You Do Need power plug adapter while traveling from Côte d'Ivoire (Ivory Coast) to Sierra Leone.

Here is Why You Need An Adapter

The outlet and plug type used in Sierra Leone are D and G and in Côte d'Ivoire (Ivory Coast) are C and E. This is how they look like.

Côte d'Ivoire (Ivory Coast)

In Côte d'Ivoire (Ivory Coast), outlets of type C and E are in use.

Type C

Type E

Sierra Leone

In Sierra Leone, outlets of type D and G are in use.

Type D

Type G