Abstract:
Manganese dioxide (MnO2) is the effective electrocatalysts used as a cathode for Zn-Air batteries (ZABs) accounted for the acceleration of the oxygen reduction reaction (ORR). There are various studies on the ORR activity of MnO2 rather than deactivation mechanisms. In this work, the deactivation mechanisms of α-MnO2 and β-MnO2 was investigated by density functional theory and computational hydrogen electrode. It was found that, the phase transformation from the α-MnO2 (211) to β-MnO2 (110) shows that the catalyst deactivation is due to the higher overpotential of β-MnO2 (110) making electrocatalyst efficiency low. For Ov surfaces, it illustrates that the performance is decreased in Ov α-MnO2 (211), while, Ov β-MnO2 (110) can be enhanced. The poisoning intermediates, *OOH found in ORR of perfect catalysts, exhibit deactivation on α-MnO2 (211) and β-MnO2 (110). In addition, the activity of poisoning β-MnO2 (110) on 2e- ORR is higher than that of β-MnO2 (110) on 4e- ORR. The poisoning intermediate cases reveal that the ORR can operate, although the catalyst surfaces are covered by *OOH rich. Therefore, the prevention of Ov for α-MnO2 is the key to keep the high activity of α-MnO2 electrocatalysts, while, the Ov can improve the catalytic performance of β-MnO2.
