The effect of sodium stannate as the electrolyte additive on the electrochemical performance of the Mg–8Li–1Y electrode in NaCl solution

Abstract

The effect of different concentrations of sodium stannate (Na₂SnO₃) as the electrolyte additive in 0.7 mol L⁻¹ NaCl electrolyte solution on the electrochemical performance of the Mg–8Li–1Y alloy electrode prepared by the vacuum induction melting method have been investigated by means of potentiostatic current–time, potentiodynamic polarization, and electrochemical impedance spectroscopy measurements as well as scanning electron microscopy. The performances of the magnesium–hydrogen peroxide (Mg–H₂O₂) semi-fuel cells with the Mg–8Li–1Y alloy as the anode were also determined. From the study, it has been found that the corrosion potential of the Mg–8Li–1Y electrode is slightly shifted to the negative direction and the corrosion current density is markedly decreased when different concentrations of Na₂SnO₃ are added to a 0.7 mol L⁻¹ NaCl electrolyte solution. The electrochemical impedance spectroscopy measurements show that the polarization resistance of the Mg–8Li–1Y electrode reduces in the following order with different concentrations of Na₂SnO₃: 0.20 mmol L⁻¹ > 0.00 mmol L⁻¹ > 0.05 mmol L⁻¹ > 0.10 mmol L⁻¹ > 0.30 mmol L⁻¹. The electrochemical performance, illustrated by potentiostatic current–time curves, of Mg–8Li–1Y electrode in 0.7 mol L⁻¹ NaCl electrolyte solution containing 0.30 mmol L⁻¹ Na₂SnO₃ is better than that in 0.7 mol L⁻¹ NaCl electrolyte solution containing Na₂SnO₃ in other concentrations. The addition of Na₂SnO₃ to the NaCl electrolyte solution loosens the product film and changes the size and thickness of the micro-clumps of the oxidation products. The Mg–H₂O₂ semi-fuel cell with the Mg–8Li–1Y anode in 0.7 mol L⁻¹ NaCl solution containing 0.30 mmol L⁻¹ Na₂SnO₃ presents a maximum power density of 112 mW cm⁻² at room temperature.