MnO /C composites as electrode materials II. Reduction of oxygen on bifunctional catalysts based on manganese oxides

Carbon-supported manganese oxide nanoparticles as electrocatalysts for oxygen reduction reaction (orr) in neutral solution

“…The XRD peak at 2h = 36.8°w as moved to a lower angle with doping; indicating metal insertion between the manganese oxide layers (Fig. 1), in agreement with previous reports [11,13]. A volume average diameter of ca.…”

“…19 and 9 A g À1 MnO 2 (at 0.00 V vs. SHE) for Ni-MnO x /Monarch and MnO x /Monarch, respectively, compared with 100 A g -1 Pt for 20 wt.% Pt/Vulcan XC72 ( Table 1). The positive effect of nickel doping on the ORR, has also been reported in alkaline medium and was explained by the ability of transition metal atoms to exist in several valencies [11][12][13]. Thus the transition metals assist the charge transfer to oxygen, leading to increased electronic interactions with the stabilized Mn III produced from MnO 2 by proton insertion in the ORR potential range.…”

“…In the low current density range (E [ -0.2 V vs. SHE), the value of n (between 2 to 3) for both carbon supports increased with the addition of MnO x (Fig. 5a): manganese oxides have previously been shown to effectively decompose peroxides [11]. It was likely that the main part of the 2-electron reduction pathway was due to the presence of carbon.…”

“…The manganese oxide nanoparticles were chemically deposited onto the carbon substrate as follows [10,11]: 4 g of carbon was mixed with a 70 cm 3 (mL) of an aqueous solution containing 10 mmol (mM) of MnSO 4 (Aldrich). The suspension was maintained at a controlled temperature (80°C) for 20 min under magnetic stirring, in order to allow impregnation of the carbon by manganese sulphate.…”

“…Carbon-supported manganese oxides nanoparticles were found to exhibit good ORR activity in alkaline media [9][10][11][12][13]. In addition the doping of MnO x /C by the divalent ions Ni II , Mg II or Ca II , was found to be extremely promising, since the Me-MnO x /C catalysts exhibited ORR activity close to that of a benchmark Pt/Vulcan XC72 from E-Tek [12,13].…”