From Mn<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si123.svg" display="inline" id="d1e956"><mml:msub><mml:mrow/><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub></mml:math>O<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si124.svg" display="inline" id="d1e964"><mml:msub><mml:mrow/><mml:mrow><mml:mn>4</mml:mn></mml:mrow></mml:msub></mml:math> thin film towards MnO<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si87.svg" display="inline" id="d1e972"><mml:msub><mml:mrow/><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:math>: Surface reactivity and the role of O<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si87.svg" display="inline" id="d1e981"><mml:msub><mml:mrow/><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:math> and H<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si87.svg" display="inline" id="d1e989"><mml:msub><mml:mrow/><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:math>O exposures investigated by X-ray Photoelectron Spectroscopy at Near-Ambient Pressure
E. Annese, Fernando Stavale
Abstract
MnO 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 ∼ 400 °C in presence of p(O 2 ) and p(H 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(O 2 )= 2 mbar at ∼ 450 °C, and it is modified into δ -MnO 2 phase at ∼ 480 °C when p(O 2 ) pressure is suddenly reduced to below 10 −9 mbar. Thus, the OH spectral feature becomes the main signature in O 1s core level spectral regions and a Mn 4 + related feature is identified in Mn 2p energy range. The multiple step reaction follows the proposed mechanism for the MnO 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.