Facile synthesis MnCo₂O_4.5@C nanospheres modifying PbO₂ energy-saving electrode for zinc electrowinning

The oxygen evolution reaction kinetics in industrial zinc electrowinning is sluggish, resulting in low electrocatalytic activity and substantial energy expenditure (about one-third of energy was wasted due to the strong polarization effect). Herein, the paper described a core-shell structured MnCo₂O_4.5@C modified PbO₂ electrode through the pyrolysis and co-electrodeposition as a promising candidate for zinc electrowinning. As a result, the obtained Pb-0.2%Ag/α-PbO₂/β-PbO₂-MnCo₂O_4.5@C composite electrode showed a sandwich-like structure, where Pb-0.2%Ag as a core, α-PbO₂ as a mid-layer, and β-PbO₂-MnCo₂O_4.5@C served as an electrocatalytic layer. It also possessed improved OER catalytic activity, only required 680 mV to achieve a current density of 50 mA cm^-2 and a Tafel slope of 216.04 mV dec^-1 in an acidic solution containing 50 g L^-1 Zn²⁺ and 150 g L^-1 H₂SO₄. The current efficiency increased by 0.7% and the cell voltage reduced by 360 mV as compared to a conventional Pb-0.76%Ag alloy electrode, leading to a remarkable energy-consumption reduction of 283.5 kW h for producing per ton metallic zinc. Furthermore, Pb-0.2%Ag/α-PbO₂/β-PbO₂-MnCo₂O_4.5@C exhibited a prolonged service life, which worked about 44 h under an ultra-high current density of 2 A cm^-2. Hence, this paper provides the strategy to design and construct non-precious, high-performance catalyst for electrolysis and other applications.