Cathodic deposition of birnessite from alkaline permanganate solutions: Tools to control the current efficiency, morphology and adhesion

Birnessite deposition on Pt, Ni, and carbon supports resulting from electrochemical permanganate reduction in alkaline medium is optimized. The goal is to obtain the material for alkaline electrochemical devices under the same alkaline conditions. Optimization of electrodeposition mode assumes the choice of deposition potentials and permanganate concentration providing high enough current efficiency and the deposit mechanical stability. Deposition on carbon supports is accented. Voltammetric and rotating disc experiments discover the principle phenomenon responsible for deposition kinetics: solid oxide formed either in the course of Mn(V) disproportionation, or by means of cathodic reduction which inhibits the formation of soluble Mn-containing reduced species. Manifestations of inhibition for various electrode materials are discussed. Oxidative treatment of glassy carbon is found to favor the formation of homogeneous deposits with close to 100 % current efficiency. The specific features of birnessite coatings fabricated at different potentials are examined by XRD and SEM techniques and discussed in the context of collected kinetic information. •Electrodeposition and operation under the same conditions•Birnessite microstructure controlled by deposition potential•Inhibition of permanganate reduction with soluble species formation