Coatings Electrode Electrolysis Nickel Sulfide Doped With Nickel Foam

The aim of this thesis is to study the influence of Ni-S electrode has been various doped elements （Co, La, Mo, Ru, Pd） on the hydrogen evolution reaction （HER） activity in water electrolysis. A special process has been developed to prepare Ni-S coating electrode with high HER performance. The elements doped Ni-S electrodes have been prepared on foam nickel substrate by electrodeposition. The structure and the HER performance have been studied by polarization curves, circulated volt-ampere curves, chronopotentiometry, SEM, EDX, XRD and corrosion testing. The electrodes’ catalytic activity and mechanism for HER have been investigated. The mainly conclusions and findings can be summarized as follows: 1) All doped elements can improve the HER performance of amorphous Ni-S coating electrode, but the electrodes doped with only cobalt or lanthanum has better electrochemical stability and corrosion resistance, thus it can be practically used in water electrolysis. 2) The relationship between catalytic ability and the conditions of electrodeposition has been studied: electrode with Co²⁺ can enhance the cathode polarization; current density influence the nucleation velocity of coating; temperature can determine the activation energy of electrodeposition; time influence the thickness of the coating; pH value influence the current efficiency. The optimal conditions of electrodeposition has been determined: 10g/L in COSO₄·7H₂O doping content, 50mA/cm² in current density, t50℃in emperature, 40 min in deposition time, 4 in pH value. Ni-S-Co gradient-coated electrode own better electrochemical stability and HER performance due to special structure which has stronger intensity inside and high HER activity on the surface; 3) The electrode has large specific area with La³⁺ doped in electrolyte, which enhance cathode polarization and hinder the growth of coating, The optimal conditions of electrodeposition has been determined: 1g/L in LaCl₃ doping content, 30mA/cm² in current density , 40℃in temperature, 4 in pH value; 4) Activation energy of three electrodes for HER were calculated: 49.5 kJ/mol for foam nickel electrode, 40.3 kJ/mol for Ni-S electrode and 49.5 kJ/mol for Ni-S-Co electrode. Thus the higher HER performance of Ni-S-Co coating electrode was disclosured. 5) The HER mechanism of the Ni-S-Co electrode on the foam nickel substrate in alkaline media is determined to be a electrochemical desorption, a fast Volmer reaction followed by a slow Heyrovsky reaction. During the process of electrolysis, a large number of hydrogen atoms will be absorbed in such electrode. Desorption of hydrogen atoms in HER can be accelerated in ultrasonic wave.