Effect of B sites on the catalytic activities for perovskite oxides La_.6Sr_.4Co_xFe_1-xO_3-δ as metal-air batteries catalysts

The effect of B sites on the catalytic activities of oxygen evolution reaction (OER) for perovskite oxides La_0.6Sr_0.4Co_xFe_1-xO_3-δ (x = 0, 0.2, 0.4, 0.6, 0.8, 1, denoted as LSF, LSCF-28, LSCF-46, LSCF-64, LSCF-82 and LSC, respectively) prepared by a convenient and simple method of electrospinning technique is reported. The prepared La_0.6Sr_0.4Co_xFe_1-xO_3-δ catalysts possess almost same crystal structures, similar morphologies (except for the LSC catalyst) and slightly different BET surface areas. Upon the optimization of the Co/Fe atomic ratio, the optimal LSCF-82 catalyst exhibits the OER performance with a low onset potential of 1.541 V, a small Tafel slope of 80.56 mV dec^-1, a high charge-transfer rate and a large electrochemical surface area in 0.1 M KOH solution. LSCF-82 catalyst exhibits the long-term stability under the catalytic operation condition for 12 h. Such catalytic activity may mainly cause by the synergy of higher catalytic activity Co and lower catalytic activity Fe. Thus, the reasonable optimization of the transition metal composition in B sites for the perovskite oxides is in favor of the improvement of OER performance.