Carbon nanotubes sheathed in lead for the oxygen evolution in zinc electrowinning

Abstract

Oxygen evolution in harsh high acidic condition is a challenge to both zinc electrowinning and hydrogen production. In the present work, the carbon nanotubes (CNTs) sheathed in lead hybrid anode has been fabricated through electrochemical codeposition, and its electrochemical performances under zinc electrowinning condition have been discussed extensively. It is also the first time to coat CNTs by Pb with tunable method via metal oxide. The CNTs/Pb composite anode shows ten times larger exchange current density and electrochemically active surface areas (ECSA) than those of pure Pb, which indicates an extra high electro-catalytic activity. The lower overpotential and polarization resistance of the CNTs/Pb composite anode for oxygen evolution are due to integrity for efficient charge transport between matrix and PbO2 by penetrating through PbO layer. Under industrial condition of current density 500 A m−2, the overpotential can be decreased by about 120 mV compared with pure Pb during the long-term durability test. Moreover, the hybrid anode comprising ~ 0.6 wt% CNTs is also cost effective. The CNTs/Pb composite anode can be a promising and cost-effective anode in harsh high acidic condition and potentially applied in zinc electrowinning practice due to high hardness and scalable production.