X-ray Photoelectron Spectroscopy
X-ray Photoelectron Spectroscopy measurements were carried out to estimate the oxide stoichiometry for the
MnOx catalyst and to confirm the Mn:Ti ratio. In Figure S2a the Mn3s spectra can be seen for a Ti-MnO2
catalyst, together with the energy difference for the Mn3s multiplet, 4.7 eV. In Figure S2b the Mn2p peak for
the same sample is shown, with indication of the energy difference between the Mn2p½ and its satellite. These
two energy differences are consistent with MnO2 spectra in the literature.1,2 In Figure S2c the Ti2p peak is
shown for a Ti-MnO2 sample as prepared and in Figure S2d for a tested Ti-MnO2 sample. These spectra were
used to evaluate the Mn:Ti ratio which was found to be 80:20 both before and after the stability tests
described in the main text.
Figure S2. a) Mn3s spectrum where the distance for the multiplet is indicated. b) Mn2p spectrum where the
distance for the Mn2p½ satellite is indicated. c) Ti2p spectrum used for evaluation of the Mn:Ti ratio. d) Ti2p
spectrum for a sample tested two hours both at 1.8 VRHE and 2 hours at 1.9 VRHE.