| The excessive consumption of fossil fuels has led to a series of environmental problems and energy depletion.Therefore,the development of new energy sources is vital for our healthy life and social progress.Hydrogen energy as the secondary energy has the advantages of being clean,non-toxic,renewable and high energy density.It has been applied in the industrial field and has a broad pr ospect in the future.With the increasing demand for hydrogen energy,hydrogen production technologies are also developing.Electrochemical water splitting is expected to be the most effective method for hydrogen production,but th e technology requires efficient electric catalyst to reduce energy consumption.At present,platinum based noble metal catalysts have high catalytic performance in electrochemical water splitting for hydrogen production,but their high cost and scarce reserves limit practical application.Therefore,it is particularly important to select and design efficient and cheap electric catalysts.Molybdenum carbide（Mo2C）,as transition metal carbide,has Pt-like d-band electronic structure,cheap price,abundant sources and good electrical conductivity,and is considered to be one of the most potential catalysts to replace noble metals.However,high temperature carbonization for Mo2C can easily lead to particle agglomeration,structural collapse and small specific surface area,which is not conducive to catalytic hydrogen evolution reaction（HER）.Based on the above description,this paper prepared nano-molybdenum carbide/carbon with different morphologies,excellent properties and good dispersion by simple sol-gel method.The research contents are as follows:（1）Carbon-based molybdenum carbide materials were prepared by the complex reaction of ammonium molybdate and tartaric acid（TA）using the sol-gel method.The effects of the content of molybdenum source and carbonization temperature on the morphology and hydrogen evolution performance of molybdenum carbide were investigated.Finally,the highly dispersed molybdenum carbide nanocrystals（Mo2C/C-0.5）on 3D cage-like carbon was synthesized at 900°C.The average particle size of the nanocrystals is 2 nm and the specific surface area reaches 115.8m2 g-1,which show that it has excellent catalytic performance.At the current density of 10 m A cm-2,the overpotentials of Mo2C/C-0.5 in alkaline and acidic electrolytes are 164 mV and 198 mV,and the corresponding Tafel slopes are 66 mV dec-1and 79mV dec-1.Both the CV curves scanning of 2000 cycles and the i-t curve test at constant pressure show good stability.This is the surface constraint of 3D cage-like carbon on molybdenum carbide at hi gh temperature,which promotes the high dispersion of nanoparticles and is benefical to the hydrogen evolution reaction.（2）Carbon-based molybdenum carbide materials were prepared by self-assembly of gelatin,polyethylene glycol（PEG）and ammonium molybda te in a new gel system using sol-gel method.The effects of the content of PEG and carbonization temperature on the morphology and hydrogen evolution properties of molybdenum carbide were investigated.Finally,the 3D flower clusters-like nano-molybdenum carbide/carbon（GMC-0.05）was synthesized at 900°C.GMC-0.05 is mesoporous material with fine nanoparticles and specific surface area of 90.2 m2 g-1,showing the best HER performance.At the current density of 10 m A cm-2,GMC-0.05 has overpotential of 147 mV and 166 mV in alkaline and acidic electrolytes,corresponding the Cdlvalues for 25.26 m F cm-2 and 21.25 m F cm-2,respectively.Through CV curves scanning of 2000 cycles and i-t curve test under constant pressure,it has remarkable stability in acidic electrolyte.This may be because the flower clusters-like molybdenum carbide has good dispersion and abundant nanochannels,which provide more active sites and improve the performance.（3）Carbon-based molybdenum carbide materials were prepared by self-assembly of gelatin,D-sorbitol,citric acid（CA）and ammonium molybdate using sol-gel method.The optimal gel system was obtained by adjusting C A content.Based on this,the effects of the content of molybdenum source on morphology and hydrogen evolution performance of molybdenum carbide were investigated.Finally,the self-assembled 3D/2D nano-molybdenum carbide/carbon（GMCC-2.0）was synthesized at 800°C.GMCC-2.0 possesses 3D bulk morphology of nano-thickness,which is formed by 2D lamellar with abundant nanoporous,showing superior the HER performance.At the current density of 10 m A cm-2,the required overpotentials of GMCC-2.0 in alkaline and acidic electrolytes are 123 mV and 168 mV,and the Tafel slopes are 62.3 mV dec-1 and 73.8 mV dec-1.The results indicate that the system can be helpful to optimize the carbonization temperature and further improve the catalytic performance. |
