Electrochemical Hydrogen Evolution Activity Of Low-Loading Platinum Catalyst

Hydrogen is an environmentally friendly and efficient clean energy source.And it is attracting attention as the most promising alternative to fossil fuels in the future.The most easy preparation method for hydrogen is prepared by hydrogen evolution reaction?HER?.Pt is the best hydrogen evolution electrocatalyst in HER.In this paper,we discussed the problem of high Pt usage in electrode materials and low hydrogen evolution activity of low-load Pt catalysts.The preparation method,structural characteristics and electrochemical hydrogen evolution activity of low-load Pt catalysts are mainly investigated.At the meanwhile,we improved hydrogen evolution activity test analysis methods and obtained good hydrogen evolution electrocatalyst.This ultra-low Pt loading hydrogen evolution electrocatalyst has high apparent activity,mass specific activity and electrochemical area specific activity.The details are as follows.?1?Different mass fractions of Pt/C catalysts were prepared.Electrochemical analysis showed that the smaller the loading of Pt,the greater the activity of mass and electrochemical area in the HER.Different quality Pt films were deposited on the surface of Ti foil by magnetron sputtering.The deposition state of Pt was characterized by X-ray powder diffractometry?XRD?,transmission electron microscopy?TEM?and X-ray photoelectron spectroscopy?XPS?.When the deposition time is 10s,the particle size of Pt is only 0.89nm,and the particle size of Pt increases with the deposition time.Electrochemical analysis showed that when the loading of Pt was below 3.516?g cm^-2,the HER activity of mass and electrochemical area remained unchanged with the change of Pt loading.A certain amount of Pt film was deposited on the surface of Au film.The surface morphology and structure of Pt/Au were characterized by atomic force microscopy?AFM?,XRD and XPS.The Au film makes the surface of the Pt/Au electrodes of different apparent areas uniform and consistent.Electrochemical analysis of Pt/Au electrodes with different areas that the larger the hydrogen evolution current,the greater the electrochemical activity was affected by the solution H⁺concentration and the iR drop between the solution and the electrode.Therefore,when comparing the hydrogen evolution activities of different electrocatalysts,a catalyst having the same loading amount and apparent area should be selected for comparison.?2?PtOx/Au hydrogen evolution electrocatalyst with ultra-low Pt loading(0.48?gcm^-2)was prepared by high vacuum magnetron sputtering combined with electrochemical anodic oxidation.Compared with commercial Pt/C and Pt electrodes,the PtO_x/Au electrode has ultra-high mass specific activity(152.95 A mg_Pt^-1 for PtOx/Au-1;12.53 A mg_Pt^-1 for 0.5 wt%Pt/C;17.82 A mg_Pt^-1 for Pt-1@?=150 mV)and ultra-high electrochemical surface area specific activity(?=90 mV for PtOx/Au-1;?=237 mV for 0.5wt%Pt/C;?=225 mV for Pt-1@100 mA cm^-2)without lowing the apparent activity(115mA cm^-2 for PtOx/Au-1;85 mA cm^-2 for 20 wt%Pt/C;127 mA cm^-2 for 40 wt%Pt/C@?=200 mV).The analyses by cyclic voltammograms?CVs?,X-ray photoelectron spectroscopy?XPS?and CO adsorption-stripping curves suggest that the catalytic active site of PtOx/Au comes from the AuPtOx.Only when Au and Pt was oxidized at the same time,its HER activity can be remarkably improved.The emergence of Pt⁴⁺components on the Pt/Au surface may be due to the induced oxidation of AuOx in the anodic oxidation process.Density functional theory?DFT?calculations elucidated the?G_H*?absolute value?of PtOx/Au surface is close to that of Pt?111?,indicating its outstanding HER activity originates from its optimal?G_H*value.?3?Different molar ratios of AuxTiy catalyst were prepared by high vacuum magnetron sputtering.AFM and XRD analysis showed that the incorporation of titanium?Ti?can change the deposition morphology of Au,making the Au deposition particle size smaller.Electrochemical analysis showed that that the incorporation of Ti can increase the electrochemical area and hydrogen evolution activity.XPS and electrochemical test analysis show that Ti is oxidized to form TiO in air,Ti on the surface of AuTi can easily combine with oxygen to form a composite oxide structure of Au-O-Ti.When a small amount of Pt is deposited on the surface of AuTi,Pt/Au₃Ti has excellent hydrogen evolution activity,and its Tafel slope(37.1 mV dec^-1)is similar to Pt(33.9 mV dec^-1).At a current density of 10 mA cm^-2,the overpotential?63 mV?is almost the same as Pt?62 mV?.At the same time,Pt/Au₃Ti has excellent stability.