Influence of sodium oleate on manganese electrodeposition in sulfate solution

• NaOL presents a multiple effect on cathodic current efficiency.
• Active Mn species are MnSO4, Mn(SO4)22 −, Mn2 + and Mn(NH3)2 +.
• Main active species of NaOL are OL− and (OL)22 −.
• NaOL increases the overpotential of hydrogen evolution.

The influence of sodium oleate (NaOL) on manganese electrodeposition from sulfate solution was systematically investigated in terms of cathode current efficiency, solution chemistry calculation and thermodynamic analysis, polarization curves and Fourier transform infrared spectroscopy (FT-IR) analysis. The experimental results show that NaOL concentration and pH present a multiple effect on cathode current efficiency. According to the solution chemistry calculations of sulfate electrolyte and NaOL, it is found that MnSO4, Mn(SO4)22 −, Mn2 +, Mn(NH3)2 +, and OL− and (OL)22 − are the main active species, respectively. The reaction trend between OL− and Mn2 + ions was evaluated by thermodynamic analysis. Finally, the influence of NaOL on hydrogen evolution reaction and manganese electrodeposition was investigated. And the coordination reaction of OL− and Mn2 + was analyzed by FT-IR.