Synthesis of alkali-metal cobalt kambaldaite by precipitation method

Abstract Alkali-metal cobalt kambaldaite (alkali-metal cobalt carbonate hydroxide hydrate; ideal structure, M 2 Co 8 (CO 3 ) 6 (OH) 6  · 6H 2 O; M-CoKBL) was prepared by the addition of a cobalt nitrate solution into a solution containing a large excess of alkali-metal bicarbonate followed by aging at 50 °C for 2–3 h. Hydrated alkali-metal ions are present in the channels of the kambaldaite structure; therefore, we tried to ion-exchange the K-CoKBL sample with various metals. However, collapse of the kambaldaite structure took place easily because of low pH of the ion-exchange solution. The catalytic activity of Co 3 O 4 obtained by the calcination of “ion-exchanged” K-CoKBL was dependent on the residual potassium content in the catalyst.