Modified With Low Pd Loading On W Electrode As Hydrogen Evolution Electrocatalyst

The development of renewable energy and clean energy is becoming more and more important for solving the continuously deteriorating environmental problems and the shortage of fossil energy.Hydrogen is considered to be a clean energy carrier that is expected to replace fossil fuels and can be produced by electrocatalytic water splitting.The electrocatalytic decomposition of water is a green and sustainable way to produce hydrogen.It has received extensive attention in recent years.In order to drive the hydrogen release reaction（HER）with high energy efficiency,there is an urgent need for high-efficiency electrocatalysts that can minimize overpotential.In this paper,different methods are used to prepare Pd@W/Ti as the cathode hydrogen evolution reaction catalyst.Through the synergy between Pd and the substrate W,the utilization of Pd is improved by improving the dispersion of Pd on the surface,and the electrocatalysis of Pd@W/Ti is improved.Hydrogen evolution activity.The main research contents are as follows:（1）A small amount of metallic Pd(70μg cm^-2)was modified on the surface of W substrate by liquid-phase reduction method to prepare Pd _LR@W/Ti electrode.First of all,XPS analysis shows that the electrons of W are transferred to Pd,and there is a strong interaction between Pd and W,which is beneficial to improve the desorption rate and hydrolytic adsorption capacity of hydrogen adsorbed on the surface of Pd.The addition of W improves Pd _LR@W/Ti and HER activity.When the overpotential is0.2 V,the apparent hydrogen evolution activity of Pd _LR@W/Ti electrode is 78.9 m A cm^-2,which is 1.67 times that of Pd _LR@Ti.Through electrochemical area normalization,the area specific activity of Pd _LR@W/Ti(7.616 m A cm^-2)is 2.2 times that of Pd _LR@Ti,and is higher than that of commercial Pt/C with the same precious metal loading.In addition,Pd _LR@W/Ti shows excellent stability during multi-turn variable potential scanning and long-term constant potential scanning.However,a certain accumulation of Pd occurred on the surface of Pd _LR@W/Ti,which is not conducive to the expression of catalyst activity.（2）The Pd_ED@W/Ti electrode(20μg cm^-2)was prepared by electrodeposition method,which improved the dispersion of metal Pd on the W surface,and further reduced the Pd loading on the basis of the previous chapter.SEM analysis shows that Pd on the surface of Pd _ED@W/Ti is uniformly distributed in spherical shape and has excellent hydrogen evolution activity.When the overpotential is 0.2 V,the current density of Pd _ED@W/Ti is 60.33 m A cm^-2,which is 4.8 times that of Pd _ED@Ti,which is slightly higher than that of commercial Pt/C(59.5 m A cm^-2).The mass specific activity of Pd _ED@W/Ti(3.175 A mg^-1_（Pd）)is 4.9 times that of Pd _ED@Ti,which is even higher than that of commercial Pt/C,and the utilization rate of Pd has been improved.In addition,the area specific activity(308.6 m A cm^-2)of Pd _ED@W/Ti is also much higher than that of Pd _ED@Ti and Pt/C,which are 2.6 times and 22.4 times that of them,respectively.It is especially important that Pd on the surface of Pd _ED@W/Ti is uniformly distributed and does not aggregate.It is precisely because of the improvement of surface Pd dispersion and the interaction between Pd and substrate W that the adsorption and desorption rate of H on the electrode surface is improved.Pd _ED@W/Ti also has excellent stability,which shows that Pd _ED@W/Ti is a promising hydrogen evolution catalyst.（3）High-vacuum magnetron sputtering can achieve uniform coverage of materials at low dosages to obtain nano-scale highly dispersed materials.Using high vacuum magnetron sputtering to modify a small amount of highly dispersed metal Pd on the surface of the W substrate,and further reduce the load to 10μg cm^-2,which is only 1/2 of Pd _ED@W/Ti,which is Pd _LR@W/1/7 of Ti.Although the Pd loading is very low,Pd _MS@W/Ti also has excellent hydrogen evolution activity.When the overpotential is 0.2 V,the current density of Pd _MS@W/Ti is 73.9 m A cm^-2,which is8.7 times that of Pd _MS@Ti and 1.73 times that of Pt/C.Compared with Pd _MS@Ti and commercial Pt/C,Pd _MS@W/Ti has a larger electrochemically active area(62.79 m²g_Pd^-1),higher mass specific activity(7.39 A mg^-1_（Pd）)and Area specific activity(39.229m A cm^-2).In addition,the mass specific activity of Pd _MS@W/Ti prepared by magnetron method is higher than that of liquid phase reduction method and electrodeposition method.This is because both Pd and W prepared by magnetron sputtering have high dispersibility and small particle size,which further improves the utilization rate of Pd and achieves good hydrogen evolution activity.