(A) Tafel plots derived from RDE-voltammetry in pH 1 H2SO4-solution for four catalysts: (i) O-catalyst, (ii) AW-catalyst obtained by acid washing the O-catalyst in 0.1 M H2SO4, filtering, rinsing and drying, (iii) a chemically-reactivated catalyst obtained by acid-washing the O-catalyst, filtering, base-washing the filtrate in 0.1 M NaOH, rinsing and drying, and (iv) the AW-catalyst re-heat-treated in Ar at 300°C.
(B) X-ray photo-electron spectra of S2p for the O-catalyst, AW-catalyst and chemically reactivated catalyst