Co-doped Ni–Fe spinels for electrocatalytic oxidation over glycerol.

A series of Co-doped Ni–Fe spinels (NiCo x Fe (2-x) O 4 , x = 0.2, 0.4, 0.6, 0.8, 1.0, 1.4, 1.8, 2) were prepared at optimum calcination temperature (700 °C) by the sol-gel method and then applied for the electrocatalytic oxidation over glycerol. Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), Tafel curve, and chronoamperometry (i-t) were performed to investigate electrochemical performance of as-prepared spinel catalysts. The results showed that NiCo 0·8 Fe 1·2 O 4 exhibited distinct redox peaks and the larger CV area (626.2 ± 0.03 μV A cm−2), lower Rct (42.42 ± 0.03 Ω) and Tafel slope (21 mV dec−1) than that of pristine NiFe 2 O 4 and NiCo 2 O 4 , signifying Co-doped NiFe 2 O 4 is beneficial to accelerate the catalytic oxidation of glycerol. Moreover, the ECSA and stability of NiCo 0·8 Fe 1·2 O 4 were also observably improved. This excellent performance is comparable to that of commercial Pt/C (20 wt.%)-SA. The enhanced electrocatalytic property of NiCo 0·8 Fe 1·2 O 4 is ascribed to the uneven distribution of oxygen in NiFe 2 O 4 structure caused by Co doping, thus forming oxygen defect sites. [Display omitted] • Co-doped Ni–Fe spinels were prepared and applied for electrocatalytic oxidation over glycerol. • ECSA of NiCo 0·8 Fe 1·2 O 4 is larger than that of pristine NiFe 2 O 4 and NiC 2 O 4 spinels. • Electrocatalytic property of NiCo 0·8 Fe 1·2 O 4 is comparable to that of commercial Pt/C. • The doping of Co can cause uneven distribution of oxygen in NiFe 2 O 4 structure. • The enhanced performance of NiCo 0·8 Fe 1·2 O 4 is due to the forming of oxygen defect sites. [ABSTRACT FROM AUTHOR]