0428同步年報-2021-全

Physics and Materials Science 019 researchers showed that a double perovskite oxide compound Sr 2 CoIrO 6−δ exhibits an unprecedentedly small overpotential of 210 mV to achieve a current density of 10 mA cm –2 . This result makes Sr 2 CoIrO 6−δ the most efficient perovskite-based solid-state catalyst for OER. The authors carried out an extensive set of measurements on polycrystalline Sr 2 CoIrO 6−δ to identify the real active sites and to understand the mechanism of OER. Polycrystalline samples of Sr 2 CoIrO 6−δ were synthesized with a solid-state reaction method. The crystal structure and morphology were investigated with X-ray diffraction and a transmission electron microscope to prove that approximately 90% of the Co/Ir ions were ordered on alternate sites in three dimensions of the double perovskite structure. Linear sweep voltammetry was implemented to quantify the OER activity of the electrocatalysts; the results showed an activity order of Sr 2 CoIrO 6−δ > IrO 2 > SrIrO 3−δ > SrCoO 3−δ . It was further shown that Sr 2 CoIrO 6−δ exhibited an iridium mass activity 0.84 A mg -1 Ir , which was approximately 7.0 and 5.6 times that of SrCoO 3−δ (0.12 A mg -1 Ir ) and IrO 2 Fig. 1 : Rapid operando spectral characterizations. (a,b) Co-K edge and Ir-L 3 edge XANES spectra of Sr 2 CoIrO 6−δ electrocatalyst at varied applied voltage. (c,d) 3D operando Fourier transforms of EXAFS spectra at (c) Co-K edge and (d) Ir-L 3 edge as a function of applied potential, with corresponding enlarged-scale 2D contour plots of the Co-O and Ir-O ranges. The EXAFS data are not corrected for phase shift. (e,f) Co-O and Ir-O bond lengths in Sr 2 CoIrO 6−δ electrocatalyst under applied potential extracted from EXAFS fitting. The applied voltage is referred to the reversible hydrogen electrode. [Reproduced from Ref. 1]