Versatile synthesis of sub-10 nm sized metal-doped M_xCo_3-xO₄ nanoparticles and their electrocatalytic OER activity

Metal-doped spinel MxCo3-xO4 nanoparticles are promising catalysts for the electrochemical oxygen evolution reaction (OER). We here report a robust and scalable route for the synthesis of metal-doped spinel MxCo3-xO4 nanoparticles (M = Al, V, Cr, Mn, Fe, Ni; x = 0.05, 0.1, 0.2) by thermal decomposition of cobalt(ii) acetylacetonate and the respective metal acetylacetonate or nitrate. The resulting spherical nanoparticles show uniform sizes between 8 and 10 nm and homogeneous dopant distribution as shown by powder X-ray diffraction (PXRD), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), infrared spectroscopy (IR) and X-ray photoelectron spectroscopy (XPS). The Fe-doped samples were further investigated by Fe-57-Mossbauer spectroscopy. The effect of the metal doping on the electrocatalytic OER activity of the nanoparticles was examined by linear sweep voltammetry (LSV). The OER activity was found to either increase (V, Cr, Fe, Ni) or decrease (Al, Mn) with increasing dopant concentration. An influence on the cobalt redox behavior during catalyst conditioning via cyclic voltammetry (CV) was observed as a result of metal doping.