The electrodeposition of manganese dioxide is obtained by using Pt/C GDE rather than the traditional electrode (Cu) in order to save energy and protect the environment. Thus, the energy-saving mechanism of Pt/C gas diffusion electrode (Pt/C GDE) in high temperature and strong acid MnSO4 media is studied. The cell voltage and the cathode potential of Pt/C GDE and Cu electrode are tested in 30 g/dm(3) H2SO4 + 120 g/dm3 MnSO4 at 80 +/- 2 degrees C to exhibit the energy-saving effect. The results show that the cell voltage can be reduced more than 1.13 V using Pt/C GDE as cathode instead of the traditional electrode (Cu), and the electric energy consumption of electrolysis with Pt/C GDE can save 60% at 80 A/m(2). The CV curves and polarization curves of Pt/C GDE and the polarization curve of hydrogen evolution reaction on a Cu electrode are researched. The results indicate that the polarization curve of Cu electrode is much more negative than that of the Pt/C GDE at same current density. The reaction of Pt/C GDE is oxygen reduction at the cathode. The amperometric oxygen reduction current of the GDE with Pt/C is about 28 times higher than that of GDE without Pt/C at 0.4 V vs. Ag/AgCl. The Pt/C catalyst particle sizes range from 2 nm-6 nm by HRTEM. The oxygen reduction reaction mechanism of Pt/C GDE is researched in strong acid containing manganese ion by rotating disk electrode (RDE). The D-O2 and CO2 values are 0.715 x 10(-9) m(2)s(-1) and 3.3 mol.m(-3) in electrolyte. Koutecky-Levich analysis indicates that the oxygen reduction reaction of Pt/C GDE adopts a 4electron transfer process as main process as the main process in electrolyte (O-2 + 4H(+) + 4e -> 2H(2)O). Therefore, the major causes of the new method for saving energy is that the oxygen reduction reaction of Pt/C GDE, rather than the hydrogen evolution reaction of tradition cathode (Cu), is used, and that the high catalytic activity (the 4-electron transfer process) of Pt/C catalyst also contributes. (C) 2015 Elsevier Ltd. All rights reserved.