Design Of Noble Metal Nano-Materials And Their Electrocatalytic Hydrogen Evolution Performances

With the development of economy and the growth of population,the consumption of non-renewable fuels on the earth and its impact on the environment are accelerated,which promotes the development and utilization of renewable energy（such as solar energy,wind energy,hydropower and tidal energy）.However,the intermittence and instability of these renewable green energy sources limit their further utilization.Renewable hydrogen energy which can be stored is considered as an ideal energy carrier because of its cleanness and high efficiency.In addition,the development of hydrogen energy is in line with the strategy of zero carbon or carbon reduction advocated now,and the technology of electro-catalytic moisture decomposition of hydrogen by using renewable electricity can well adapt to the requirements of environmental protection and sustainable energy development.It is a great challenge to develop electrocatalytic materials that can reduce the activation energy barrier and improve the reaction kinetics in the hydrogen evolution reaction of electrolytic water.It is required to design and control the size and morphology of the catalyst,and adjust the electronic structure by alloying and interfacial support effect,so as to improve the intrinsic activity of the catalyst and increase the number of active sites.In this paper,nano electrocatalysts with3D self-support were prepared by ultrasonic reductant reduction method and in-situ electrochemical reduction method,and the main research findings were summarized as follows:（1）We prepared an electrocatalyst loaded with Pt on Ti H₂ substrates with different hydrogenation times.Hydrogen is introduced to the substrate by in situ electrochemical hydrogenation,and this hydrogen can regulate the coordination of Ti and thus the electronic structure,reducing Ti O₂ to Ti H₂.Pt is loaded on the substrate by pyrolysis under reducing atmosphere,and the hydrogen molecules of the substrate can give electrons to Pt,producing an interfacial effect and immobilizing Pt on the catalyst surface.In addition,the loading of Pt,a noble metal,was reduced to reduce the catalyst cost while improving the catalyst performance.The overpotentials of 14,82,102 m V and the tafel slope of 41.71 m V dec^-1 at current densities of 10,100,and 1000 m A cm^-2,respectively,can work stably for 150 h at a current density of 100 m A cm^-2.Density flooding theory calculations demonstrate that H₂O adsorption on the Pt-Ti H₂ surface has a low dissociation energy barrier.At the same time Pt adsorbs two H*and generates H₂molecules on the surface for release,so HER is extremely easy to occur.The good stability is further explained by the high adsorption energy of the catalyst for calcium and magnesium ions,thus it is less likely to adsorb calcium and magnesium ions to form insoluble substances to block the catalyst.（2）We propose a new simple,convenient,environmentally friendly,and record-breaking method for the rapid synthesis of NMAs.combining the reductant Na BH4 and the action of ultrasound into the gelation process,which generates huge energy under the cavitation effect of ultrasound,accompanied by heating and stirring effects,the gelation reaction can be carried out rapidly,even within tens of seconds,which is much faster than previously reported much faster.It can successfully complete the gelation process in a wide concentration range（0.02-62.5 mmol/L）.The method is suitable for the synthesis of single-metal aerogels（Au,Ag,Ru,Rh,Pd）.Bimetallic and trimetallic aerogels（Au-Ag,Au-Rh,Au-Ru,Au-Pt,Au-Pt-Pd）,while alloy aerogels have a ligament size of 10 nm or even smaller.We also found excellent electrocatalytic properties of this noble metal aerogel material in HER and EOR.This work reports a rapid and effective method for the synthesis of NMAs,which is beneficial for their further application in electrocatalysis.