Influence Of Metal Impurity Ions On Hydrogen Production By30%KOH Solution Electrolysis

Hydrogen is an ideal and clean source of energy. It has lots of advantages, such asstorable, environmental, non-pollution, renewable, and so on. The electrolysis of alkalinewater is an important method to product hydrogen widely. Metal impurity ions in theelectrolyte may affect the process of electrolysis, but related research is very little. The effectof metal impurity ions of electrolysis30%KOH solution to product hydrogen was studied bythe method of cyclic voltammetry curves, cathodic polarization curves and galvanostaticcathodic polarization in this paper, in detail, it contains the maximum dissolved,electrodeposition and co-deposition of metal impurity ions in30%KOH solution, and itseffect to electrocatalytic activities and energy consumption in this kind of solution.Based on conclusion on experiment, the highest dissolved concentrations of Ti³⁺andGd³⁺in30%KOH solution were separately20.5mg/L and117.8mg/L.Mo6+, Cr³⁺, Gd³⁺and Ti³⁺in30%KOH solution can not be deposited individually. Fe³⁺and Cu²⁺, Fe²⁺and Cu²⁺, Fe³⁺and Mo6+,Fe³⁺and Zn²⁺in30%KOH solution can beco-deposited, while Fe³⁺and Ni²⁺, Cu²⁺and Cr³⁺nether.Keep Ni electrode in30%KOH solution containing Fe³⁺and Cu²⁺with200mA/cm2current density cathodic polarization for30minutes, the evolution of hydrogen over potentialin200mA/cm2is approximately550mV and450mV at temperature20and85respectively.Under the same condition, the evolution of hydrogen over potential for Ni electrode in Fe²⁺and Cu²⁺solution is approximately540mV at20°C and440mV at85°C, the evolution ofhydrogen over potential electrode for Ni in Fe³⁺and Mo6+solution is approximately450mVat20°C and380mV at85°C, the evolution of hydrogen over potential electrode for Nielectrode in Fe³⁺and Zn²⁺solution is approximately420mV at20°C. when the temperature is85, the evolution of hydrogen over potential electrode for Ni electrode in Fe³⁺and Ni²⁺solution, in Fe³⁺and Cr³⁺solution and in Fe³⁺solution are about450mV, the evolution ofhydrogen over potential electrode for Ni electrode in Cu²⁺and Cr³⁺solution and inCu²⁺solution are about500mV, in other words, Ni2or Cr³⁺make no difference onelectrocatalytic activities. After deposition of these impurity ions, the evolution of hydrogenover potential of Ni in this solution lower than Ni and increases over300mV than the Ni-Mo,Ni-Fe-Zn which is about180mV. Therefore, in30%KOH solution, the deposition of metalions on the Ni surface reduces the cathode activity of hydrogen evolution and currentefficiency of electrolysis water, and increase power consumption. The effect of these metal impurity ions on cathodic hydrogen evolution activity andco-deposition in the electrolytic water are proposed firstly.