Design Of Pt-Based Nanomaterials And Study Of Their Performance In Water Electrolysis

Hydrogen energy has many advantages such as high energy density,natural abundance and clean and non-polluting,making it the optimal choice for green energy.Hydrogen production by electrolysis of water is one of the most efficient ways to produce high purity and clean H₂.Pt-based catalysts are the material of choice for efficient electrolysis of water due to their fast kinetics and low overpotential.However,its high cost and scarcity hinders its large-scale application,and maintaining its durability in acidic solutions is a major challenge.In order to improve the utilisation of Pt atoms and their durability in acidic media,this thesis reduces the buried inactive Pt atoms through strategies such as nanosized and alloying,and reduces hydrogen poisoning at the active site by exploiting the hydrogen spillover effect.The above strategies improve their reaction performance in electrocatalytic hydrogen evolution reaction as well as in electrocatalytic electrocatalytic overall water splitting,with the following main studies.（1）In this chapter,we have designed a series of Pt@N-X-CNC（X=0.5,1,2）materials loaded with ultra-small particle size PtNPs with different N-doping through a nanosizing strategy.It is found that the carbon material with N atom doping can provide H*desorption site for the hydrogen spillover process,which makes it have great potential as the catalysts support for hydrogen spillover.Based on this finding,we develop the hydrogen spillover catalyst with electron-rich Pt sites loaded on N-doped carbon nanocage（N-CNC）with adjustable work function,and through a series of comprehensive electrochemical tests,proved the existence of hydrogen spillover,and demonstrated the pyrrolic-N can activate adjacent carbon sites as the desorption sites for hydrogen spillover by the in-situ tests for the first time.The Pt@N-1-CNC with the minimum work function difference（ΔΦ）between PtNPs and support shows superior hydrogen evolution performance,only needs overpotential of 12.2 mV to reach current density of 10 mA cm^-2,outstanding turnover frequency（TOF）(44.7 s^-1@100 mV)and superior durability under the 360 h i-t test at current density of 50 mA cm^-2.（2）In this chapter,we have designed a series of Pt/H-TiO_2-x-Xmin（X=40,60,80,100）materials loaded with electron-rich PtNPs with different degrees of hydrogenation by means of a nanosizing strategy.By varying the thickness of the hydrogenated layer on the support surface,the electronic state of Pt can be modulated,thus improving the performance of the acidic HER.By optimizing,it was found that the Pt/H-TiO_2-x-80min catalyst exhibits excellent HER performance in 0.1 M HClO₄.The Tafel slope of Pt/H-TiO_2-x-80min is 26.2 mV dec^-1,revealing that it is the Volmer-Tafel mechanism.Moreover,it has excellent intrinsic activity,the turnover frequency（TOF）of Pt/H-TiO_2-x-80min up to 41.7 s^-1 at 100 mV,which is 6.6 times that of Pt/TiO₂ and 2.2 times that of commercial Pt/C,respectively.The mass activity up to 9.58 A mg_Pt^-1 at 100 mV,it is6.8 times that of commercial Pt/C and 14.1 times that of Pt/TiO₂.At the same time,it is applicable to large currents and exhibits remarkable stability and even suitable for proton exchange membrane（PEM）electrolyzer,indicating the great potential of its practical application.（3）In this chapter,we have designed a stable charge redistribution through strong metal-support interactions ultra-small particle size Pt-RuO₂@KB catalyst constructed by alloying.Where the presence of Pt acts as a stable electron donor and the transfer of electrons from Pt to RuO₂ can form a stable charge redistribution.It achieves significant water splitting performance in acidic media.Benefiting from the Pt-RuO₂heterostructures,the strong metal-support interaction（SMSI）between Pt-RuO₂ and KB as well as the stable charge redistribution between Pt and RuO₂,the Pt-RuO₂@KB exhibits ultrahigh intrinsic activity(the turnover frequency（TOF）value is 34.5 s^-1@300 mV for oxygen evolution reaction（OER）and 20.2 s^-1@100 mV for hydrogen evolution reaction（HER）,respectively)and outstanding overall water splitting performance(only need 1.54 V at a current density of 10 mA cm^-2).Notably,the Pt-RuO₂@KB with the stable charge redistribution exhibits striking stability for overall water splitting,during the 150h continuous v-t test,the voltage maintains well without noticeable degradation in 0.1 M HClO₄.Density functional theory（DFT）calculations verify that the charge redistribution between Pt and RuO₂ can dramatically lower water splitting barrier and raise the vacancy formation energy of atoms in catalyst,which could effectively inhibit the dissolution of atoms in Pt-RuO₂@KB in acidic medium and achieve superior water electrolysis performance.