Formation of secondary crystallites during electrochemical cycling of hydrogen molybdenum bronze

Powder samples of hydrogen molybdenum bronzes (HxMoO3) were effectively stabilized by the addition of 30 mass% polyethylene (PE) powder, pressing and a following thermal treatment. The composite material does not degrade in 0.05 mol 1−1 H2SO4 but shows 1–3 μm wide cracks in the surface and the formation and growth of small hydrated bronze crystals (1–10 μm) during electrochemical cycling. An electrochemical dissolution/precipitation mechanism is presented and discussed.