In Situ Construction Of Porous Zinc-based Alloy On The Surface Of Metal Foam And Their Performance For Water Splitting

The excessive consumption of traditional fossil fuels has lead to harmful pollution to the environment,which makes it urgent to explore renewable energy sources.Hydrogen has obvious advantages such as convenient storage and transportation,high energy density,and only water as the product of combustion,making it one of the most promising alternatives to traditional energy sources.Among many methods for producing hydrogen,electrolytic water has the advantages of simple preparation process,high hydrogen purity,and zero carbon emissions.In this context,developing low-cost and highly active catalysts for hydrogen evolution reaction（HER）,oxygen evolution reaction（OER）,and overall water splitting have ushered in unprecedented strategic opportunities.The electrolytic water reaction involves two-half reactions,namely,the hydrogen evolution reaction produces hydrogen on the cathode and the oxygen evolution reaction produces oxygen on the anode.However,the actual voltage of water electrolysis is greater than the theoretical voltage（1.23V）due to the overpotential caused by ion migration and solution resistance during the reaction process.As a result,the widespread commercial application of water electrolysis is hindered by the essentially sluggish HER and OER kinetics.Therefore,it is urgent to seek highly active electrocatalysts to overcome high overpotentials.Among the existing electrocatalysts for water electrolysis,noble-metal based materials exhibit enhanced activity and performance.However,due to its scarcity and high cost,its widespread commercial applications are extremely limited.Transition metal zinc-based materials are widely available and inexpensive,and are considered as promising alternative materials for HER,OER and overall water splitting.However,they have issues of low activity and poor stability during long-term testing during the electrolysis of water.Therefore,developing catalysts with high activity,low cost,and high stability is crucial for achieving efficient electrolysis of aquatic hydrogen.Designing nanoporous structures and heterogeneous interfaces is an important strategy for constructing efficient and stable electrocatalysts.Firstly,three-dimensional nanoporous materials have abundant pores,and their high specific surface area shows unique structural advantages in increasing the density of active site,promoting site accessibility and improving intrinsic catalytic activity.Secondly,the construction of heterogeneous interfaces can significantly improve the charge transfer efficiency and expose more active site,optimize the electronic structure of the catalyst,adjust the adsorption/desorption free energy of the catalyst surface to the intermediate,reduce the reaction barrier,and promote the catalytic kinetic process.In conclusion,this paper takes transition metal zinc based materials as the research object,and adopts the strategy of“electrodeposition heat treatment dealloying”to in situ construct porous zinc based alloys on a series of metal foam and use them to study the performance of electrolytic water.The main research contents are as follows:（1）In situ fabrication of double-layered multi-scale porous Cu Co Zn/Ni Zn-Ni alloy heterojunction with triple interface on the surface of nickel foam and their performance for overall water splittingThe double-layered multiscale porous Cu Co Zn/Ni Zn-Ni alloy heterostructure with triple interfaces were fabricated on the surface of nickel foam by an electroplating-annealing-dealloying strategy.Due to the design of the double-layered multiscale porous structure and multiple interface heterostructures,the prepared Cu Co Zn/Ni Zn-Ni/NF sample exhibits excellent HER activity comparable to commercial Pt/C with an overpotential of 188 m V at the current density of 600 m A cm^-2,and the overpotential of 310 m V for OER at the current density of 100 m A cm^-2.In addition,the prepared Cu Co Zn/Ni Zn-Ni/NF only requires a low cell voltage of 1.54 V to achieve the current density of 50 m A cm^-2 and can be tested stably for 40 h at 20m A cm^-2 for overall water splitting.（2）In-situ building of double-layered multiscale porous Ni Fe Zn/Ni Zn-Ni alloy heterojunction with triple interface on the surface of nickel foam and their performance for overall water splittingThe double-layered multiscale porous Ni Fe Zn/Ni Zn-Ni alloy heterostructure with triple interfaces were fabricated on the surface of nickel foam by an electroplating-annealing-dealloying strategy.Benefiting from the synergistic effect of multi alloy,multi interface engineering and the construction of three-dimensional porous conductive framework,the catalytic activity and structural stability of the catalyst have been significantly improved.The Ni Fe Zn/Ni Zn-Ni/NF sample shows a low overpotential of 237 m V for HER and 361 m V for OER at the current density of 1000 m A cm^-2.Moreover,it can continuously and stably generate hydrogen and oxygen for 150 h at the high current density of 50 m A cm^-2.Especially,the assembled electrolytic cell with the Ni Fe Zn/Ni Zn-Ni/NF as both cathode and anode can export the electrolysis current of 600 and 1000 m A cm^-2 at a low cell voltage of 1.796 and 1.901 V with the unique stability at 50 m A cm^-2 over 100 h.（3）In situ construction of nanoporous Ni Co Fe Zn/Ni Fe Zn-Fe₃Ni₂ alloy heterojunction on the surface of Ni Fe foam and synergistic enhancement of the performance for overall water splittingThe nanoporous Ni Co Fe Zn high entropy alloy,the Ni Fe Zn alloy,and the Fe₃Ni₂intermetallic heterostructures were fabricated on the surface of Ni Fe foam as the conductive substrate through the electroplating-annealing-dealloying strategy.Benefiting from the preparation of two different zinc-based alloys,the design of heterogeneous structures,as well as the integrated multi-level porous structure and the preparation of high entropy alloys,The prepared Ni Co Fe Zn/Ni Fe Zn-Fe₃Ni₂ sample exhibits excellent electrocatalytic activity and excellent structural stability for OER and HER with a low overpotential of only 255 m V for HER and a low overpotential of only 369 m V for OER at the current density of 1000 m A cm^-2.In addition,the prepared sample has high corrosion resistance for overall water splitting,and can continuously and stably operate for 200 h in an alkaline solution.