Preparation And Properties Of Electrode Materials For Hydrogen Production From Hydroiodic Acid/Sulfuric Acid-Sulfuric Acid System

With the continuous development of global science and technology,people are increasingly demanding quality of life and the environment,and actively seeking a renewable cleaner energy.In recent years,many researchers have carried out studies on large-scale hydrogen production.Sulfur iodine（S-I）thermal cycle is considered to be one of the most effective methods to promote water splitting to produce hydrogen.However,the HI/H₂SO₄ mixed acid system in the thermal cycle of sulfur iodine is the key to achieve effective cycle.At present,the most promising solution is direct electrolysis of HI/H₂SO₄-H₂SO₄ system.Electrolysis of mixed acid solution requires electrocatalyst with good performance to reduce the overpotential of hydrogen evolution and iodine evolution.There are not many electrocatalysts which can be used in acidic system,and the main application is noble metal catalysts such as platinum（Pt）electrodes.Due to the shortage of precious metal resources such as platinum,it is difficult to produce on a large scale,so it is urgent to develop electrocatalyst materials with high catalytic performance,mass production and low cost.he main factors affecting the catalyst performance are（1）the number and activity of active sites exposed in the electrolyte;（2）Internal structure of materials.In this paper,carbon matrix composites,bimetallic composites and transition metal compound composites were formed with carbon cloth substrate or nickel foam substrate by impregnation,high-temperature carbonization method,thermal evaporation method and hydrothermal method as iodine and hydrogen evolution catalysts.This paper studies and achievements.（1）Carbon spheres and needle-like composites were prepared by impregnation of phenolic resin with carbon cloth substrate under high temperature carbonization.The in-situ composite of carbon-based materials and substrates effectively transferred electrons,showing excellent electrocatalytic activity.The current density of PR-1/CC reaches100 mA/cm² at the overpotential of 419 mV,which is better than that of carbon electrode in acidic electrolyte.Compared with pure carbon cloth,PR-1/CC has better stability,and the current efficiency is close to 100%at1200 mV.The combination of carbon matrix and carbon fiber to form carbon-carbon composites provides more possibilities for non-noble metal composites.（2）Nano-silver thin films were electrodeposited on nickel foam by thermal evaporation method.The corrosion resistance of nickel foam itself was enhanced in a strong acid system,and the amount of precious metals was reduced by improving the electrocatalytic activity through bimetallic composite.In the acidic system,the current density of Ag-30/Ni is 100mA/cm² at 300 mV,the Tafel slope is 59 mVdec^-1,and the current efficiency in 600 mV electrolysis is close to 100%.Provide more direction for bimetal composites.（3）MoS₂nanosheets prepared by hydrothermal synthesis of carbon cloth have high durability for hydrogen evolution under acidic conditions.MoS₂/CC-20 can reach a current density of 100 mA/cm² at 250 mV,the Tafel slope is 67 mVdec^-1,and it has good electrolysis stability under 270mV overpotential for 24 h.The current density is close to 100%at 324 mV for 30 min.Carbon cloth substrate provides a good support for MoS₂,not only high stability,superior performance,provides the possibility for recycling.