Preparation Of Nickel Sulfide-based Electrode Materials And Research On Catalytic Performance For Water Electrolysis

Hydrogen production from water splitting can convert the electrical energy generated by wind energy and tidal energy into hydrogen energy for storage.However,water splitting is affected by the solution resistance and the multi-step proton-coupled electron transfer process of anodic oxygen evolution,which increases the reaction energy barrier and reduces the efficiency.Research and development of low-cost,high-activity catalytic materials to reduce the reaction energy barrier is a good solution.Nickel-based sulfides often undergo oxidative reconstruction due to poor thermodynamic stability in strong oxidizing environments,exposing a large number of active sites,which can accelerate the electrolysis of water.In this paper,nickel-based sulfide with hydrogen precipitation and oxygen precipitation is successfully synthesized to explore the structure evolution process in oxygen precipitation reaction;Fe element doping is used to regulate the surface electron distribution and chemical structure of composite Fe Ni S/NF-C to accelerate the induced structure reconstruction and increase the reaction active site.The main content of this article is as follows:（1）Deciphering the structure evolution and active origin for electrochemical oxygen evolution over Ni₃S₂.Ni₃S₂/NF catalysts with excellent catalytic activity and good stability were obtained by adjusting the temperature of hydrothermal vulcanization by using nickel foam（NF）as the catalytic material substrate.The catalyst was reconstructed to Ni OOH/Ni₃S₂/NF by electrooxidation,which exhibits an OER overpotential of only 255.4 m V dec^-1 and Tafel slope of 26.46 m V dec^-1 at a current density of 10 m A cm^-2.Structural characterization and OER polarization curves endorse that stepwise S leaching combined with OH^-adsorption is conducive to boosting structure evolution of Ni₃S₂/NF into Ni OOH/Ni₃S₂/NF.In addition,pristine Ni₃S₂/NF can also drive HER at an overpotential of 68 m V to generate a current density of 10 m A cm^-2.Remarkable electrocatalytic performance for overall water splitting is achieved with Ni OOH/Ni₃S₂/NF and Ni₃S₂/NF as anode and cathode,respectively,featured for 1.57 V（vs.RHE）to powering overall water electrolysis with current density of 10 m A cm^-2.（2）Synthesis of nickel-iron-sulfur composites and research on the properties of electrolyzed water.Fe Ni S/NF-C nanomaterials were prepared by adjusting the molar ratio of Fe and Ni atoms during hydrothermal growth.XRD and Raman characterizations indicated that Fe was successfully introduced,and TEM analysis confirmed that Fe Ni S/NF-3with a Fe/Ni ratio of 1:1 had a larger surface area.The Fe element can adjust the coordination environment of Ni and S in Fe Ni S/NF-3,and contribute to the covalent strengthening between Ni 3d-S 2p orbitals.At the same time,Fe synergistically promoted the electrochemical evolution,and induced a large amount of Ni²⁺to Ni³⁺to form highly active Ni OOH and a small amount of Fe OOH,so that Fe Ni S/NF-3 in 1 M KOH solution at 10 m A cm^-2 current density,the OER overpotential is only 221 m V,and the Tafel slope is as low as 24.11 m V dec^-1.In addition,Fe Ni S/NF-3 also has excellent HER performance to catalyzes hydrogen production at a low overpotential of 61 m V.Using Fe Ni S/NF-3 as the cathode and anode of overall water splitting electrolytic cell,it can drive water splitting at 1.502V and achieve a current density of 10 m A cm^-2.