Pulse electrodeposition synthesis of Ti/PbO2-IrO2 nano-composite electrode to restrict the OER in the zinc electrowinning

Abstract

Pulsed and constant direct current electrodepositions were applied to synthesize PbO2-IrO2 nano-composites on Ti substrate. By compositing PbO2 with nano-sized IrO2 particles, a suitable anode was prepared for zinc electrowinning that decreases the electrocatalytic activity for oxygen evolution reaction overpotential (OER) while increasing the electrochemical active surface area and the electrocatalytic activity for OER. To provide PbO2-IrO2 nano-composites on Ti substrate with Sb2O3 interlayer, current density, temperature, and time of anodization are optimized using the one-at-the-time method. The optimal condition for the anode involves a DC time of 1 h, incorporating 2 g L-1 of IrO2 nanoparticles, maintaining a current density of 50 mA cm− 2 for the DC mode, and setting the pulse off-time (toff) to 770 ms. Based on the electrochemical evaluations in a simulated zinc electrowinning electrolyte, the effect of IrO2 nanoparticles on the catalytic activity of Ti/β-PbO2 anode for OER was determined. Anodic polarization curves showed that the OER overpotential of PbO2-IrO2 micro-composite and PbO2-IrO2 nano-composites at a current density of 10 mA cm-2 decreased to 0.471 V, respectively, compared to 0.711 V for pure PbO2. The Nyquist plots in the OER zone confirm that the PbO2-IrO2 nano-composite anode exhibits the lowest Rct 2.79 Ω compared to 6.0 Ω and 9.46 Ω for PbO2-IrO2 micro-composite and pure PbO2, which can be attributed to the presence of electro-catalytic IrO2 nanoparticles.