| With the development of human society,the demand of energy increases rapidly.In the past few decades,huge amount of fossil fuel has been consumed,bringing severe problems of pollution and energy exhaustion.For the long term development of human society,it is necessary to promote the usage of clean energy.Nowadays,many advanced energy technologies,such as fuel cell and electrochemical hydrogen production,rely on the supplement of Pt which can be served as electrocatalyst toward oxygen reduction reaction and hydrogen evolution reaction.The high price and low reserves of noble metal Pt increase the cost of clean energy greatly.Therefore,it is necessary to development efficient Pt-free electrocatalyst toward ORR and HER.In this dissertation,we have designed two kinds of Pt-free electrocatalyst toward ORR and HER.Firstly,we have developed a new kind of triazine-ring doped carbon material(triNC).Through polymerization of organic cyanide and further carbonization,triazine-ring doped carbon was achieved experimentally.The doping of triazine-ring is confirmed by Fourier transform infrared spectroscopy(FTIR)and X-ray photoelectron spectroscopy(XPS).A unique coordination of one C atom with two neighboring N atoms(C-N2 site)exists in triazine-ring structure.In electrochemical measurement,triNC exhibits excellent ORR performance which is better than traditional pyri-N doped carbon and it outperforms Pt/C.By density function theory(DFT)calculation,we find that the origin of high ORR performance of triNC is the unique C-N2 sites in triazine,which shows higher degree of localization and stronger oxygen binding ability than tradition pyri-N doped carbon material.The reaction path simulation also reveals a much lower energy barrier of ORR on C-N2 site.After that,triNC was used as a carbon support to load Ru nanoparticles,making a HER electrocatalyst,Ru/triNC.To identify the influence of carbon support on HER performance,carbon black and N doped carbon black were also used as carbon supports to load Ru nanoparticles by the same method.Through X-ray photoelectron spectrum(XPS)and ultra-violate photoelectron spectrum(UPS),it was found that contract electrification between Ru and carbon would happen due to the difference of work function.The degree of electron transfer from Ru to carbon support varies from the work function of carbon support.In Ru/triNC,the highest degree of electron transfer is detected.Combining electrochemical HER measurement,a positive correlation between HER performance and degree of contract electrification is observed.Ru/triNC exhibit better HER performance than commercial Pt/C,as well as lower cost of hydrogen production.Through DFT calculation,the electron transfer between Ru and carbon support is confirmed.This electron transfer process can influence the hydrogen adsorption property on surface of Ru,and further determines the HER performance. |
