Chemical hydrogen insertion into γ-manganese dioxide exhibiting low microtwinning

Abstract

Hydrogen has been inserted by chemical methods into a syntheticγ-manganese dioxide characterized by 41% de Wolff disorder and a low amount of microtwinning. 23 Compounds covering the insertion range 0.00≤s≤0.82 where s is the value in MnO _1.966 H _s were prepared. Both XRD and FTIR evidence indicated homogeneous insertion in the range 0.00≤s≤0.34 followed by heterogeneous reaction in the range 0.34≤s≤0.82. Starting from the position that the structure of the predominant ramsdellite type lattice may be characterized by the distance z between the apical oxygens normal to the c axis of the manganese occupied octahedra and the angle β that the apical vector makes with the b axis a map was developed enabling the structure of the inserted compounds to be followed. In the homogeneous range, where H ⁺ and e are mobile, insertion led to expansion of z with little change in β whereas in the heterogeneous range, where H ⁺ is relatively immobile in the final product, a large change in β was observed which is believed to result from the location of H ⁺ in the final product.