Unveiling the contribution of catalytic particles to the electrochemical performance of a Pb-dispersed particle composite anode for nonferrous metal electrowinning

Abstract

Incorporating oxygen evolution catalytic particles into the Pb matrix via a powder mixing-pressing-sintering process is an effective strategy to develop efficient lead-dispersed particle (Pb-DP) composite anodes for nonferrous metal electrowinning. Catalytic particles are demonstrated to significantly reduce the anodic potential of Pb-DP anodes. However, the intrinsic contribution of catalytic particles to the electrochemical performance of Pb-DP anodes remains obscure. Herein, Pb-DP anodes with different dispersed particles (chemically inert Si or C, catalytic Co3O4 or MnCo2O4) were prepared. The anodic potential, microstructure and phase composition of the oxide layer, and oxygen evolution behavior of these Pb-DP anodes were investigated and compared with those of the Pure-Pb anode (prepared without dispersed particles). The results showed that compared with the Pure-Pb anode, Pb-Si and Pb-C anodes present similar microstructures and phase compositions of the oxide layer. However, they exhibit a larger Tafel slope for the oxygen evolution reaction (OER). Although the incorporation of catalytic particles (Co3O4 and MnCo2O4) reduced the thickness and specific surface area of the oxide layer and inhibited PbO2 growth, the presence of Co3O4 and MnCo2O4 significantly reduced the Tafel slope and charge transfer resistance (Rct) of the OER. Consequently, the anodic potentials of Pb-Co3O4 and Pb-MnCo2O4 are approximately 45 mV and 69 mV lower than that of Pure-Pb, respectively. It is demonstrated that the lower anodic potential of the Pb-Co3O4 and Pb-MnCo2O4 composite anodes originates from the catalytic activity of the dispersed particles rather than the physical effect of the dispersed particles.