Ru And Nonnoble Metal Element Composite Catalysts For Efficient Hydrogen Evolution Reaction

Traditional fossil energy is hard to meet the requirements for green and environmentfriendly society along with the rapid development of global economy.Hydrogen energy has attracted much attention because of its advantages such as pure byproducts and strong applicability.Electrochemical water splitting is an environment-friendly way to produce hydrogen,but has been strongly limited by its slow reaction kinetics.Therefore,it is of great significance to develop the low-cost,efficient and stable catalyst for promoting hydrogen evolution reaction(HER),which is the half reaction of electrochemical water splitting.In this study,efficient and stable alkaline HER catalysts were prepared on the basis of nickel foam by controlling the morphology and optimizing the electronic structure.Synchrotron radiation X-ray absorption spectroscopy(XAS)has been used to reveal the catalytic active sites and probe catalytic mechanism.The contents and highlights of this thesis are described as follows:1.We have prepared an effective e-RuNiPO catalyst for alkaline HER.The catalyst comes from the favorable long-term reconstruction of b-RuNiPO during HER for 10 h,which shows a huge morphology change from bulk sphere to highly exposed layered structure with more active Ru sites.The layered substrate with Ni can also accelerate the water dissociation and offer a H+abundant local environment for better HER.According to the XAS results,the electrocatalysis induced reconstruction can also modify the electronic structure of catalyst,leading to an electron transfer from Ru to Ni for better interfacial interaction and quick charge transfer.Then the exposed Ru sites can work as efficient HER catalyst,while the Ni-based substrate will provide more H+ around Ru and also work as an electron storage layer to facilitate the reaction.The obtained e-RuNiPO catalyst only requires a very low overpotential of 15 mV to achieve the current density of 10 mA cm-2,with an excellent stability for more than 100 h,which outperforms the performance of benchmark 20 wt%Pt/C catalyst(24 mV at 10 mA cm-2)by using a much lower Ru content.2.A highly efficient alkaline HER catalyst(N-CoMoOx/NF)was prepared by annealing CoMoO4 at high temperature in NH3 atmosphere.The catalyst shows a low overpotential of 16 mV at 10 mA cm’2 and exhibits a low Tafel slope of 41 mV dec-1.NCoMoOx/NF shows excellent performance at high current densities,with low overpotential of 64 and 240 mV to achieve 100 and 1000 mA cm-2,respectively.The catalyst also shows an excellent stability for more than 130 h.XAS reveals that Mo has been reduced in NH3 to accelerate the electron transfer.Meanwhile,metallic Ni and Co can not only improve the conductivity of the catalyst,but also promote the production of hydrogen as the catalytic active site,so as to improve the catalytic efficiency.The produced nitride is also favorable for the hydrogen adsorption.This work provides a new strategy for the rational design of efficient HER catalysts with high current density.