Silver Doped Amorphous MnO2 as Electrocatalysts for Oxygen Reduction Reaction in Al-Air Battery

Abstract

Manganese dioxide is a low-cost catalyst for oxygen reduction reaction (ORR) in alkaline media. In this paper, the amorphous MnO2 (AMO) was prepared, its characteristics and the effects of mixed with carbon nanotubes (CNTs), doped with silver nanoparticles on catalytic performance were investigated. The experimental results show that the performance of the AMO is slightly worse than that of the β-MnO2, which is possibly caused by the absence of the high catalytic activity (110) surface in the amorphous state. However, the addition of carbon nanotubes significantly improves the catalytic properties of AMO. Furthermore, the nanoscale silver particles doped AMO was prepared and characterized, and it is shown that the AMO/CNTs catalyst with 10 wt% Ag nanoparticles owns the best catalytic performance. Quantum chemical calculation on the ligand effect by electron structure shows that the interaction between Ag and Mn can shift the d-band center of Ag and lower the activation barrier of the O–O bond fracture, while Ag can low the adsorption of O2 for Mn. However, when the Ag content in MnO2 up to 20%, the adsorption will be weakened and the break kinetics of O–O bond will be reduced, which leads to the catalytic effect reduced.