements.Therefore,it is of great practical significance to study new preparation methods to meet the needs of large-scale preparation of self-supporting structures.In view of the above problems,this paper first summarizes the design principles that need to be considered in the large-scale preparation strategy.First of all,for the purpose of reducing cost,the choice of materials is non noble metal;second,for the purpose of simplifying the process and reducing the interface resistance,selfsupporting system is the best structure research.Finally,for the purpose of high efficiency service,the improvement of catalyst material activity should be considered.Therefore,the following two aspects of the preparation of self-supporting electrocatalyst and its electrocatalytic performance were studied in this paper.First of all,considering that plasma can effectively enhance the activity of chemical substances,this paper studies the rapid regulation of doping and the electrochemical performance of corresponding materials by means of plasma assistant.Using the foam iron material as the substrate,the carbon,sulfur and phosphorus anions were doped by plasma assisted.The cycle of the synthesized bulk type electrocatalyst can be controlled for about 1 hours by optimizing the process.Among them,the carbon doped samples show the best electrocatalytic performance on the side of her,only needing 195 m V to reach the current density of 50 m A cm-2,which is 130 m V lower than the over potential of the original samples without doping;the phosphorus doped samples show the best electrocatalytic performance on the side of OER,only needing 270 m V to reach 10 m A cm-2,which is 54 m V lower than that of the original sample.The reason why carbon doping has the best effect on the improvement of her catalytic activity is that the proportion of metal Fe and Fe2+ is increased to the greatest extent after carbon doping,which is conducive to the rapid electron transport and proton adsorption;while the reason why phosphorus doping has the best effect on the improvement of oer catalytic activity is that the proportion of Fe3+ is increased to the greatest extent after phosphorus doping,which is conducive to the adsorption of Oh active species.However,both carbon and phosphorus can only improve the one-sided half reaction.From the perspective of total water decomposition,sulfur is the most suitable doping element for the preparation of bifunctional electrocatalyst.Furthermore,in order to further improve the catalytic activity of the selfsupporting electrocatalyst,a wet chemistry strategy for rapid preparation of large-scale nanostructured catalyst electrodes was proposed.Through the combined strategy of insitu corrosion and chemical bath sulfur doping for bulk type cobalt foam,the low activity bulk cobalt foam material can be converted into a highly active sulfur doped hydroxides based nano array electrocatalyst(Co Ni-OH|S)in a few minutes.Among them,the uneven corrosion rate on the surface of the material under the acid corrosion environment leads to the appearance of nano chips,which is conducive to the exposure of high active sites;the subsequent chemical bath sulfur doping process further improves the whole water decomposition electrocatalytic activity.On the one hand,the introduction of sulfur species on the surface of nanostructures is beneficial to proton adsorption,thus improving her catalytic activity;on the other hand,sulfur doping greatly enhances the low coordination Co3+ site,which is conducive to accelerating the deproton process of intermediate species of Ooh,thus improving oer activity.The results showed that the synthesized nano array of Co Ni-OH|S showed excellent electrocatalytic performance,and the current density of 10 m A cm-2 could be achieved for HER and OER with 167 m V and 270 m V,respectively.It is worth noting that the wet chemistry strategy proposed in this paper has the advantages of low time consumption and energy consumption,and can guarantee the one-time preparation of tens of square centimeters of large area electrodes in a few minutes.In this paper,aiming at the problems of high energy consumption and timeconsuming in the field of self-supporting electrocatalyst preparation,the rapid preparation process of doping electrocatalyst is developed,and the wet chemistry strategy of macro preparation of self-supporting nanostructured electrocatalyst is proposed,which provides very useful experience for the large-scale production and application of self-supporting electrocatalyst and the promotion of electrocatalysis water decomposition technology.