Preparation Of Metal/Transition Metal Nitride Micro-Nano Composites For Alkaline Hydrogen Evolution Reaction

As a type of clean energy,hydrogen is an effective substitute for traditional fossil fuels.Hydrogen production from electrolytic water is an effective method.Although platinum based noble metal materials show good catalytic activity in hydrogen evolution from electrolytic water,their high price and limited reserves greatly limit their commercial application.Therefore,the research and development of efficient and cheap non platinum based hydrogen evolution catalyst is the key to realize the wide application of hydrogen production from electrolytic water.At present,researchers have developed a variety of non platinum based catalysts,but their performance is still far behind that of platinum based catalysts.On this basis,the preparation of transition metal nitride catalyst and its application in alkaline hydrogen evolution were studied.In this paper,the transition metal nitrides were modified by a small amount of Pd or Ru loading,and the composite catalytic materials with high efficiency,stability and low price were prepared.In this paper,Ru supported Ta₃N₅microrod composite catalyst（Ru/Ta₃N₅）and Pd modified Ni₄N/C micro rod composite catalyst（Pd-Ni₄N/C）were synthesized.The morphology and structure of the materials were analyzed by a series of characterization techniques,and their electrochemical properties were tested and evaluated.Based on the composition of the materials,the relationship between the electrochemical properties and the morphology,composition and structure of the materials was discussed.It includes the following contents:（1）In this part,rod-like Ta₃N₅supported with Ru nanoparticle composites was successfully prepared and their catalytic performances for hydrogen evolution were studied.The alkaline hydrogen evolution performance of Pt/C（20%）can be obtained by using only about 5%Ru loading.The excellent hydrogen evolution performance of Ru/Ta₃N₅（5%）is due to the synergistic effect and electronic effect between Ru and Ta₃N₅.The overpotential of Ru/Ta₃N₅（5%）composite is only 64.6 m V at 10 m A/cm²,and its activity is comparable to that of commercial Pt/C（20%）.The tafel slope is86.41 m V/dec and the catalyst has good stability.In addition,we also studied the effects of different Ru loading and reducing agents on the performance of the catalyst,and obtained the best preparation scheme.（2）In this part,we have successfully designed Pd modified Ni₄N/C nanosheets,which have the similar catalytic hydrogen evolution performance as commercial platinum carbon in alkaline medium,and have good stability.Nickel nitride nanosheets have high electron transport rate and atomic thickness of the oxide surface layer,which is an effective electron transport pathway.At the same time,it provides an active site for the decomposition of water into the hydrogen intermediate H_ad,which is adsorbed on the Pd nanoparticles to further generate H₂.The introduction of carbon can also improve the conductivity and reduce the resistance of charge transfer.The overpotential of Pd-Ni₄N/C（5%）catalyst at 10 m A/cm²is only 84.6 MV,which is close to the activity of commercial Pt/C,and Pd-Ni₄N/C（5%）catalyst can still maintain more than 100%activity after 20 h continuous test.In addition,we also studied the effects of different nitriding temperature,different kinds of noble metals,different Pd introduction ratio and other conditions on the performance of the catalyst,and obtained the best preparation scheme.