Study On The Preparation Of Pd-based Catalyst And Its Hydrogen Evolution Performance

Hydrogen is a very promising clean renewable energy source.Electrolysis of water is an efficient and continuous method of hydrogen production.Hydrogen evolution reaction（HER）is the key step in the production of hydrogen from electrolyzed water.In order to reduce the energy consumption required by HER and improve the energy efficiency,the use of electrocatalysts is essential.Among many catalysts,Pt-based catalysts are widely used due to their excellent catalytic activity,but the precious metal Pt has the disadvantages of higher cost and limited reserves,which limits its large-scale application in production.The precious metal Pd is cheap,rich in reserves,and belongs to the same family as Pt,has the same atomic size and face-centered cubic crystal structure,and can be used as an ideal replacement metal for Pt.In this paper,Pd NN nano-network catalysts and Pd NPs nano-particles catalysts were synthesized by the mediation of Nafion,and their HER catalytic activities were systematically studied.1.A Pd nano-network（Pd NN）catalyst was synthesized by a one-step reduction method.The morphology and size of Pd NN catalyst were adjusted by changing the concentration of Pd precursor.Through TEM testing,it was found that the Pd NN-4.5catalyst formed a well dispersed nano-network structure from nanoparticles with a radius of 4.87 nm.The electrochemical performance of the prepared Pd NN catalyst was found to be better than that of commercial Pd/C.Among them,the Pd NN-4.5catalyst showed the best HER performance,with an overpotential of 59 m V and a Tafel slope of only 54 m V dec-1 at 10 m A cm-2.The calculated Pd loading mass of the Pd NN-4.5 catalyst is only 0.39 times that of commercial Pd/C.In addition,the Pd NN-4.5 catalyst also has high ECSA（20.32 m2 g-1）and excellent stability.2.PdNPs catalysts were synthesized by reduction after film formation.The dispersion of Pd nanoparticles was adjusted by changing the concentration of Nafion.The experimental results show that when the Nafion concentration is 0.05 w%,the Pd nanoparticles in the catalyst has the best dispersibility and have excellent HER performance.With 0.05 w%Nafion,Pd NPs catalysts were synthesized by the same method.The morphology and size of Pd NPs catalysts will change with the Pd precursor concentration.The Pd NPs-6 catalyst exhibited a nano-particle structure with an average particle diameter of 3.24 nm.Electrochemical testing of Pd NPs catalysts shows that the HER catalytic performance of the synthesized Pd NPs is significantly better than that of commercial Pd /C.The Pd NPs-6 catalyst exhibits the most excellent catalytic activity: an extremely low overpotential（24 m V）,a small Tafel slope（35 m V dec-1）,and a high ECSA value（115.8 m2 g-1）.In addition,the Pd NPs-6catalyst also showed good catalytic activity in 1M KOH solution: lower overpotential（183 m V）,smaller Tafel slope(161 m V dec^-1),and good stability.