Effects of the Substitution of Β-Site Ion on Oxygen Reduction Electrode Properties of Pb₂Ru₂O_{7- δ} in Aqueous Solutions

Abstract

The activities of the pyrochlores Pb2Ru2-xMxO7-δ (M=Mn,Fe,Co,Ni)[PRM(0x)] toward electrochemical oxygen reduction (EOR) were examined in 0.1 M KOH and 0.05 M H2SO4 aqueous solutions. The onset voltage (Vo) and the efficiency (E4) of 4-electron reduction of oxygen for PRM(0x) were evaluated by semi-steady state voltammetry with rotating ring-disk electrodes. In PRM01, the order of the EOR activities was PRMn01 > PRCo01 > PRNi01 > PRFe01 in both solutions. This was consistent with the variation of the lattice parameters, i.e. PRM01 with a smaller lattice parameter showed higher EOR activity. In addition, PRMn05 showed higher EOR activity than PRMn01. The onset voltages Vo were 0.95 and 0.50 V vs. reversible hydrogen electrode in 0.1 M KOH and 0.05 M H2SO4, respectively, while E4 was almost 100 % in both solutions. These results indicate that the EOR activity of PRM(0x) depends on the incorporated metal ions on the B-sites and their contents.

Electrocatalytic O2 Reduction Properties of Pyrochlore-Type Oxides for Alkaline DAFCs

“…In the previous work [6,9], we demonstrated that the Mn substitution for the Ru-site was quite effective to improve the ORR activity of PbR. Therefore, the Mn substitution is also attractive for the LnR samples.…”

“…All the potentials shown in this paper were recalculated to RHE. The efficiency (Eff 4 ) of 4-electron reduction of oxygen was estimated by the following equation [6][7][8][9][10][11]: ECS Transactions, 16 (2) 891-900 (2008) 4 where i D and i R are the disk and ring currents, respectively, N is collection efficiency. The value of N = 0.372 was calculated from the geometrical area of the ring-disk electrodes.…”

Electrocatalytic Activity of the Pyrochlores Ln2M2O7−δ (Ln = Lanthanoids) for Oxygen Reduction Reaction

“…In the previous work [6,8,9], we demonstrated that the substitution of Mn ion for the Ru-site (B-site) in PbR and LnR (Ln = Pr, Nd) was considerably effective in improving the ORR activity. Therefore, the Mn substitution is also attractive for the LaZ samples.…”

“…Sample electrodes were prepared by the following procedure [6][7][8][9]: 15.4 mg of the oxide sample milled for one hour at 500 rpm (Planetary ball mill P-6, Fritsch Japan) and 4.6 mg of carbon black (Vulcan XC-72R, Cabot) as an electric assisting additive were mixed with 2 mL of 2 mass% Nafion ethanol solution with an ultrasonic equipment for 30 min. The mixed paste (5 lL) was coated on the grassy carbon (GC) disk electrode of RRDE and dried at room temperature.…”

“…All the potentials shown in this paper were recalculated to RHE. The efficiency (Eff 4 ) of 4-electron reduction of oxygen was estimated by the following equation [6][7][8][9]:…”