Studies of electrodeposition from Mn(II) species of thin layers of birnessite onto transparent semiconductor

This paper describes successful electrodeposition of very homogeneous, adherent and well-crystallized thin layers of birnessite on a cheap transparent semiconductor substrate, SnO2, in neutral sulphate solutions. Birnessite, a layered manganese oxide, plays an important role in environmental chemistry due to its large surface area. A coupled approach based on electrochemical measurements and pH measurements allowed us to give information about electrodeposition mechanism of birnessite. An intermediary Mn(III) compound, α-MnOOH (groutite), is formed in deaerated solutions leading to mixed thin layers of birnessite and groutite. But, thin layers of pure birnessite can be efficiently electrodeposited in aerated solutions due to the oxidation of groutite by dissolved oxygen in such solutions. Thin layers of pure birnessite are well suitable for studies devoted to environmental applications as hazardous waste remediation or chemical sensors but also as electrode material for energy storage.