From Mn3O4 3 O 4 thin film towards MnO2: 2: Surface reactivity and the role of O2 2 and H2O 2 O exposures investigated by X-ray Photoelectron Spectroscopy at Near-Ambient Pressure

MnO2 2 phase of manganese oxide was identified as the final product of a multiple steps reaction in near ambient pressure-X-ray photoemission (NAP-XPS) chamber. At the first stage of the reaction, an intermediate stable manganese hydroxide film was obtained at similar to 400 degrees C in presence of p(O2) 2 ) and p(H2O) 2 O) and verified by the formation of sizeable hydroxide peak, OH, at binding energy 531.4 (1) eV. The Mn hydroxide film is kept unaltered even when is subsequently exposed to p(O2)= 2 )= 2 mbar at similar to 450 degrees C, and it is modified into S-MnO2 2 phase at similar to 480 degrees C when p(O2) 2 ) pressure is suddenly reduced to below 10-9 -9 mbar. Thus, the OH spectral feature becomes the main signature in O 1s core level spectral regions and a Mn4+ 4+ related feature is identified in Mn 2p energy range. The multiple step reaction follows the proposed mechanism for the MnO2 2 formation in electrolytic cell and it is the first observation in a controlled way in NAP-XPS chamber. The findings open new roots for the birnessite manganese oxide phase formation and its manipulation.