Electrochemical Behavior Research Of Acid Molecules On Platinum Electrode

Electrocatalysis is a great application with great promise of hydrogen evolution and green technology of hydrogen production.H+ + e-? 1/2 H2 is the most basic reaction by electrode,has been widely research scholars.But previous studies focus mainly on the adsorption stripping properties of hydrogen and oxygen in + 1.30 V?-0.30 V(vs.Ag/AgCl sat.)on the electrode.It was studied on the electrochemical behaviors of small acid molecules,such as HCI,HClO4,HCOOH,H3PO4,H4P2O7 and H8C6O7,on polycrystalline Pt at-1.1 V?+ 0.2 V by cyclic voltammetry in this paper.The main research contents and conclusions of this thesis are listed as follows:In the first chapter,it was about review section.First introduced the energy development concisely,and the rapid development of the new hydrogen energy at the moment.Then introduced the electricity and hydrogen evolution mechanism of catalytic activity.Finally put forward the topic of this paper.In the second chapter,it was studied about cyclic voltammetric curves of the HCl-0.5 M KCl system by platinum disk electrode and platinum microelectrode within + 0.1 V?-0.8 V.First of all,put forward the cathode electrode reaction H+ + e-? 1/2 H2 and anode reaction 1/2 H2-e-H+ on the surface of the platinum disk electrode by studying the nature of the REDOX peak at-0.35 V(vs.Ag/AgCl sat.).Second,investigate the influence of acidity(pH = 1.02?5.43)on peak height.It is about pH = 1.02?3.33 with the emergence of REDOX peaks.pH = 1.02?1.36,cyclic voltammetric curve has fluctuations under low potential,and reversibility is poor;pH = 1.71?2.99,the curve is smooth,peaks are symmetric,and reversibility is good.According to equation-formula of peak current ip?c0*linear relationship,diffusion coefficient of H+(pH = 1.02?2.99)and H2(pH = 1.71?2.99)were 9.7 × 10-5 cm2 s-1 and 5.5 × 10-5 cm2 s-1.Then,study the effect of scanning speed on peak height.According to the linear relationship of ip?v1/2,0.5 M KCl-HCl pH = 2.05 and 0.5 M KClO4-HClO4 pH = 2.07,diffusion coefficient of H+ were 8.2 × 10?5 cm2 s-1 and7.9 × 10-5 cm2 s-1,diffusion coefficient of H2 were 5.4 × 10-5 cm2s-1 and 4.4 ×10-5 cm2 s-1,the rate of reaction constant k0 were 0.044 cm s-1 and 0.031 cm s-1.According to the linear relationship iss?CH+*of the platinum microelectrode,the diffusion coefficient of H+ were 9.6 × 10-5 cm2 s-1(HCl-0.5 M KC1 pH = 1.71?3.33)and 19 × 10-5 cm2 s-1(HCl pH= 1.36?3.33).In the third chapter,it was studied about cyclic voltammetric curves of weak acid system(HCOOH-0.5 M KC1)by platinum disk electrode within + 0.1 V?-1.1 V.Experimental results show that the cathode electrode reactions are H+ + e-? 1/2 H2 and HCOOH + e-?1/2 H2 + HCOO-,anode electrode reactions are 1/2 H2-e-? H+ and 1/2 H2 + HCOO--e-? HCOOH at the formic acid solution(pH ?2.57).In the fourth chapter,it was studied about cyclic voltammetric curves of multiple weak acid(H3PO4-0.5 M KCl)by platinum disk electrode within + 0.1 V?-1.1 V.It is found that the cathodic reactions from right to left are H+ +e-? 1/2 H2 and H3PO4 + e-?H2PO4-+ 1/2 H2,H2PO4-+ e-? HPO42-+ 1/2 H2,HP0O42-+ e-? PO43-+ 1/2 H2 and 1/2 H2-e-? H+,by changing the pH of solution,scan rate and concentration of phosphoric acid and other conditions,anodic reactions are opposite.Finally,it was briefly introduced about cyclic voltammetric curves of the pyrophosphate system and citric acid system by platinum disk electrode within + 0.1 V?-1.1 V.