An iron oxyhydroxide includes a plurality of iron oxyhydroxide octahedra components, a plurality of chloride components and at least one of germanium hydroxide components or germanium oxide components. The iron oxyhydroxide octahedra components form a tunnel-type structure. The chloride components are disposed in a tunnel of the tunnel-type structure and bonded to at least one of the iron hydroxide octahedra components. The germanium hydroxide components or the germanium oxide components substitute for at least one of the chloride components.