Hightly Efficient And Stable Bistratal Non-noble Metal Catalysts For Water Splitting

With the huge consumption of fossil energy and the increasingly serious harm to the environment,the efficient and clean renewable energy has been widely concerned.Among them,hydrogen energy is regarded as one of the most promising new energy materials because of its safe and pollution-free characteristics.Water electrolysis technology,which involves hydrogen evolution reaction(HER)and oxygen evolution reaction(OER),is an effective way to produce hydrogen without polluting the environment.The preparation of efficient catalysts is the key of water electrolysis technology.Pt based catalysts are currently the most efficient hydrogen evolution reaction(HER)electrocatalysts,while Ru/Ir-based oxides have been well-known to be the benchmark for their best OER activity.However,the high-cost and scarcity severely limit their practical application.Therefore,the preparation of non-noble metal catalysts with low cost and high electrocatalytic properties is of great significance for the electrochemical water splitting.In this thesis,we prepared two-layer non-noble metal catalysts by simple and practical deposition methods on carbon paper and nickel mesh respectively.The porous structure,rich interface and the synergy between different transition metal speed up the charge transfer,improve the catalytic performance,and thus implement the stable and efficient electrolysis of water.The main research contents are as follows:(1)Fabrication of Ni(oxy)hydroxide/Fe(oxy)hydroxide double layer catalyst and the study of its electrocatalytic characteristics.Firstly,Fe(oxy)hydroxide is integrated on carbon papers by an electrodeposition method,and then a few drops,containing Ni ion with DI water,are dropped on the(oxy)hydroxide/CP surface.After the electrochemical reaction,the two-layer catalyst structure of Ni(oxy)hydroxide/Fe(oxy)hydroxide compound(named as Ni/Fe/CP)was formed.The porous structure on the surface of Fe(oxy)hydroxide compounds provides rich sites for electrocatalytic reaction,and the synergistic action between Fe and Ni ions enhances the intrinsic catalytic activity of the catalyst.The as-prepared product of Ni/Fe/CP exhibits a good OER performance,with a low overpotential of 223 mV(relative to the reversible hydrogen potential)at 10 mA/cm2 and a super stability of above 100 h continuous testing under 50 mA/cm2.In addition,the HER activity of the iron-rich catalyst illustrates that it can be improved through self-optimization in the basic solution.After self-optimization,the Ni/Fe/CP is capable of an efficient bifunctional catalyst for water splitting with only 1.53 V cell voltage required to achieve 10 mA/cm2.This double layer structure provides a new strategy for the future design of cheap,efficient and stable electrocatalysts.(2)The efficiency and stability of the current industrial catalysts for electrochemical water splitting need to be improved.Based on this,porous FeCo(oxy)hydroxide/Ni(OH)2 electrocatalysts on Ni mesh(named as FeCo/Ni(OH)2/Ni)were prepared by water bath deposition method.It exhibited excellent OER catalytic performance in the environment of high temperature and strong alkali(3 M NaOH,90?),with a low overpotential of 105 mV at 10 mA/cm2.At the same time,in order to meet the demand of hydrogen production under industrial large current density,we tested the prepared electrode under the environment of large current density,and found that the electrode exhibited excellent OER catalytic performance,with a low overpotential of 175 mV at 500 mA/cm2.Subsequently,we conducted a corresponding stability study.FeCo/Ni(OH)2/Ni electrode had a super stability of above 200 hours continuous testing under 200 mA/cm2.We put the FeCo/Ni(OH)2/Ni as both the anode and cathode into a two-electrode electrochemical cell for water splitting in the basic solution.Only 1.76 V cell voltage is required to achieve 100 mA/cm2,while the Raney Ni electrode exhibited the relative poor OER performance,with the potential of 1.8 V at 110 mA/cm2.Finally,ultrasonic treatment under the same conditions proved that FeCo/Ni(OH)2/Ni was more stable than the industrial Raney Ni/Ni mesh.Therefore,a cheap,efficient and stable nano-porous bifunctional electrocatalyst was prepared by a simple water bath deposition method.This study provides a possible alternative to industrial Raney Ni.