Cobalt (Co) based nanomaterials are widely used to construct glucose enzyme-free electrochemical sensors. However, the correlation between anion species and the electrocatalytic activity of Co based nanomaterials remains unproven. In this paper, Co 3 X 4 with different anions (X = O, S, Se) were synthesized for electrochemical sensing of glucose. Co 3 X 4 was characterized by transmission electron microscopy (TEM), energy-dispersive X-ray spectrometry (EDX), powder X-ray diffractometry (XRD), and electrochemical techniques. The results showed that anion substitution had a significant effect on the electrocatalytic properties of Co 3 X 4 , and Co 3 Se 4 showed the strongest electrocatalytic activity for the oxidation of glucose. The sensor based on Co 3 Se 4 exhibited excellent performance for glucose analysis with a linear range from 2 μM to 0.71 mM, a high sensitivity of 1327.6 μA mM −1 cm −2 and a low detection limit of 0.3 μM, which demonstrates Co 3 Se 4 as a new nonenzymatic electrocatalyst for glucose sensing.
Pei Zhu,Yan Wang,Minghang Zhang,Yingdong Wu,Wangfeng Cai
In order to investigate the influence of the anions on the electrochemical performance of cobalt-based compounds, Co 3 O 4 and Co 3 Se 4 are studied and theoretically analyzed with the density functional theory (DFT). Avoiding of the traditional synthesis of the high-temperature annealing for the transition metal oxides, the cubic spinel phase Co 3 O 4 on a nickel foam (NF) substrate with a simple two-step hydrothermal method and Co 3 Se 4 with the core-branched structure by anions exchange method are prepared. The electrochemical measurements show that the capacitance and conductivity of Co 3 Se 4 are significantly better than those of Co 3 O 4 , and Co 3 Se 4 still maintain high capacity at high current density. Furthermore, the kinetics of electrode material Co 3 O 4 and Co 3 Se 4 are analyzed and compared. According to the calculation of the density of states, the results show the band gap of Co 3 O 4 is 2.18 eV and the Fermi energy line of Co 3 Se 4 enters into the conduction band, which means the conductivity of Co 3 Se 4 is better than that of Co 3 O 4 . Additionally, three redox reactions during the charge and discharge process of Co 3 O 4 are determined and the band gaps changes are also calculated.
Regulating the electronic structure is of great importance for improving the performance, stability, and selectivity of seawater splitting catalysts. Herein, cobalt-based oxide and chalcogenide (Co 3 X 4 , X = O, S, and Se) are synthesized to investigate the effect of anions on the electronic structure, catalytic performance and selectivity of the seawater oxidation catalysts. The theoretical calculations predict the possible active sites of oxygen evolution reaction and hypochlorite evolution reaction. Then the experimental characterization and calculation results demonstrate that S and Se substitution could regulate the electronic structure and d-band center of Co site, enhance the metallicity of catalysts. Moreover, the energy barrier of Cl* conversion to ClO - could be modulated for preventing the formation of ClO - by anions regulating. Consequently, Co 3 S 4 could stably operate at a current density of 100 mA cm −2 in 0.1 M KOH + 0.6 M NaCl for 100 h and in neutral seawater for 20 h.
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