Fig. 2

Analysis of surface structure reconstruction. a High-resolution transmission electron microscopy (HRTEM) images of pristine and cycled m-SrIrO₃ (by 5 cycles, scale bar, 5 nm). b The HRTEM image of the exsolution of nanoparticles with increased size from m-SrIrO₃ after a short-term electron beam illumination. The fast Fourier transformed (FFT) pattern from the nanoparticle can be indexed to a F m\(\overline 3\)m space group of Ir metal. The exsolution of nano Ir particles has no apparent effect on the crystallinity of surface region. c HRTEM images of pristine and cycled SrCo_0.9Ir_0.1O_3−δ (by 5 cycles, scale bar, 5 nm). The white curves in a and c indicate the interfaces between the crystallized region and the reconstructed region. The FFT patterns from the bulk of corresponding HRTEM images can be well indexed based on space groups of C 2/c for m-SrIrO₃ and P nma for SrCo_0.9Ir_0.1O_3−δ. As reflected in the FFT patterns from the surfaces of cycled m-SrIrO₃ and cycled SrCo_0.9Ir_0.1O_3−δ, no long-range order exists in the surface regions. d Sr_3d XPS for m-SrIrO₃ before and after 5 cyclic voltammetry (CV) cycles. e Sr_3d and Co_2p XPS for SrCo_0.9Ir_0.1O_3−δ before and after the electrochemical tests. f The surface (Sr + Co):Ir ratio in m-SrIrO₃ and SrCo_0.9Ir_0.1O_3−δ before and after the electrochemical cycling