Doping iron would greatly enhance the catalytic efficiency of transition-metal oxides for oxygen evolution reaction (OER), but the phase transition and redox reaction during OER make this system much complicated. In this work, we discussed the intrinsic material properties of iron-doped metal oxides with various iron-content, relating to their catalytic performance. For demonstration, iron-doped cobalt oxides were prepared and showed better performance (ηj=10 mA = 230 mV) than that of bare cobalt oxide (ηj=10 mA = 290 mV) in 1 M KOH(aq). From X-ray absorption spectroscopy, it was found that iron ions preferentially occupied the octahedral sites in the lattice and further lowered the oxidation number of lattice cobalt. Cobalt would be confined in tetrahedral sites, considered as the active sites for OER. This phenomenon facilitated the recovery of lattice cobalt from phase transition due to the rule of Pourbaix diagram as well as that of high oxidation states during catalytic cycles. As excessive iron ions entered into the lattice, they gradually occupied the tetrahedral sites of original cobalt, revealing the deteriorated electrochemical activity of the catalyst. This material-related insight provides a possible indication for the conception and fundamental study of OER.

Effect of geometrical site confinement in high-efficient iron-doped cobalt oxides electrocatalysts toward oxygen evolution reaction

253rd National Meeting (2017)

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