In this study, a co-precipitation method was used for the synthesis of undoped ferrites (Fe2O3/Fe3O4-R) and nickel-doped ferrites from nickel reagents (NiFe2O4-R) and from nickel recycled from spent Ni-MH batteries (NiFe2O4-B). Ferrite structure and composition were confirmed by X-ray diffraction and inductively coupled plasma optical emission spectrometry. Energy dispersive X-ray analysis showed the presence of iron, oxygen, and nickel in the surface composition of the nickel-doped ferrites. Scanning electron microscopy showed agglomerated particles of different sizes and shapes. Transmission electron microscopy revealed spherical particles of 50 nm. NiFe2O4-B is a multifunctional material that can be used as a catalyst and pseudocapacitor. The catalytic properties of NiFe2O4-B were analyzed by measuring the decolorization of methylene blue (MB) in a photo-Fenton process under solar radiation. Pseudocapacitive properties, analyzed by cyclic voltammetry, showed that NiFe2O4-B composites exhibit favorable characteristics for application as electrochemical pseudocapacitors.